The pig stop catches the pig in the T-stations. So the pig can be used as a closure device.
The pig retainer is holding the pig in the launching or receiving station. It prevents the pig from being pulled out of its home position into the pipeline through high flow speed of the product.
The operation of the pig stop and the pig retainer can be done manually (with hand lever up to DN 100 / 4") or automatically (with actuator).