ELECTRICAL AR 2401427 - Caterpillar

Table 2
Ambient Temperature versus Charging Pressure for the 391-6390 Hydraulic Accumulator Gp (High pressure)
Ambient Temperature Charging Pressure(1)
−18° C (0° F) 8010 kPa (1162 psi)
−12° C (10° F) 8200 kPa (1189 psi)
−7° C (20° F) 8359 kPa (1212 psi)
−1° C (30° F) 8550 kPa (1240 psi)
4° C (40° F) 8709 kPa (1263 psi)
10° C (50° F) 8900 kPa (1291 psi)
16° C (60° F) 9091 kPa (1319 psi)
21° C (70° F) 9250 kPa (1342 psi)
27° C (80° F) 9441 kPa (1369 psi)
32° C (90° F) 9600 kPa (1392 psi)
38° C (100° F) 9791 kPa (1420 psi)
43° C (110° F) 9950 kPa (1443 psi)
49° C (120° F) 10140 kPa (1471 psi)
54° C (130° F) 10300 kPa (1494 psi)
60° C (140° F) 10490 kPa (1522 psi)
(1) 462 kPa ( 67 psi)Introduction
The cushion-hitch accumulators allow the tractor to be cushioned from sudden shock movement of the scraper.Machine Preparation
Move the machine to a smooth, horizontal location. Move the machine away from other operating machines and away from personnel. Place the transmission direction control switch in the NEUTRAL position. Engage the parking brake. Lower the work bowl to the ground. Stop the engine and put chocks in front of the wheels and behind the wheels. Turn off the engine. Make sure that the engine has not been operating for at least 5 minutes. This time period is long enough to allow the hydraulic oil to flow out of the bottom chamber of the accumulator. The piston in the accumulator must be on the bottom of the cylinder in order to charge the accumulator correctly.The precharge pressure of the 388-2070 Hydraulic Accumulator Gp (Low pressure) is 2500 125 kPa (363 18 psi) at a temperature of 21°C (70° F). The precharge pressure of the 391-6390 Hydraulic Accumulator Gp (High pressure) is 9250 462 kPa (1342 67 psi) at a temperature of 21° C (70°F).The air temperature outside the accumulator is the ambient temperature. Before the dry nitrogen pressure in the accumulator may 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 pressure for the 388-2070 Hydraulic Accumulator Gp (Low pressure) at a given ambient temperature.Use Table 2 in order to determine the correct charging pressure for the 391-6390 Hydraulic Accumulator Gp (High pressure) at a given ambient temperature.
Illustration 1 g03489081
(A) Low-pressure accumulator
(B) High-pressure accumulator Checking the Dry Nitrogen Pressure in the Cushion-Hitch Accumulator
Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures" to check the dry nitrogen pressure of the cushion-hitch accumulator. Charging the Cushion-Hitch Accumulator
Increase the nitrogen pressure in the accumulator according to the following steps:
Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures" to charge the cushion-hitch accumulator. Charging a Rebuilt Cushion-Hitch Accumulator
When the accumulator