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STUDENT WORKSHOP EXPERIENCE PROGRAM 2010
NAME: AMOO KEHINDE OLAWALE
MATRIC NO: 08CF07632
PROGRAM: CHEMICAL ENGINEERING
A TECHNICAL REPORT WRITTEN IN PARTIAL FULFULLMENT OF GEC 229
SCHOOL OF ENGINEERING, COLLEGE OF SCIENCE AND TECHNOLOGY, COVENANT UNIVERSITY, OTA.
This report is dedicated to the Almighty God for granting me the grace to complete this report.
My sincere gratitude goes to my parents, Dr. and Dr (Mrs.) Amoo for their firm support towards the completion of this report. I also wish to thank Engr. Leramo for his immense contribution during the period of SWEP. Finally, I acknowledge the Almighty God for His grace upon my life.
page TITLE PAGE DEDICATION 1 AKNOWLEDGEMENT 2 TABLE 3 INTRODUCTION 6 CHAPTER ONE: CONSTRUCTION
Foundation 9 Beams 24 Slabs 25 and Columns
CHAPTER TWO: WATER PRODUCTION AND PRESERVATION
Process 28 Reverse 32 Arsenic 34 Heavy 34 Metals
Water Osmosis Removal Removal
Desalination 35 Surface 37 Nitrates 39 Water 39 Waste 40 Water Water Treatment Removal Softening Treatment
CHAPTER THREE: BREAD MAKING 3.1. The 45
Formulation 47 Flour 48 Liquids 49 Leavening 49 Chemical 49 Yeast 50 Bread 50 Industrial 51 Scale Bread Leavening Leavening Improvers Making
CHAPTER FOUR: PRINTING PRESS
How 53 Offset 53 Digital 55 Printing 57
works Press Printing Techniques
CHAPTER FIVE: SOAP, FACIAL MASK AND CREAM MAKING
Soap 63 Facial 64 Cream 65 Mask
Making Production Making
CHAPTER SIX: ELECTRICITY
Electrical 67 Electrical 68 Electric 70 Three-phase 71 Generation 73 Electricity 73 and electric Distribution of electric Wire
Wiring code Lights Power Power mains
CHAPTER SEVEN: ROAD CONSTRUCTION AND MARKING
Road 75 Road 78 Road 80
Construction Kerbs Marking
CHAPTER EIGHT: MACHINES
Complex 82 Threading 86 Industrial 87 Tool
Machines Gauge Mixer
CONCLUSION 89 REFERENCES 90
Engineering is the application of science in the design, planning, construction, and maintenance of buildings, machines, and other manufactured things. The term engineer properly denotes a person who has received professional training in pure and applied science, but this term is often misused by the public as an operator of an engine i.e. locomotive engineer or stationary engineer. In modern terminology, these latter occupations are known as crafts or trades. Between the professional engineer and the craftsperson or tradesperson, however, are those individuals known as sub professionals or paraprofessionals, who apply scientific and engineering skills to technical problems; typical of these are engineering aides, technicians, inspectors, draftsmen, and so on. The scientific and technical advances of the 19th century greatly broadened the field of engineering and introduced a large number of engineering specialties, and the rapidly changing demands of the socioeconomic environment in the 20th century have widened the scope even further thereby creating more fields in engineering namely; 1. Military Engineering 2. Civil Engineering 3. Mechanical Engineering 4. Chemical Engineering 5. Petroleum Engineering 6. Electrical and Electronics Engineering 7. Computer Engineering 8. Nuclear Engineering 9. Aeronautical and Airspace Engineering 10.Safety Engineering
Furthermore, safety in engineering cannot be over emphasized in the protection from industrial accidents to the engineers and also to the general public. Therefore, in recent years engineers have attempted to develop a systems approach (termed safety engineering) to industrial accident prevention. Because accidents arise from the interaction of workers and their work environments, both must be carefully examined to reduce the risk of injury. Injury can result from poor working conditions, the use of improperly designed equipment and tools, fatigue, distraction, lack of skill, and risk taking. The systems approach examines the following areas: all work locations to eliminate or control hazards, operating methods and practices, and the training of employees and supervisors. The systems approach, moreover, demands a thorough examination of all accidents and near misses. Key facts about accidents and injuries are recorded, along with the history of the worker involved, to check for and eliminate any patterns that might lead to hazards. Thus, Safety engineering is an applied science strongly related to systems engineering and the subset System Safety Engineering. Safety engineering assures that a life-critical system behaves as needed even when pieces fail. Ideally, safety-engineers take an early design of a system, analyze it to find what faults can occur, and then propose safety requirements in design specifications up front and changes to existing systems to make the system safer. In an early design stage, often a fail-safe system can be made acceptably safe with a few sensors and some software to read them. Probabilistic faulttolerant systems can often be made by using more, but smaller and lessexpensive pieces of equipment. Additionally, failure mitigation can go beyond design recommendations, particularly in the area of maintenance. There is an entire realm of safety and reliability engineering known as Reliability Centred Maintenance (RCM), which is a discipline that is a direct result of analyzing potential failures within a system and determining maintenance actions that can mitigate the risk of failure. This methodology is used extensively on aircraft and involves understanding the failure modes of the serviceable replaceable assemblies in addition to the means to detect or predict an impending failure. Every automobile owner is familiar with this concept when they take in their car to have the oil changed or brakes checked. Even filling up one's car with fuel is a
simple example of a failure mode (failure due to fuel exhaustion), a means of detection (fuel gauge), and a maintenance action (filling the car's fuel tank). For large scale complex systems, hundreds if not thousands of maintenance actions can result from the failure analysis. These maintenance actions are based on conditions (e.g., gauge reading or leaky valve), hard conditions (e.g., a component is known to fail after 100 hrs of operation with 95% certainty), or require inspection to determine the maintenance action (e.g., metal fatigue). The RCM concept then analyzes each individual maintenance item for its risk contribution to safety, mission, operational readiness, or cost to repair if a failure does occur. Then the sum total of all the maintenance actions are bundled into maintenance intervals so that maintenance is not occurring around the clock, but rather, at regular intervals. This bundling process introduces further complexity, as it might stretch some maintenance cycles, thereby increasing risk, but reduce others, thereby potentially reducing risk, with the end result being a comprehensive maintenance schedule, purpose built to reduce operational risk and ensure acceptable levels of operational readiness and availability. It is also common practice to plan for the failure of safety systems through containment and isolation methods. The goal of all such containment systems is to provide means of limiting the damage done by a failure to a small localized area and less catastrophic effect on the public and the environment.
CHAPTER ONE CONSTRUCTION
1.1. Foundation Foundation can be defined as part of a building, usually below the ground, that transfers and distributes the weight of the building onto the ground. A building without a strong and durable foundation is liable to sudden and an unprecedented collapse. Therefore there two(2) major types of foundations namely; 1. Shallow Foundations 2. Deep Foundations Shallow foundations Shallow foundations are those founded near to the finished ground surface; generally where the founding depth (Df) is less than the width of the footing and less than 3m. These are not strict rules, but merely guidelines: basically, if surface loading or other surface conditions will affect the bearing capacity of a foundation it is 'shallow'. Shallow foundations (sometimes called 'spread footings') include pads ('isolated footings'), strip footings and rafts. Shallows foundations are used when surface soils are sufficiently strong and stiff to support the imposed loads; they are generally unsuitable in weak or highly compressible soils, such as poorly-compacted fill, peat, recent lacustrine and alluvial deposits, etc. There are three(3) major types of shallow foundations which are;
I. II. III.
Pad foundations Strip foundations Raft foundations
I. Pad foundations Pad foundations are used to support an individual point load such as that due to a structural column. They may be circular, square or rectangular. They usually consist of a block or slab of uniform thickness, but they may be stepped or haunched if they are required to spread the load from a heavy column. Pad foundations are usually shallow, but deep pad foundations can also be used.
Fig 1.1 II. Strip foundations Strip foundations are used to support a line of loads, either due to a loadbearing wall, or if a line of columns need supporting where column positions are so close that individual pad foundations would be inappropriate.
Fig 1.2
III. Raft foundations Raft foundations are used to spread the load from a structure over a large area, normally the entire area of the structure. They are used when column loads or other structural loads are close together and individual pad foundations would interact. A raft foundation normally consists of a concrete slab which extends over the entire loaded area. It may be stiffened by ribs or beams incorporated into the foundation. Raft foundations have the advantage of reducing differential settlements as the concrete slab resists differential movements between loading positions. They are often needed on soft or loose soils with low bearing capacity as they can spread the loads over a larger area.
Deep foundations Deep foundations are those founding too deeply below the finished ground surface for their base bearing capacity to be affected by surface conditions, this is usually at depths more than 3 m below finished ground level. They include piles, piers and caissons or compensated foundations using deep basements and also deep pad or strip foundations. Deep foundations can be used to transfer the loading to a deeper, more competent strata at depth if unsuitable soils are present near the surface. There are four(4) major types of deep foundations namely; I. II. III. IV. Piles Piers Caissons Compensated foundations
Piles are relatively long, slender members that transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock strata having a high bearing capacity. They are used when for economic, constructional or soil condition considerations it is desirable to transmit loads to strata beyond the practical reach of shallow foundations. In addition to supporting structures, piles are also used to anchor structures against uplift forces and to assist structures in resisting lateral and overturning forces. Piled foundations can be classified according to The type of pile (different structures to be supported, and different ground conditions, require different types of resistance) and The type of construction (different materials, structures and processes can be used). Types of pile
End bearing piles Friction piles Settlement reducing piles Tension piles Laterally loaded piles Piles in fill
Piles are often used because adequate bearing capacity can not be found at shallow enough depths to support the structural loads. It is important to understand that piles get support from both end bearing and skin friction. The proportion of carrying capacity generated by either end bearing or skin friction depends on the soil conditions. Piles can be used to support various different types of structural loads.
End bearing piles
Fig 1.3 End bearing piles are those which terminate in hard, relatively impenetrable material such as rock or very dense sand and gravel. They derive most of their carrying capacity from the resistance of the stratum at the toe of the pile.
Friction piles
Fig 1.4 Friction piles obtain a greater part of their carrying capacity by skin friction or adhesion. This tends to occur when piles do not reach an impenetrable stratum but are driven for some distance into a penetrable soil. Their carrying capacity is derived partly from end bearing and partly from skin friction between the embedded surface of the soil and the surrounding soil.
Settlement reducing piles
Fig 1.5 Settlement reducing piles are usually incorporated beneath the central part of a raft foundation in order to reduce differential settlement to an acceptable level. Such piles act to reinforce the soil beneath the raft and help to prevent dishing of the raft in the centre.
Tension piles Structures such as tall chimneys, transmission towers and jetties can be subject to large overturning moments and so piles are often used to resist the resulting uplift forces at the foundations. In such cases the resulting forces are transmitted to the soil along the embedded length of the pile. The resisting force can be increased in the case of bored piles by under-reaming. In the design of tension piles the effect of radial contraction of the pile must be taken into account as this can cause about a 10% - 20% reduction in shaft resistance.
Laterally loaded piles Almost all piled foundations are subjected to at least some degree of horizontal loading. The magnitude of the loads in relation to the applied vertical axial loading will generally be small and no additional design calculations will normally be necessary. However, in the case of wharves and jetties carrying the impact forces of berthing ships, piled foundations to bridge piers, trestles to overhead cranes, tall chimneys and retaining walls, the horizontal component is relatively large and may prove critical in design. Traditionally piles have been installed at an angle to the vertical in such cases, providing sufficient horizontal resistance by virtue of the component of axial capacity of the pile which acts horizontally. However the capacity of a vertical pile to resist loads applied normally to the axis, although significantly smaller than the axial capacity of that pile, may be sufficient to avoid the need for such 'raking' or 'battered' piles which are more expensive to install. When designing piles to take lateral forces it is therefore important to take this into account.
Piles in fill
Fig1.6 Piles that pass through layers of moderately- to poorly-compacted fill will be affected by negative skin friction, which produces a downward drag along the pile shaft and therefore an additional load on the pile. This occurs as the fill consolidates under its own weight.
Types of pile construction
Displacement piles Non-displacement piles
Displacement piles cause the soil to be displaced radially as well as vertically as the pile shaft is driven or jacked into the ground. With nondisplacement piles (or replacement piles), soil is removed and the resulting hole filled with concrete or a precast concrete pile is dropped into the hole and grouted in.
Displacement piles
Totally preformed displacement piles Driven and cast-in-place displacement piles Helical (screw) cast-in-place displacement piles Methods of installation
Sands and granular soils tend to be compacted by the displacement process, whereas clays will tend to heave. Displacement piles themselves can be classified into different types, depending on how they are constructed and how they are inserted.
Totally preformed displacement piles These can either be of precast concrete; full length reinforced (prestressed) jointed (reinforced) hollow (tubular) section or they can be of steel of various section.
Driven and cast-in-place displacement piles This type of pile can be of two forms. The first involves driving a temporary steel tube with a closed end into the ground to form a void in the soil which is then filled with concrete as the tube is withdrawn. The second type is the same except the steel tube is left in place to form a permanent casing.
Helical (screw) cast-in-place displacement piles This type of construction is performed using a special type of auger. The soil is however compacted, not removed as the auger is screwed into the ground. The auger is carried on a hollow stem which can be filled with concrete, so when the required depth has been reached concrete can be pumped down the stem and the auger slowly unscrewed leaving the pile cast in place.
Methods of installation
Dropping weight Diesel hammer Vibratory methods of pile driving Jacking methods of insertion
Displacements piles are either driven or jacked into the gound. A number of different methods can be used.
Dropping weight The dropping weight or drop hammer is the most commonly used method of insertion of displacement piles. A weight approximately half that
of the pile is raised a suitable distance in a guide and released to strike the pile head. When driving a hollow pile tube the weight usually acts on a plug at the bottom of the pile thus reducing any excess stresses along the length of the tube during insertion. Variants of the simple drop hammer are the single acting and double acting hammers. These are mechanically driven by steam, by compressed air or hydraulically. In the single acting hammer the weight is raised by compressed air (or other means) which is then released and the weight allowed to drop. This can happen up to 60 times a minute. The double acting hammer is the same except compressed air is also used on the down stroke of the hammer. This type of hammer is not always suitable for driving concrete piles however. Although the concrete can take the compressive stresses exerted by the hammer the shock wave set up by each blow of the hammer can set up high tensile stresses in the concrete when returning. This can cause the concrete to fail. This is why concrete piles are often prestressed.
Diesel hammer Rapid controlled explosions can be produced by the diesel hammer. The explosions raise a ram which is used to drive the pile into the ground. Although the ram is smaller than the weight used in the drop hammer the increased frequency of the blows can make up for this inefficiency. This type of hammer is most suitable for driving piles through non-cohesive granular soils where the majority of the resistance is from end bearing. This type of pile foundation is mostly used in the construction of bridges.
Vibratory methods of pile driving Vibratory methods can prove to be very effective in driving piles through non cohesive granular soils. The vibration of the pile excites the soil grains adjacent to the pile making the soil almost free flowing thus significantly reducing friction along the pile shaft. The vibration can be produced by electrically (or hydraulically) powered contra-rotating eccentric masses attached to the pile head usually acting at a frequency of about 20-40 Hz. If
this frequency is increased to around 100 Hz it can set up a longitudinal resonance in the pile and penetration rates can approach up to 20 m/min in moderately dense granular soils. However the large energy resulting from the vibrations can damage equipment, noise and vibration propagation can also result in the settlement of nearby buildings.
Jacking methods of insertion Jacked piles are most commonly used in underpinning existing structures. By excavating underneath a structure short lengths of pile can be inserted and jacked into the ground using the underside of the existing structure as a reaction.
Non-displacement piles
Small diameter bored cast-in-place piles Large diameter bored cast-in-place piles Partially preformed piles Grout or concrete intruded piles
With non-displacement piles soil is removed and the resulting hole filled with concrete or sometimes a precast concrete pile is dropped into the hole and grouted in. Clays are especially suitable for this type of pile formation as in clays the bore hole walls only require support close to the ground surface. When boring through more unstable ground, such as gravels, some form of casing or support, such as a bentonite slurry, may be required. Alternatively, grout or concrete can be intruded from an auger rotated into a granular soil. There are then essentially four types of non displacement piles. This method of construction produces an irregular interface between the pile shaft and surrounding soil which affords good skin frictional resistance under subsequent loading.
Small diameter bored cast-in-place piles
Fig 1.8 These tend to be 600mm or less in diameter and are usually constructed by using a tripod rig. The equipment consists of a tripod, a winch and a cable operating a variety of tools. The basic tools are shown in this diagram. In granular soils, the basic tool consists of a heavy cylindrical shell with a cutting edge and a flap valve at the bottom. Water is necessary to assist in this type of excavation. By working the shell up and down at the bottom of the bore hole liquefaction of the soil takes place (as low pressure is produced under the shell as the liquified soil is rapidly moved up) and it flows into the shell and can be winched to the surface and tipped out. There is a danger when boring through granular soil of over loosening the material at the sides
of the bore. To prevent this a temporary casing should be advanced by driving it into the ground. In cohesive soils, the borehole is advanced by repeatedly dropping a cruciform-section tool with a cylindrical cutting edge into the soil and then winching it to the surface with its burden of soil. Once at the surface the clay which adheres to the cruciform blades is paired away.
Large diameter bored cast-in-place piles
Fig1.9 Large boreholes from 750mm up to 3m diameter (with 7m under-reams) are possible by using rotary drilling machinery. The augering plant is usually crane or lorry mounted. A spiral or bucket auger as shown in this diagram is attached to a shaft known as a Kelly bar (a square section telescopic member driven by a horizontal spinner). Depths of up to 70m are possible using this technique. The use of a bentonite slurry in conjunction with bucket auger drilling can eliminate some of the difficulties involved in drilling in soft silts and clays, and loose granular soils, without continuous support by casing tubes. One advantage of this technique is the potential for under reaming. By using an expanding drilling tool the diameter at the base of the pile can be enlarged, significantly increasing the end bearing capacity of the pile. However, under23
reaming is a slow process requiring a stop in the augering for a change of tool and a slow process in the actual under-reaming operation. In clay, it is often preferable to use a deeper straight sided shaft.
Partially pre-formed piles This type of pile is particularly suitable in conditions where the ground is waterlogged, or where there is movement of water in an upper layer of the soil which could result in cement being leached from a cast-in-place concrete pile. A hole is bored in the normal way and annular sections are then lowered into the bore hole to produce a hollow column. Reinforcement can then be placed and grout forced down to the base of the pile, displacing water and filling both the gap outside and the core inside the column.
Grout or concrete-intruded piles The use of continuous flight augers is becoming a much more popular method in pile construction. These piles offer considerable environmental advantages during construction. Their noise and vibration levels are low and there is no need for temporary borehole wall casing or bentonite slurry making it suitable for both clays and granular soils. The only problem is that they are limited in depth to the maximum length of the auger (about 25m). The piles are constructed by screwing the continuous flight auger into the ground to the required depth leaving the soil in the auger. Grout (or concrete) can then be forced down the hollow shaft of the auger and then continues building up from the bottom as the auger with its load of spoil is withdrawn. Reinforcement can then be lowered in before the grout sets. An alternative system used in granular soils is to leave the soil in place and mix it up with the pressured grout as the auger is withdrawn leaving a column of grout reinforced earth.
Piers foundations
Piers are foundations for carrying a heavy structural load which is constructed insitu in a deep excavation.
Caissons foundations
Caissons are a form of deep foundation which are constructed above ground level, then sunk to the required level by excavating or dredging material from within the caisson.
IV. Compensated foundations Compensated foundations are deep foundations in which the relief of stress due to excavation is approximately balanced by the applied stress due to the foundation. The net stress applied is therefore very small. A compensated foundation normally comprises a deep basement.
1.2Beams and Columns The beam is a very sturdy structure. A beam is a horizontal pole. It is usually shaped as a rectangle so there is more balance between the poles. A beam is held up by one or two columns. If there are two columns, they are placed on either side of the beam. If there is one column, it is placed in the middle of the beam so each side is balanced. Beams are found in many places - in buildings, in homes, and in moving structures. Beams can either be made of concrete which is reinforced with iron rods or strong steel or iron bars. A beam is used to transfer load from the slab of a building to the columns, which then transfers to the foundation then to the ground.
2.1 Fig 2.0 shows monkey bars that are made of horizontal beams supported on four columns while Fig 2.1 shows the application of beams on culverts which allow the passage of excess water. The column is a vertical support structure made of either concrete that is reinforced with iron rods or just strong steel. The columns receive the load from the slab and the beam then transfers it the foundation. Columns do not have to be rectangular, they can be round, tapered or of classical types.
Post and lintel construction is often found in homes in our area for windows and doorways. The post and lintel holds everything that is above an opening. Stonehenge is a well known example of an ancient post and lintel construction. Two vertical posts on either side of a beam (or lintel) hold up the beam and everything above the opening. This is a strong support when the structure is level and gravity pulls down evenly on the structure. The weight of the wall above the lintel is the load.
1.3Slabs
A concrete slab is a common structural element of modern buildings. Horizontal slabs of steel reinforced concrete, typically between 10 and 50 centimetres thick, are most often used to construct floors and ceilings, while thinner slabs are also used for exterior paving. In many domestic and industrial buildings a thick concrete slab, supported on foundations or directly on the sub soil, is used to construct the ground floor of a building. In high rise buildings and skyscrapers, thinner, pre-cast concrete slabs are slung between the steel frames to form the floors and ceilings on each level. On the technical drawings, reinforced concrete slabs are often abbreviated to r.c.slab or simply r.c
In casting a slap there are two main thermal considerations to observe; The first is the question of insulating a floor slab. In older buildings, concrete slabs cast directly on the ground can drain heat from a room. In modern construction, concrete slabs are usually cast above a layer of insulation such as expanded polystyrene, and the slab may contain under floor heating pipes. However, there are still uses for an uninsulated slab, typically in outbuildings which are not heated or cooled to room temperature. In those cases, casting the slab directly onto a rocky substrate will maintain the slab at or near the temperature of the substrate throughout the year, and can prevent both freezing and overheating. The second consideration is the high thermal mass, which applies to walls and floors, or wherever the concrete is used within the thermal envelope. It is a disadvantage where the rooms are heated intermittently and require a quick response, as the concrete takes time to warm up, causing a delay in warming the building. But it is an advantage in climates with large daily temperature swings,
where the slab acts as a regulator, keeping the building cool by day and warm by night. For a suspended slab, there are a number of designs to improve the strength-toweight ratio. In all cases the top surface remains flat, and the underside is modulated:
Corrugated, usually where the concrete is poured into a corrugated steel tray. This improves strength and prevents the slab bending under its own weight. The corrugations run across the short dimension, from side to side. A ribbed slab, giving considerable extra strength on one direction. A waffle slab, giving added strength in both directions.
