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Discussion Starter · #1 ·
Not farm related,but maybe someone on this forum has an answer.I work in residential construction and use a picker truck.For the last three winters the telescoping cylinder creeps down,never at all any other season.We were told this is because of ice crystals in the oil so we put on water absorbing hydraulic filters,but still have problems.Does anyone know of a way to absorb tiny amounts of water from the oil tank?Draining the entire system would be a major task because a large percentage of the oil is in the large cylinder inside the boom.Any thoughts and advise would be appreciated
 

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i have put a liter or two of methyl hydrate in my boom trucks, seems to work well. a bulk oil dealer probably has a better product. i broke my three hundred dollar yard light from frost in the valves.
 

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Just a thought, could it be a seal on its way out? If it is starting to get hard and then gets cold in the winter, maybe it would shrink a bit and let some oil by pass? I can't see ice crystals in the oil, as stated above it should separate from the oil.
 

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As far as I know water is an incompressible fluid. I don't know how old the equipment is but I would suspect that it may have a hydraulic leak across the piston or in the control valve you run the ram with. As was pointed out, water will pool to the bottom of the reservoir and if there is water in the system, you should be able to open up at the bottom of the reservoir and see if there is any water present in the system. It would take serious turbulence to stir this water up into the oil. If the oil is foamy, you may have air entrained in the hydraulics. Air is compressible and will cause major problems. Examine the fluid in the tank and see if it is clear.
 

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I would put some winter grade diesel fuel in your hydraulic oil. Both paraffin and a small amount of absorbed water is in most heavy petroleum products. The additives in light diesel fuel will keep them both liquified. This is essential in a diesel system to allow them to pass through the paper in the fuel filter. I would think adding 5% would solve your problem.
 

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What make of picker and what size or model:confused:

There are lock out valves on both the boom lift and boom telescopic cylinders that only should open when pressure is applied. There is also a synchronizing valve that only operates under pressure if you have more than one live section in the boom.
If you have undesired movement, it has nothing to do with your oil, you got a malfunctioning valve. It is common that some problems only arise in cold operating conditions.

As for oil, you should be running ATF at least for winter temperatures.

I was one of a team of three who babysat the oldest 28 truck fleet of pickers in the Alberta oilfield for many years...got just a bit of experience with this kind of issue;)
 

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Any time we have had condensation in trans-hydraulic it turns creamy and foamy and looks like snot. If that was going on, you would see it right away, and the only cure is to flush it all out and change the filters. By all means inspect the oil to see that it is clear, but I'm inclined to agree with AB and blackdirtfarmer... I think you have a valve or old hardened seal that are letting oil escape in the cold weather.
 

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Discussion Starter · #9 ·
This is the way it was explained to us,a large percentage of the oil is in the cylinders where any water can settle out and freeze,this can happen through out the day even if the pump is running,oil goes through the pump to the relief and returned to the tank.When the crane is used this ice breaks up and interferes with the seals in the cylinder.If we retract and extend the cylinder it occasionally throughout the day it seems to help.
Alberta Buck this is a National crane.Model #671C,we have hydraulic oil in it.It is mounted on a 91 International 4900,I believe the crane is the same age.We are the third owners,so not to sure on its age.The reservoir holds approx 50-70 gallons and I would guess the system holds nearly that much again(very big cylinders).What is the best way to change the fluid?The boom cylinder is the only one out of eight that is accessible without major disassembly.I might be better off to let someone else do this one,I don t want the liability issues that this guy had this summer.4814
 

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Creamy, foamy, and cold day tells me that you have a leak between the tank and the pump. When it is cold the fluid is thick and makes the problem more noticeable. It is sucking air in or your oil is too thick. Depending how deep the suction tube is in the oil can also be a problem in the cold, if so with all cylinders retracted adding oil above full may cure the problem. Look closely at the pump intake system you may find one of these problems. The foam is from the air in the system. I can bet money your pump has a wine to it caused by cavitation (the sound of the air bubbles popping when they are compressed in the oil)
 

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This is the way it was explained to us,a large percentage of the oil is in the cylinders where any water can settle out and freeze,this can happen through out the day even if the pump is running,oil goes through the pump to the relief and returned to the tank.When the crane is used this ice breaks up and interferes with the seals in the cylinder.If we retract and extend the cylinder it occasionally throughout the day it seems to help.
Alberta Buck this is a National crane.Model #671C,we have hydraulic oil in it.It is mounted on a 91 International 4900,I believe the crane is the same age.We are the third owners,so not to sure on its age.The reservoir holds approx 50-70 gallons and I would guess the system holds nearly that much again(very big cylinders).What is the best way to change the fluid?The boom cylinder is the only one out of eight that is accessible without major disassembly.I might be better off to let someone else do this one,I don t want the liability issues that this guy had this summer.4814
Yikes, hopefully no one got hurt when your picture took shape:eek: That is classic example of the results of improper operation.

