VALVE GP-CHECK 2289695 - Caterpillar

Illustration 5 g02137770
(1) Hydraulic accumulator
Illustration 6 g02137575
(HPS) Pressure tap for the charge pressure of the accumulator
Attach tooling (A) or (B) to pressure tap (HPS). Pressure tap "HPS" is for the charge pressure of the accumulator.Test Procedure (Accumulator Precharge 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.
Return the implement control to the HOLD position. The charge pressure at pressure tap (HPS) should be 3930 170 kPa (570.00720 25 psi).
Stop the engine. Without restarting the engine, place the key in the ON position.
Make sure that the implement lockout switch is in the UNLOCKED position.
Refer to Table 2 for the appropriate accumulator charge.
Quickly move the implement control out of the HOLD position in any direction in order to actuate a function. Return the handle to the hold position.
With the handle in the HOLD position between activations, note the reading on tooling (A) or (B) .
Repeat Step 8 and Step 9 noting the reading each time the handle is returned to the HOLD position.
When the pressure at tooling (A) or (B) is within 345 kPa (50 psi) of the expected precharge pressure, slow the movement of the joystick in Step 8 and Step 9 down.
When the accumulator precharge is reached, the pressure at tooling (A) or (B) will drop rapidly to approximately 0 kPa (0 psi). There may be some residual pressure in the system.
The last pressure reading that was recorded on tooling (A) or (B) before the quick pressure drop is a close approximation of the nitrogen precharge in the accumulator.
If the precharge of the original accumulator is out of the specifications, the accumulator will need to be replaced. The replacement accumulator has a charging valve and may be charged if needed.Charging Procedure for the Accumulator
Dry nitrogen is the only gas approved for use in the accumulator. Charging the accumulator with oxygen gas will cause an explosion. This danger will not happen if nitrogen cylinders with standard CGA (Compressed Gas Association, Inc.) Number 580 connections are used. When you order nitrogen gas, be sure that the cylinders are equipped with CGA No. 580 Connections. Do not use color codes or other methods of identification to tell the difference between nitrogen and oxygen cylinders.
Gas pressure is variable with the temperature. The accumulator must be at the same temperature as the surrounding air before the accumulator can be charged. Use the following chart for the correct nitrogen charge. Use dry nitrogen.
Table 2
Charging Pressure for the Accumulator at Different Temperatures    
Temperature     Pressure    
−40° C (−40° F)    
661 kPa (95 psi)    
−34.4° C (−30° F)    
679 kPa (98 psi)    
−28.9° C (−20° F)    
697 kPa (101 psi)    
−23.3° C (−10° F)    
716 kPa (104 psi)    
−17.8° C (0° F)    
734 kPa (106 psi)    
−12.2° C (10° F)    
752 kPa (109 psi)    
−6.7° C (20° F)    
770 kPa (112 psi)    
−1.1° C