Hydraullic crane question

[Simon BarrParticipant @simonbarr48213]

I'm hoping someone here might have some hydraulics knowledge and be able to help me out. I have a Clarke 1 tonne hydraulic engine crane that I recently purchased second hand. It's obviously been left outside at some point in it's life but seems structurally sound and works OK.

In tests with a 56lb weight it dropped an inch or two over a couple of days, I thought this was acceptable as I won't be leaving anything suspended. As a precaution I changed the oil today and what came out was black so it wasn't a day too soon.

I used a brand new ISO32 oil which I thought would be suitable but it now drops a few inches in ten minutes with the same 56lb weight. Could this be an indicator of using the wrong grade of oil, perhaps it needs something thicker, or am I looking at some other problem? I have raised it to full height and lowered it a few times in case it needed bleeding but it still does it.

Any pointers appreciated.

Simon

[Simon BarrParticipant @simonbarr48213]

Have I used the wrong oil?

[StueeeeParticipant @stueeee]

Pretty well all this type of hydraulic stuff uses ISO 32 oil. It's possible that the previous owner has put in something thicker like ISO 68 to provide a temporary fix/bodge. Have you looked at the price of new ram/jack units? when my 2 tonne crane started to fail a year ago, i was going to strip it and fit new seals until I saw the price of a new replacement ram/jack weblink Bought one of these (probably from one of the many different other  sellers) It's Still working fine at the moment.

Edited By Stueeee on 02/07/2023 20:47:21

[not done it yetParticipant @notdoneityet]

It’s a one way ram, so unlikely to be the actual ram if it is not leaking oil. That leaves leak-back through the pumping mechanism. Fresh O rings should be a few pence as a fix – unless the castings have corroded. It is likely the lowering valve that is not seating properly and may need fettling (with valve grinding paste?).

It is worth investigating, at least – as nowt to lose. It may only need a good clean. Good luck.

[DalboyParticipant @dalboy]

Try something simple first and that is to flush the system out and strip and clean the release mechanism as any dirt will tend to settle at the bottom where that valve is. While at it you may as well check the pump unit seals/O rings as already suggested.

[Martin CargillParticipant @martincargill50290]

It will have a relief valve (to prevent overloading) these are normally a ball bearing pushed by a spring. They are often under a plug marked "do not touch" or similar. Take the plug out and remove the spring and ball. Clean the seat and the ball, then use a punch and reseat the ball with a sharp tap. Reassemble and test again.

[noel shelleyParticipant @noelshelley55608]

The most likely if its been outside is that the cylinder is corroded at the bottom or the release valve is not seating. Strip and clean out all the crud and try again. Look out for balls or small springs.Make sure the release valve is done up TIGHT. Noel.

[John Doe 2Participant @johndoe2]

Posted by not done it yet on 02/07/2023 21:36:01:

It’s a one way ram, so unlikely to be the actual ram if it is not leaking oil. That leaves leak-back through the pumping mechanism. Fresh O rings should be a few pence as a fix –

Yes, that's what I assumed, when repairing my car trolley jack. It had developed a leak past the pump piston, so I took it to bits, and the pump O ring was as hard as plastic, flattened, and it broke into three pieces, when I extracted it.

So I measured the ID, OD and cross sectional diameter. Unfortunately none in my O ring kit were close enough to fit correctly, so I contacted a hydraulic supplier to get a new one. One comedian wanted £10 + postage for a single ~13mm O ring !!!

I just ignored his email and got the nearest larger size O ring with the correct ID from my kit and filed down the OD and profile by spinning it mounted around a bolt in an electric drill, and holding a file against it. Fitted and worked perfectly.

(And, no; I never rely on the trolley jack to support the car; I always use axle stands before going underneath.)

[Maurice TaylorParticipant @mauricetaylor82093]

Posted by John Doe 2 on 03/07/2023 00:06:36:

Posted by not done it yet on 02/07/2023 21:36:01:

It’s a one way ram, so unlikely to be the actual ram if it is not leaking oil. That leaves leak-back through the pumping mechanism. Fresh O rings should be a few pence as a fix –

Yes, that's what I assumed, when repairing my car trolley jack. It had developed a leak past the pump piston, so I took it to bits, and the pump O ring was as hard as plastic, flattened, and it broke into three pieces, when I extracted it.

