Lift Table Hydraulic Ram Lowering Issue

Hi Everyone
I am seeking some assistance with a hydraulic ram. I obtained the table with a fault and thought it was simply a case of needing to bleed the ram. Once fully bled, it was evident that the ram would not retract.

I have attached 4 pictures, the first is of the table itself (or very similar).

Note that the table does not have the more recent cable release mechanism but a rod type arrangement which turns a release valve. The other pictures show the RAM with components removed and labelled to indicate their respective ports.




The issue I am having is that the ram will not retract. While bleeding the ram it was able to, however once I have finished bleeding the ram then it no longer retracts. I have an instinct that there is a spring missing in the release valve on the basis that the other ports have springs and balls.

Does anyone have any thoughts on the release valve (A) components, does it look correct? Am I missing something, should there be a ball in the release valve or something else?
Any help appreciated,
Many thanks
Freddy

freddy602 said:

Hi Everyone
I am seeking some assistance with a hydraulic ram. I obtained the table with a fault and thought it was simply a case of needing to bleed the ram. Once fully bled, it was evident that the ram would not retract.

I have attached 4 pictures, the first is of the table itself (or very similar).
View attachment 283580
Note that the table does not have the more recent cable release mechanism but a rod type arrangement which turns a release valve. The other pictures show the RAM with components removed and labelled to indicate their respective ports.
View attachment 283583
View attachment 283581View attachment 283582


The issue I am having is that the ram will not retract. While bleeding the ram it was able to, however once I have finished bleeding the ram then it no longer retracts. I have an instinct that there is a spring missing in the release valve on the basis that the other ports have springs and balls.

Does anyone have any thoughts on the release valve (A) components, does it look correct? Am I missing something, should there be a ball in the release valve or something else?
Any help appreciated,
Many thanks
Freddy

Click to expand...

what does the parts manual show.

This is a standard HF/Clarke Chinese unit, manual is avail online.

I have a table similar to that one. Not long ago I had a problem with it raising so I took the little plug out and filled it to the opening with fluid. It went up fine after I filled it but then it wouldn't go down. Apparently being a self contained unit without any kind of reservoir, you need space in the cylinder for the fluid to flow back into. I drained about a cup or two out of the cylinder and it worked fine. Kind of a DUH moment for me. Make sure it does not have too much fluid in it or it will not go down. Nowhere for the fluid to go.

crossthread said:

I have a table similar to that one. Not long ago I had a problem with it raising so I took the little plug out and filled it to the opening with fluid. It went up fine after I filled it but then it wouldn't go down. Apparently being a self contained unit without any kind of reservoir, you need space in the cylinder for the fluid to flow back into. I drained about a cup or two out of the cylinder and it worked fine. Kind of a DUH moment for me. Make sure it does not have too much fluid in it or it will not go down. Nowhere for the fluid to go.

Click to expand...

Usually with over filling, the leetle rubber plug just blows out when the table is sent down. (along with a mess of oil & air all over the place)

No. Nothing like that ever happens to me Digger. And I never lose small parts that are launched by my wire wheel either.

@digger doug
I have been looking online at various manuals but I can not find the one relating to this ram in particular. The clarke HTL300/HTL500 is a cable type mechanism rather than a rod/lever.
I have attached a picture of from the manual I have here but it does not show an exploded parts diagram of the actual ram.


@crossthread
Good call on the space in the cylinder, in this case there is no rubber plug, it is a short allen bolt. I released this bolt, allowed a volume of oil out and then the ram seemed to work correctly.

So, the saga then continues, I tested to ensure that the ram expands and contracts. This worked without issue although it was not under any real pressure.
Once I re-attached it to the table, a different problem presented itself, it will not raise take any pressure from the table. It holds the weight of the table, I can let the table down, but it will not pump the table up.
I have tried various adjustments on valve C (relief valve?) from the original pictures to no effect so far. It seems as though the pump cylinder or relief valve is not actually pressurizing the circuit, i am thinking that it is not actually closing the circuit back to the oil reservoir.

Any suggestions appreciated.
Many thanks
Freddy

I have a Wel-Bilt lift table that has a pump that looks exactly like yours. I don't have a manual.

I had it apart some months ago, to replace the seals, but I don't remember all the details.

I am pretty sure A (lowering ball ) does not need a spring.

C is the pressure relief valve. Try tightening this up to increase the lifting capacity.

A common problem with these type of units is that the seals deteriorate from age and fall apart. The chunks of

broken rubber seal material get into the check valves and keep them from closing.

The pump intake check ball needs a very light spring, (or possibly no spring) to allow the pump piston to fill.

@js412000

I have been looking for lots of diagrams of these pumps and following your pointer regarding the pump intake check ball, the issue is now solved.

To resolve the issue, I removed the spring next to the intake checkball as indicated in the picture below.



Thank you to everyone for your replies.
Many thanks
Freddy