Reinforcement design
A one way slab has structural strength in shortest direction. A two way slab has structural strength in two directions.
A concrete slab may be prefabricated(precast) or in situ. Prefabricated concrete slabs are built in a factory and transported to the site, ready to be lowered into place between steel or concrete beams. They may be pre-stressed (in the factory), post-stressed (on site), or unstressed. It is vital that the supporting structure is built to the correct dimensions, or the slabs may not fit. In situ concrete slabs are built on the building site using formwork i.e. a type of boxing into which the wet concrete is poured. If the slab is to be reinforced, the iron bars are positioned within the formwork before the concrete is poured in. Plastic tipped metal, plastic bar or biscuits are used to hold the bar away from the bottom and sides of the form-work, so that when the concrete sets it completely envelops the reinforcement. For a ground slab, the form-work may consist only of sidewalls pushed into the ground. For a suspended slab, the form-work is shaped like a tray, often supported by a temporary scaffold until the concrete sets. The formwork is commonly built from wooden planks and boards, plastic, or steel. On commercial building sites today, plastic and steel are more common as
they save labour. On low-budget sites, for instance when laying a concrete garden path, wooden planks are very common. After the concrete has set the wood may be removed, or left there permanently. In some cases formwork is not necessary - for instance, a ground slab surrounded by brick or block foundation walls, where the walls act as the sides of the tray and hardcore acts as the base.
CHAPTER TWO WATER PRODUCTION AND PRESERVATION
Water Production is an industrial process in which large quantity of water (unclean) is treated in plants for safer consumption by the public, this production can be by water processing. Drinking water can be produced from any natural sources like groundwater, lakes and rivers (surface waters) or seawater. Drinking water standards are set by the World Health organisation. Drinking water must be free of suspended solids/particles, microorganisms and toxic chemicals. Mineral concentration recommendations vary from country to country but most of the minerals have a maximum concentration recommended to ensure safe, equilibrated and pleasant water to drink.
For municipal drinking water, a special focus is carried on the corrosivity and scaling potential of the water to maintain distribution piping in good shape. Typical pH 8, TAC 8 and TH 8 are applied, when possible. For bottled water, taste can vary upon calcium, magnesium, sulphate and iron content.
Process water covers the wide range of boiler feed water, cooling water for heat exchangers or engine, chemicals dilution, etc... It should typically have a conductivity ranging from 0.1 to 50 uS/cm, with little to no hardness to avoid scaling in heating system. Oxygen and carbon dioxide should be removed to prevent corrosion Tap water or fresh ground water are the most widely used source of water to produce process water. Process water treatment plant can combine various technology, depending on the purity required: Source 500-2000 uS/cm Quality required 5-20 uS/cm < 5 uS/cm < 1 uS/cm < 500 uS/cm < 5 uS/cm < 1 uS/cm Technology applied Reverse Osmosis 2-pass reverse Osmosis 2-pass reverse Osmosis + Mixed bed Ion exchange Ion exchange + Mixed bed
Once demineralised, process water should be conditioned according to manufacturer's specification, usually up to pH 9 by adding caustic soda or ammonia. Further demineralisation is also possible to obtain ultra-pure water
Disinfection There are a variety of techniques to disinfect fluids and surfaces with much emphasis on environmental friendly solutions. The techniques are:
Ozone Ultra-Violet (UV) Chlorine dioxide Chlorine Hypochlorite
In the table below a few applications of the techniques can be found: Technology Applications
Ozone disinfection UV
Pharmaceutical industry, drinking water, process water, ultra pure water, surface disinfection Process water, drinking water, ozone breakdown, ultra pure water, surface disinfection
Chlorine dioxideDrinking water, disinfection of piping
Ozone can be artificially produced, so that it can be used for water treatment. Ozone generators can create ozone artificially by means of extremely high voltages or by means of UV-light. Both methods involve the decomposition of the oxygen molecule. This causes oxygen radical formation. These oxygen radicals can bind to oxygen molecules, forming ozone (O3). Ozone is one of the strongest known oxidants. It can be used to technically burn dissolved compounds (oxidation). The extra oxygen radical in an ozone molecule quickly binds to each component that comes in contact with ozone molecules. This is because of the instability of ozone and its inclination to return to its original form (O2). Both organic and inorganic substances may be oxidized by ozone (oxidation), but also microorganisms such as viruses, bacteria and fungi (disinfection). This causes the extra oxygen radical to be released from the ozone molecule and to bind to other materials, so that only pure and stable oxygen molecules (O2) are left. As a result of the above-mentioned reaction mechanisms, ozone can be used for a large variety of purposes. Ozone is mainly applied in waste water and drinking water purification (for disinfection). The application of ozone in the industrial branch is increasing. The food industry uses ozone for disinfection and the textile industry uses ozone for colour removal. The largest benefit of ozone is its pure character. It only oxidizes substances, and as a result by-product formation rarely occurs.
Fig2.5 Fig 2.5 shows an ozone system CFV high range (0.75 kg/h to 14.8 kg/h)
Ultra-Violet (UV) Ray
When exposed to sunlight, germs are killed and bacteria and fungi are prevented from spreading. This natural disinfection process can be utilised most effectively by applying UV radiation in a controlled way. Packaging materials can be efficiently and easily disinfected using UV-C (Ultra Violet Control) radiation. Likewise, the shelf life of several foodstuffs is improved using UV radiation. Surface disinfection makes most sense when the products have minimum resistance to microbic contamination. The Blue Light disinfection module consists of a UV cassette and power supply unit, designed for easy installation and handling. The lamps are protected against splash water by a sealed quartz glass window. The reflectors inside the lamps guarantee uniform radiation of the surface.
Chlorine dioxide (ClO2) at a flow rate of 150 g/h is used in horticulture, bottled water disinfection or CIP applications. The following criteria should be followed to get maximum results; ClO2 concentrations Water flow rate Reagent 1 Reagent 2 - 0.2 to 2.5 mg/L - up to 100 m3/h - Purogene (NaClO2 at 3.36%) - HCl (15%)
The recommended concentrations include:
Horticulture: 2.5 mg/L Bottled water: 0.2 mg/L Drinking water: 0.8 mg/L
Osmosis is based upon the fundamental pursuit for balance. Two fluids containing different concentrations of dissolved solids that come in contact with each other will mix until the concentration is uniform. When these two fluids are separated by a semi permeable membrane (which lets the fluid flow through, while dissolved solids stay behind), the fluid containing the lower concentration will move through the membrane into the fluid containing the higher concentration of dissolved solids. After a while the water level will be higher on one side of the membrane. The difference in height is called the osmotic pressure. By applying a pressure that exceeds the osmotic pressure, the reverse effect occurs. Fluids are pressed back through the membrane, while dissolved solids stay behind. To purify water by Reverse Osmosis membrane, the natural osmosis effect must be reversed. In order to force the water of the brine stream (high salt concentration) to flow towards the fresh stream (low salt concentration), the water must be pressurized at an operating pressure greater than the osmotic pressure. As a result, the brine side will get more concentrated. The operating pressure of seawater is around 60 bar.
Fig 2.7 Fig 2.7 shows that water flows from a column with a low dissolved solid content to a column with a high dissolved solid content. Osmotic pressure is the pressure that is used to stop the water from flowing through the membrane, in order to create balance By pursuing pressure that exceeds the osmotic pressure, the water flow will be reversed; water flows from the column with a high dissolved solids content to the column with a low dissolved solids content illustrated in the figure below;
Arsenic Removal
The WHO (World Health Organization) advices a maximum concentration of 10 ppb. Although arsenic may be found in surface water, groundwater is the main source of arsenic in water. Consequently, concentrations above 10 ppb may be found naturally in groundwater. In groundwater arsenic exists as water-insoluble inorganic arsenic As-V anions or As-III molecules. In Nigeria, Bangladesh, India, Sudan and some other countries, the
groundwater concentrations of arsenic may exceed 100 ppb on some locations which is not good for consumption. Arsenic can be removed from water by means of adsorptive media which is titanium based.
Heavy Metals Removal
Heavy metals are present in ground water and are usually Nickel, Lead, Cadmium and Zinc, these metals are not good for drinking, therefore have to be removed. These metals are present in water at ppb(parts per billion) level under cationic form such as Zn2+, Ni2+, Cd2+ and Pb2+. Reverse Osmosis can be performed at removing low level of heavy metals, although in aerobic conditions metal oxides can clog the membranes. Also, RO (Reverse Osmosis) is not a very cost efficient method, unless the water salt content requires further demineralisation. The best method for groundwater heavy metal removal is the use of a selective ion exchange resin called Lewatit TP 207 or Lewatit TP 208. The Lewatit 208 resin is usually non regenerable, given the low level of heavy metals in the aquifers (150ft - 250ft). On another hand, the selective resin can also be regenerated on site by acid and caustic soda if necessary, usually for leachate treatment or mining waste waters. II.5 Desalination
Nowadays, desalination has become a very affordable solution to cope with fresh water shortage typically in tropical as well as of off-shore areas. The desalination core process is based on Reverse Osmosis Membrane technology, but stand alone, it doesn't provide safe drinking water, nor does it guarantee an efficient plant. The pre-treatment includes all the necessary treatment step ahead of the reverse osmosis plant. It is determining for plant life time and to minimise chemical cleaning and membrane replacement. It has a direct impact on the plant performance.
There are as many membrane types as applications. They range from "high rejection" to "ultra low energy" or " high boron rejection". The reverse osmosis process can also be built with one or two passes, depending on the product water requirements and the seawater salinity and temperature. In most cases, 1(one) pass is sufficient to reach the EU drinking water standards, especially regarding the boron content (1 mg/L). To reach WHO boron guideline (0.5mg/L), a second pass might be necessary (Boron removal process) The energy recovery device is the key factor that determines the plant electrical costs. It must be chosen carefully based on the local energy costs and environment policies Post treatment or polishing steps are required to condition the water after the reverse osmosis membrane process to make it suitable to drink. Brine disposal can be an environmental and economical issue in some areas where the fauna and flora are sensitive to local seawater salinity increase. Brine disposal should be studied and engineered case by case. The art of desalination is to determine and combine available technologies to optimize water production costs and quality. To adapt our Desalination Plants to needs, it should be noted that containerized mobile units from Intake to Distribution up to a production capacity of 200 m3/h of desalinated water be used. The types of water that can be produced from a desalination plant are: - WHO or EU drinking water - Irrigation water - Process water : boiler feed water, cooling water - Demi or Ultra pure water The types of natural seawater source that can be treated are; - Shallow Surface seawater - Deep seawater
- Brackish river water - Beach well seawater
Essential process steps in desalination plants is shown in Fig 2.9
Due to the high cost of drinking water and the fact that water is not always available, more and more industries and municipalities use treated surface water. Normally the surface water needs to be treated before it has the required water quality. Surface water typically contains a high suspended solids content, bacteria, algae, organic matter, creating bad taste and odour. In some areas, like river estuaries, surface water can be brackish, reaching up to 8000 mg/L of salts. The two processes that are commonly used to treat surface water are:
- Conventional treatment including clarification (coagulation/flocculation, sedimentation or dissolved air flotation), sand filtration, activated carbon adsorption and disinfection. - Advanced treatment based on ultra filtration technology.
