Relay valve ALS Mk-3 brake system : construction and working

The relay valve ALS Mk-3 is a important part of the air brake system. The realy valve is operated by air and helps to apply brake into the rear wheel.


Construction of relay valve ALS Mk-3 :-

Relay valve ALS Mk-3 have two air inlets. One from dual brake valve and second from 50 ltr air reservoir. Relay valve ALS Mk-3 have one air outlet to spring brake chamber. 

Relay valve divided into two part like top cover and valve body. The top cover and valve body both are connected with each other. Inside the top cover there is a cup type piston is fitted. 

Relay valve ALS Mk-3

Inside the valve body there is a relay valve fitted and to retain the relay valve a returning spring is provided. For normal cleaning the incoming air it have a gauge filter. 


Working of relay valve ALS Mk-3 :-

In normal condition the air from 50 ltr air reservoir always remains filled till under the relay valve. But the relay valve keeps close the outlet in normal condition. 

When driver apply the brake then the pressurized air from dual brake valve comes and enter at upside of the cup type piston and push the cup type piston downward. Moving downward of the cup type piston the leg of the cup type piston push the realy valve to downward. 

Relay valve ALS Mk-3

Because of the relay valve moving downward there is some clearance take place between relay valve and its seating. Now the air is coming from 50 ltr air reservoir goes to the spring brake chamber through clearance and outlet. 

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