SEAT GP 1075977 - Caterpillar

Sudden movement of the machine or release of oil under pressure can cause serious injury to persons on or near the machine.To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system.
Cold ambient temperatures could result in the loss of secondary braking capability due to inadequate hydraulic accumulator nitrogen pre-charge. The loss of the secondary braking system as well as the main hydraulic pressure will result in little or no braking capability and a potential for injury or death.It is recommended to perform a brake accumulator check anytime the machine has been idle for longer than two hours below −25 °C (−13 °F). Refer to Operation and Maintenance Manual before performing any check of the brake accumulator.
Reference: Refer to Testing and Adjusting, "Machine Preparation for Troubleshooting" before you begin the test.Specification
Table 1
Accumulator Precharge Pressure/Temperature Relationship for a Typical 5000 kPa (725 psi) Brake Accumulator
Temperature Pressure(1)
-1°C (30°F) 4630 kPa (672 psi)
4°C (40°F) 4717 kPa (685 psi)
10°C (50°F) 4808 kPa (698 psi)
16°C (60°F) 4902 kPa (711 psi)
21°C (70°F) 5000 kPa (725 psi)
27°C (80°F) 5102 kPa (740 psi)
32°C (90°F) 5208 kPa (756 psi)
38°C (100°F) 5263 kPa (764 psi)
43°C (110°F) 5376 kPa (780 psi)
49°C (120°F) 5495 kPa (798 psi)
(1) The tolerance on the nominal pressure is 248 kPa ( 36 psi).Introduction
The brake accumulators are mounted ahead of the right front wheel well. The purpose of the accumulator is to store pressure. This stored pressure will allow the machine operator to bring the machine to a stop in the event of an interruption of pressure from the brake pump.The following procedure will determine if the accumulator is charged to the appropriate pressure.Accumulator Charge Procedure
Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures". Lowering the Piston in Brake Accumulators
Hydraulic accumulator contains gas and oil under high pressure. Improper removal or repair procedures could cause severe injury. To remove or repair, instructions in the service manual must be followed. Special equipment is required for testing and charging.
Relieving the pressure in the brake circuit will not release the nitrogen precharge pressure in the brake accumulators.
Remove the pressure from the brake system by pumping the service brake pedal at a rate of one second ON and one second OFF. Continue to pump the brakes until the pressure at the TF port on the fan/brake manifold is less than 140 kPa (20 psi). Do not assume that the pressure is removed from the circuit if the brake pedal has no resistance. In order to charge the accumulator, the piston in the brake accumulator must be on the bottom of the cylinder. The air temperature outside the accumulator is the ambient temperature. Before the dry nitrogen pressure in the accumulator can be accurately checked, the temperature of the accumulator must be equal to the ambient temperature. Before the accumulator may be correctly charged, the temperature of the accumulator must be equal to the ambient temperature.Use Table 1 in order to determine the correct charging