Yale Pallet Stacker: MPB040-E [B827], MPW045-E [B802] Workshop Service Manual

Maintenance :$/,( +<'5$8/,& 6<67(06 MPB040E [B827]; MPW045E [B802] PART NO. 524154894 1900 YRM 1018 Yale

SAFETY PRECAUTIONS MAINTENANCE AND REPAIR • When lifting parts or assemblies, make sure all slings, chains, or cables are correctly fas- tened, and that the load being lifted is balanced. Make sure the crane, cables, and chains have the capacity to support the weight of the load. • Do not lift heavy parts by hand, use a lifting mechanism. • Wear safety glasses. • DISCONNECT THE BATTERY CONNECTOR before doing any maintenance or repair on electric lift trucks. • Disconnect the battery ground cable on internal combustion lift trucks. • Always use correct blocks to prevent the unit from rolling or falling. See HOW TO PUT THE LIFT TRUCK ON BLOCKS in the Operating Manual or the Periodic Maintenance section. • Keep the unit clean and the working area clean and orderly. • Use the correct tools for the job. • Keep the tools clean and in good condition. • Always use YALE APPROVED parts when making repairs. Replacement parts must meet or exceed the specifications of the original equipment manufacturer. • Make sure all nuts, bolts, snap rings, and other fastening devices are removed before using force to remove parts. • Always fasten a DO NOT OPERATE tag to the controls of the unit when making repairs, or if the unit needs repairs. • Be sure to follow the WARNING and CAUTION notes in the instructions. • Gasoline, Liquid Petroleum Gas (LPG), Compressed Natural Gas (CNG), and Diesel fuel are flammable. Be sure to follow the necessary safety precautions when handling these fuels and when working on these fuel systems. • Batteries generate flammable gas when they are being charged. Keep fire and sparks away from the area. Make sure the area is well ventilated. NOTE: The following symbols and words indicate safety information in this manual: WARNING Indicates a condition that can cause immediate death or injury! CAUTION Indicates a condition that can cause property damage!

Walkie Hydraulic Systems Table of Contents TABLE OF CONTENTS General ................................................................................................................................................................ 1 Operation ............................................................................................................................................................. 1 Lifting a Load................................................................................................................................................... 1 Lowering a Load.............................................................................................................................................. 1 Hydraulic Lines................................................................................................................................................ 2 Hydraulic Oil .................................................................................................................................................... 2 Cleanliness...................................................................................................................................................... 3 Sound Level .................................................................................................................................................... 4 Hydraulic Unit ...................................................................................................................................................... 4 Remove ........................................................................................................................................................... 4 Special Precautions ........................................................................................................................................ 5 Install ............................................................................................................................................................... 5 Hydraulic Pump ................................................................................................................................................... 6 Remove ........................................................................................................................................................... 6 Install ............................................................................................................................................................... 6 Hydraulic Pump Reservoir ................................................................................................................................... 8 Remove ........................................................................................................................................................... 8 Install ............................................................................................................................................................... 8 Hydraulic Cylinder ............................................................................................................................................... 9 Remove ........................................................................................................................................................... 9 Repacking ....................................................................................................................................................... 10 Install ............................................................................................................................................................... 10 Relief Valve Adjustment ....................................................................................................................................... 11 Troubleshooting ................................................................................................................................................... 13 Lift Assemblies ................................................................................................................................................ 13 Hydraulic Cylinders ......................................................................................................................................... 13 Hydraulic Pump ............................................................................................................................................... 14 This section is for the following models: MPB040E [B827]; MPW045E [B802] ©2002 Yale Materials Handling Corp. i

1900 YRM 1018 Operation General The hydraulic system provides the force required to lift the loads on all motorized lift trucks. The hydraulic system on the motorized lift truck consists of the following individual components: • Pump Motor Assembly • Hydraulic Pump Assembly • Solenoid Lowering Valve • Pilot Relief Valve • Lift Cylinder • Reservoir The hydraulic pump and motor assemblies are mechan- ically joined together as a compact unit combining the reservoir, pump, and motor together as a single assembly. The pump is located inside of the hydraulic tank and coupled to the motor by an adapter plate, coupler drive, and four capscrews. Hydraulic unit servicing is best performed by removing the unit from the truck to a clean work area. Operation LIFTING A LOAD To raise a load the lift button must be depressed. De- pressing this switch will activate the pump motor. This torque is transferred to the pump from the motor through the motor shaft and shaft coupling. Hydraulic oil is pumped through the system as the pump begins to operate. A vacuum created inside of the pump draws oil out of the reservoir through the suction line. Air which is drawn into the reservoir through the breather displaces the pumped oil allowing it to be sent through the system. See Figure 1, Figure 2, and Figure 3. If the breather is clogged or blocked the ability of the system to lift a load will be greatly reduced. As oil is pushed out of the pump, it passes through a one-way check valve to the lift cylinder. The check valve prevents oil from flowing back to the pump when lifting ceases, holding the lift cylinder in the raised position until lowered. The piston will begin to lift the load when fluid pressure acting against it is high enough to overcome the weight of the load at rest on the forks/platform. When the piston is fully extended to the end of its stroke or if the load is too heavy, pressure will continue to build until the rated pressure needed to operate the relief valve is reached. When this occurs, the relief valve, which is normally closed, is forced back against its spring creating a path for the fluid to flow back to the reservoir. Once relief valve pressure is reached, hydraulic oil will continue to be diverted from the lift cylinder to the reservoir until the lift button is released or electrical power is interrupted. LOWERING A LOAD A load is lowered by depressing the lower button. When the lower button is depressed, electric current is sent to the normally closed solenoid lowering valve which causes it to change position and open a path for the trapped hydraulic oil to flow from the cylinder back to the reservoir. Figure 1. Hydraulic Schematic 1 Lowering Solenoid Valve To Lift Cylinder Check Valve Suction Line Pilot Operated

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Yale Pallet Stacker: MPB040-E [B827], MPW045-E [B802] Workshop Service Manual

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