A control unit assembly is a system of two or more control rods placed across an expansion joint from flange to flange to minimize possible damage to the expansion joint caused by excessive motion of the pipeline.
This excessive motion could be caused by the failure of an anchor or some other piece of equipment in the pipeline. When expansion joints are installed to absorb axial motion, control units are set at the maximum allowable expansion and/or contraction of the joint and will absorb the static pressure thrust developed at the expansion joint.
When used in this manner, they are an additional safety factor, minimizing possible failure of the expansion joint and possible damage to the equipment. Control units will adequately protect the joints, but the user should be sure that pipe flange strength is sufficient to withstand total force that will be encountered. Unisource expansion joints are manufactured to the specifications of the FSA, Rubber Expansion Joint Division. Standard control units assemblies consist of two rods, four triangular gusset plates, and necessary nuts, metal washers and rubber grommets. Unisource grommets are a cloth inserted rubber product of approximately 1/4” thick overall gauge to absorb vibration that could be transferred across the rods. Note, more than two rods may be needed depending on the system pressure. Consult the FSA standards for maximum pressure rating by number of rods.