As for yours, on a National, there is a valve on each load carrying cylinder, I believe they call them holding valves. These are the lock out valves I mentioned earlier. Unless they are malfunctioning, these valves will not allow oil to leave the piston side of the cylinder except under pressure sensed when the control valve is operated. I strongly suspect there might be some crap or a damaged oring or such in one of your valves. If I recall correctly, you said the boom is retracting under load, so be fairly easy to pinpoint where the problem is, as I believe that model only has two live sections. Once its determined where the leak is occurring, time to go after it. And yes, can be a ***** when the boom gotta come apart to get at these components.

As for the packings leaking on the cylinder piston, I know many many out there will say I am full of it, but so many times a leaking valve is blamed on the cylinder and falsely diagnosed as the issue. Even if a cylinder has no packings of any kind, once in position, if all valves are closed, when placed under load there will be negligible movement. This is due to the simple physics of displacement and inability to compress or create a vacuum with a fluid. The two sides of the cylinder are not the same displacement, therefore if the oil is trapped within the cylinder, there is no where for anything to go...cylinder stays static in original position.

To drain out and change oil in the system is easier than you think. You need to determine your hydraulic flow on each cylinder, and with the cylinders retracted, you disconnect the line from the rod end of the cylinder and attach a hose extension so you can dump the oil into whatever you are draining it into. Assuming you have already drained and changed oil in the tank, using the picker hydraulics, extend the cylinder in question. As you do so, new oil fills the one end as the old oil is pushed out thru your disconnected hose. Once cylinder is fully extended, shut everything down, and reconnect your hose. Your boom extend cylinders will need to be done in proper sequence. Refill your reservoir as needed. Repeat as needed untill all are done. Easiest place to access hoses for any boom related cylinders is inside the house under the turret on most machines. Or you can go to the valve bank itself as well. Will never get every drop of old oil, but you will get most of it. We had built ourselves a portable electric hydraulic pump setup for testing components and flushing system after a pump failure, something like that is more convenient than using the picker's own system, but not likely you have access to such.

If your system is collecting water, this is occurring somewhere besides the cylinders, as when they are full of oil, it is impossible for condensation to occur. Source of that water needs to be determined and addressed.

If its not something you are familiar with, by all means, let someone who does deal with it. Safety is important and should always be high priority;)
 

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Discussion Starter · #13 ·
Yikes, hopefully no one got hurt when your picture took shape:eek: That is classic example of the results of improper operation.

As for yours, on a National, there is a valve on each load carrying cylinder, I believe they call them holding valves. These are the lock out valves I mentioned earlier. Unless they are malfunctioning, these valves will not allow oil to leave the piston side of the cylinder except under pressure sensed when the control valve is operated. I strongly suspect there might be some crap or a damaged oring or such in one of your valves. If I recall correctly, you said the boom is retracting under load, so be fairly easy to pinpoint where the problem is, as I believe that model only has two live sections. Once its determined where the leak is occurring, time to go after it. And yes, can be a ***** when the boom gotta come apart to get at these components.

As for the packings leaking on the cylinder piston, I know many many out there will say I am full of it, but so many times a leaking valve is blamed on the cylinder and falsely diagnosed as the issue. Even if a cylinder has no packings of any kind, once in position, if all valves are closed, when placed under load there will be negligible movement. This is due to the simple physics of displacement and inability to compress or create a vacuum with a fluid. The two sides of the cylinder are not the same displacement, therefore if the oil is trapped within the cylinder, there is no where for anything to go...cylinder stays static in original position.

To drain out and change oil in the system is easier than you think. You need to determine your hydraulic flow on each cylinder, and with the cylinders retracted, you disconnect the line from the rod end of the cylinder and attach a hose extension so you can dump the oil into whatever you are draining it into. Assuming you have already drained and changed oil in the tank, using the picker hydraulics, extend the cylinder in question. As you do so, new oil fills the one end as the old oil is pushed out thru your disconnected hose. Once cylinder is fully extended, shut everything down, and reconnect your hose. Your boom extend cylinders will need to be done in proper sequence. Refill your reservoir as needed. Repeat as needed untill all are done. Easiest place to access hoses for any boom related cylinders is inside the house under the turret on most machines. Or you can go to the valve bank itself as well. Will never get every drop of old oil, but you will get most of it. We had built ourselves a portable electric hydraulic pump setup for testing components and flushing system after a pump failure, something like that is more convenient than using the picker's own system, but not likely you have access to such.

