This critical component in commercial vehicle pneumatic braking systems is designed to protect the air supply. It functions by ensuring a minimum level of air pressure is maintained within the reservoirs. For example, if a significant leak develops in a connected system, this device will close off affected components, preventing the complete depletion of the air supply and allowing for a degree of controlled stopping power to remain available.
Its presence is vital to operational safety, particularly for large vehicles such as trucks and buses. Historically, failures in air brake systems due to pressure loss were a significant cause of accidents. The implementation of these protective devices significantly reduced the risk associated with complete air loss. This contributes to driver confidence and, more importantly, reduces the potential for catastrophic braking failures in emergency situations.