Probably more accidents connected with refrigeration systems are associated with the piping system than with any other subsystem. To avoid the chance of damage, particularly damage that would result in a release, care should be exercised in several categories: (1) choice of pipe and fittings, (2) support and anchoring of pipe, (3) location of pipe runs and valves where they are least likely to suffer damage, and (4) cleanliness of the pipe.
• Choice of pipe and fittings. Regardless of pressure, the pipe should be Schedule 80 for 1–1/2-in size and smaller. Use Schedule 40 pipe for 2- to 6-in lines and Schedule 20 for 8- to 12-in lines. It may seem illogical to specify the thick Schedule 80 pipe for small diameter, but the reason is not to better contain internal pressure, it is to provide more rigidity should a heavy weight fall on or against the pipe. Joints in pipe of size 1–1/2-in and larger should be welded, not threaded. In fact many contractors weld all joints in 3/4-in pipe and larger.
• Support and anchoring of pipe. Pipe hangers should be of the trapeze type and all hanger materials should be galvanized or painted. Hangers should be attached to the building structure or primary supports. Pipe hangers should be placed not more than 3 m (10 ft) apart and should be located not more than 0.7 m (2 ft) from each change of direction. Supports of piping on roofs should be sturdy, painted, or galvanized. The support should rest on a concrete paver or wood sleeper with the roof beneath protected by a membrane material.
• Location of pipe runs and valves. When possible, long lines between the machine room and refrigerated space should be run on the roof. When pipes must be inside storage or process areas, they should be in protected locations. Valves should be located in and out of each component of the same size as the connecting pipe. Hand valves should close against the flow, and the stems should be oriented horizontally. Screwed connections to valves should not be used for sizes larger than 1 in. Horizontal piping shall have only eccectric reducers with the straight sides on the bottom, except at a pump inlet where the straight side should be on top.
• Cleanliness of pipe. For installation, the pipe must be clean, new and free of rust, scale, sand, and dirt. Pipe should be stored inside, out of the weather and the ends should be capped. Some contractors install a liberal number of filter/driers which are replaced periodically.