Whenever the surface temperature of a piping system differs significantly from that of its surrounding environment, the potential need for an insulation system exists. An insulation system serves three principal purposes:
The significant reduction in the transfer of thermal (heat) energy to or from the surface of the piping system
The prevention of moisture formation and collection on the surface of the piping system due to condensation
The prevention of potentially injurious personnel contact with the surface of the piping system
The reduction in heat transfer to or from the surface of a piping system will minimize the gain or loss in temperature of the process fluid, thus maximizing the capability of the fluid to perform its intended function. Minimizing heat exchange between the piping system and the environment also minimizes the unwanted heating or cooling of the environment. This improves the comfort level for the inhabitants, or improves the operating conditions for equipment.
Most insulating systems used above ground consist of preformed components that are mechanically attached to the pipe. Low-temperature insulation is frequently made of expanded cellular plastic or foam rubber materials. Moderate-temperature insulations are frequently made from glass-fiber products. High-temperature insulation is usually made of preformed cementations or refractory materials or blankets made from ceramic fibers. Insulation used for buried pipe is frequently in loose granular form, so it can be poured loosely into the trench to surround the pipe and isolate it from the ground environment.
If the surface temperature of a piping system is less than the dew point of the surrounding air, water vapor in the air will condense on the surface of the pipe. This condition can be detrimental. The condensation can collect and drip onto surfaces below the pipe, thus doing damage. The condensate can also saturate the piping insulation, thus significantly increasing its thermal conductivity and reducing its insulating capability. To prevent condensation on an insulated pipe, the airborne water vapor must be prevented from reaching the pipe surface. This is normally accomplished by providing a vapor barrier at the outer surface of the insulation. An adequate vapor barrier may be constructed from a well-fitted metal jacket, an extruded plastic or rubber coating, or a spiral-wrapped impervious tape coating. Whatever the form, the vapor barrier must prevent the airborne water vapor from entering the pores of the insulation and migrating toward the cool pipe surface, where condensation can occur.
Extremely hot or cold piping systems can pose a contact safety hazard to personnel in the vicinity. Surface temperatures above 135 deg F (57 deg C) can cause severe burns to unprotected skin, and temperatures below approximately 20 deg F(-7 deg C) can cause freeze damage. Thermal insulation can be designed such that the insulation surface temperature is maintained in a safe range.
Frequently piping systems that are otherwise un-insulated will have insulation installed in accessible areas to provide personnel protection.