![]() Intermediate anchors are required to withstand the spring force generated when the expansion joint is deflected, but the need for main anchors is eliminated. The main anchors must resist the sum of the above two forces:Ģ5,200 Lbs + 2,628 Lbs = 27,828 Lbs Managing Pressure ThrustĪs mentioned, installing restrained expansion joints to a system is one way to manage pressure thrust in a system. Find the force due to the bellows deflection:ģ. Axial Spring Rate of the 10” Bellow = (SR) = 5,255 Lbs/inįorce due to the pressure = Pressure thrust = (P) x (Aeff)Ģ.Pipe growth between anchors (?) = 0.5 in (compression).Effective Area = (Aeff) of 10” part = 126 in2.If the expansion joint in unrestrained, the piping system must withstand the force or restraints, such as hinges, gimbals and/or tie rods can be installed on the expansion joint to constrain the thrust force. Determining Pressure Thrust ForceĪll expansion joints exert a force that pushes the pipe ends apart, pressure thrust which is proportional to the operating pressure and the diameter of the bellows. The main anchors must be able to resist the pressure thrust force and a small amount of force due to the deflection of the bellows. This can lead to permanent deformation and/or immediate bellows failure.Īdding main anchors and pipe guides into the piping system will prevent the expansion joint from overextending. ![]() When you replace the pipe with an unrestrained metal bellows without anchors or guides, the bellows will eventually extend due to the pressure thrust which can result in bellows squirm, or over-pressurization. The longitudinal rigidity of the pipe prevents extension to a point. With rigid pipe installed between two closed flanges, the internal pressure is restrained by the strength of the pipe. All ducting or piping systems, with or without expansion joints, can have pressure. ![]()
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