This topic contains 8 replies, has 4 voices, and was last updated by Abdul Basit 2 years, 11 months ago.
- March 4, 2014 at 2:35 pm #25585
another scratch on the head for already 2 days, do anyone here have a kind heart to give some advice ,
we have a crane on one of our project site , the problem was the main hoist, within the range of 30 to 60 tons
its working normally, i mean normally no overheating of hydraulic systems , charge pressures were checked but normal, line high pressures were also normal
together with the servo pressures, but when the load exceeds 70 tons up to maximum the load drag down, i mean something like a mechanical crane that has a free
fall switch, the only thing is its not . The control sticks were working normally and we already change the small accumulator with new one just to make sure
its not the source of the problem, but the same trouble occur and during the occurrence of the problem the pressure reading on the high line pressures fluctuates a little with a zipper like sound,
its was not operators error because hes following the load chart,
the hydraulic circuit for the main hoist is a close loop with cooling system,
we already pull out the crane from the site for safety purpose,March 4, 2014 at 6:41 pm #29113
Rodel, is it a rexroth pump? You can check that the pressure over ride is not washed out or faulty. If no POR then I would check that the systems main reliefs are not causing you the grief. They are most likely port reliefs dumping pressure above your llift pressure. That would give you a muffled chatter or a lowd hiss if they are cracking and closing really fast, they will also produce a lot of heat In a hell of a hurry. The other place I would look would be in your hot oil shuttle, dumping too much oil to the low pressure side of the loop under higher pressure loads.March 5, 2014 at 1:38 am #29118
thnx RON !! that would be a big help!! ill try to check it out !!
i think a temperature gun tester might help me solve the problem,
because i come to think of it from high pressure to sudden drop of pressure or shall we say internal leaking
causes abnormal rise of temperature , so ill try to check all relief and shuttle valves also the hose pipe and fittings for signs of to much dumping of oil,
well i will try to check the pressure readings during higher loads from 70 tons up again just to make sure,
cause im sure of it that its not the pump or motor faulty cause the system is not overheating i mean no excessive heat occur.March 11, 2014 at 9:02 am #29131
hi guys !! its been a while since i posted this topic, we already solve the problem last day and i just wanted to share it with you guys
hoping it might give some points to anyone including me ! who will encounter this type of problem again.
well to someone who already encountered this problem it must be easy for them, but for me and to someone new to this field of work
it will be helpful,
during troubleshooting i remember the time when i was disassembling a 25tons LRT LORAIN rough terrain crane, although its smaller
but it came to my mind that the hoist system were quit similar although not in size but in design and structure,
their were clutch pack inside & also a piston like a power shift transmission.
so we remove it and well never mind the weigh cause its really a back breaking thing and disassemble it and their it is a bunch of disc
commonly we can see it on planetary gear automatic transmission clutch pack.
Their worn out so if it is burned out it should slip, that’s why during heavier loads the cable drag down or like free falling.
so it was not hydraulic issue after all, but the piston rings should be consider also.March 11, 2014 at 9:04 am #29132
HI RON thanx for the advice it gave me a hint that the problem was not with the hydarulicsMarch 11, 2014 at 6:32 pm #29133
Well, glad it helped out. Once the hydraulics were eliminated it forced you to think and work back to the source of the problem. Once the trouble shooting is over the fun goes away and it becomes just nuts and bolts. The burnt out clutch pack, on the winch?March 12, 2014 at 11:36 pm #29137
In essence it works like a brake spring applied hydraulically released so under load if one is burnt the n it causes slippage I have seen this on several cranes over the years. Good find and thanks for sharing.March 20, 2014 at 2:26 am #29147
yes RON it was the clutch pack on the winch !!
hope this info can help to anyobdy !!April 15, 2016 at 3:11 pm #35898
If out rigger have leaked than also hoist jerking while lift and lower the weight. To confirm this issue put solid Stoll under the out rigger beams and check the hoist with load.