Analysis and Testing of Freezing Phenomena in Piping Systems

Abstract

From time to time installed piping systems, including wet sprinkler, potable water and cooling water systems, have failed due to freezing. The cost of such events is significant due to the need for system repair, the loss of service, and the secondary water damage that results. The presumption is often that the pipe was frozen at the point of failure. This paper describes the theory, calculations, and experiments that demonstrate that freezing of a pipe causes pressure in the system to rise between the frozen section of pipe and the blind end of the system. The piping system typically fails at a weak link in the system at a significantly elevated pressure. The location of the breech is almost always at a point in the system where the water is still liquid at the time of the breech. An additional consideration is that the high system pressure depresses the freezing temperature of the water, and a flash-freeze within the pipe occurs when the pressure suddenly drops after a piping system rupture. Armed with this knowledge, the site of the actual system freeze can often be found remote from the point of failure where remedy can be best effected to eliminate the root cause.