What is the difference between a pressure relief valve and a self-acting pressure regulator?

The working principles of pressure relief valves and self-acting pressure regulators are different. Pressure relief valves typically rely on external power sources (such as springs or pneumatic/electric devices) to adjust the valve opening and maintain a set downstream pressure. It is typically used for regulating the pressure of gases or liquids, and it can automatically adjust the valve opening in response to changes in downstream pressure in order to maintain stable pressure. A self-acting pressure regulator does not require external energy; it uses the pressure of the medium downstream as its power source. When the pressure downstream of the pipeline changes beyond the set value, the self-acting pressure regulator automatically adjusts the valve opening based on the changes in medium pressure in order to maintain a constant downstream pressure. If the valve downstream closes, pressure relief valves and self-acting pressure regulators can typically detect an increase in downstream pressure and accordingly close the valve or reduce its opening degree to prevent further pressure rise. If the valves and the system are operating properly, there should be no leaks. However, if the valve seal is poor or damaged, there may be leaks. If the valve of the downstream pipeline is closed, both the pressure relief valve and the self-acting pressure regulator will usually close due to the increase in pressure. If the valve is not closed or is not sealed properly, it may cause the pressures in the pipes before and after it to be equal. In such a case, if the set pressure of the safety valve in the pipe behind it is low, the safety valve may activate to release pressure and prevent the piping system from being damaged due to overpressure. .