Demystifying Airbrakes 2: Spring brake valve

Demystifying Airbrakes 2:  Spring brake valve

The valve is a Tramec TEV 70psi spring brake valve. A spring brake valve basically accomplishes two tasks. Releasing parking brakes by compressing the springs in brake chambers, and filling air tanks. A great article (PDF) from Tramec can be found at the link below. A Sealco 110700 valve is very similar to this Tramec valve, but is more common and of much better quality. If you need to replace a spring brake valve, I recommend using Sealco parts. Trust me.

A viewer, Brake Nut, provided me with the following information. Sometimes I just can’t explain things well enough so I’m glad to have other people share what they know.

“That little valve you couldn’t remove at 2:40 ish is a one way check valve.. Anti Compounding is simply a protection system that won’t allow the pressure to be ADDED to the service side of the chambers if the park spring are released. With the red button out, air has been exhausted from the spring brake cavity and the push rods are pushed forward mechanically with the heavy spring of the chamber.. If you make a service brake application with the spring brakes applied, you compound the forces on the slack. Anti Compounding.. in this case.. with no pressure on the supply side of the piston (in the valve) .. the same service signal (blue line) applying air to the service side of the pots .. that same signal is entering the trailer emerg valve and will push through the check valve and through the orifice you described.. and begin filling the spring brake side of the chamber pushing on the large diaphragm in the pot Just imagine a cut-away spring brake chamber.. you’ll have equal pressure pushing on the service and pushing on the park side.. proportionally.. ”
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Air dump valve problem.wmv

Air dump valve problem.wmv

Chucked the vid cam on the passenger seat while I pulled out onto the highway. The air dump you can hear every 5 seconds or so is the air dryer which has some sort of problem.
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