Cat 277c Hydraulic Accumulator Precharge Pressure

[Quki22]

Replacing the hydraulic accumulator on my Cat 277C (JWF01714) and the label states 0psi precharge but tech is stating that it needs to be precharged to approx 280psi. Has anyone come across this before?

 

[Nige]

Slightly confusing I know but 352-6990 is an UNCHARGED accumulator sold as a service replacement.



Shipping charged accumulators requires compliance with the same sort of regulations that are required for shipping explosives. That's the reason why a lot of "service replacement" accumulators sold in the Parts system are shipped uncharged these days.

Unless it contains nitrogen gas under some sort of pressure an accumulator can't do it's job. The top of your photo is cut off. Does the new accumulator have a charging valve on the top like in the illustration below.?

 

[Cmark]

New accumulators come uncharged. It's to do with airfreight safety regulations. If you don't have the equipment to charge it yourself, it's cheapest to take it to someone who can charge it before you install it.

 

[Nige]

New accumulators come uncharged. It's to do with airfreight safety regulations. If you don't have the equipment to charge it yourself, it's cheapest to take it to someone who can charge it before you install it.

That would probably be the best way TBH.

 

[Nige]

the label states 0psi precharge but tech is stating that it needs to be precharged to approx 280psi.

Acksherley the precharge pressure listed in the 277C Service Manual for that particular Part Number of accumulator is 130 ± 15 psi.

 

[Quki22]

Sorry about cutting the photo off. Yes it has the charging port on top

 

[Quki22]

They set it to 280psi. I guess I need to go back and have them set it at 130. The one that came out said to charge to 130 but it is a sealed unit. So I thought maybe the precharged changed with the new style.

 

[Nige]

They set it to 280psi. I guess I need to go back and have them set it at 130. The one that came out said to charge to 130 but it is a sealed unit. So I thought maybe the precharged changed with the new style.

The procedure for checking the gas pressure of a sealed precharged accumulator is somewhat different that for to charging/checking an uncharged one. See attached which also mentions the precharge pressure specification.

If you want a look at the REHS5464 charging procedure (35 pages) please ask.

 

[Quki22]

Thanks again Nige. I will go back to Cat and have them relieve the pressure to 130psi. Install it and go from there!!!

 

[Nige]

I will go back to Cat and have them relieve the pressure to 130psi.

You mean to say it was a dealer that charged it..? When you go back ask them is their SIS broken........!!

 

[Quki22]

Yes it was cat dealer that charged it. I went to see them this morning and explain my concern. They told me that for the new part number this is what the charge is. I told them that I thought the charge was related to the system pressure it is working with. So at a lost. Will it hurt anything if it is over charged?

 

[Quki22]

I also shared to document you sent me. That’s when they told me that was for the old part

 

[Nige]

They told me that for the new part number this is what the charge is.

I'm going digging. I have a new pick & shovel to work with but this may take a while.........

 

[Quki22]

Thank Nige. Let me know if you need any info.

 

[Nige]

Well my digging in all sorts of areas normally regarded as "not open to the public" revealed a grand total of nothing.

One of my contacts wrote thusly (referring to the 280 psi precharge pressure your dealer says is correct) - "I have no idea where the dealer plucked that number from" and "I wouldn't hesitate precharging it to 130psi as per the current T&A documents. I can't see anything that would make me consider charging it to anything else."

So my suggestion is the following. Get back to the dealer and ask them very nicely to provide you with documentary proof based on your Serial Number why the accumulator should NOT be charged to 130 ± 15 psi as stated in KENR5113 (attachment in Post #3) that applies to your JWF-prefix machine.

 

[Quki22]

Will do. Thank you

 

[Quki22]

If I were to decide to take it else where to get it corrected, who does this kind of work or is Cat my only choice

 

[Nige]

If I were to decide to take it else where to get it corrected, who does this kind of work or is Cat my only choice

You would need a mechanic who has a nitrogen charging kit containing the correct connector (there are various) to fit the charging valve on the top of the accumulator. At this time you need to refer to REHS5464 which is attached.

 

[Quki22]

So I was searching the internet on this issue and came across this from AVSparts. I highlighted the spec that calls for a pre charge of 261psi. Thought I share to see if anyone may recognize where this info may have come from.

 

[Nige]

I highlighted the spec that calls for a pre charge of 261psi. Thought I share to see if anyone may recognize where this info may have come from.

Excavator application. I found the same text that you found in AVspare in the Specification section of both KENR9854 (316E) and KENR5513 (320E RR), but nowhere else.

Thinking out loud - I wonder if someone at the dealer had replaced an excavator pilot accumulator recently and instead of looking up the precharge pressure spec based on your JWF Serial Number simply assumed it would be the same pressure that the excavator accumulator used.?