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  1. #1
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    Default Air hydraulic press - retraction problem.

    I bought a 50 ton air hydraulic press a few months agoTWM 50 ton.png. When I first got it the ram was retracting fully and fairly quickly, however I discovered quickly that I was only getting 160mm of ram stroke and not the 200mm of stroke that was specified and this was because I was running out of oil. I added the lightest hydraulic oil I had at the time which was ISO 46 to 80% of the reservoir capacity which had only been half full. I was then able to get the full 200mm of ram stroke, but then the ram was roughly about 15mm short of being fully retracted (slower to retract) (fairly hard to push back by hand). I spoke to the suppliers mechanic who said ISO 32. I got some ISO 32 and put that in after draining all the other oil out, with the ISO 32 in the press it still wouldn't fully retract and actually was close to about 20mm short of retraction so the problem was getting worse. When I was removing the ram cylinder I left it out the 20mm to see if the ram would spring when I undone the hydraulic hose - no joy. I sent the ram cylinder away to the supplier who sent it to the wholesale distributor for repair/replacement ( when I removed the ram cylinder I found I could pull the ram out fairly easily so there was no tension on the return spring ie broken spring, or detached spring). The ram cylinder came back repaired and with tension on the spring (the ram cylinder uses an internal spring to retract the ram). I re-installed the ram cylinder on Saturday (still with the ISO 32) and the ram still won't fully retract. I left the ram out about 25mm and removed the line but it didn't spring back though I could push it back by hand fairly easily.
    I googled a lot of manuals of basically the same presses over the weekend and all but one was saying '22#( ISO6743)hydraulic jack oil' the other was saying 32 grade hydraulic oil. Does anyone know whether this might be just an oil problem ie the iSO32 is just a bit thick, one hydraulic guy I spoke to this morning suggested that the return spring is to weak which is what I originally thought from the get go but it did retract well originally.. The opening on the elbow on the cylinder where it connects to the hydraulic hose is fairly small about 4mm at a guess - with the hose disconnected I can push the ram back fairly easily but it's harder to push when its hooked up. The press has been bled so it's not an air problem. Sorry about being so long winded just after some ideas before I buy some ISO 22 hydraulic oil which is my next step and if anyone has an air hydraulic press with an internal spring what oil are you using ?. Thanks in advance.

    All The Best steran50 Stewart

    The shortest way to do many things is to do only one thing at once.

  2. #2
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    Default

    I think that if you can push it up to the end of its travel by hand then the problem is not the oil, the spring was likely made out of recycled rickshaw wheels and has not sprung back to its full length after being compressed, at a guess.....

    I might mention also that it is a good thing you changed the oil, am sure that the oil that is used in chinese hydraulic equipment is extracted from fish out of the yangtze river.

    cheers, shed

  3. #3
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    All I can tell you that wit my garbage Chinese 40 ton press cyl as soon as I put decent seals in it it stopped retracting because the return spring is pissweak.

  4. #4
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    ISO 32 is all we ever used in systems like these.
    I`d say the return spring is the problem.

    Tony

  5. #5
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    Hi Guys,

    A guy that I know has a press similar. He has fitted a plate over the ram and two springs externally for the same reason. I don't know if he has removed the original spring.
    Best Regards:
    Baron J.

  6. #6
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    Thanks for the replies. I messaged the supplier today to let them know that the Ram still wouldn't fully retract and they were suggesting a new ram cylinder but they are going to talk to the wholesale distributor about it. I don't think another Ram is going to fix the problem as they are probably all the same. I'm inclined to agree with shedhappens in that it's a weak spring, because when I had the hose off I could push the ram back the last part easily so there was only a little resistance there. Actually the original hydraulic oil looked good, though I remember that my DM45 Mill Drill had recycled oil in it and I know that because I had the oil tested to find out it's viscosity. I think the seals in these presses are ok quality judging by the spare seals that I asked for and the supplier gave me when they sent the Ram back to me. I had thought about external springs which is quite do able though I would like to keep it like this if I can. I'm going to wait and see what the wholesale distributor wants to do (if anything) and if no luck I'll pull the ram apart and see if a hydraulic shop or engineering supplies can help with a better spring.
    All The Best steran50 Stewart

    The shortest way to do many things is to do only one thing at once.

