DA-2392 -- Expansion Joints for Low-Temperature Above-Ground Water Piping Systems ✓ Most Recent

In underground water distribution systems, relatively little compensation for expansion and contraction is needed since the pipes are buried at a depth at which ground temperature variations are small. In permafrost regions, however, water piping systems are often installed above ground. These may be permanent water distribution systems, as in a utilidor system, or merely water pipelines which are operational only during the summer months. In either case the piping must be designed to allow for expansion and contraction commensurate with the full range of air temperatures. This range may be as large as 160 deg F which for steel pipe translates into a length change of 1 1/4 in per 100 ft of pipe. In the case of a water distribution system in which water at approximately 40 deg F is constantly circulated, the pipe would not normally experience the full range of air temperatures; however, these systems must on occasion be shutdown and drained for the purposes of maintenance or modification.

Operation experience compiled by the Canadian Department of the Environment with in-line-type expansion joints in above ground water piping systems has shown that failures frequently occur if the pipe must be shutdown and drained during the winter. Failures have been observed to occur with a type of internally supported bellows joint and with piping systems using dresser-type couplings. From these observations it was surmized that the reason the expansion joints were failing was that either the joints were becoming stiffer at the cold temperatures or that ice formed from the residual water left in the joint after the pipe was drained preventing the normal operation of the expansion joint.

A study was proposed to evaluate the behavior of a number of types of expansion joints used in steel piping systems under low temperature (subfreezing) conditions. In particular. their ability to expand and contract both with and without water frozen inside them was to be investigated by simulating these conditions in the laboratory. The primary objective was to find expansion joints which will perform satisfactorily in northern climates.