SHIM 4646161 - Caterpillar

Nitrogen gas pressure varies with the temperature. To obtain the most accurate nitrogen charge, the temperature of the accumulator must be identical to the air temperature around the accumulator.Note: Adjust the pressure for ambient conditions, as required. Refer to the following table for the accumulator precharge pressure/temperature relationship.
Table 1
Accumulator Precharge Pressure/Temperature Relationship for the 700 kPa (102 psi) Accumulator    
Temperature     Pressure    
-7°C (20°F)    
598 kPa (87 psi)    
-1°C (30°F)    
618 kPa (90 psi)    
4°C (40°F)    
639 kPa (93 psi)    
10°C (50°F)    
659 kPa (96 psi)    
16°C (60°F)    
680 kPa (99 psi)    
21°C (70°F)    
700 kPa (102 psi)    
27°C (80°F)    
720 kPa (104 psi)    
32°C (90°F)    
741 kPa (107 psi)    
38°C (100°F)    
761 kPa (110 psi)    
43°C (110°F)    
782 kPa (113 psi)    
49°C (120°F)    
802 kPa (116 psi)    
Table 2
Accumulator Specification    
Date     Equipment ID Code    
Item     Specification     Actual     Engine Speed    
Accumulator Charge Pressure    
3300 150 kPa (479 22 psi)         High Idle    Introduction
The accumulator stores hydraulic oil pressure that can be used to lower the implements when the engine is off. The accumulator is located on the pilot manifold.The following procedure will determine if the accumulator for the pilot system is charged to the appropriate pressure.Required Tools
Illustration 1 g02726620
Tooling (B)
Table 3
Tool    Item    Qty    Part Number    Description    
B     B1     1     8T-0856     Pressure Gauge
(0 to 6,000 kPa (0 to 870 psi))    
B2 1     6V-3989     Fitting    
B3 2     6V-4143     Quick Connect Coupler    
B4 1     177-7860     Hose As (10 ft)    Test Preparation - Accumulator Charge Pressure
Move the machine to a smooth horizontal location.
Engage the parking brake.
Lower all of the implements.
Stop the engine.
Turn the key to the ON position. Make sure that the implement lockout switch is turned to the UNLOCKED position. Move the implement control levers to all positions several times in order to release any pressure in the hydraulic system.
Illustration 2 g02788228
Attach tooling (B) to pressure tap (1) located by the filter.Test Procedure (Accumulator Charge Pressure)
Start the engine. Warm the hydraulic oil to a minimum temperature of 65° C (150° F).
Operate the engine at HIGH IDLE.
Exercise the implement hydraulics. At the accumulator, the pilot pressure at tooling (1) should be approximately 3585 kPa (520 psi).Note: There is no test for checking the actual charge pressure of the accumulator on the machine.Charging Procedure - Accumulator Charge
Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures".
Illustration 3 g02788256
The accumulator is located underneath the operator in the cab. Charging valve (2) is located on the top of the accumulator.Note: Do not attempt to charge the accumulator until all pressure has been removed from the pilot accumulator.
When all of the adjustments are complete, remove all tooling and reinstall all guards.