The principle of operation of a differential pressure controller

Principle of operation of a pressure differential regulator with a membrane sensor, spring setpoint, single-seat valve, and two external impulse lines.

The regulator design includes a chamber separated by a membrane. The membrane is rigidly connected to the valve closure such that, by shifting in one direction or another, it will move the valve and change the water flow through the regulator. On one side of the membrane, pressure from the supply pipe (a higher value) acts via impulse lines, while on the other, pressure from the return pipe (a lower value) acts. The pressure difference is balanced by the force of the spring compressing the membrane, causing it to assume a central position. The stronger the compression of the regulator spring, the greater the pressure differential it can maintain.

Increasing the difference between the pressures at the impulse line connection point relative to the set value disturbs the balance in the membrane chamber. The force of the water exceeds that of the spring, bending the membrane and moving the valve to block the water flow. The valve throttles the water flow through the regulator, and the pressure differential at the impulse line connection point is established at the set level.

Proportional pressure differential regulators of direct action are so named because the valve opening speed and degree are proportional to the speed and degree of pressure differential change relative to the set value.

Depending on the design, pressure differential regulators may open or close the valve when the controlled pressure increases.