QUICK RELEASE VALVES AND DIFFERENTIAL QUICK RELEASE VALVE

Figure 3 - Midland Differential Quick Release Valve

TM-5-3820-256-24-4 Drilling System Well Rotary Truck Mounted Air Transportable 600 Feet Capacity Model LP-12 NSN 3820-01-246-4276 Manual
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QUICK RELEASE VALVES AND DIFFERENTIAL QUICK RELEASE VALVE DESCRIPTION Quick release valves are used to release air from air brakes at the brake chamber. This makes the release of brakes quicker than a system where the chamber air has to flow back through the brake piping to the foot valve. There are two types of quick release valves, the basic type and the differential type. These valves are usually mounted on the frame close to the brake chambers they control. The line connected to the top port is the delivery line from the brake valve. The two side ports are the brake chamber connections, and the bottom port is the exhaust. In most cases it also functions as a tee and connects two air brake chambers to the line from the foot valve. The valves that are used by International Harvester are supplied by Bendix and by Midland. BENDIX QR-1 TYPE QUICK RELEASE VALVE The Bendix valve can be distinguished by having a cast body and cover (Figures 1 and 4). Figure 1 - Bendix QR-1 Quick Release Valve The brake foot valve port is in the body and the other ports are in the cover. MIDLAND TYPE QUICK RELEASE VALVE The Midland valve can be distinguished by having a cast or plastic body and stamped cover (Figures 2 and 5). The brake foot valve port and the brake chamber ports are in the body. The exhaust port is a set of holes pierced in the center of the stamped cover. Figure 2 - Midland Quick Release Valve MIDLAND DIFFERENTIAL QUICK RELEASE VALVE The Midland differential quick release valve can be distinguished by having a cast or plastic body and cover like the Bendix valve, but having the brake chamber ports in the cover (Figures 3 and 6). OPERATION QUICK RELEASE VALVE When a brake valve application is made, air pressure enters the top (brake valve) port of the valve (Figures 4 and 5). This will move the diaphragm down closing the exhaust port. At the same time, the air pressure forces the edges of the diaphragm down. The air will then flow to the brake chambers. When the brake chamber pressure beneath the diaphragm equals the air pressure being delivered in the brake valve, the outer edges of the diaphragm will seal against the cover seat. The exhaust port is still sealed by the center portion of the diaphragm. When the brake valve is released, air pressure above the diaphragm is exhausted. This will allow the diaphragm to raise, opening the exhaust port. It will then allow the brake chamber pressure to release through the exhaust port. CTS-4079A-CHAPTER V - Page 2

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