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Engine compressor
When the compressor comes up to pressure the governor purges the dryer and air stops building pressure, what does the compressor do to stop building pressure, and where does the air go?
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3 Replies
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Air System Info
The heart of the air supply system is the engine driven air compressor. It feeds an air dryer that removes moisture and oil. The dryer feeds the wet tank and a return line to the compressor mounted governor. The governor signals the air compressor to stop producing pressurized air and the dryer “sneezes” to unload the pressure line when the governor set air pressure has been met.
The wet tank then supplies air to the front and rear brake main tanks and the auxiliary tank. To isolate the front and rear braking systems, air entering these tanks does so through a check valve at each tank. Once air is in the main brake tanks it cannot escape back into the supply feed.
The auxiliary air system cannot have the same priority to supply air as the braking systems. To ensure the braking systems are fulfilled before the auxiliary system, the supply line is fed through a protection valve to the auxiliary tank. The protection valve opens when either side of the valve reaches a specific pressure which is somewhere between 60 and 75psi. If your coach’s air systems leak over time you may have noticed that air builds in the front(secondary brake) and rear(primary brake) systems first. At the rating of the protection valve you then hear the rush of air entering the auxiliary system.
That is basically the entire supply air system. It supplies all 3 main air subsystems, rear braking, front braking, and auxiliary. Once those systems are filled the governor effectively turns off the compressor and each of the 3 systems are protected from their air returning to the supply air system.
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The compressor unloader valves open. The compressor continues to rotate. No air is being compressed.
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I replaced the unloader valves when I 1st got bus,so the governor must control the unloader valves.
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