Fig. 7 Cross Section of Pressure Limiting Valve

Fig. 9 Crow Section of Emergency Relay 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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SERVICE MANUAL Fig. 7 Cross Section of Pressure Limiting Valve 1 Piston 5 Piston "O" Ring 2 Valve Guide Wire 6 Exhaust Vent 3 Inlet Valve Spring 7 Pressure Regulating 4 Inlet & Exhaust Spring Valve If pressure in the delivery line exceeds the pressure setting of the pressure limiting valve, the force exerted by the air pressure below the piston will be greater than the spring force above the piston. The piston will move up from the exhaust valve, permitting air to pass by the exhaust valve, through the hollow piston and valve guide and escape through the slot in the adjusting cap. When the force of the spring above the piston overcomes that of the air pressure below the piston, the exhaust valve is seated, and the pressure in the delivery line is the same as the setting of the pressure reducing valve. MAINTENANCE Every 6 months or 80,000 km (50,000 miles). Connect a test gauge to the delivery line and observe at what pressure the inlet valves closes, which is the delivery pressure. If the pressure delivered by the pressure reducing valve varies more than plus or minus 35 kPa (5 psi) from the pressure setting of the pressure reducing valve, the valve should be adjusted. The lock nut should be tightened after each adjustment and lockwire seal replaced if used. Every year or every 160,000 km (100,000 miles) perform the SERVICE CHECKS. SERVICE CHECKS Operating Check Connect an accurate test gauge to the delivery line and observe what pressure the inlet valve opens which is the delivery pressure. If delivery pressure varies more than 35 kPa (5 psi), adjust the valve to the specified setting. To raise the delivery pressure the adjusting cap should be turned clockwise. Tighten locknut after each adjustment and replace lockwire and seal if used. Leakage Check No leakage is permitted at the exhaust vent in the slot of the adjusting cap when making the operating check. Leakage at this point would indicate a leaking piston O- ring or a leaking exhaust valve seat. If the pressure limiting valve does not function as described or leakage is excessive, it is recommended that it be replaced. REMOVE Apply parking brakes or block wheels to prevent vehicle from moving. Drain service and isolated reservoirs. Disconnect air lines from the pressure reducing valve. Loosen valve mounting bolts and remove. REINSTALL Check and clean air lines to valve. Mount valve securely with bolts and lockwashers. Reconnect lines to the valve. Disassembly and reassemble of Pressure Limiting Valve is not recommended as it is serviced as a complete assembly. CTS-4079 - CHAPTER III PRINTED IN UNITED STATES OF AMERICA Page 7

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