Surface water treatment processes in Fig 3.0
Fig 3.0 Special attention is brought to disinfection since surface waters contain a wide range of coliforms (E.Coli), viruses and protozoa. The use of chlorine should be used with care since it reacts with natural organic matter to form disinfection by-products like trihalomethanes.
Nitrates Removal
Nitrates level in drinking water is recommended below 50 mg/L, especially for babies. Since their digestive systems are immature, and thus more likely to allow the reduction of nitrate to nitrite. The nitrite in the digestive tract of babies can cause methenoglobinemia which is the unusual form and the deformity of the haemoglobin. Nitrates can be removed by ion exchange using strong anionic resin in Clform. Reverse Osmosis is also efficient means to the removal of nitrates, although the hydrophilic properties of the molecule does not allow an optimal removal. Biological denitrification is used in municipal waste water treatment plant.
Hardness in water is caused by certain salts. The main hardness causing ions are Calcium (Ca2+), Magnesium (Mg2+) and Bicarbonate (HCO3-). These ions or minerals are normally addressed as scale in the water industries, causing scaling of pipes and equipment in drinking water and process water systems. Softening units offer a water purification solution for hard water and lime scale removal. In many applications, e.g. the preparation of drinking water, water in breweries and sodas, but also cooling water and boiler feed water, the hardness of the water is of importance. The hardness is normally measured in German degree, French Hardness or (equivalent) concentration Ca2+. Softeners are specific ion exchangers which are designed to remove ions with a multiple positive charge. Water softener units are automatically regenerated with salt (NaCl). Brackish water softeners are also available using specific resins and regenerated with HCl and NaOH.
i. Biological wastewater treatment Biological wastewater treatment processes are primarily designed for the removal of dissolved and suspended organic matter from wastewaters. The environmental conditions are optimised to encourage growth of the microorganisms which use the organic compounds as substrate. Biological wastewater treatment is also capable of removing other wastewater components, including suspended solids, nitrogen, phosphorus, heavy metals and xenobiotics. In general the biological wastewater treatment is the most efficient and economic way of removing organic pollution from a wastewater. ii. Membrane bioreactors (MBR) The Membrane Bioreactor or MBR is based on the conventional wastewater process, but the separation of micro-organisms is performed by filtration with membranes.
iii. Moving Bed Bio film Reactor (MBBR) Moving Bed Bio film Reactor (MBBR) offers an economical solution for wastewater treatment if the "bulk" of the pollution load must be disposed of (as means of cost reduction) or if applicable discharge regulations are not as strict. With this application, advanced wastewater treatment solutions for the industrial and municipal markets are realised. These solutions significantly increase the capacity and efficiency of existing wastewater treatment plants, while minimizing the size of new plant deployments. This method makes it possible to attain good efficiency results of disposal with low energy consumption. This process is used for the removal of organic substances, nitrification and denitrification. The MBBR system consists of an activated sludge aeration system where the sludge is collected on recycled plastic carriers. These carriers have an internal large surface for optimal contact water, air and bacteria.
Fig 3.1 Fig 3.1 shows the carrier material used inside a MBBR system. The bacteria/activated sludge grow on the internal surface of the carriers. The bacteria break down the organic matter from the waste water. The aeration system keeps the carriers with activated sludge in motion. Only the extra amount of bacteria growth, the excess sludge will come separate from the carriers and will flow with the treated water towards the final separator. The system can consist of a one stage or more stage system (see underneath schedule), depending on the specific demands. The specific bacteria remain in their own duty tank because of the fact that the carriers remain in only 1 tank, protected by screens.
Fig 3.2 The MBBR process can be used for a variety of different applications to attain the desired results, depending on the quality of the wastewater and the discharge regulations. Industrial applications Capacity increase Quality Improvement Nitrogen Removal Fast recovery from Process Upsets
Limited Footprint Future Expansion Minimize Process Complexity and Operator Attention
Benefits Economical very attractive Compact (saves space) Maintenance-friendly Strong High volume load Simply to extend Financial savings on discharge costs
CHAPTER THREE BREAD MAKING
Bread is a staple food prepared by cooking dough of flour and water and frequently additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed, fried, or baked on an unoiled skillet. It may be
leavened or unleavened. Salt, fat and leavening agents such as yeast and baking soda are common ingredients, though bread may contain other ingredients, such as milk, egg, sugar, spice, fruit (such as raisins), vegetables (such as onion), nuts (such as walnuts) or seeds (such as poppy seeds). Bread is one of the oldest prepared foods, dating back to the Neolithic era, and is referred to colloquially as the "Staff of life". The development of leavened bread can probably also be traced to prehistoric times. Fresh bread is prized for its taste, aroma, quality, appearance and texture. Retaining its freshness is important to keep it appetizing. Bread that has stiffened or dried past its prime is said to be stale. Modern bread is sometimes wrapped in paper or plastic film, or stored in a container such as a breadbox to reduce drying. Bread that is kept in warm, moist environments is prone to the growth of mold. Bread kept at low temperatures, in a refrigerator for example, will develop mold growth more slowly than bread kept at room temperature, but will turn stale quickly due to retrogradation. The soft, inner part of bread is known to bakers and other culinary professionals as the crumb, which is not to be confused with small bits of bread that often fall off, called crumbs. The outer hard portion of bread is called the crust. Bread is one of the oldest prepared foods, dating back to the Neolithic era. The first bread produced was probably a cooked version of a grain-paste, made from ground cereal grains and water, and may have been developed by accidental cooking or deliberate experimentation with water and grain flour. Yeast spores are ubiquitous, including the surface of cereal grains, so any dough left to rest will become naturally leavened. There were multiple sources of leavening available for early bread. Airborne yeasts could be harnessed by leaving uncooked dough exposed to air for some time before cooking. Pliny the Elder reported that the Gauls and Iberians used the foam skimmed from beer to produce "a lighter kind of bread than other peoples." Parts of the ancient world that drank wine instead of beer used a paste composed of grape juice and flour that was allowed to begin fermenting, or wheat bran steeped in wine, as a source for yeast. The most common source of leavening, however, was to retain a piece of dough from the previous day to use as a form of sourdough starter. A major advance happened in 1961 with the development of the Chorleywood Bread Process, which used the intense mechanical working of dough to
dramatically reduce the fermentation period and the time taken to produce a loaf. The process, whose high-energy mixing allows for the use of inferior grain, is now widely used around the world in large factories. Recently, domestic bread makers that automate the process of making bread have become popular in the home. There many types of breads, of which are;
White bread is made from flour containing only the central core of the grain (endosperm). Brown bread is made with endosperm and 10% bran. It can also refer to white bread with added colouring (often caramel colouring) to make it 'brown'; commonly labeled in America as "Wheat" bread (as opposed to "Whole Wheat" bread.) Whole meal bread contains the whole of the wheat grain (endosperm and bran). It is also referred to as 'whole grain' or 'whole wheat' bread, especially in North America. Wheat germ bread has added wheat germ for flavoring. Whole grain bread can refer to the same as 'whole meal bread', or to white bread with added whole grains to increase its fibre content (i.e. as in "60% whole grain bread"). Roti is a whole wheat based bread eaten in South Asia. Chapatti is a larger variant of Roti. Naan is a leavened equivalent to these. Granary bread is bread made using flaked malted wheat grains malt. Trademarked to Hovis, it is made from white or brown flour and flaked malted wheat grains. The standard malting process is modified to maximise maltose/sugar content but minimise residual alpha amylase content. Other flavour components are imparted from partial fermentation due to the particular malting process used and to Maillard reactions on flaking / toasting. Rye bread is made with flour from rye grain of variable levels. It is higher in fiber than many common types of bread and is often darker in color and stronger in flavor, rye is a popular type of bread.
Unleavened Bread or Matzah used for the Jewish feast of Passover, does not include yeast, thus it does not rise. Sourdough bread is made with a starter. Researchers at the Agricultural Research Service are inventing new whole-grain oat and barley breads that offer more antioxidants and fibers than traditional whole-grain breads.
3.1 The Manufacturing Process 1 Mixing and kneading the dough
The sifted flour is poured into an industrial mixer. Temperaturecontrolled water
is piped into the mixer. This mixture is called "gluten" and gives bread its elasticity. A pre-measured amount of yeast is added. Yeast is actually a tiny organism which feeds off the sugars in the grain, and emits carbon dioxide. The growth of the yeast produces gas bubbles, which leaven the bread. Depending on the type of bread to be made, other ingredients are also poured into the mixer. Modern mixers can process up to 2,000 pounds (908 kg) of dough per minute.
The mixer is essentially an enclosed drum that rotates at speeds between 35 to 75 revolutions per minute. Inside the drum, mechanical arms knead the dough to the desired consistency in a matter of seconds. Although modern bread production is highly computerized, the ability of the mixing staff to judge the elasticity and appearance of the dough is critical. Experienced personnel will be able to determine the consistency by the sound of the dough as it rolls around the mixer. The mixing process takes about 12 minutes.
2 Fermentation
Three methods are used to ferment the dough. In some plants, the highspeed machinery is designed to manipulate the dough at extreme speeds and with great force, which forces the yeast cells to rapidly multiply.
Fermentation can also be induced by the addition of chemical additives such as 1-cysteine (a naturally occurring amino acid) and vitamin C. Some breads are allowed to ferment naturally. In this instance, the dough is placed in covered metal bowls and stored in a temperature-controlled room until it rises. 3 Division and gas reproduction
After the dough has fermented, it is loaded into a divider with rotating blades that cut the dough into pre-determined weights. A conveyer belt then moves the pieces of dough to a molding machine. The molding machine shapes the dough into balls and drops them onto a layered conveyer belt that is enclosed in a warm, humid cabinet called a "prover." The dough moves slowly through the prover so that it may "rest," and so that the gas reproduction may progress.
4 Molding and baking
When the dough emerges from the prover, it is conveyed to a second molding machine which re-shapes the dough into loaves and drops them into pans. The pans travel to another prover that is set at a high temperature and with a high level of humidity. Here the dough regains the elasticity lost during fermentation and the resting period. From the prover, the pans enter a tunnel oven. The temperature and speed are carefully calculated so that when the loaves emerge from the tunnel, they are completely baked and partially cooled. While inside the tunnel, the loaves are mechanically dumped from the pans onto shelves. The baking and cooling process lasts approximately 30 minutes.
5 Slicing and packaging
The bread continues to cool as it moves from the oven to the slicing machine. Here vertical serrated blades move up and down at great speeds, slicing the bread into consistently sized pieces. Metal plates hold the slices together while picking up each loaf and passing it to the wrapping machine. Pre-printed plastic bags are mechanically slipped over each loaf. At some bakeries, workers close the bags with wire twists. Other plants seal the bags with heat.
6 Quality Control Commercial bread making is held to strict government guidelines regarding food production. Further, consumer preferences compel bread producers to maintain a high quality standard of appearance, texture, and flavor. Therefore, quality checks are performed at each step of the production process. Producers employ a variety of taste tests, chemical analyses, and visual observation to ensure quality. Moisture content is particularly critical. A ratio of 12 to 14% is ideal for the prevention of bacteria growth. However, freshly baked breads have a moisture content as high as 40%. Therefore it is imperative that the bakery plants be kept scrupulously clean. The use of fungicides and ultraviolet light are two popular practices.
