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Hydraulic accumulator - what does it do and should I replace it?

materthegreater

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Could someone explain to me what a hydraulic accumulator does in a mini excavator? My 2009 Bobcat (Doosan) E60 seems to have lost its ability to relieve circuit pressure when shut off/key on. I'm suspecting the accumulator but want to make sure I'm understanding it's role first.
 

SLK001

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From my understanding, an accumulator is entirely passive - ie, no moving parts. The only way it could be screwed up, is that something broke upstream and parts are now clogging the entrance port.
 

Nige

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G..G..G..Granville.........!! Fetch your cloth.
From my understanding, an accumulator is entirely passive - ie, no moving parts.
Not entirely correct I would say. A piston-type accumulator has seals on the (moving) piston that can fail, in a bladder-type accumulator the (moving) bladder can rupture. Both types of failure can cause the nitrogen gas charge to be lost and under those conditions the accumulator will cease to function as desired, whatever function that might be. As @Vetech63 mentioned on many excavators the accumulator is only there to provide a limited oil supply to allow the equipment to be lowered if the engine is out of commission.

I've seen hydraulic systems where the accumulator was an integral part of the system and supplied additional oil flow for short intervals when the demands of the system were in excess of what the pump could supply.
 

92U 3406

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I've seen a few of those gas accumulators on the small stuff that are non-serviceable. Apart from putting in a gauge to see if the circuit retains pressure after shutdown I don't really know of any other way to test a non-serviceable one.

If it has a charge valve on it you can always hook the kit to it and see how much pressure is in the gas side. If its got oil in the gas side then the bladder is blown.
 

materthegreater

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Thanks guys, helpful info. I don't believe this one is serviceable, but I will look again for a port on the gas side. A new one is $87 from the garden excavator dealer so I'll probably just replace it.
 

Nelo

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Could someone explain to me what a hydraulic accumulator does in a mini excavator? My 2009 Bobcat (Doosan) E60 seems to have lost its ability to relieve circuit pressure when shut off/key on. I'm suspecting the accumulator but want to make sure I'm understanding it's role first.
It’s used as a shock absorber and some machines have a button to where it allows the bucket to free move only while traveling so the terrain doesn’t beat up the holding valves.
 

Welder Dave

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Can/does an accumulator give faster hydraulic response for a short time than just the pump alone?
 

materthegreater

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It’s used as a shock absorber and some machines have a button to where it allows the bucket to free move only while traveling so the terrain doesn’t beat up the holding valves.
Sounds like you are referring to use in wheel loaders. I'm referring to mini excavators.
 

materthegreater

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Thanks guys, helpful info. I don't believe this one is serviceable, but I will look again for a port on the gas side. A new one is $87 from the garden excavator dealer so I'll probably just replace it.
Turns out that $87 part has been superceded by a $200+ part. So I think I can live without it since it doesn't seem to affect the machine's function during normal use.
 

hvy 1ton

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I've seen a few of those gas accumulators on the small stuff that are non-serviceable. Apart from putting in a gauge to see if the circuit retains pressure after shutdown I don't really know of any other way to test a non-serviceable one.
If it shows no pressure when off and system pressure when running, the bladder is torn.
 

Vetech63

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Turns out that $87 part has been superceded by a $200+ part. So I think I can live without it since it doesn't seem to affect the machine's function during normal use.
It is probably tied into the pilot pressure system as most of that type are. It gives you just enough pressure to move a main spool with pilot pressure to lay your boom/crowd on the ground.
 

materthegreater

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It is probably tied into the pilot pressure system as most of that type are. It gives you just enough pressure to move a main spool with pilot pressure to lay your boom/crowd on the ground.
Yes, it used to do that, now nothing at all.
 
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