COVER A. 1H5497 - Caterpillar

Table 1
Tools Needed    
Tool    Part Number    Part Description    Qty    
A     7S-5437     Nitrogen Charging Apparatus     1    
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 checked or charged. Use the following chart to get the correct nitrogen charge.
Table 2
Charging Pressure and Temperature Relationship for the Accumulator    
Temperature    Pressure (1)    
-7°C (20°F)    
3100 kPa (450 psi)    
-1°C (30°F)    
3170 kPa (460 psi)    
4°C (40°F)    
3240 kPa (470 psi)    
10°C (50°F)    
3310 kPa (480 psi)    
16°C (60°F)    
3375 kPa (490 psi)    
21°C (70°F)    
3445 kPa (500 psi)    
27°C (80°F)    
3515 kPa (510 psi)    
32°C (90°F)    
3580 kPa (520 psi)    
38°C (100°F)    
3650 kPa (530 psi)    
43°C (110°F)    
3720 kPa (540 psi)    
49°C (120°F)    
3790 kPa (550 psi)    
( 1 ) The allowable tolerance on nominal pressure is 70 kPa (10 psi).Note: For an accumulator precharge of 345 kPa (500 psi), the pressure change is 70 kPa (10 psi) per 5.5°C (10°F) difference from the operating temperature.Do not use an adapter to connect the nitrogen charging equipment to a valve that can be used on oxygen cylinders or gas cylinders. Use dry nitrogen.The pressure of the hydraulic oil on the accumulator must be removed before the accumulator is tested or charged. Shut off the engine and perform the procedure to discharge the accumulator.Testing the Nitrogen Charge
Illustration 1 g00281220
Nitrogen charging apparatus (1) Pressure gauge. (2) Connection to nitrogen cylinder valve. (3) Regulator assembly. (4) Valve. (5) Pressure gauge. (6) Pressure regulating screw. (7) Valve handle. (8) Chuck.
Remove the cap from the top of the accumulator.
Close valve (4). Use 6890 kPa (1000 psi) gauge (5) to check the nitrogen charge in the accumulator.
Install chuck (8) on the valve of the accumulator.
Turn valve (7) on chuck (8) clockwise. Check the temperature of the air around the accumulator. The pressure on the gauge must be within the tolerances that are listed in Table 2.
If the pressure reading on the gauge is too high, lower the pressure by slowly opening valve (4) .
If the pressure reading on the gauge is too low, charge the accumulator.Charging the Accumulator
Connect the hose from the nitrogen cylinder to valve (4) .
Close valve (4) .
Open the valve on the nitrogen cylinder. Adjust screw (6) on the regulator assembly until gauge (1) is at the pressure that