The amount of flour is the most significant measurement in a bread recipe, as it affects texture and crumb the most. Professional bakers use a system of percentages known as Bakers' Percentage in their recipe formulations, and measure ingredients by weight instead of by volume. Measurement by weight is much more accurate and consistent than measurement by volume, especially for the dry ingredients. Flour is always stated as 100%, and the rest of the ingredients are a percent of that amount by weight. Common table bread in the U.S. uses approximately 50% water, resulting in a finely textured, light, bread. Most artisan bread formulas contain anywhere from 60 to 75% water. In yeast breads, the higher water percentages result in more CO2 bubbles, and a coarser bread crumb. One pound (~ 450 g) of flour will yield a standard loaf of bread, or two French loaves. Calcium propionate is commonly added by commercial bakeries to retard the growth of molds.
Flour is a product made from grain that has been ground into a powdery consistency. It is flour that provides the primary structure to the final baked bread. Commonly available flours are made from rye, barley, maize, and other grains, but it is wheat flour that is most commonly used for breads. Each of these grains provides the starch and protein necessary for the production of bread. The quantity of the proteins contained in the flour serves as the best indicator of the quality of the bread dough and the finished bread. While bread can be made from all-purpose wheat flour, for quality bread , special bread flour, containing more protein, is recommended. If one uses a flour with a lower (9-11%) protein content to produce bread, a longer mixing time will be required to develop gluten strength properly. This extended mixing time leads to oxidization of the dough which gives the finished product a whiter crumb, instead of the cream color preferred by most artisan bakers. Wheat flour in addition to its starch contains three water-soluble protein groups,( albumin, globulin, protease), and two non-water soluble protein groups, (glutenin and gliadin). When flour is mixed with water, the water-soluble proteins dissolve, leaving the glutenin and gliadin to form the structure of the resulting dough. When worked by kneading, the glutenin forms strands of long thin chainlike molecules while the shorter gliadin forms bridges between the strands of glutenin. The resulting networks of strands produced by these two proteins are known as gluten. Gluten development improves if the dough is allowed to autolyse.
Water, or some other liquid, is used to form the flour into a paste or dough. The volume of liquid required varies between recipes, but a ratio of 1 part liquid to 3 parts flour is common for yeast breads, while recipes that use steam as the primary leavening method may have a liquid content in excess of one part liquid to one part flour by volume. In addition to water, other types of liquids that may be used include dairy products, fruit juices, or beer. In addition to the water in
each of these, they also contribute additional sweeteners, fats, and/or leavening components. 3.5 Leavening
Leavening is the process of adding gas to a dough before or during baking to produce a lighter, more easily chewed bread. Most bread consumed in the West is leavened. However, unleavened breads have symbolic importance in Judaism and Christianity. Jews consume unleavened bread called matzo during Passover. They are also used in the Roman Catholic Christian liturgy. On the other hand, the Orthodox Church always uses leavened bread.
Chemical leavening
A simple technique for leavening bread is the use of gas-producing chemicals. There are two common methods. The first is to use baking powder or a selfrising flour that includes baking powder. The second is to have an acidic ingredient such as buttermilk and add baking soda. The reaction of the acid with the soda produces gas. Chemically leavened breads are called quick breads and soda breads. This technique is commonly used to make muffins, pancakes, American-style biscuits, and sweet breads such as banana bread.
Yeast Leavening
Many types of bread are leavened by yeast. The yeast used for leavening bread is Saccharomyces cerevisiae, the same species used for brewing alcoholic beverages. This yeast ferments carbohydrates in the flour, including any sugar, producing carbon dioxide. Many types of bread are made from straight dough, which means that all of the ingredients are combined in one step, and the dough is baked after the rising time. Alternatively, dough can be made using a preferment, when some of the flour, water, and the leavening are combined a day or so ahead of baking, and allowed to ferment overnight. On the day of the baking,
the rest of the ingredients are added, and the rest of the process is the same as that for straight dough. This produces a more flavourful bread with better texture. Most yeasted pre-ferments fall into one of three categories: poolish or pouliche, a loose-textured mixture composed of roughly equal amounts of flour and water (by weight); biga, a stiff mixture with a higher proportion of flour; pte fermente, which is simply a portion of dough reserved from a previous batch.
Fig 3.3 Fig 3.3 shows the stages of a dough before yeast leavening to the rising of the dough and then the proofing in a tin, ready to bake.
Bread Improvers
Bread improvers are frequently used in the production of commercial breads to reduce the time that the bread takes to rise, and to improve the texture and volume of bread. Chemical substances commonly used as bread improvers include ascorbic acid, hydrochloride, sodium metabisulfate, ammonium chloride, various phosphates, amylase, and protease. Sodium/salt is one of the most common additives used in production. In addition to enhancing flavor and restricting yeast activity, salt affects the crumb and the overall texture by stabilizing and strengthening the gluten. The addition of salt to the dough, and leaving it to rest for about 20 minutes. This is known as an autolyse, and is done with both refined and with whole grain flours.
Industrial Scale Bread Making
There are eight steps are common to industrial-scale bread production in many parts of the world:
1) Grain, yeast, water, and other ingredients are combined to form bread dough. The dough is kneaded by repeatedly pressing, turning, and folding it to develop the gluten in the flour and create air pockets. The dough is then allowed to stand for a few hours, enabling the yeast to enlarge the air pockets, making the bread rise;
2) The dough is fed into an automatic slicing machine that divides the dough into uniformly sized loaves and deposits them into bread pans;
3) The loaves slowly pass through a temperature- and humidity-controlled environment, where they rise a second time;
4) The loaves pass through a hot-air convection oven where they are baked;
5) Before the loaves can be sliced and packaged, they must be cooled in a chamber where air flows over and around the loaves to lower their internal temperature;
6) The bread pans are separated from the loaves and routed on a conveyer belt through a dishwasher;
7) The cooled loaves are sliced and wrapped;
8) The loaves are loaded into trucks that deliver the fresh bread to retail outlets.
Fig 3.4 Fig 3.4 shows an illustration on the making of bread industrially.
CHAPTER FOUR PRINTING PRESS
Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing. A printing press is a mechanical device for applying pressure to an inked surface resting upon a print medium (such as paper or cloth), thereby transferring the ink. Typically used for texts, the invention and spread of the printing press are widely regarded as the most influential event in the second millennium.
How a Printing Press Works
A printing press, in its classical form, is a standing mechanism, ranging from 5 to 7 feet long, 3 feet wide, and 7 feet tall. Types arranged into pages is placed in a frame to make a forme, which itself is placed onto a flat stone or 'bed'. The type is inked, and the paper is held between a frisket and tympan (two frames covered with paper or parchment). These are folded down, so that the paper lies on the surface of the inked type. The bed is rolled under the platen, using a windlass mechanism, and the impression is made with a screw that transmits pressure through the platen. Then the screw is reversed, the windlass turned again to move the bed back to its original position, the tympan and frisket raised and opened, and the printed sheet removed. Such presses were always worked by hand. After around 1800, iron presses were developed, some of which could be operated by steam power. There many types of printing press namely;
Offset printing is a widely used printing technique where the inked image is transferred (or "offset") from a plate to a rubber blanket, then to the printing surface. When used in combination with the lithographic process, which is based on the repulsion of oil and water, the offset technique employs a flat (planographic) image carrier on which the image to be printed obtains ink from ink rollers, while the non-printing area attracts a film of water, keeping the nonprinting areas ink-free. Currently, most books and newspapers are printed using the technique of offset lithography. Other common techniques include:
Flexography used for packaging, labels, newspapers. Hot wax dye transfer Inkjet used typically to print a small number of books or packaging, and also to print a variety of materials from high quality papers simulate offset printing, to floor tiles; Inkjet is also used to apply mailing addresses to direct mail pieces. Laser printing mainly used in offices and for transactional printing (bills, bank documents). Laser printing is commonly used by direct mail companies to create variable data letters or coupons, for example.
Pad printing popular for its unique ability to print on complex 3dimensional surfaces. Relief print, (mainly used for catalogues). Rotogravure mainly used for magazines and packaging. Screen-printing from T-shirts to floor tiles.
Fig 3.5 3.6 4.3 Digital Printing
Digital printing accounts for approximately 9% of the 45 trillion pages printed annually around the world. Printing at home or in an office or engineering environment is subdivided into:
small format (up to ledger size paper sheets), as used in business offices and libraries Wide format (up to 3' or 914mm wide rolls of paper), as used in drafting and design establishments.
Some of the more common printing technologies are:
Blueprintand related chemical technologies.
Daisy wheelwhere pre-formed characters are applied individually. Dot-matrixwhich produces arbitrary patterns of dots with an array of printing studs. Line printingwhere pre-formed characters are applied to the paper by lines. Heat transferlike early fax machines or modern receipt printers that apply heat to special paper, which turns black to form the printed image. Inkjetincluding bubble-jetwhere ink is sprayed onto the paper to create the desired image. Electro photographywhere toner is attracted to a charged image and then developed. Lasera type of xerography where the charged image is written pixel by pixel by a laser. Solid ink printerwhere cubes of ink are melted to make ink or liquid toner.
Vendors typically stress the total cost to operate the equipment, involving complex calculations that include all cost factors involved in the operation as well as the capital equipment costs, amortization, etc. For the most part, toner systems beat inkjet in the long run, whereas inkjets are less expensive in the initial purchase price. Professional digital printing (using toner) primarily uses an electrical charge to transfer toner or liquid ink to the substrate it is printed on. Digital print quality has steadily improved from early color and black & white copiers to sophisticated colour digital presses like the Xerox iGen3, the Kodak Nexpress, the HP Indigo Digital Press series and the Info Print 5000. The iGen3 and Nexpress use toner particles and the Indigo uses liquid ink. The Info Print 5000 is a full-color, continuous forms inkjet drop-on-demand printing system. All handle variable data and rival offset in quality. Digital offset presses are also called direct imaging presses, although these presses can receive computer files and automatically turn them into print-ready plates, they cannot insert variable data. Small press and fanzines generally use digital printing. Prior to the introduction of cheap photocopying the use of machines such as the spirit duplicator, hectograph, and mimeograph was common.
Printing Techniques
Printing Techniques, several different ways in which printing may be accomplished, such as lithography, letterpress, flexography, gravure, and screen printing. All of these printing techniques use simple mechanisms for rapidly applying colorants to substrates such as paper or plastic to form multiple reproductions of original images for mass distribution.
1) Lithography Lithography is about the most important and versatile printing process today is offset lithography. The underlying principles were established at the end of the 18th century by a German map inspector, Aloys Senefelder, who was experimenting with methods of producing limestone relief printing surfaces using an acid etching process. Senefelder found that a wet limestone surface would repel an oil-based printing ink, and that an image drawn on the surface with a grease pencil would repel water and attract ink. Any drawing on the stone surface could be reproduced by bringing a damp sheet of paper into contact with the freshly inked image. This cycle could be repeated several hundred times before the drawing could no longer be faithfully reproduced. The process, called chemical printing by Senefelder, quickly became a popular art medium because it enabled artists to produce multiple copies of freehand drawings. By the late 19th century, multiple stones were being used to transfer as many as 30 (thirty) separate colours to a single sheet of paper to produce exquisite colour lithographs that resembled fine watercolour paintings. Modern colour lithography uses only four inks for a wide range of natural colours. Lithographic plates are the least expensive printing surfaces available today, and this fact has contributed greatly to the success of the process. Aluminium plate materials have a thin surface coating of light-sensitive material, such as a photopolymer, that undergoes a solubility change when
exposed to an intense source of blue and ultraviolet light. Images are transferred to the surface by exposing the plate through a film positive or negative Some materials can be exposed directly, as in a graphic-arts camera or by a computercontrolled laser beam, thereby eliminating the expense of film and speeding up the plate making process. Modern offset lithographic presses range in size from small sheet-fed duplicators used for small, single-colour jobs such as brochures and newsletters to massive web presses capable of printing millions of copies of magazines, catalogs, mailing pieces, and packaging materials in full colour. No other process has such a broad range of applications.
