Bellows Expansion Joints are great for accommodating axial, lateral and angular movements for a wide array of piping applications. Some applications may contain high flow velocities, which can induce severe vibration and lead to premature failure to the bellows element. The way to address this is to utilize a bellows expansion joint containing an internal sleeve, also known as a flow liner.
A flow liner within a bellows expansion joint protects the integrity of the bellows element by redirecting the media (air, gas, steam, water, etc.) away from flowing directly over the bellows convolutions as it passes through.
Internal liners or baffles are a recommended accessory to extend the life of many metallic pipe expansion joints because of their ability to protect the convolutions from direct flow impingement, which can cause erosion and flow-induced vibration. Internal liners should be used when internal flow conditions exceed the following criteria:
The liner is a longitudinally welded tube attached at one end to the upstream end connection. The diameter of the liner is small enough that the free, downstream end will not interfere or contact the downstream end connection during lateral or angular deflections. When a standard pipe expansion joint is selected from this catalog with the internal liner accessory, the expected lateral deflection should be stated so that the liner diameter can be properly sized.
If expected flow rates will be very high, such as at steam safety relief valves or in turbine exhaust and extraction steam applications, the internal liner should be of heavier construction. Usually, the liner material can be the same as the system pipe material, such as carbon steel, with liner thickness' of 1/8-inch and greater depending upon flow rate and diameter.
Internal liners are almost always welded into the pipe expansion joint. However, if the Van-Stone flange end connection is specified, the PT&P liner will have its own flange and will be captured between the flanges at the upstream connection into the piping.