Vented Cover for Rotary Piston Pumps
The automatic pressure regulation protects the pump from failure and mechanical problems.
The “spring” and “piston” of the vented packing normally send pressure towards the portions of the pump that are in contact with the liquid.
When the pressure inside the pump (or portions in contact with the liquid) becomes higher than the pressure exerted by the spring, the pressure difference pushes the vented packing up in the opposite direction from the portions in contact with the liquid. This causes the liquid to reverse its flow through bypasses A and B, suppressing the pressure increase inside the pump (portions in contact with the liquid).