When connecting against high residual pressure and the substances are either displaceable or compressible couplings with screw locking mechanisms are a good choice. The thread side (usually the swivel nut) is on the adaptor, and the counter thread is placed on the coupling.
Our screw type couplings have either a ball bearing or slide bearing between the housing and the locking sleeve, in order to minimise friction. Because threaded connections do not have defined end positions, the operator must determine whether or not the desired coupling connection has been implemented correctly. A partially attached coupling has a smaller valve opening, which limits the desired flow rate (CV value).