Pressure (safety or pop-off) valve

A pressure regulator is a valve that automatically cuts off the flow of a liquid or gas at a certain pressure. Regulators are used to allow high-pressure fluid supply lines or tanks to be reduced to safe and/or usable pressures for various applications. Also called a 'pop-off' or 'safety' valve


Pressure regulator's primary function is to match the flow of gas through the regulator to the demand for gas placed upon the system. If the load flow decreases, then the regulator flow must decrease also. If the load flow increases, then the regulator flow must increase in order to keep the controlled pressure from decreasing due to a shortage of gas in the pressure system.

A regulator includes a loading element, a measuring element, and a restricting element.

Restricting Element: This element is a type of valve arrangement. It can be a globe valve, butterfly valve, poppet valve, or any other type of valve that is capable of operating as a variable restriction to the flow.

Loading Element: This element is what applies the needed force to the restricting element. This can be any number of things such as a weight, a spring, a piston actuator, or more commonly the diaphragm actuator in combination with a spring.

Measuring Element: This element tells us when the inlet flow is equal to the outlet flow. The diaphragm is widely used because not only is it used for measuring but as well for loading purposes.

In the pictured single-stage regulator, a diaphragm is used with a poppet valve to regulate pressure. As pressure in the upper chamber increases, the diaphragm is pushed upward, causing the poppet to reduce flow, bringing the pressure back down. By adjusting the top screw, the downward pressure on the diaphragm can be increased, requiring more pressure in the upper chamber to maintain equilibrium. In this way, the outlet pressure of the regulator is controlled.

Modern gas regulators can vary its operation by the use of stiffer springs, pre-amplification, velocity boosting, and lever ratio.