How the differential pressure controller works

Operating principle of the differential pressure controller with a membrane sensor, spring setpoint, single-disc valve, and two external impulse lines.

The controller's design includes a chamber divided by a membrane. The membrane is rigidly connected to the valve shutter in such a way that when it moves in one direction or another, it shifts the shutter and changes the water flow through the controller. The impulse lines apply pressure on the membrane, with higher pressure from the supply side and lower pressure from the return side. The pressure difference is balanced by the spring compression force acting on the membrane, positioning it in a middle position. The more the regulator spring is compressed, the greater the pressure difference it maintains.

When the pressure difference at the impulse line connection points exceeds the set value, the balance in the membrane chamber is disrupted, the water force surpasses the spring force, bending the membrane and moving the shutter to restrict water flow. The shutter throttles the water flow passing through the controller, and the pressure difference at the impulse connection points is set to the specified level.

Proportional differential pressure controllers are called so because the speed and degree of shutter opening are proportional to the rate and degree of deviation of the pressure difference from the set value.

Depending on the design, differential pressure controllers may open or close the shutter when the controlled pressure increases.

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