There are two basic versions of UNI couplings:

• GRIP – axially restrained joint, with rubber seal and resilient metal rings which bite into the pipe surface,
• FLEX – axially unrestrained joint, flexible – with rubber seal only.

Both types of couplings are designed to join pipe ends to each other tightly and firmly, however the piping system must consist of pipe sections which are properly supported, anchored and correctly guided. The couplings do not absorb axial loads, bending or twisting. FLEX and REP couplings can absorb axial displacement during operation (change of distance between the ends of connected pipes) up to 5 mm for standard FLEX couplings up to 172 mm in size. Installation is quick and simple though relevant mounting instructions must be followed (contact Tubes International). Always check the distance between pipe ends (Cmax), their angular deflection, misalignment, pipe diameters, roundness error, potential axial displacement – and determine if they are within acceptable limits set for the given type of couplings. Smooth clean pipes do not require any pipe-end preparations. While joining plastic pipes special inserts should be used as reinforcement. A torque wrench is required for installation. The bolts must be tightened alternately to the torque value indicated on the coupling. For applications under vacuum (from 0,5 bar), at external pressure or for chemicals that may cause the seal to swell, use an internal metal strip insert.