In recent months, we have been asked to examine damage to water piping allegedly damaged by freezing. Frost damaged pipes are nothing new and are well documented. It is well known that when copper pipes fail, ice will cause the pipe to "bulge" as a result of the formation of ice inside the pipe. The "bulge" signals that the pipe or fitting has been placed in tension and is pulling the pipe or fitting wall apart. When the strength of the wall has been exceeded, a crack typically develops. A typical failure is shown in figure 1.
Figure 1
The same failure mode holds true for steel piping. That is, the pipe or fitting wall will crack in response to the stress imposed by the expansion of ice. However, steel usually will not display a buldge like copper does. It should be noted that ice expands to approximately 9% of its original volume. The source of the stresses that causes the material failure is this expansion. Figure 2 shows a steel elbow that was filled with water, capped at both ends, and placed in a freezer for approximately fourteen hours. The end result was the crack in the fitting wall.
Figure 2
Figure 3
However, we have seen something new and unusual. Figure 3 shows a cast steel elbow with a hole that was allegedly caused by freezing. At first glance, the material that filled the hole seems to have been blown out. In order to do so, the stress on the material would have had to have been applied uniformly in the "circular" pattern that failed. In addition, the material would have had to fail simultaneously at all points. Otherwise, the failed piece would still be attached to the elbow. It appears then that this type of failure is not related to freezing. In the absence of other evidence to explain how the failure occurred, it is thought that the failure is the result of a defect in the manufacturing process. It should be noted that standards are in place that dictate how cast steel fittings are to be made.
