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Category: Plant Basics
Question: Where can I find some details about applying and maintaining insulation on LPG (liquefied petroleum gas) lines (cold application)?
Keywords: lpg,liquefied,petroleum,gas,insulation,condensation,problems
Answer: BACKGROUNDLately, after operating our gas based LPG unit for more than 10 years, I am noticing a lot of 'on-the-surface' water condensation on some lines and vessels without any major changes in process or atmospheric conditions. We use glasswool and expanded foams with Al-cladding for insulation. ANSWERFirst and foremost: insulation in this type of application is the toughest to deal with and is directly subject to the technique, scrutiny and craftsmanship used in specifying, applying, inspecting and maintaining it. The aluminum or metal cladding jacket used is of minor insulation importance other than mechanical protection. The real important issue in this application is the VAPOR BARRIER employed in the installation. The ability to effectively seal the insulation substance from infiltration by atmospheric moisture determines the success or failure of the application. I have used FoamGlas, styrofoam, Polyurethane foam, and glasswool and can state from field experience in this type of process that any of the above will last efficiently as long as the respective vapor barrier is effectively keeping out the destructive effects of atmospheric moisture condensing and subsequently solidifying at the interphase of the cold vessel wall and the insulation. Once this occurs, the effectiveness of the insulation is neutralized and diminished from a practical point of view. All you have left as insulation is the insulating effect of the water ice formed and the insulation has to be removed due to saturation and water logging. The manual labor involved can be so expensive that normally the insulation's salvage is not justified.That is why, although more expensive, FoamGlas is more desirable over a long term. This insulation has impermeable glass cells that are not penetrated by moisture. However, any unsealed seams between the blocks of FoamGlas are subject to infiltration by the atmospheric moisture. So, you again have a problem that is directly attributable to lack of good craftmanship. The selection of an experienced, responsible and serious contractor is of primary importance in these engineered installations. Do not be misled into selecting a contractor based on price alone.Your gas plant seem to be a candidate for a complete re-insulation job. You should already have an engineering specification that clearly and accurately details out the insulation specifications for the contractor to follow and for you to inspect, check and approve in the field. All bidders should follow the same specifications. I have participated in the preparation of some of these type of specification packages and I can attest to the fact that they can get very technical, detailed and voluminous. You have a serious job on your hands because from what you describe, you are approaching a situation where the incremental loss of insulation effect and mechanical disintegration will force you to have to re-insulate the plant. When properly done, cold insulation has lasted me for 12 to 15 years with watchful and detailed maintenance of the vapor barrier. If your location is a humid one, your maintenance is more important. However, even plants in desert or arid areas are subject to vapor barrier maintenance.From your description, I believe you're facing a complete re-insulation job. For easier future maintenance, use a zoning method to allow for future patching without having moisture infiltrate all of your insulation.


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