OPERATOR AR 4724925 - Caterpillar

Steering Accumulator Pressure And Precharge Check
Make reference to the on the first page of Testing And Adjusting section.
Side View Of Combination Valve On Machine
(1) Pressure switch port. (2) Supply port for valve group. (3) Supply port for valve group. (4) Steering signal. (5) Steering relief valve. (6) Signal relief valve. (7) Pump signal. (8) Signal bleed valve. (9) Control valve signal. (10) Hydraulic pump pressure test port. (11) Auxiliary return port. (12) Implement relief valve. (13) Valve group return port. (14) Hydraulic tank return port. (15) Steering supply port. (16) Steering accumulator port. (17) Supplemental steering pump port. Do not check the accumulator charge pressure by installing a pressure gauge directly into the top of the steering accumulator. Excessive nitrogen leakage will result during installing and removing the gauge.1. With the engine stopped, turn the steering wheel back and forth several times to relieve the steering accumulator pressure.2. Remove the steering supply (15) line from the combination valve. Install the tee and nipple into the steering supply port. Install the supply line to the tee. Connect the coupling and the pressure gauge to the tee.3. Start the engine and operate at high idle rpm.4. Steer the front wheels left or right against their stops. The pressure gauge should read 19 300 690 kPa (2800 100 psi). This is maximum steering pressure.5. Release the steering wheel and stop the engine.6. Oil pressure will lower slowly until it reaches the steering accumulator precharge pressure. The nitrogen precharge for the accumulator is 6900 kPa (1000 psi). When oil pressure reaches this pressure, the gauge will suddenly drop off to zero. Make note of the pressure that the gauge suddenly drops. This is the accumulator precharge. At zero pressure, the steering accumulator has completely purged the stored oil. It takes ten to twelve minutes to purge the stored oil in the steering accumulator. To speed up the purge time, slowly turn the steering wheel back and forth. This will use up the pressure oil stored in the steering accumulator causing it to discharge quickly. However, it is difficult to read the steering accumulator precharge pressure with oil pressure dropping off so fast.7. If the steering system pressure in Step 4 was incorrect, see Steering System Maximum Pressure section.If the accumulator precharge pressure in Step 6 was incorrect, see Testing And Charging The Steering Accumulator section.Testing And Charging The Steering 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.
In any application, never use an adapter to connect the nitrogen charging equipment to a valve that can be used on oxygen or other