2) Relief Printing Relief printing processes work on the same principle as a rubber stamp. Ink is applied to the raised portions of the printing surface, and is then transferred by pressure to paper or some other substrate. The two forms of relief printing are letterpress and flexography which are currently in use, distinguished by the physical characteristics of their printing surfaces and inks. Letterpress printing is accomplished using a hard metal or plastic printing surface and a highly viscous ink. Flexography employs a soft rubber or plastic printing surface and a fluid ink. Originally, letterpress printing surfaces were prepared by assembling thousands of pieces of metal type on which individual letters or letter combinations were cast in relief to create pages of text called type forms. Ink was applied to the raised areas of the form and then transferred under pressure to paper or vellum. Woodcuts and engravings could be combined with type to produce composite pages containing both text and graphics. The first letterpress printing plate was created by making a plaster mould of a type form and then casting a metal duplicate of the original, called a stereotype. Stereotyping became an extremely important technology during the Industrial Revolution because it yielded a one-piece printing surface that could be used in place of the original type form on a variety of automated printing presses. Curved stereotypes cast from papier-mch moulds were used on rotary letterpresses for printing daily newspapers until the early 1970s, when hot-metal machine typesetting was largely replaced by computer typesetting.
Another important duplicate plate, called an electrotype, was made by electroplating a thin layer of copper onto a wax impression of the original type form and then filling the resulting copper shell with type metal. Electrotypes retained more detail from the original relief surface than stereotypes and were therefore preferred to stereotypes for higher-quality letterpress printing. The soft plates and highly fluid inks used in flexography make the process ideal for printing on nonporous materials such as foil laminates and polyethylene. Originally, all flexographic plates were made of moulded rubber, which is still the preferred material when multiple copies of the same image are needed on a single printing cylinder. Rubber plate moulds are impressions of original relief surfaces, such as type forms or engravings, and are normally used to make several duplicate rubber plates. The preparation of a printing cylinder using moulded rubber plates is a time-consuming process because many rubber plates are mounted on a single cylinder and each plate must be carefully positioned in relation to the others. In the 1970s photopolymer plate materials were introduced, and the time required to manufacture and mount a set of plates was reduced significantly. This has allowed the process to enter new markets, most notably newspaper printing. In addition, water-based inks can be used in flexography, eliminating the need for toxic solvents. Flexographic printing presses are simple in design because the fluid ink is easily distributed to the printing surface without an elaborate inking system. Printing is usually done on rolls or webs of substrate rather than on cut sheets, and the printed rolls are then converted into finished products in a separate manufacturing process.
3) Gravure Gravure, also called rotogravure, is a high-volume printing process employing an ink transfer mechanism that is fundamentally different from that of relief printing. The printing surface is a polished metal cylinder covered with an array of tiny recesses, or cells (as many as 50,000 per sq in), that constitute the images to be printed. The cylinder, which can be 2.5 m (8 ft) or more in length, is partially immersed in a reservoir of solvent-based fluid ink. As the cylinder
rotates, it is bathed in ink. A steel blade called a doctor blade running the entire length of the cylinder wipes the ink from the polished surface, leaving ink only in the cells. The ink is then transferred immediately to a moving web of paper forced against the cylinder under great pressure. Gravure cylinders are constructed of steel with a thin surface layer of electroplated copper. The copper can be either chemically etched or electronically engraved to form the cells that will transfer ink. Once the cells have been created, the cylinder is electroplated with a thin layer of chromium to produce a hard surface for the doctor blade. Each cell transfers a tiny spot of ink to the paper. The cells can be made to vary in depth from one part of a cylinder to another, causing the darkness of the resulting ink spots to vary also. This enables gravure to print a wide range of gray tones and thus to render excellent reproductions of photographic originals. Colour printing is accomplished by using separate printing cylinders for the cyan, magenta, yellow, and black inks. Each cylinder is housed in a separate printing unit. The web is transported by rollers from unit to unit and can reach speeds of close to 900 m (3000 ft) per minute. After each color is printed, the web passes through a dryer, where the solvent base of the ink is evaporated. The solvent is either reclaimed or burned to produce energy. Some gravure printers have begun to use water-based inks. This trend is likely to continue because of health and environmental threats posed by the use of hydrocarbon-based solvents. The expense of manufacturing a set of gravure cylinders has restricted its use to long-run jobs (millions of reproductions). Mass-circulation monthly magazines, mail-order catalogs, and packaging are natural markets for the process. Gravure is also used to reproduce a variety of textures and patterns on decorative materials. Most of the simulated wood grains on inexpensive furniture, for example, are printed by gravure. New methods of manufacturing gravure cylinders using computer-controlled electronic engraving machines have reduced the time required to prepare a set of cylinders, but they are still far more expensive than lithographic printing surfaces. Intaglio printing is a specialized process related to gravure that employs engraved rotary printing surfaces of steel to print currency, bonds, stock certificates, and high-quality business stationery. Ink is transferred from
engraved recesses on the printing surface directly to sheets of paper transported through the press. Intaglio printing excels at reproducing artwork that consists of fine lines and small solid areas. It cannot be used to reproduce photographic images or to print large unbroken solids. The use of past ink and deeply recessed printing surfaces gives intaglio printing a distinctive raised texture. (Powdered resins can be heat-fused to freshly printed wet lithographic or letterpress inks to simulate this effect at far less expense, which is why engraved business cards and stationery are usually produced in this manner.) 4) Screen Printing Originally called silk-screen printing because of its silk-based stencils, screen printing has become important in the production of a wide array of manufactured items, including decorative panels, printed circuit boards, touchsensitive switches, plastic containers, and printed garments. Stencils for commercial screen printing are usually produced by photomechanical means. A fine synthetic fabric or metal mesh is stretched over a rectangular frame, and a photopolymer coating is applied to the entire surface. Exposure of the photopolymer through a film positive causes it to harden in the areas not intended to print. The unexposed material is then washed away to create the open areas of the stencil. In the printing press, this screen is pressed against the surface to be printed, and ink is forced through the open areas of the stencil with a rubber squeegee. Presses for screen printing range from simple manual devices for the smallscale printing of T-shirts and banners to large sheet-fed presses for multicolour, high-volume commercial applications. The process is distinguished by its ability to print finely detailed images on practically any surface, including paper, plastics, metals, and three-dimensional surfaces. It is also the only major printing process that is routinely used to produce images that are not meant to be viewed. The circuit patterns in touch-sensitive switch panels, for example, are screen-printed with special conductive inks.
Fig 3.7 Fig 3.7 shows a Silk Screening machine A form of stencilling, silk screening allows ink to pass through the parts of a nylon or silk screen that are not blocked by an impenetrable membrane. Here, an even layer of ink is applied to a screen laid on top of a flat surface.
SOAP, FACIAL MASK AND CREAM MAKING
5.1 Soap Making Soap, cleansing agent or detergent made from animal and vegetable fats, oils, and greases; chemically, the sodium or potassium salt of a fatty acid, formed by the interaction of fats and oils with alkali. Oils and fats used are compounds of glycerin and a fatty acid, such as palmitic, or stearic acid. When these compounds are treated with an aqueous solution of an alkali, such as sodium hydroxidea process called saponification, they decompose, forming glycerin and the sodium salt of the fatty acid. The fat palmitin, for example, which is the ester of glycerin and palmitic acid, yields sodium palmitate (soap) and glycerin upon saponification. The fatty acids required for soap making are supplied by tallow, grease, fish oils, and vegetable oils such as coconut oil, olive oil, palm oil, soybean oil, and corn oil. Hard soaps are made from oils and fats that contain a high percentage of saturated acids, which are saponified with sodium hydroxide. Soft soaps are semi fluid soaps made from linseed oil, cotton-seed oil, and fish oils, which are saponified with potassium hydroxide. Tallow used in soap making ranges from the cheapest grades, recovered from garbage and used for cheaper soaps, to the best edible grades, used for fine toilet soaps. Tallow alone yields a soap that is too hard and too insoluble to provide satisfactory lathering, and therefore it is usually mixed with coconut oil. Coconut oil alone yields a hard soap that is too insoluble for use in fresh water; it lathers in salt water, however, and is used as marine soap. Transparent soaps usually contain castor oil, high-grade coconut oil, and tallow. A fine toilet soap made of high-grade olive oil is known as castile soap. Shaving soap is a potassium-sodium soft soap, containing stearic acid, which gives a lasting lather. Shaving cream is a paste that is a combination of shaving soap and coconut oil. Most soaps remove grease and other dirt because some of their components are surface-active agents, or surfactants. Surfactants have a molecular structure that acts as a link between water and the dirt particles, loosening the particles from the underlying fibres or other surfaces to be cleaned. The molecule can perform this function because one end is hydrophilic (attracted to water) and the other is hydrophobic (attracted to substances that are not water soluble). The hydrophilic end is similar in structure to water-soluble salts. The hydrophobic
part of the molecule frequently consists of a hydrocarbon chain that is similar to the structure of grease, oil, and many fats. The net result of this peculiar structure permits soap to reduce the surface tension of water (by increasing wetting) and to adhere to and make soluble substances otherwise insoluble in water. Soap powder is a hydrated mixture of soap and sodium carbonate. Powdered soap, which is used in dispensers, is a dry soap that has been pulverized to a fine powder. Liquid soap is a solution of soft potassium soap dissolved in water. Due to the increasing concern over the pollution of water resources, the inclusion of harmful chemicals, such as phosphates, in soaps and detergents was actively discouraged. Instead, biodegradable agents that are easily broken down and digested by bacteria came into wide use.
5.2 Facial Mask Production The main ingredient in face masks is either clay i.e. bentonite or algae products. Clay (bentonite) has been used both internally and externally for healing purposes with excellent results for many centuries. Clay is a solid, fat and moist earth that can be red, green, brown, grey, pink, yellow or white. Each type has its own properties which are determined by where it comes from and how deeply it is mined. Clay is not only suitable for making Face Masks, you can make Clay Body Packs to stimulate blood and lymph circulation and it is mixed with water or herbal infusions and other active ingredients in Creams, Bath and Hair products, etc. The colour in Green Clay comes from the 44.5% Silica content which is the most important mineral for the skin. Clay is rich in minerals and active enzymes. Clay treatments stimulate the circulation of blood and lymph, remove dead skin cells and absorb dirt and other surface fats. They also tone and strengthen the connective tissues. Clay stimulates blood circulation and draws toxins and superfluous fat from the skin. It contracts and tones the skin and strengthens the connective tissue. Clay is used for dirty and flaccid skin, acne, for poor blood circulation and to soothe eczema and sunburn. There are different clay types for different skin types namely; For sensitive skin the best type of clay to use is White Clay. For dry and sensitive skin use Pink Clay.
