Expansion joints installed in piping systems that are anchored on both sides of the joint.
No control rods are necessary. If control rods are installed as a safety measure, the locking nuts must be backed off with a clearance equal to the specified axial movement. The expansion joint will exert a thrust force on the anchors. To calculate pressure thrust on anchors use the following equation:
Pressure Thrust = (Pressure Thrust Area) x (Rated Working Pressure)
Expansion joints installed in unanchored piping or connected to isolated equipment.
Control rods are necessary. Once control rods are installed the joint will no longer act as an expansion joint, since the pressure will extend the joint to the nuts of the control rods. The joint will no longer take up axial motion. It will make up for misalignment, transverse and possibly angular motion. The nuts of the control rods should be threaded against control rod gussets, thereby preventing joint from extending.