Steven L. Folkman, A. P. Moser, Thomas Fronk
Papers # 2010 Vancouver
Manufacturers of large diameter PVC pipe place a mark on the spigot of the pipe to indicate the proper insertion depth into the adjoining bell during installation. If proper installation procedures are followed, inserting the spigot into the bell does not create significant stresses in the pipe. Additionally, small angle changes between two joined pipes may be accommodated in the joint without inducing pipe stresses. When pipe joint failures occur, in most instances the pipe was inserted well beyond the manufacturers recommended mark. This is referred to as “Over-Belled” pipe. Initial pipe assembly requires a relatively large force to get the spigot inserted past the gasket. After the bevel on the spigot moves past the gasket, insertion forces are much lower. When backhoes are used to insert the pipe, the beveled end of the spigot can be forced into the tapered throat of the bell with the potential of creating large stresses. This paper documents results of a nonlinear finite element model of the stresses created by over belling for a 24-inch (610 mm) C900 DR25 PVC pipe. Also investigated are additional stresses created by creating a 1.5 degree angle change in the joint and due to pressurization of the pipe. This paper documents how stresses can be created that will cause pipe failure on assembly, or shortly after the pipeline has been put into operation.
