The herein disclosed invention is that of a multi-piece plastic removable and reusable insulation jacket for insulating elbows and pipe sections in a chilled fluid piping system. More generally, this invention relates to an insulation cover for insulating any component in a fluid piping system including, but not limited to, valves, fittings and pipes for temperatures of both below and above ambient.
A significant void exists in the availability of effective insulation for pipes, valves and fittings for low (sub-ambient) temperature fluids. Currently, the most common and effective insulation applications for pipes, valves and fittings are for high (above ambient) temperature fluids. Differential temperatures in the majority of low temperature installations are on the order of 100 F. or less, compared to high temperature installations where differentials exceeding 1000 F. are not uncommon, with the majority of these installations having differentials between 200 F. and 700 F. One can easily recognize the cost savings that will accrue from insulating high temperature piping systems, while the actual cost savings of effectively insulating low temperature piping systems is not so obvious, because the comparatively small temperature differentials between a cold piping surface and a warmer and moist environment is misleading in that, unlike high temperature piping installations, the ambient humidity becomes a dominant factor.
In high temperature piping applications, ambient humidity is and remains in the vapor state, while in low temperature piping applications the ambient humidity or water vapor tends to condense or change state from a vapor to a liquid or solid on the low temperature piping system surface. As heat is withdrawn from the ambient environment through heat gain by the cooler low temperature piping system, ambient water vapor molecules lose energy and concentrate in the boundary layer of the piping system surface. As ambient air near the piping system surface reaches its dewpoint, moisture begins to condense or freeze on the piping system surface and then cools to the surface temperature of the piping system. This change of state or phase for water is the result of the heat transfer to the chilled circulating fluid in the piping system due to the water vapor's latent heat of vaporization, which typically doubles the apparent heat gain from the ambient temperature change alone. Thus the value of effective low temperature insulation is double, on a thermal gain basis alone, what is typically perceived from only the temperature differential. Therefore, if an insulation system on low temperature piping systems is to be effective, the insulation system must economically isolate the piping system from the ambient moisture laden environment. Another reason isolation is so important is because as insulation becomes wet with condensation the wet insulation loses its thermal resistance and the effectiveness of the insulation is diminished. Also, as ambient water vapor condenses on a chilled water piping system due to the insulation not totally isolating the piping system, a vapor pressure differential is developed between the inside and outside of the insulation. This vapor pressure differential is the force that causes the vapor migration to continue into the pipe insulation. Therefore, effective low temperature pipe insulation must not only provide thermal resistance, but also water vapor isolation and impermeability.
Today, low temperature or chilled water piping systems are insulated primarily for one or more of the following reasons:
1. Conservation of energy. PA1 2. Control and prevention of condensation. PA1 3. Optimization of equipment sizing. PA1 4. Process control. PA1 1. Dripping pipes that damage ceilings, walls, floors, equipment and/or furnishings. PA1 2. Initiation of mold and mildew and the potential for associated health problems. PA1 3. Corrosion of pipes, valves and fittings promoted by water condensation and/or chemicals leached by the moisture passing through the insulation itself. PA1 4. Heat gained from no or failed insulation. PA1 1. The efficiency of the sealing and latching system in preventing moisture intrusion within the air gaps. PA1 2. The efficiency of the system in preventing moisture from condensing on the outer surface of the covers.
By controlling and preventing condensation, designers also eliminate or minimize four problems commonly associated with chilled water insulation systems:
Due to the above problems, the importance of effectively insulating chilled water systems can not be understated.
Recent surveys have revealed that chilled water distribution systems have a high incidence of failure, as stated in an article entitled "Insulating Chilled Water Systems" in Insulation Outlook magazine, May, 1993. Failures occur even though many insulated chilled water distribution systems are typically indoors or in protected areas not subject to physical abuse or weather. The cause of failure is due to moisture which permeates the insulation material itself as well as the minor imperfections at joints and fittings. This moisture penetration is caused by driving vapor pressure differences prevalent between the outside of the insulation and the cold pipe surface. The results of failure in chilled water systems are dripping water from the insulated surface, pipe and fitting corrosion, increased operating costs due to lost efficiency, and mold/mildew formation.
While dripping condensation may be easily recognizable, moisture vapor intrusion is generally not obvious and can progress for relatively long periods of time before any visible evidence is noticed. During this period, not only has the insulation lost its thermal resistance due to moisture, but also the pipe and pipe fittings have been rusting and corroding. Disregarding the cost of replacing corroded valves, pipe and fittings, the insulation must be replaced and experienced engineers have suggested that replacement costs of the insulation can easily run two to three times the initial installed insulation cost.