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.


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