I subscribe to a hydraulic news letter as seen below. what is a double rod cylinder as mentioned above? I have one of my Lulls that would creep down to the gound over night or with a load it will settle on the scaffold in 10-15 minutes if it is 4-5" above the scaffold. What is my problem? No external leaks just small weep when in use. I am going to rebuild the cylinders soon I guess I'll check the cylinder bores visually an by feeling them? Any other tips? This machine has been doing it since I got it in 1985 with a few hundred hours on it. I was thinking the internal seals were crappy from day one? Thanks for any help you can offer.
The double rod cylinder has a rod on bothe ends and the piston in the center so it uses the same amount oil either direction.The only place I see them used is on steering axels on farm tractor's and maybe some front loaders.It Make's the seering wheel rotate an equal amount of time's whether turning left or right.Most of my equipment has some type of suction screen,I could see how a fine screen might hurt the pump on the cold weather start up's,"thick oil".I know what he's talking about the cylinder eqilizing pessure and locking even without a seal on the piston.In a classroom on a chalk board He could probley back up his theory.But with that said, my experience is if you halve a cylinder creeping its the seal on the piston or in the valve body.On a crane and some tellehandlers ,"Load check valves at the base of the cylinder act as safetys if you blow a line. they also help "creeping" if your valve body has some internal leakige.I would rebiuld the cyliders and valve body .Hope this help's.
Thanks for the tips the load check cylinders are now exstinct so I have to spend 1,000 to get new ones. I have to buy a pair to match 500 each. I guess I'll try the cylinder rebuild first.
Has anyone purchased any of Brendan Caseys hydraulics books? What are they like?
lot of info here from him http://www.hydraulicsupermarket.com/technical.html
I guess you can say whatever you want, in a book or magazine, about certain things in hydraulics. Nobody can directly disagree with what you said. I will say running a pump without a suction strainer is the kiss of death. Hydraulic oil does not always go through a return filter before it gets back to the tank. Blown packing, internal linings of hoses and debris that got dumped into the tank are the kinds of things that those strainers catch. More than once I have found someone filled the hydraulic tank with dirt and the strainer saved thousands of dollars in repairs. Have a major failure of a motor or cylinder and that strainer will look awfully cheap compared to a new pump. I've seen more than my share of leaking piston packings and drifting cylinders. You have three areas that can leak internally and I make it a practice of working from the least expensive to the most. Cylinder packing is relatively cheap and pulling the cylinder apart is easier in most cases than changing a valve body. It's not uncommon to have a barrel swelled in the middle or out of round. I have a bore gauge I use when I pull cylinders down but it doesn't go all the way into most cylinders. At the least you should run your hand into the barrel as far as possible and feel for grooves or nicks. You might try swapping the load check cartridges from side to side before you pull the boom cylinders. Good Luck!
thanks!
i would say your cylinder is bypassing internally. every forklift and telehandler i have had that crept down and wasn't pizzing hyd. fluid everywhere had a leaking internal seal. RE-packing the cylinders always solved the problem
Few weeks it will be repacked. I am finishing another machie this weekend second psiton. Then it is four more pistons to go after that. Then 12 steering cylinders :bash:bash This is the only machine I ever had that leaked down over night. It did it from the day I got it in 86 when it had 200-300 hrs. hope the bore isn't massed up. I guess both lift cylinders have to leak for it to go down?
The Packing in the cylinder is the easiest fix ... but in your Lull ..there's a directional control valve and possibly a holding valve .. if the machine is shut off and you move the boom lever into the down position and it sinks down ..its more than likely it does not have a holding valve.. Good luck with it ......in most case's where the boom creeps down the holding valve is the culprit ... if it dosent have one ..then the packings ..or control valve should be explored ..
It has a safety valve on each piston. This machine has done this since almost new. New safety valves are 500 each. Their is no parts for the ones on their. You have to buy the updated models and new hoses. I have no clue what parts are in there. I'll pop a picture tomorrow and post it here. Thanks all for the help here.:drinkup
You have to buy the updated models and new hoses That kinda says it all right there ...updated parts is a close as your gonna get to "we have had problem's and this is the solution "Ive had different machines that creep-ed and the parts you get are not entirely like the one's on there ...and the price is a little more.... it sucks when that happens ... Case in point ...having to change an entire transmission mounting bracket , just to change a $100 pneumatic cylinder .. a total cost in dealer parts at over $900...and get this ..if i didn't change all that gear just to re-and re the cylinder ..i would have voided the power train warranty .. some days man
Well if I have to buy two new safety valves then I have a spare for the other machine where the little knob broke off the valve. Thanks for the help!
If after you repack and it still creeps or even before you repack you can see ware the problem is. Just install ball valves on the lift and return on each cylinder raise it shut the valves. If it doesn't creep much it's the control valve. Pilot popit relief valve, warn, warped or bad spool. Everything I have creeps, Good luck.
I recently acquired a CAT E120B excavator and realized I had a leaking piston. Would like to know what it would cost to bring it to a shop for repair, and secondly, what special tools I would need to repack the piston myself. I had not previously owned heavy equipment. Thanks
I don't know what a shop charges these day's,I rebuild all my cylinders.It generally dosent take to many special tools,spanner wrench ,oring pick,socket set.I just rebuilt an out rigger cylinder and posted it in the crane section under "out rigger repack"with several pictures,it might help.Welcome to the forum strzempk83.
The tools aren't special in theory, but the piston retainer nut or bolt can be VERY tight or Very large.
For me they won't do it in the field so that means move the machine and that is 800 two ways. I'm guessing they would want at least 1500 for my hoist cylinder in addtion to the move. They would not even give a price even on a best case senerio. I can now do large 5' hoist cylinder in 3-4 hours. I didn't do the machine that creeps yet.