For all kinds of skin problems and most skin types and conditions, especially oily skin, use Green Clay. For normal skin use Red Clay. For normal and oily skin use Yellow Clay. Out of all of the different clays, green clays draw best and so are very good for treating oily skin. A Green Clay Pack is very good on swollen knee problems together with Macerated Arnica Oil (10% ) or Arnica Tincture (5%), plus Comfrey Oil (10%) or Comfrey Leaf Tincture (5%). Make it into a fine paste and use it as Compress over the knee. Use the same amount of liquid as the amount of clay powder youre using. Mix the appropriate essential oils in at the end. Red Clay is good for Body Packs for weight loss. Make a paste & apply. White Clay is good to use if you have been in the sun for too long. The white clay is also appropriate for, apart from generally sensitive skin, enlarged capillaries and red and sore babies bottoms.
Minerals found in all the Clays Silica - at approximately 50%. It regenerates and softens the skin. Magnesium - 0.2 to 5% Calcium - 0.2 to 8%. It stimulates cell regeneration. Calcium - 1 to 5%. Mangan - 0.15% in the Green, Red and Yellow Clays. Sodium - 0.01 to 0.3% in all Clays except the Red Clay. It helps to maintain the skins elasticity and stimulates cell regeneration.
5.3 Cream Making Materials required: Emulsifying wax, oil, water, a colorant, and a fragrance. Mix the oils and water in with your emulsifying wax. This will create the base of your lotion. Add your essential oils or fragrance oils. Essential oils will make your body lotion scented and can provide aromatherapy effects. Fragrance oils can also be used to give your lotion a nice scent.
Add your colorants. Natural coloring agents like paprika, mica, or oxides can also be used. You can now place your lotions into a jar, tube or into a pump or squirt bottle. In addition to making a basic body lotion you can also add things to the lotion to make it special. One popular additive to body lotion is glitter. Other popular additives for body lotions are SPF and tint.
Electricity, one of the basic forms of energy. Electricity is associated with electric charge, a property of certain elementary particles such as electrons and protons, two of the basic particles that make up the atoms of all ordinary matter. Electric charges can be stationary, as in static electricity, or moving, as in an electric current. Electrical activity takes place constantly everywhere in the universe. Electrical forces hold molecules together. The nervous systems of animals work by means of weak electric signals transmitted between neurons (nerve cells). Electricity is generated, transmitted, and converted into heat, light, motion, and other forms of energy through natural processes, as well as by devices built by people. Electricity is an extremely versatile form of energy. It can be generated in many ways and from many different sources. It can be sent almost instantaneously over long distances. Electricity can also be converted efficiently into other forms of energy, and it can be stored. Because of this versatility, electricity plays a part in nearly every aspect of modern technology. Electricity provides light, heat, and mechanical power. It makes telephones, computers, televisions, and countless other necessities and luxuries possible.
1.1 Electrical Wiring Electrical wiring in general refers to insulated conductors used to carry electricity, and associated devices. It describes the general aspects of electrical wiring as used to provide power in buildings and structures, commonly referred to as building wiring. Electrical wiring are of 2 (two) types namely; 1. Surface Wiring, done on the surface (not hidden) 2. Conduit Wiring, done inside of the structures before finishing touches (hidden)
6.2 Electrical Wire Coding Electrical wires have markings stamped or printed on the outside sheath of the cable. These markings tell what type and size of wire that you have. But looking deeper, the colour of the wires inside of the sheath, like in type NM cable, will reveal that different colour wires serve different purposes. Black Wires Black wires are always used for hot wires. These wires may feed a switch or outlet and are often used as switch legs. Never used a black wire for a neutral or ground connection. Red Wires Red wires are also used for hot wires, switch legs (like to a ceiling fan), and are the second hot wire in 220-volt installations. Another useful application is the interconnect wire between two hardwired smoke detectors. Blue and Yellow Wires Blue and yellow wires are used as hot wires. These wires are usually pulled in conduit. The blue wires are generally used for travellers in three-way and fourway switch applications. They also are used as switch legs to things like lights and fans. Yellow wires are generally used for switch legs. These control things like light, fans, and switched outlets. Green and Bare Copper Wires Green wires and bare copper wires are used only for grounding. These wires will ground devices and shall be bonded to junction boxes and appliance connections for safety. Wire Colour Exceptions In certain instances, wire colours may be used for connections that don't follow these general rules. For instance, a white wire in a two-conductor cable may be used for the second hot wire on a 240-volt appliance or outlet connection. Another application is using the white wire for a switch leg for lighting or running a three-way switch application. This white wire should be properly
marked to show that it is being used for something other than a neutral. Simply mark the end of the wire with black or red electrical tape. That way, no one will be confused and accidentally use it for something else. A Typical House Wiring shown in Fig 3.8
The table below shows The International Electro technical Commission (IEC) coding
Function Protective earth Neutral Line, single phase Line, 3-phase Line, 3-phase Line, 3-phase
label PE N L L1 L2 L3
Colour, IEC green-yellow Blue brown brown Black Grey
Colour, old IEC green-yellow Blue brown or black brown or black brown or black brown or black
1.1 Electric Lights Electric lights are used both at night and to provide additional light during the daytime. These lights are normally powered by the electric grid, but some run on local generators, and emergency generators serve as backups in hospitals and other locations where a loss of power could be catastrophic. Battery-powered lights, usually called "flashlights" or "torches", are used for portability and as backups when the main lights fail. The most efficient source of electric light is the low-pressure sodium lamp. It produces an almost monochromatic orange light, which severely distorts color perception. For this reason, it is generally reserved for outdoor public lighting usages. Low-pressure sodium lights are favoured for public lighting by astronomers, since the light pollution that they generate can be easily filtered, contrary to broadband or continuous spectra.
6.4 Three-phase Electric Power Three-phase electric power is a common method of alternating-current electric power transmission. It is a type of polyphase system, and is the most common method used by electric power distribution grids worldwide to distribute power. It is also used to power large motors and other large loads. A three-phase system is generally more economical than others because it uses less conductor material to transmit electric power than equivalent single-phase or two-phase systems at the same voltage.
In a three-phase system, three circuit conductors carry three alternating currents (of the same frequency) which reach their instantaneous peak values at different times. Taking one conductor as the reference, the other two currents are delayed in time by one-third and two-thirds of one cycle of the electrical current. This delay between phases has the effect of giving constant power transfer over each cycle of the current, and also makes it possible to produce a rotating magnetic field in an electric motor. Three-phase systems may have a neutral wire. A neutral wire allows the threephase system to use a higher voltage while still supporting lower-voltage singlephase appliances. In high-voltage distribution situations, it is common not to have a neutral wire as the loads can simply be connected between phases (phase-phase connection). Three-phase has properties that make it very desirable in electric power systems:
The phase currents tend to cancel out one another, summing to zero in the case of a linear balanced load. This makes it possible to eliminate or reduce the size of the neutral conductor; all the phase conductors carry the same current and so can be the same size, for a balanced load. Power transfer into a linear balanced load is constant, which helps to reduce generator and motor vibrations. Three-phase systems can produce a magnetic field that rotates in a specified direction, which simplifies the design of electric motors.
Three-phase system is the lowest phase order to exhibit all of these properties. Most household loads are single-phase. In some countries, three-phase power generally does not enter homes. Even in areas where it does, it is typically split out at the main distribution board and the individual loads are fed from a single phase. Sometimes it is used to power electric stoves and washing machines. The three phases are typically indicated by colors which vary by country.
1.1 Generation and Distribution of Electric Power At the power station, an electrical generator converts mechanical power into a set of three alternating electric currents, one from each coil (i.e. "winding") of the generator. The windings are arranged such that the currents vary sinusoidally at the same frequency, but with the peaks and troughs of their wave forms offset to provide three complementary currents with a phase separation of one-third cycle (120 or 2/3 radians). The generator frequency is typically 50 Hz or 60 Hz, varying by country. Large power generators provide an electrical current at a potential of a few hundred to about 30,000 volts. At the power station, transformers step this voltage up to one suitable for transmission. After numerous further conversions in the transmission and distribution network, the power is finally transformed to the standard utilization voltage for lighting and equipment. Single-phase loads are connected from one phase to neutral, or between two phases. Three phase loads such as motors must be connected to all three phases of the supply. The diagram below shows the typical transmission and distribution of electricity.
1.2 Electricity Mains Mains is the general-purpose alternating current (AC) electric power supply. It is usually referred to as by several names including household power, household electricity, power line, domestic power, wall power, line power, AC power, city power, street power, and grid power. The voltages are generally in the range
100240 V (always expressed as root-mean-square voltage). The two commonly used frequencies are 50 Hz and 60 Hz. Some territories use standards different from those of the countries they belong to (such as Hong Kong in China, similar voltage but different AC power plugs and sockets). Foreign enclaves, such as large industrial plants or overseas military bases, may have a different standard voltage and frequency from the surrounding areas. Some city areas may use standards different from that of the surrounding countryside (e.g. in Libya). Regions in an effective state of anarchy may have no central electrical authority, with electric power provided by incompatible private sources. Many other combinations of voltage and utility frequency, including direct current, were formerly used, with frequencies between 25 Hz and 133 Hz and voltages from 100 to 250 V. The modern standard combinations of 230 V/50 Hz and 120 V/60 Hz did not apply in the first few decades of the 20th century and are still not universal. Industrial plants with poly phase power systems will have different, higher voltages installed for large equipment (and different sockets and plugs), but the common voltages listed here would still be found for lighting and portable equipment.
CHAPTER SEVEN ROAD CONSTRUCTION AND MARKING
A road is an identifiable thoroughfare, route, way or path between two places which may or may not be available for use by the public; public roads, especially major roads connecting significant destinations are termed highways. Modern roads are normally smoothed, paved, or otherwise prepared to allow easy travel. 7.1 Road Construction Road construction requires the creation of a continuous right-of-way, overcoming geographic obstacles and having grades low enough to permit vehicle or foot travel and may be required to meet standards set by law or official guidelines. The process is often begun with the removal of earth and rock by digging or blasting, construction of embankments, bridges and tunnels, and removal of vegetation (this may involve deforestation) and followed by the laying of pavement material. A variety of road building equipment is employed in road building. After design, approval, planning, legal and environmental considerations have been addressed alignment of the road is set out by a surveyor. The Radii and gradient are designed and staked out to best suit the natural ground levels and minimize the amount of cut and fill. Great care is taken to preserve reference Benchmarks. Roadways are designed and built for primary use by vehicular and pedestrian traffic. Storm drainage and environmental considerations are a major concern. Erosion and sediment controls are constructed to prevent detrimental effects. Drainage lines are laid with sealed joints in the road easement with runoff coefficients and characteristics adequate for the land zoning and storm water system. Drainage systems must be capable of carrying the ultimate design flow from the upstream catchment with approval for the outfall from the appropriate authority to a watercourse, creek, river or the sea for drainage discharge. A Borrow pit (source for obtaining fill, gravel, and rock) and a water source should be located near or in reasonable distance to the road construction site.
Approval from local authorities may be required to draw water or for working (crushing and screening) of materials for construction needs. The top soil and vegetation is removed from the borrow pit and stockpiled for subsequent rehabilitation of the extraction area. Side slopes in the excavation area not steeper than one vertical to two horizontal for safety reasons.
