The principle of operation of a water pressure regulator

The principle of operation of a water pressure regulator is considered using the example of a membrane regulator with a spring-loaded controller and a single-seated valve.

The regulator's design includes a sealed chamber divided by a membrane into two chambers. The central part of the membrane is rigidly connected to the valve stem, and the periphery is connected to the housing. The elasticity of the membrane allows it to move, displacing the stem and the valve.

Through the impulse line, water enters one chamber of the membrane chamber, while the other is open and filled with air at atmospheric pressure. As the water pressure is higher than atmospheric pressure, the membrane tends to bend and move the stem, but it is counteracted by the force of the compressed spring, which is directed in the opposite direction. The position of the valve is determined by the balance of forces on the stem.

"After self" pressure regulators maintain pressure at the outlet of the valve, so exceeding the set value leads to the closure of the valve. In the absence of pressure, the regulator opens completely, which is why they are also called "normally open". The animation shows the operation of an "after self" pressure regulator.

"Before self" pressure regulators maintain pressure at the inlet of the valve, so exceeding the set value leads to the opening of the valve. In the absence of pressure, the regulator closes completely, which is why they are called "normally closed". Compared to the animation shown, the direction of the spring force and water pressure in "before self" pressure regulators is opposite.

Proportional direct-acting pressure regulators are so named because the speed and degree of valve opening are proportional to the speed and degree of pressure change relative to the set value set by spring compression.

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