SWITCH 2911746 - Caterpillar

Charge Procedure
Dry nitrogen is the only gas approved for use in the accumulators. The charging of oxygen gas in an accumulator will cause an explosion. An explosion can be eliminated by using nitrogen gas cylinders with standard CGA (Compressed Gas Association, Inc.) No. 580 connectors. When nitrogen gas is ordered, make sure to order the cylinders with CGA No. 580 connectors.Do not rely on color codes or other methods of identification to tell the difference between nitrogen and oxygen cylinders. In any application, never use an adapter to connect your nitrogen charging group to a valve outlet used on both nitrogen, oxygen, or other gas cylinders. BE SURE YOU USE DRY NITROGEN (99.8% purity).
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products.Dispose of all fluids according to local regulations and mandates.
Table 1
Required Tools
Part Number Description
7S-5437 Nitrogen Charging Equipment Stop the engine. Depress the brake pedal repeatedly until there is no brake pressure.To ensure that the nitrogen charge is correct, each brake accumulator piston must be at the bottom of the accumulator cylinder. Nitrogen gas pressure varies with the temperature. To obtain the most accurate nitrogen charge, the temperature of each accumulator must be identical to the air temperature around the accumulators.If an accumulator has less than half of the required amount of precharge pressure, the accumulator should be charged, and then charged again after operating the service brakes several times. This prevents trapping a quantity of oil in the accumulator which will give an inaccurate precharge reading.However, the temperature of the accumulators could be higher than the air temperature around the accumulators. In this case, the temperature of the accumulator should be used instead of the surrounding air temperature.Note: The pressures in the following table are for an ambient air temperature of 21°C (70°F). Adjust the pressure for other ambient conditions, as required.
Table 2
Accumulator Precharge Pressure/Temperature Relationship for the 5520 kPa (800 psi) Service Brake Accumulator
Temperature Pressure
−7°C (20°F) 5000 kPa (726 psi)
−1°C (30°F) 5105 kPa (741 psi)
4°C (40°F) 5235 kPa (760 psi)
10°C (50°F) 5340 kPa (775 psi)
16°C (60°F) 5420 kPa (787 psi)
21°C (70°F) 5500 kPa (798 psi)
27°C (80°F) 5605 kPa (813 psi)
32°C (90°F) 5735 kPa (832 psi)
38°C (100°F) 5840 kPa (848 psi)
43°C (110°F) 5920 kPa (859 psi)
49°C (120°F) 6000 kPa (871 psi)
Illustration 5 g00495846
Nitrogen Charging Equipment
(5) Nipple. (6) Coupling assembly. (7) Pressure gauge. (8) Hose assembly. (9) Coupling assembly. (10) Nipple. (11) Valve. (12) Pressure gauge. (13) Regulator assembly. (14) Pressure regulating screw. (15) Chuck for the nitrogen cylinder valve. (16) Valve handle. (17) Chuck. (18) Hose assembly.
Illustration 6 g00553685
Brake Accumulator
(19) Cover. (20) Cap.
Apply the service brakes 20 to 30 times. This will release any