Insulation is required for refrigeration piping to prevent moisture condensation and prevent heat gain from the surrounding air.

The desirable properties of insulation are that it should have a low coefficient of heat transmission, be easy to apply, have a high degree of permanency, and provide protection against air and moisture infiltration.

Finally, it should have a reasonable installation cost. The type and thickness of insulation used depends on the temperature difference between the surface of the pipe and the surrounding air and also on the relative humidity of the air.

It should be clearly understood that although a system is designed to operate at a high suction temperature, it is quite difficult to prevent colder temperatures occurring from time to time.

This may be due to a carrying over of some liquid from the evaporator or the operation of an evaporator pressure valve. Interchangers are preferable to insulation in this case.

One of the safest pipe insulations available is molded cork or rock cork of the proper thickness. Hair-felt insulation may be used, but great care must be taken to have it properly sealed. For temperatures above 40 degrees F, wool felt or a similar insulation may be used, but here again, success depends on the proper seal against air and moisture infiltration.

Liquid refrigerant lines carry much higher-temperature refrigerant than suction lines; and if this temperature is above the temperature of the space through which they pass, no insulation is usually necessary.

However, if there is danger of the liquid lines going below the surrounding air temperatures and causing condensation, they should be insulated when condensation will be objectionable.

If they must unavoidably pass through highly heated spaces, such as those adjacent to steam pipes, through boiler rooms, etc., then the liquid lines should also be insulated to ensure a solid column of liquid to the expansion valve.

There were four types of insulation in use before the discovery of modern insulation materials. Those you may encounter that were in general use for refrigerator piping, are cork, rock cork, wool felt, and hair felt.

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