So I measured the ID, OD and cross sectional diameter. Unfortunately none in my O ring kit were close enough to fit correctly, so I contacted a hydraulic supplier to get a new one. One comedian wanted £10 + postage for a single ~13mm O ring !!!

I just ignored his email and got the nearest larger size O ring with the correct ID from my kit and filed down the OD and profile by spinning it mounted around a bolt in an electric drill, and holding a file against it. Fitted and worked perfectly.

(And, no; I never rely on the trolley jack to support the car; I always use axle stands before going underneath.)

Hi, I never trust axle stands ,always use short lengths of railway sleeper.

Maurice

[Nigel McBurney 1Participant @nigelmcburney1]

I have had a 1 ton garage crane,for a number of years, when collecting a stationary engine from a fair distance I took my crane on the trailer,I dismantled the crane and laid it flat in the trailer,did not use it in the end as the seller had a forklift,after that trip the I could not get the ram to lift,did the usual things ,bleeding,topping oil,draining oil (there was swarf in the oil) etc ,no luck ,concluded that it must be the pump valve not seating,no acess to the valve as it was well and truly staked in and as I mostly use the crane for lifting valuble engines and machine tool accessries I bit the bullet and bought a new ram,not that expensive, better to have a new ram than wreck a load which could be many many more times expensive. The one thought was that the ram on the crane had probably shipped from the far east and survived delivery shaking and banging and worked ok yet laying flat in my trailer for a mere 100 mile journey it shook some swarf into the valve. Rearding axle stands ,a friend many years ago had his car up on axle stands and was underneath pulling on a long spanner resulting on the stands tilting and the car rolling off onto him,resulting in some cracked ribs, I said at the time that I did not trust axle stands much prefering to use decent size timber blocks,and blocks front and back on the wheels on the other axle,to stop the gar rolling,I do now own sone axle stands which are used to keep my trailer wheels off the ground when stored for any time.Timber is so much safer less likely to slip,if you look back at old photos in steam days,traction engines were always up on very sturdy timber blocks during repairs.

[noel shelleyParticipant @noelshelley55608]

The operation of such devices is simple ! There is a pump, this draws oil from the resovoir through a suction non return valve and pumps it past a delivery non return valve into the ram, this causes the ram to extend. A second valve in the pressure circuit is opened to release the fluid back to the resovoir and the ram due to a spring or other force will return to it's closed or retracted position. If the pump seal is damaged it will leak or fail to raise pressure, likewise if the non return does not seat then no, or little pressure will be generated. In the case of the delivery non return it may cause the pump piston lift if faulty. If the ram seal is faulty then there will be an obvious external leak and the cylinder under load will retract. If the release valve does not seat properly then the ram will slowly retract, this may be very obvious or may take many hours or more. Replacing the seals should be easy, once you can get the seals, reseating valves may be more difficult. The passages the oil flows through are quite small, so using the right oil is important, to thick and the pump will be starved and try to pump air. A slow and steady pumping speed will be more effective the pumping fast. Ordinary hydraulic oil is 10w or iso 32, good for most oil cans and all general oiling. Noel.

[Peter SansomParticipant @petersansom44767]

I bought a 2nd hand hoist about 5 years ago. Shortly after purchasing it I was lifting a cast iron bath, had lifted it ca couple of days previously, no problems., It would not support the lift.

Pulled apart and found the ram seals had failed, Found replacement seals online, about 3rd the cost of a replacement ram and much cheaper shipping.

Peter

[Simon BarrParticipant @simonbarr48213]

Thanks everyone for your replies. It has given me a few avenues to go down. Knowing I've used the right oil is good to know.

I had kind of budgeted for a new ram (as a possible cost) before buying the crane so I know they are fairly cheap and I have ordered one today anyway. Given the oil I got out was black I am thinking maybe the insides might not be in the best order so maybe a replacement is best. However I am going to investigate the one I have further to learn what the insides are like and maybe fix it too if I'm lucky, then it can become a spare. The parts drawing in a manual I found online is a bit vague and doesn't even include the safety release valve. Clarke doesn't supply seals for this model any longer either.

I need the crane at the end of the week so hopefully one way or another it will be up and running again.

Thanks again, Simon.

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