The A106-Dynamic Lifter (DL) sewage pressure relief valve is a direct acting spring loaded relief valve.
The valve is adjusted to open when the pressure exceeds the set-point, which is approximately 10% above the normal operating pressure. The valve closes drip-tight when pressure falls below the set-point. The DL is connected on a tee off the main line and usually discharges relief flow back to the main sump to reduce the surge over-pressure. A speed control permits adjustment of the closing speed.
The opening force is boosted by the line pressure operating, via the separation chamber, on the piston. By applying external pressure to the test connection, the valve may be cycled open for routine maintenance.
For more information on the A106-DL Dynamic Lifter Spring Pressure Relief Valve: