This invention relates to the maintenance and efficient operation of equipment designed to transport or process hot, dust-laden gases. In one aspect, this invention relates to maintenance equipment designed to prevent or retard the deposit of sticky solids on the interior walls and internal components of the hot, dust-laden gas transport/process equipment while in another aspect, the invention relates to such maintenance equipment that impacts or causes a temporary deformation or vibration of the interior wall of the transport/process equipment. In yet another aspect, the invention relates to design improvements to such maintenance equipment.
Hiltunen and Ikonen, U.S. Pat. No. 5,443,654 which is incorporated herein by reference, provide a reasonably good description of the problem of deposit buildup in equipment designed and operated for transporting and/or processing hot, dust-laden gases. Hiltunen and Ikonen teach this problem in the context of a gas cooler inlet duct, but this problem is common to most equipment through which hot, dust-laden gases pass. As here used, xe2x80x9cdust-ladenxe2x80x9d includes gases containing molten or evaporated material. As such gases cool and condense, the dust components may, depending upon their composition, become sticky and adhere to one another and the internal walls and components of the equipment in which the gas is contained. These deposits can grow quickly and interfere with the safe and efficient operation of the gas transport/processing equipment. For example, these deposits can block gas flow and/or reduce the efficiency of heat transfer between the hot gas and the gas transport/processing equipment walls and internals, e.g., heat-exchange tubes. Moreover, depending upon the design and materials from which the transport/processing equipment is constructed, e.g., metal, ceramic, etc., removal of these deposits can be difficult or less than 100% effective if the deposits are allowed to accrete beyond a certain size.
Various methods are known for preventing or retarding deposit formation within hot, dust-laden gas transport and/or processing equipment, and these methods include increasing the gas volume and/or turbulence, various scrubbing techniques, and imparting a slight but frequent deformation to the walls and/or components of the equipment to which the sticky, cooled dust is likely to adhere. As noted by Hiltunen and Ikonen, these deposits tend to be brittle and subject to removal through mechanical deflection of the wall or structure upon which they are deposited.
Various methods are known for imparting a mechanical force to a surface to which a deposit may or has formed to either prevent or remove the deposit. Hiltunen and Ikonen teach one such method. Another is taught in FIGS. 1, 2, 4, 6, 8, 10 and 12 in which like numerals are employed to designate like parts throughout the Figures. Various items of equipment such as electrical connections, fittings and the like are omitted so as to simply the drawings.
FIG. 1 illustrates a xe2x80x9crapperxe2x80x9d 100 attached by any conventional means, here by brace 101, to the wall (shown in partial section) of a waste-heat boiler. The wall comprises exterior metal skin 102 and ceramic insulation 103. The waste-heat boiler contains a plurality of heat-exchange tubes 104 (only one of which is shown) over and around which hot, dust-laden gases from any source, e.g., a metallurgical furnace, circulate. The tubes contain any suitable heat-exchange fluid (not shown) designed to capture by convection through the tube wall at least part of the latent heat of the gas. This transfer of heat from the gas to the heat-exchange fluid within the tube causes the gas to cool, and thus the dust components within the gas to condense and deposit on, among other places, the exterior walls of the tubes. Since the deposits of this example tend to be brittle in nature, their formation is impede or if formed, then easily removed, by imparting a mechanical force in the form of a small deflection or vibration to the wall of the heat-exchange tube. These tubes are often placed in contact with one another, and thus the vibration imparted to one tube is readily transferred to all of the other tubes to which it is in direct or indirect contact.
Rapper 100 imparts a mechanical force to heat-exchange tube 104 through the action of hammer 105 striking anvil 106. Hammer 105 operates in a manner described below such that it periodically is retracted to a predetermined distance from the face of the anvil (e.g., 12-14 inches), and then released such that the face of the hammer impacts the face of the anvil with a predetermined amount of force. This force is transferred from the face of anvil 106 through disc spring 107 and anvil rod 108 to I-bar 109 and ultimately to tube 104 (and those tubes in direct or indirect contact with tube 104). I-bar 109 and anvil rod 108 are embedded in insulation 103 in such a manner that the majority of the mechanical force is transfer to tube 104 and not skin 102 or insulation 103.
The principal components of the rapper are shown in FIG. 2. The power to activate the hammer is provided by electric motor 201 which is operationally connected to gear reducer 202. Shaft 203 of gear reducer 202 connects to and drives hammer assembly 204 by way of chain drive assembly 205 which consists of small chain sprocket 206, chain 207 and large chain sprocket 208. The chain drive assembly rotates hammer shaft assembly 210 and lever shaft assembly 209 (both shown in exploded format in FIG. 4), which in turn provide the action by which the hammer periodically is retracted and released to impact the anvil. Hammer assembly 204 is aligned within two piece hammer housing 211a and 211b such that the lever shaft assembly engages adjustable cam 212. Lever shaft assembly 209 rotates in such a manner that once each rotation it engages cam riser 213. As lever shaft assembly 209 passes over cam riser 213, the hammer shaft assembly is disengaged from the chain drive assembly, and the hammer xe2x80x9cfallsxe2x80x9d into the face of the anvil. Once the lever shaft assembly has cleared the cam riser, the hammer shaft assembly re-engages the chain drive assembly and the hammer is retracted and retained into its retracted position until the lever shaft assembly again engages the cam riser.