If your system is collecting water, this is occurring somewhere besides the cylinders, as when they are full of oil, it is impossible for condensation to occur. Source of that water needs to be determined and addressed.

If its not something you are familiar with, by all means, let someone who does deal with it. Safety is important and should always be high priority;)
Thanks for that information AB.Your method of changing fluid is much simpler than I thought it would be.I can see the lockout valves on the boom cylinder,I'm assuming the telescoping ones are up inside the boom because they are the fail safe when a hose blows.Is there a way to get to them with disassembling the boom?Breather/filler cap on on reservoir was damaged,it has been replaced.
Thankfully no one was hurt in the accident pictured,the operator is up and running with a new rig.I myself would find it very intimidating to get back on the controls again after something like that.There was an another incident in Edmonton last year,operator was lifting trusses with a zoom-boom and rolled,the boom cut right through the house right to the foundation,again thankfully no one was hurt in that one either. Thanks again
 

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Thanks for that information AB.Your method of changing fluid is much simpler than I thought it would be.I can see the lockout valves on the boom cylinder,I'm assuming the telescoping ones are up inside the boom because they are the fail safe when a hose blows.Is there a way to get to them with disassembling the boom?Breather/filler cap on on reservoir was damaged,it has been replaced.
Thankfully no one was hurt in the accident pictured,the operator is up and running with a new rig.I myself would find it very intimidating to get back on the controls again after something like that.There was an another incident in Edmonton last year,operator was lifting trusses with a zoom-boom and rolled,the boom cut right through the house right to the foundation,again thankfully no one was hurt in that one either. Thanks again
On most pickers there are access holes in the sides of the boom sections, close to where the ends of the cylinders are. However, sometimes to actually access fittings or such, you need to remove the pin in the end of the cylinder and then slide the boom section outwards along with it's cylinder, till you can reach the necessary parts inside thru the access hole. If this is required procedure, the hoses should be long enough to allow doing so.
We had dual overhead cranes in one of the bays in our shop, so dealing with the boom sections was no big deal, as for a lot of work you require two sources of lift. But with some ingenuity you should be able to figure out something if you need to got that far.
 

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Reading this thread there are a few things I might be able to contribute.

Another way to change oil and flush the system is to drain the reservoir, remove the return and case drain lines and run to a waste oil container, then carefully inspect and clean the inside of the reservoir, make sure the suction ports and strainers (if it has any) are clean and clear of debris, then refill with fresh oil. Start and run your hydraulics making sure to operate all your functions one at a time almost immediately (because if it's open center your pumping oil through the valve and just draining your tank if no functions are being used). Run all cylinders through their full stroke and the winches until new oil is coming out the return line then shut down. You have to make sure you don't run the tank out of oil while your doing this but this will displace all the oil in the whole system. If your running a multistage pump you may waste some oil but you can get around this by running a function off each pump at the same time and when one is done reattach it's return line. This way would be less messy and complex and more thorough then taking lines off each function. There is no possibility of contaminated oil getting back into the tank this way also. Don't forget to replace the return filters after doing this. I used this method to do coil rigs all the time, our rigs were easy because they were closed center hydraulics so if you weren't operating a function oil didn't flow. The closed loop side was a little more complex but not bad as all my case drains were tied together into a single hose that returned to tank.

I don't know National cranes at all but the Manitexs and Weldco cranes I worked on all had single telescoping cylinders on them regardless of the number of extensions. Three section units used a cable system and four section units used two cable systems with a "shadow boom" inside the second stage. The holding valves for these were right on the bottom end of the telescoping cylinder, kind of a bugger to work on but you didn't have to remove the boom to do it. Also I think a leaking piston seal would allow the boom to creep because I don't believe the rod side of the cylinder had a holding valve so the oil was free to return to the tank, if it did it might pressurize the holding valve on the blind end thus allowing the boom to retract. The ones I worked on only had single holding valve.

A way to check your holding valve and cylinder is to raise your boom up, extend it a bit to a stage it's retracting then remove both lines. If oil is coming out the line from the rod end then it's the piston seal, if it's coming out the blind end then it's your holding valve.

Hope this helps and good luck.
 
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