907H Ride Control Accumulator Replacement

[XSKIER]

S/N SJM00462
I noticed that the ride control is activating, but the effect is minimal. I observed that the accumulator was marked 270 psi, so I went to check it with my 300 psi "Fox shocks" air hand pump. As soon as the chuck was fitted, the gauge surged back to the 0 stop, bent the needle, and filled the gauge with an emulsified oil. I would guess It had north of 500 psi of aerated oil on the wrong side of the accumulator piston. Would the best $353 spent be to replace the accumulator with a pre-charged part? Would anyone concur that part number 345-3674 would do the job?

 

[Nige]

345-3674 is the Field Replacement Part Number but I suspect that it will come uncharged even though the parts manual refers to a "charged" accumulator. Charged accumulators cause all sorts of transport issues because they contain gas under pressure.

Digressing it's weird that the even if the accumulator piston seals had failed there should have been no pressure in the hydraulic system when you hooked up to the accumulator charge port and therefore your gauge should have registered a bit fat zero. Did you make sure the depressurize the hydraulics after shutting down the engine and before connecting the gauge.? I suspect not. The required steps are as follows: -

1. Move the machine to a smooth, horizontal location. Move the machine away from other operating machines and away from personnel.
2. Lower the work tool to the ground. Stop the engine.
3. Engage the parking brake.
4. Place chocks in front of the wheels and behind the wheels.
5. Turn the engine start switch key to the ON position.
6. Move the pilot valves to all positions in order to release the pressure in the hydraulic system. Move the steering wheel in both directions in order to release the pressure in the steering system.
7. Turn the engine start switch key to the OFF position.
8. If the machine is equipped with load control valves, release the pressure in the lift cylinders and in the tilt cylinder. To release the pressure in the lift cylinders and in the tilt cylinder, perform the Operation and Maintenance Manual, SEBU8028, "Equipment Lowering with Engine Stopped". To remove the load control valves, refer to Disassembly and Assembly, KENR5211.

 

[XSKIER]

Boom was down without work tool attached. There was no pressure on the loader side. Is it possible that a high speed collision could spike the pressure in the accumulator and force the oil to the nitrogen side?

 

[Nige]

Did you relieve pressure in the steering.?

 

[XSKIER]

No, I did not relieve steering pressure, brake pressure, fuel pressure, tire air pressure, cab a/c refrigerant pressure, or bowell pressure. Once all of those are in relief, I will update this thread.

 

[Per Eriksson]

Ok, mr smartass, we just want to make sure all pressure in the liftcircuit is relieved before pulling the tools out.

• Park the machine on a hard, smooth, level surface. The location should also be dry and free of debris.
  

• Permit only one operator on the machine. All other personnel should be kept away from the machine.

• If the machine is equipped with a ride control system, place the ride control system into “Service”.mode. Refer to “Ride Control” in this Operation and Maintenance, "Operator Controls" section.
  
  
  
  Illustration 1 g02727672

• Position the bucket or the work tool just above the ground at a slight downward angle. This position will ensure that the head end of the lift cylinders is pressurized.

• Engage the parking brake.

• Turn the engine start switch to the OFF position.

• When the engine has stopped, turn the engine start switch back to the ON position so the pilot oil can reach the main valve.

• Move the implement lockout switch to the UNLOCKED position.

• Move the lift control lever to the FLOAT position and the tilt control lever to the TILT BACK position at the same time. This action allows the bucket or the work tool to tilt back while the boom is lowered.
  The bottom of the bucket or the work tool should rest flat on the ground. The weight of the linkage should be supported by the ground. The pressure from the head end of the lift cylinders and from the ride control accumulator is now vented to the hydraulic tank.
  

• When the bucket or the work tool has settled to the ground, move both control levers to the HOLD position. Cycle the control levers through all positions several times in order to purge any remaining pressure from the implement hydraulic system. This action will completely drain the pilot accumulator.

• Turn the engine start switch to the OFF position.

• Slowly loosen the hydraulic tank filler cap in order to release the pressure from the hydraulic tank.

• After all of the pressure has been released, tighten the hydraulic tank filler cap. The hydraulic system pressure has now been released. Hydraulic lines and components can now be removed. v

 

[cuttin edge]

No, I did not relieve steering pressure, brake pressure, fuel pressure, tire air pressure, cab a/c refrigerant pressure, or bowell pressure. Once all of those are in relief, I will update this thread.

The man took the time to explain the entire process. If you already know what's wrong, stop asking stupid questions on here, and fix it yourself.

 

[XSKIER]

Removed the accumulator and dumped out about a quart of hydraulic fluid. Filled it with 100lbs of shop air and observed no air leaks. Reinstalled, works good with a light work tool, but I would imagine that a yard and a half of dirt in the bucket would be too much for the small charge. Will obtain a charging tool, and update the thread when it's back to 270 psi.

 

[Nige]

A comment. The correct gas for charging your accumulator is dry nitrogen because it's inert. Their should be a sticker somewhere on the accumulator to that effect.
By charging it with air you have introduced oxygen into close proximity of a flammable liquid under high pressure. It may be only charged with 100psi of air but when the hydraulics get up to relief and the piston in the accumulator moves that air could be at anything up to 3000psi.
You should exercise caution. With that mix there is the potential for an explosion. I would suggest to remove the air until you can get hold of both the correct charging tools & nitrogen.

 

[XSKIER]

I finally got my charging regulator today. So, after driving around for a week with 100 lbs of shop air in the accumulator I purged out the air. This time no oil was present. I filled to 270lbs with nitrogen, and tested successfully. So yes, I did have to answer my own question in that the accumulator can become oil soaked and overcharged by an impact at speed. For now it appears that this oil soaked and overcharged accumulator is back in service without replacement.