The design of cam and groove coupling is such that an increase in internal pressure will increase the clamping force on the cam (handle). Handles will not open due to pressure alone. However, there are applications that for hazardous and safety reasons, a secondary lock may be desirable.
The Secondary Coupling Lock shown here is an integral part of the coupling design. When the rotational lock is closed, the handles cannot be opened. A secondary motion is required to lock or unlock this device. This is ideal when space is at a premium, i.e. batching where multiple connections are arranged on a manifold.