PLATE AS 1245850 - Caterpillar

Boom Lowering with the Engine Stopped
To lower the boom, place the control lever into the Boom Down position. If the accumulator still has a charge, the boom will lower.If the boom fails to lower, the accumulator is empty. Use one of the following procedures to lower the boom.Boom Lowering with the Engine Stopped For Machines Not Equipped With Boom Lowering Check Valves
Use the following procedure when it is necessary to lower the boom while the engine is shut down or the hydraulic system disabled.
Be sure no one is under or near the front implements before manually lowering the boom.Keep all personnel away from the boom area when lowering the boom with the engine stopped.
Loosen screw (2) of the vent valve a maximum of 1/2turn to lower the boom. Never try to activate any valves other than the vent valve.
1. Check to be sure that no one is under and near the front implements. Slowly loosen locknut (1) and then loosen screw (2) [width across flats: 6.35 mm (.25 in)] counterclockwise a maximum of 1/2 turn. The boom will continually lower until it is seated on the ground.2. After making sure that the front implements has lowered completely onto the ground, tighten the screw and locknut.3. Contact your Caterpillar dealer and make necessary repairs. The vent valve must remain in the fully closed position unless the boom lowering is done.Boom Lowering with the Engine Stopped For Machines Equipped With Boom Lowering Check Valves
Use the following procedure instead of the previous procedure when it is necessary to lower the boom while the engine is shut down or the hydraulic system disabled and the excavator is equipped with boom lowering check valves.
Boom load may cause cylinder oil pressure to reach relief pressure of the boom lowering check valve when boom is supported by one cylinder. Boom can lower suddenly.Be sure no one is under or near the front implements before manually lowering the boom.Keep all personnel away from the boom drop area when lowering the boom with the engine stopped.
A boom lowering check valve (if equipped) is installed on each of the boom cylinders, as shown. The boom lowering check valves allow the operator to manually lower the boom with the engine stopped. The boom lowering check valves also function to prevent a sudden drop of the boom in case that there is an oil leakage in the boom line.1. Loosen the locknut of one boom lowering check valve and then slowly loosen the piston screw until it stops. Do the same for the other boom lowering check valve. The boom will start to lower slowly.2. After making sure that the front implement has lowered completely onto the ground, securely tighten the piston screw and then tighten the locknut to a torque of 10 1 N m (7 1 lb ft).3. Make any necessary repairs before placing the excavator back into service. For further information, contact your Caterpillar dealer.