The amount of force delivered to the anvil is a function, in part, of the position of the cam riser on the cam. In this manner, the amount of force delivered to the anvil by the fall of the hammer can be controlled. Gear reducer 202 is housed in gear reducer housing 214 which is fastened by any suitable means to hammer housing 211a. 
FIG. 4 is an exploded view of lever shaft assembly 209 and hammer shaft assembly 210. The lever shaft assembly comprises a lever shaft 401 carrying a middle bearing 402 and two bushings 403a and 404b. Bushing 403a carries lever 404a and bushing 403b carries lever 404b. Outside bearings 405a and 405b complete the complement of elements carried by lever shaft 401.
Shaft 401 is aligned with cam 212 and cam riser 213 such that bearing 402 engages cam riser 213 once each rotation of hammer shaft assembly 210, and bearings 405a and 405b engage hammer cams 407a and 407b, respectively. Lever shaft assembly 209 is connected to hammer shaft assembly by two-piece hammer shaft casing 408a and 408b. Casing 408a includes casing arm 409 designed to receive casing arm bushing 410 and casing arm shaft 411 to which levers 404a and 404b can attached in any conventional manner. In operation, the back of levers 404a-b engage stop pin 406 (FIG. 12) after the hammer falls into the face of the anvil. This engagement steadies (i.e., dampens the vibration of) the hammer and thus facilitates an easy re-engagement of the hammer shaft assembly with the chain drive assembly. Hammer shaft 412 is fitted to hammer 105 by way of hammer arms 413a-b each of which fare fastened to hammer 105 by any conventional means, e.g., welding. Each hammer arm contains an opening 414a and 414b respectively in alignment with one another and adapted to receive hammer shaft 412 with its complement of bushings 416a-b, 417a-b and 418. Hammer shaft 412 is fitted within bushing 418 such that it extends out of both open ends of the bushing. Openings 414a-b are fitted with bushings 416a-b, respectively. Bushing 418 with inserted hammer shaft 412 is inserted through bushings 416a-b such that it extends through both. Casing 408a-b engages bushing 418 about its central section in a compression fit, and bushings 417a-b are fitted between the respective inner surfaces of arms 413a-b and casing 408a-b. Bushing 418 has neck 418a which is fitted into sprocket opening 230 and then welded or otherwise permanently fastened to sprocket 208. Hammer arm block 419 contributes stability to the hammer assembly.
Spacer 415 also contributes stability to the hammer assembly. It is fitted over the end of bushing 418 that extends through opening 414a to occupy the space between the outer surface of arm 413a and the inner surface of housing 211b that is opposite arm 413a. Sprocket 208 provides a similar stability function by occupying the space between the outer surface of arm 413b and the inner surface of housing 211b that is opposite arm 413b. In both instances, this spacer and sprocket tend to restrict the movement of the hammer assembly relative to the hammer housing.
While the rapper described above performs reasonably well, often it proves difficult to service. Since rappers are in frequent use (a typical cycle for a rapper attached to a waste-heat boiler servicing a metallurgical furnace, e.g. a copper converter, is for the hammer to strike the anvil four or five times a minute for five minutes, remain at rest for fifteen minutes, and then repeat the cycle for as long as the furnace is in operation (which may be a year or more)), they require constant service. Rappers are often large, heavy pieces of equipment (the hammer assembly alone usually weighs more than one hundred pounds), and are often located in difficult to reach and/or service areas (e.g., high above ground, in tight corners, attached at odd angles, etc.). Moreover, on larger hot gas, dust-laden transport/processing equipment such as that associated with copper metallurgical furnaces, hundreds of rappers may be in service at one time, many located in close proximity to one another. Considerations such as these necessitate designs that favor relatively easy and inexpensive servicing.
The conventional rapper design is improved to provide longer service without maintenance and easier access at less cost when service is required. These improved results are through one or more of the following:
1. easier access to the hammer assembly and gear reducer without removal of their respective housings;
2. easier removal of the gear reducer housing and the hammer assembly housing when required;
3. easier removal of the hammer;
4. increased life of rapper components, and emphasizing inexpensive components for failure points (as opposed to expensive components); and
5. redesign of the hammer and various components of the lever and hammer shaft assemblies.
These and other features of the intention are described more filly below and by reference to the drawings.