Article
Product Testing And Hydrostatic Forces
April 5, 2010
•Article: Product Testing And Hydrostatic Forces
By EBAA Iron Sales, Inc.
This paper is a discussion of the methods and procedures used in routine and proof of design testing of EBAA restraint products.
Pressure within a closed vessel such as a pipe, acts to push outwardly and uniformly on the vessel walls. In the case of a pipe, this outward pressure induces circumferential or hoop stress around the cylinder or barrel of the pipe. When the ends of the pipe are closed, such as with the installation of a cap, the pressure also pushes on the inside surface of the cap in an attempt to separate the cap from the pipe. If the cap is somehow attached to the wall of the pipe then a longitudinal stress is also present in the pipe wall. Attaching the cap (or other fitting) to the pipe is the function of joint restraint devices such as the MEGALUG® restraint.
When a joint device is being used to hold the cap onto the pipe, the force exerted on the cap is transferred through the device and subsequently to the pipe wall. The restraint must be structurally capable of withstanding the end thrust loading while also being capable of gripping the pipe surface. The pressure and forces acting on both pipe and restraint must remain within design limits of both to assure a generous factor of safety for the system.
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