Fig 4.1 showing the construction of a road
7.2 Road Kerbs A curb or kerb is the edge where a raised pavement/sidewalk/footpath, road median, or road shoulder meets an unraised street or other roadway. Typically made from concrete, asphalt or long stones (often granite), the purpose is twofold: first as a gutter for proper drainage of the roadway, and second for safety, to prevent motorists from driving onto the shoulder, median, sidewalk or pavement Functions of Kerbs Kerbs guide water from melted snow, rain, and ice into storm drains, so that it does not gather on the road. Big puddles can be dangerous, because they can cause hydroplaning at higher speeds and loss of control of a vehicle. At lower speeds, water can spray from tires onto following vehicles, causing poor visibility. Also pedestrians can be splashed by water. Kerbs also keep vehicles on the road and prevent people from using sidewalks as a hard shoulder. There is also an aesthetic aspect, in that curbs look formal and "finished". Since curbs add to the cost of a road, they are generally limited to urban and suburban areas, and are rarely found in rural areas.
Variations There are a number of types of kerb - basic curb (the pavement abuts the curb without a gutter), combined curb and gutter (also called curb and channel - may be rolled, traversable, or barrier) and integral curb (curb constructed integrally as a part of a concrete pavement). Typical types of curb based on the cross sectional shape: insurmountable, rolled, or rounded (used in many residential areas), surmountable or traversable (used along islands at intersections allowing errant vehicles to cross), and barrier ("L" shaped and used as a boundary to prevent vehicle from exiting the pavement).
Curbs/kerbs may be squared-off, angled, or rounded. Rounded curbs are most often used at driveways, and continuously along suburban residential streets where there are many driveways and the sidewalk has a grassy setback from the street. This type starts out nearly flat like the road, curves up in a concave manner to a gentle slope, then curves back in a convex manner to nearly flat again, making it much easier to drive over, and are also known as mountable curbs in some localities. The angled type is most often used on major suburban thoroughfares, and is more modern than the other two. The square (90-edge) type is still almost always used in towns and cities, as it is a straight step down and thus less likely to be tripped-over by pedestrians.
Fig 4.4 Figs 4.2- 4.5 shows the different types of kerbs.
7.3 Road Marking Road surface marking is any kind of device or material that is used on a road surface in order to convey official information. They can also be applied in other facilities used by vehicles to mark parking spaces or designate areas for other uses. Road surface markings are used on paved roadways to provide guidance and information to drivers and pedestrians. Uniformity of the markings is an important factor in minimizing confusion and uncertainty about their meaning, and efforts exist to standardize such markings across borders. However, countries and areas categorize and specify road surface markings in different ways. There is continuous effort to improve the road marking system, and technological breakthroughs include adding reflectivity, increasing longevity and lowering installation cost. Paint Paint, sometimes with additives like reflective glass beads, is generally used to mark travel lanes. It is also used to mark spaces in parking lots or special purpose spaces for handicap parking, loading zones, or time restricted parking areas. Colors for these applications vary by locality. Paint is a low-cost marking and is being in widespread use. Paint is usually applied right after the road has been paved. The road is marked commonly by a truck called a "Striper." These trucks contain hundreds of gallons of paint stored in huge drums which sit on the bed. The markings are controlled manually or automatically by the controller who sits on the bed. Paint is run through a series of hoses under air pressure and applied to the roadway surface along with the application of reflective glass beads. After application, the paint dries fairly quickly. Painted symbols, such as turn-lane arrows or HOV lane markers, are applied manually using templates.
Fig 4.6 shows a yellow marking on a road.
A Machine is a simple device that affects the force, or effort, needed to do a certain amount of work. Machines can make a tough job seem easier by enabling a person to apply less force or to apply force in a direction that is easier to manipulate. Machines lessen the force needed to perform work by lengthening the distance over which the force is applied. Although less force is subsequently used, the amount of work that results remains the same. Machines can also increase the speed at which work makes an object travel, but increasing speed requires the application of more effort. There are four types of simple machines: the lever, the pulley, the inclined plane, and the wheel and axle. Each machine affects the direction or the amount of effort needed to do work. Most mechanical machines, such as automobiles or power tools, are complex machines composed of many parts. However, no matter how complicated a machine is, it is composed of some combination of the four simple machines. Although these simple machines have been known and used for thousands of years, no other simple machines have been discovered.
8.1 Complex Machines Some complex machines are very complicated. An automobile is one such machine. The engine contains many levers, wheels and axles, and pulleys. The whole engine is held together by threaded bolts, which are a form of inclined plane. The transmission uses gears, which are a form of wheel and axle with specially shaped teeth on the outside of the wheels. Two gears fit together and transfer force and power from one gear shaft to another. By choosing the size of the gears, the speed and direction of the rotation of the axles can be controlled. Even devices that do not seem to be mechanical use simple machines. A computer, which is thought of as an electronic device, has a cooling fan. This fan is a complex machine in which the motor shaft turns the fan, which is a form of wheel. The disk drive uses a wheel and axle to turn the disk and a system of levers to position the heads that read and write the data on the disk. 1. Lathe Machine
A lathe is a machine tool which spins the work piece to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the work piece to create an object which has symmetry about an axis of rotation. Lathes are used in woodturning, metalworking, metal spinning, and glass working. Lathes can be used to shape pottery, the best-known design being the potter's wheel. Most suitably equipped metalworking lathes can also be used to produce most solids of revolution, plane surfaces and screw threads or helices. Ornamental lathes can produce three-dimensional solids of incredible complexity. The material can be held in place by either one or two centers, at least one of which can be moved horizontally to accommodate varying material lengths. Other work holding methods include clamping the work about the axis of rotation using a chuck or cullet, or to a faceplate, using clamps or dogs. Examples of objects that can be produced on a lathe include candlestick holders, cue sticks, table legs, bowls, baseball bats, musical instruments (especially woodwind instruments), crankshafts and camshafts. Parts of a Lathe
Fig 4.7 A lathe may or may not have a stand (or legs), which sits on the floor and elevates the lathe bed to a working height. Some lathes are small and sit on a workbench or table, and do not have a stand.
Almost all lathes have a bed, which is (almost always) a horizontal beam (although some CNC lathes have a vertical beam for a bed to ensure that swarf, or chips, falls free of the bed). At one end of the bed (almost always the left, as the operator faces the lathe) is a headstock. The headstock contains high-precision spinning bearings. Rotating within the bearings is a horizontal axle, with an axis parallel to the bed, called the spindle. Spindles are often hollow, and have exterior threads and/or an interior Morse taper on the "inboard" (i.e., facing to the right / towards the bed) by which work holding accessories may be mounted to the spindle. Spindles may also have exterior threads and/or an interior taper at their "outboard" (i.e., facing away from the bed) end, and/or may have a handwheel or other accessory mechanism on their outboard end. Spindles are powered, and impart motion to the work piece. The spindle is driven, either by foot power from a treadle and flywheel or by a belt or gear drive to a power source. In most modern lathes this power source is an integral electric motor, often either in the headstock, to the left of the headstock, or beneath the headstock, concealed in the stand. The counterpoint to the headstock is the tailstock, sometimes referred to as the loose head, as it can be positioned at any convenient point on the bed, by undoing a locking nut, sliding it to the required area, and then relocking it. The tailstock contains a barrel which does not rotate, but can slide in and out parallel to the axis of the bed, and directly in line with the headstock spindle. The barrel is hollow, and usually contains a taper to facilitate the gripping of various type of tooling. Its most common uses are to hold a hardened steel centre, which is used to support long thin shafts while turning, or to hold drill bits for drilling axial holes in the work piece. Many other uses are possible. Metalworking lathes have a carriage (comprising a saddle and apron) topped with a cross-slide, which is a flat piece that sits crosswise on the bed, and can be cranked at right angles to the bed. Sitting atop the cross slide is usually another slide called a compound rest, which provides 2 additional axes of motion, rotary and linear. Atop that sits a toolpost, which holds a cutting tool which removes material from the work piece. There may or may not be a leadscrew, which moves the cross-slide along the bed.
2. Milling Machine A milling machine is a machine tool used to machine solid materials. Milling machines are often classed in two basic forms, horizontal and vertical, which refers to the orientation of the main spindle. Both types range in size from small, bench-mounted devices to room-sized machines. Unlike a drill press, which holds the work piece stationary as the drill moves axially to penetrate the material, milling machines also move the work piece radially against the rotating milling cutter, which cuts on its sides as well as its tip. Work piece and cutter movement are precisely controlled to less than 0.001 inches (0.025 mm), usually by means of precision ground slides and leadscrews or analogous technology. Milling machines may be manually operated, mechanically automated, or digitally automated via computer numerical control (CNC). Milling machines can perform a vast number of operations, from simple (e.g., slot and keyway cutting, planning, drilling) to complex (e.g., contouring, diesinking). Cutting fluid is often pumped to the cutting site to cool and lubricate the cut and to wash away the resulting swarf. In a milling machine, a workpiece is fed against a circular device with a series of cutting edges on its circumference. The workpiece is held on a table that controls the feed against the cutter. The table conventionally has three possible movements: longitudinal, horizontal, and vertical; in some cases it can also rotate. Milling machines are
the most versatile of all machine tools. Flat or contoured surfaces may be machined with excellent finish and accuracy. Angles, slots, gear teeth, and recess cuts can be made by using various cutters.
Fig 4.9 shows a CNC vertical milling center
Fig 5.0 shows CAD (top) and physical Part (bottom) made by a CNC Milling machine.
8.2 Threading Tool Gauge Threading gauges are also referred to as pitch gauges made from lathe machines and are used to measure the pitch or lead of screw threads. Thread pitch gauges are used as a reference tool in determining the pitch of a thread that is on a screw or in a tapped hole. This tool is not used as a precision measuring instrument. This device allows the user to determine the profile of the given thread and quickly categorize the thread by shape and pitch. This
device also saves time, in that it removes the need for the user to measure and calculate the thread pitch of the threaded item.
Fig 5.1 In the Fig 5.1, the top threading tool gauge is an ISO metric pitch gauge, the larger gauge in the center is for measuring the Acme Thread Form, and the lower gauge is for imperial screws.
8.3 Industrial Mixer Industrial Mixers and Blenders are used to mix or blend a wide range of materials used in different industries including the food, chemical, pharmaceutical, plastic and mineral industries. They are mainly used to mix different materials using different types of blades to make a good quality homogeneous mixture. Included are dry blending devices, paste mixing designs for high viscosity products and high shear models for emulsification, particle size reduction and homogenization. Industrial mixers range from laboratory to production line scale, including Ribbon Blender, V Blender, Cone Screw Blender, Screw blender, Double Cone Blender, Double Planetary High Viscosity Mixer, Counter-rotating, Double & Triple Shaft, Vacuum Mixer, Planetary Disperser, High Shear Rotor Stator and Dispersion Mixers, Paddle, Jet Mixer and Mobile Mixers. The Banbury mixer is effective at mixing or kneading viscous materials.
They can operate at different temperatures and pressures for mixing different solutions and can also have internal or external heating systems added to them. Options also exist where spray nozzles, CIP, PLC and pneumatic or electric
systems can be used. Systems can come equipped with hydraulic or electronic soft start mechanisms so that they start and stop smoothly.
A model Industrial Mixer
It can be concluded that engineering touches all aspects of life, engineers should therefore endeavour to put the safety of the public topmost in their priority scale. This will reduce many accidents that could have been avoided.
1.www.google.com.ng
2. Wikipedia
3.Encarta 4.Britannica
5. www.lenntech.com
6.www.yahoo.com
7. Ramsden
E (2001) A level chemistry. 4th Edition(2007),Nelson Thornes.
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