In the pneumatic brake system, compressed air is the working medium, which needs to maintain a sufficiently high and stable pressure and be clean enough to ensure the normal operation of each valve in the system. For this reason, two components, a dryer and an air pressure regulator, are installed in the system. Their function is to provide clean and dry compressed air for the brake system and keep the system pressure in a normal range (usually 8~ 10bar). In order to simplify the system, these two components are generally integrated together, collectively referred to as the driver assembly.
On this assembly, there is a pressure regulating valve, which can adjust the level of system pressure. When the system pressure reaches the specified pressure, the pressure regulating valve will open, and the compressed air pumped from the air pump will be discharged through the exhaust port of the air pressure regulator, the system pressure will no longer rise, and the air pump will run without load. If the pressure of the system is unloaded and exhausted before reaching the specified pressure, we can turn the adjusting screw of the pressure regulating valve clockwise, and the exhaust pressure of the system will increase; if the pressure of the system reaches or exceeds the specified If the pressure has not been unloaded and exhausted, we can turn the adjusting screw of the pressure regulating valve outward counterclockwise, and the exhaust pressure of the system will decrease. We adjust this screw repeatedly in this way until the exhaust pressure reaches the pressure specified by the system.
However, in practice, this pressure regulating valve is not easily damaged, and its regulating pressure generally does not change. If the air pressure of the brake system cannot rise suddenly, it is generally due to a fault such as air leakage in the system. If the compressed air is discharged from the exhaust port of the air pressure regulator, it means that the rubber seal inside it is damaged. In this case, the air pump has leaked oil or the drying tank has lost its drying effect. At this time, we should replace the dryer assembly And repair the air pump instead of simply adjusting the exhaust pressure of the pressure regulating valve.
（The article quotes Lao Hou's commentary）