Obviously the guy that wrote the spec was getting paid based on warranty claims. He must be a rich man (or gal) by now!
The only way to fail that spec is to cut the line!
jb
Loader Leaks Down
- Thread starter jimainiac
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Obviously the guy that wrote the spec was getting paid based on warranty claims. He must be a rich man (or gal) by now!
The only way to fail that spec is to cut the line!
jb
Eric_Phillips
Platinum Member
I am looking at a valve that has a spec of 15ml/hr at 120bar. That is 0.5oz/hr at 1740psi. How does that compare to what you guys would consider as normal?
J_J
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How would you measure this if it leaked internally. If it were leaking out the stem of the valve, you could collect and measure. The only way or the best way is to put it on a test bench and check it out, and if purchased at the same hydraulic supply, then they should fix or replace.
di2hunt
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Hi JJ, new to the forum but have been reading awhile. I would like to know a little more about this ck valve. It looks like a quick fix to a common problem a lot of us are having with our CUTs. I have a ck30 and it leaks down fairly quickly. It may be still under warrenty but from what I have read here, it will probably be in the acceptable range. Any info greatly appreciated.
J_J
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It is difficult to understand why a certain valve will not leak for a long time, and then some new valve leak from day one. I don't believe the manufactures test each valve, they only test a few out of a batch, unless you are talking about Mil-spec type equipment, where I believe each item is inspected and tested. That is not to say that it will not leak, but it did meet acceptable standards under testing.
If a valve is leaking down and causing problems as in using the bucket as a platform for work, that is not good. However, not many people leave their lift arms/bucket in the air. Yor would not normally leave the bucket in the air for safety reasons anyway. If this leak down is not acceptable, then you have to repair the valve if that is possible, or replace, or put a pilot operated check valve in the line. The way the check valve works is this. When your valve is in neutral, there is ball or poppet that blocks fluid from returning from lift arm down pressure caused by the weight of the bucket, and or load. the ball is kept in check until you apply pressure, about 600 lbs, and that will release the ball for fluid to flow normally. However if your bucket is also dropping, it could be that the weight of the bucket is acting like a ram and causing the bucket cylinder to bypass. You could also use a check valve in the bucket circuit.
You may have read about valves with load checks. What they are referring to is that there are load check in the valve to keep the bucket/lift arms from shifting when you go from up/neutral/down on the control valve.
So, there are four things to think about, accept the leak down, repair valve, purchase new valve, and install load checks, which is the most secure way to solve this problem.
http://www.surpluscenter.com/item.asp?UID=2009022607084017&item=9-1343&catname=hydraulic
If you put a LOCK VALVE in between the cylinder and the valve, it will hold the fluid until 4-600 psi pressure is detected, then it unlocks and allows fluid to flow. This will STOP your drift down issue.
On the down side, it will also STOP your float function.
jb
On the down side, it will also STOP your float function.
jb
Redneck in training
Elite Member
The precision is a double-edged sword. The more precise is the match between the valve body and the spool the more it is sensitive to dirt. I work with hydraulic actuators for steam inlet valves for steam turbines. The turbine oil is filtered and kept clean to pretty high standard but since the components of the positioning of the actuator are very precise they require additional filter that will catch particles measured in fraction of microns.
(1micron=0.0000394")
I suppose the tractor components design is a compromise between dirt tolerance (dirt in this context is a relative term) and perfect function.
I know few things about hydraulics in general but I am not an expert on tractor hydraulic. Having the disclaimer out of way I would propose a test.
Provided that one spool is not passing I would swap the hoses between bucket curl and FEL lift. If the bucket uncurls and the lift stays then it is the spool valve. In opposite case it is leaky cylinder. I think it could work.
(1micron=0.0000394")
I suppose the tractor components design is a compromise between dirt tolerance (dirt in this context is a relative term) and perfect function.
I know few things about hydraulics in general but I am not an expert on tractor hydraulic. Having the disclaimer out of way I would propose a test.
Provided that one spool is not passing I would swap the hoses between bucket curl and FEL lift. If the bucket uncurls and the lift stays then it is the spool valve. In opposite case it is leaky cylinder. I think it could work.
di2hunt
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I have had some training on hydralics during my apprenticeship as a millwright.
Not all of this is greek to me. I paid a little more attention to my FEL yesterday and noticed the leak down is not in the arms but in the curl cyclinders. There is no external leaks so...I intend on checking the deal out to see what he comes up with.(137 hrs on tractor) Thanks for the help here. I still won't rule out the check valve.
Not all of this is greek to me. I paid a little more attention to my FEL yesterday and noticed the leak down is not in the arms but in the curl cyclinders. There is no external leaks so...I intend on checking the deal out to see what he comes up with.(137 hrs on tractor) Thanks for the help here. I still won't rule out the check valve.
J_J
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Do you mean to say that the bucket is pulling on the curl cylinder enough to tilt the bucket down, and was the bucket loaded or unloaded? Does this occur with engine on, and off. A good test would be to lift a load of dirt up in the air, leave it for 6 or 8 hours and see how much the lift arms or bucket move.
I am reluctant to stick my nose in this, but I just can't help it.
Acceptable spool leakage is determined by a set procedure and measured in cc's.
System pressure should be at 1000 psi and oil should be 100 degrees. You have to measure the travel of the cylinders and not the loader bucket. The amount of travel in the loader bucket is all related to geometry. The valves of today are heads and tails better than the valves of yesterday. As someone else mentioned, the more you tighten spool tolerances, the more other issues you have to deal with. There is no valve that will not leak down at all. The problem people face is that they say my old loader did not leak down.... Well it did, but the loader design and cylinders sizes made it not stick out. With today''s MFWA tractors, loader engineers are having to use shorter, fatter cylinders and way different geometry to achieve the required specs AND stay out of the front tires. 10 cc's of leakage in today's loaders is WAY more noticeable than one 20 years ago. The amount of acceptable leakage is high mainly because people normally have to measure cylinder travel over a period of time and there is a large margin of error there. 1/8 of inaccurate measurement over a 10 min time frame makes for a large displacement difference. Anyone that would like an actual written out procedure for leakdown testing is welcome to PM me and I can email you one. You will have to find out your cylinder specs however and calculate your own displacement figures. Our chart is setup to tell people the allowed travel since we already new our own cylinder designs.
Acceptable spool leakage is determined by a set procedure and measured in cc's.
System pressure should be at 1000 psi and oil should be 100 degrees. You have to measure the travel of the cylinders and not the loader bucket. The amount of travel in the loader bucket is all related to geometry. The valves of today are heads and tails better than the valves of yesterday. As someone else mentioned, the more you tighten spool tolerances, the more other issues you have to deal with. There is no valve that will not leak down at all. The problem people face is that they say my old loader did not leak down.... Well it did, but the loader design and cylinders sizes made it not stick out. With today''s MFWA tractors, loader engineers are having to use shorter, fatter cylinders and way different geometry to achieve the required specs AND stay out of the front tires. 10 cc's of leakage in today's loaders is WAY more noticeable than one 20 years ago. The amount of acceptable leakage is high mainly because people normally have to measure cylinder travel over a period of time and there is a large margin of error there. 1/8 of inaccurate measurement over a 10 min time frame makes for a large displacement difference. Anyone that would like an actual written out procedure for leakdown testing is welcome to PM me and I can email you one. You will have to find out your cylinder specs however and calculate your own displacement figures. Our chart is setup to tell people the allowed travel since we already new our own cylinder designs.