  7. #7
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    Had a similar sort of issue years ago with the clutch in a car, rebuilt engine and new clutch, clutch slave was extremely reluctant to release more than a couple of mm after being depressed. The issue was a crack in the inner layers of the flexible hose connecting into the slave, when you depress the clutch the pressure entered the crack and significantly reduced the hose passage cross section, but still allowed flow to the slave cylinder. Release the pedal, and a small amount of return flow would occur but fold the reduced cross section of the hose and further reduce it, effectively blocking the hose. I.e the area with the crack effectively created a check valve in the hose. That hose was a reinforced rubber one and 20+ years old, whereas your hose is most likely PVC and only a year or so old, but it might be worth while removing the hose and checking that it has not been substantially closed at one end when they crimped the fittings on.
    I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.

  8. #8
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    Keep on the retailer/wholesales back for it to be repaired.

    Use to get stuff come into the shop I was at for repairs after the warranty had run out.
    Soft parts, seals and hoses were generally off the shelf so not had to replace.
    Hard parts are a whole different story. Parts were not available or if available could take months to turn up.

    If its not a name brand it can be a real headache.

    Tony

  9. #9
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    Quote Originally Posted by shedhappens View Post
    I might mention also that it is a good thing you changed the oil, am sure that the oil that is used in chinese hydraulic equipment is extracted from fish out of the yangtze river.
    does that mean its got a lot of heavy metals in it, or just mud?...with the odd dead fish?

  10. #10
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    Quote Originally Posted by eskimo View Post
    does that mean its got a lot of heavy metals in it, or just mud?...with the odd dead fish?
    Yeah I guess so...... you don't really know what you are getting, I remember reading something somewhere a few years ago where a bloke reckoned his chinese cutlery set was radioactive....think about that next time you are enjoying a nice juicy T bone

    cheers, shed

  11. #11
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    Quote Originally Posted by shedhappens View Post
    Yeah I guess so...... you don't really know what you are getting, I remember reading something somewhere a few years ago where a bloke reckoned his chinese cutlery set was radioactive....think about that next time you are enjoying a nice juicy T bone

    cheers, shed
    Thats the new cook while yer cut knife set
    ....................................................................

  12. #12
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    PB1.pngPB2.pngIt's definately not the hose Malb, the hose looks like reinforced rubber to me. As I stated at the start of the thread I have actually undone/removed the hose when the ram was still partially out (where it stopped retracting). The wholesale distributor rang me yesterday to apologise about the problem. They said that when they repaired my ram cylinder they shortened the spring a bit. They just pulled another unit out of its box yesterday and it's the same. They have informed the factory in china about the problem, but as they said sometimes they just don't listen. Unfortunately there is nothing they can do at the moment, they have my name and number an if anything develops they will let me know ( I could have been pushy, but I could tell the Guy was being genuine). They suspect that all the presses are like that, but I'm the only one thats complained.
    I do know from looking at the different manuals for the same 50 ton presses with the internal return springs that there is two methods of holding the springs in place. My press spring is open top and bottom and uses two internal nuts (actually round rod threaded outside and internally) top and bottom for example. A socket head cap screw or similar is threaded from the outside into the 'nut' to secure the spring. The 'Baileigh' press for example uses one internal nut at the bottom of the ram cylinder and a cross pin at the upper part of the ram cylinder (the spring has a hook at one end and is open at the other end). When I get a chance I'm going to have a look at modifying my cylinder to take a cross pin at the upper part of the ram cylinder. I'm thinking that going that way is going to give me more chance to fit a slighter shorter stronger spring and the cross pin will stop the spring turning whilst I screw a long socket head cap screw into the internal nut at the bottom. I will most likely be talking to a hydraulic place or engineering supplies to get a suitable spring. I know I can fit external springs as well, but I would like to keep it the way it is if I can. The local garage that I used to do RACV for has just bought a 50 ton press as well and it uses the second method of holding the return spring. They haven't used there press yet, but at least I have one to physically look at and I will be checking with them next week or so to see how there's is going.
    I've just added two screenshots of from the Baileigh Manual which shows the spring is held the 50 Ton SGS press is the same. I'm not so sure BTS as the hydraulic hose on my cylinder enters on the side about where the pin would go where as the Baileigh, SGS and the Summit (local garage has the summit) brand of presses have the hydraulic attaching to the middle of the top of the ram cylinder. I need to check the press at the local garage to check the position of the cross pin in relation to the hose entry on my ram cylinder.
    Last edited by steran50; 23rd Aug 2019 at 08:18 AM. Reason: SCREENSHOTS OF SPRING HOLDING
    All The Best steran50 Stewart

    The shortest way to do many things is to do only one thing at once.

  13. #13
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    I don`t know that you will be able to convert to pin retainer setup.
    Enerpac use this system quite a bit. The cylinder bases have extra meat in them so they can be machined to take the pin.

    Nothing wrong with the 2 bolt system. Depending on construction usually bolt one end up first, assemble the ram then fit the second bolt.

    Tony

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