Expansion joints and pump connectors are not designed to support weight or limit pipe movement. Excess movement may be the result of abnormal temperature fluctuations, pressure surges, or insufficient anchoring or guiding of the piping. Where these situations occur, control units must be used to limit the amount and direction of movement to within the design limits of the flexible connection. Control units consist of adaptor plates which are bolted to the back of the mating pipe flanges. These plates are connected by a tie rod which limits the axial extension. In cases where excess compression is anticipated, an optional sleeve is fitted over the tie rod to limit movement in both directions. The minimum number of control rods needed in a control unit is two; however depending on size or pressure, more may be required. The chart below can be used to determine the requirements for your application.