hydraulic system complete failure - mis-diagnosis or possible?

[chainsaw_louie]

A friend of mine was responsible for repairing a small hydraulic system on an apple cider press. The system is the same as on a log splitter ie 2way cylinder , detent valve , pump (electric). The unit is probably 20 years old but has been kept indoors and is only used for a few weeks every 2 years.  His ended up replacing almost everything in the system.  I don't understand the details of hydraulics and what goes wrong with them, so it would be good to hear your opinions of this:

1. took apart the pump/tank assembly , found it clogged and dirty , replaced the pump, cleaned out crud from the tank, cleaned intake screen ,  re-assembled/refilled with new oil.  Tried it but  it continued to clog,  oil would come out of the open line for a while then stop.

2.  took it to the repair place , they said 'should never have done anything without replacing the old hoses'.  Apparently old hydraulic hoses were shedding rubber crud into the system and causing clogging.  Replaced all hoses. Added filter.

3. Refilled system still didn't work .  Took off hydraulic cylinder and took to power shop.   They   opended hydraulic cylinder , found it was full of rubber crud,  said cylinder is rusty .  Told friend to take cylinder to hydraulic repair shop, there  was told cylinder needs to be replaced. Installed new cylinder.

4.  Tried system, still doesnt work ,  only thing left is the valve ,  replaced the valve .  System works.

Just wondering if this problem analysis could this have been done differently ?  Could all these parts have needed to be replaced or was that just the 'easy' way.
I am curious about these hydraulic systems as I use a log splitter which is the same system.  Was the cause of this complete system failure due to mis-diagnosis , bad advice or accurate and caused by non-use for 2 years of an aged system and a break down off all components.

Thanks!

[North River Energy]

If I found solids in the tank, I'd have probably pulled the cylinder first, then flushed/cleaned to remove any residue in the lines/valve.

Would guess that the cider press runs much cooler than your splitter, thus condensate in the system, then rust, then accelerated cylinder packing wear/shedding.

Sounds like he went after the symptom rather than the disease.
A good learning experience, and on a relatively 'cheap' system no less.

[grassfed]

Mechanical equipment that sits unused breaks down. If you want something to work reliably you have to use it a minimum of once a month. So I vote for "non-use for 2 years of an aged system and a break down off all components." If something is going to sit for a long time there are storage procedures that can help some. Anything with hydraulics and oil should be checked for moisture in the oil. When it sits the water will separate and rust valves and such.

[kiko]

When ever a hydraulic system is contaminated the entire system must be addressed.  So the process he went through would be normal.  I have had machines with catastrophic pump failures where this had to be done.  Two men and two weeks to remove and disassemble every hose valve and cylinder.

[Den-Den]

No doubt the the problem analysis could have been done differently but that is hindsight.  I would have expected that the pump,  cylinder and valve would be repairable unless contaminated by water and rusted.  Those hoses must have been very old to decompose like that (unless the oil had additives not compatible with them).

[svart ole]

Depending on how this whole process took place the system could still be contaminated. If each of the repairs was done one at a time and then the machine was run the crud just got moved around. When you have a contamination problem you need to take everything apart and clean, inspect and replace what is needed, then put it all back together clean. Then if it still does not work you can look at individual components. Pump, valve (Main or port relief is so equipped) Just a thought, a press like that may have a "load lock valve" to hold the pressure on the squeezins when the valve is released. Never had hoses go bad like that on the inside. I have had a chunk of the inner rubber crack and form a flap that made a real nice one way check valve. More common in systems where there is lots of heat and flexing. 

[mclean]

Was some rubber aggressive hydro oil..  Any idea what it was?

Once the systems contaminated, all effected areas would need rebuilt or replaced anyway.  Shame to have replaced and recontaminated that way.  Keep an eye on the screen and any filters..

[chainsaw_louie]

Thanks for all the responses.
So a few follow up questions ....
  1. )  Are you saying not all hydraulic oils are the same, we risk damage to the system if we get the wrong hydraulic oil ie some oil properties are not compatible with the rubber hoses we have ?

  2. )  Moisture in the system,  I understand that this can cause corrosion,  but its a sealed system, how can water get in ?  What is the standard practice to prevent moisture getting in and  getting  the water out?
   - regular use, 
   - or a 'dryer' like on air systems (does it exist for hydraulic systems) ?

Thanks !

[grassfed]

It is probably not a sealed system. Most reservoir tanks have vents often vented caps. Rubber hoses breakdown over time as do tires and  hoses. Ozone and natural decay...If you want something to be reliable you need to establish and follow a PMS Preventive Maintenance Schedule.  If you had one it might have told you to replace the hoses 10 years ago. The point is that a good PMS will have you changing parts before failure. This is not always the most economical way to maintain equipment but it gives you the best state of readiness. Nobody will die if an apple press that is used a couple of times a year fails so you would not likely need as strict a PMS for that piece of equipment as you would need for a fire engine or ship. That said changing the hydraulic oil every couple of years and putting on new hoses when they get hard and stiff would make sense. Experience really helps .   

[Corley5]

  I've known guys that have come pretty close to dying as a result of PMS.  Been real close a couple times myself  ;) ;D :D :D :D

[barbender]

Corley, is there a PMS for PMS?  :D

Louie, your friend should have cleaned out the whole system when contamination was discovered in one part. A lot of the parts may have needed replacing anyhow, but failure to remove contamination results in damage to the new parts, especially with an unfiltered system. Just my .02, oh and btw, it's not unusual for old hydraulic hoses to disintegrate like that.

[whitepine2]

 Most cider presses I've seen have used water rather than oil because of contamination
of a food product. It might have used veggy oil or some other liquid that would not
contaminate,possibly this could have caused hose fairer. Just my 2 cents. 

[Gadrock]

Most hydraulic oils are emulsefied, so that should water be introduced somehow, the system does not die. Flush the system out and replace with new oil after it looks milky.
     Other oils do not have an emusifier agent so oil and water do not mix, for long. But you could drain the water/ condesate after a settling period.
    Now day we have a "Sierra Grade" hydraulic oil that is Earth friendly. It is used widely on golf courses where any hydraulic leak could last a whole growing season. Perhaps others can expand on the subject.
    In my logging business we have very complex hydraulic systems. May are hydro assist, some are electro-hydro, some direct hydro, but the complex compensated circuits are most demanding. And there are hydrstatic drive systems too.

[whitepine2]

 Gadock most of the fishing fleet in New Bedford use the green oil now so if a leak
happens they don't need the Coast fining them an arm and a leg good stuff.

[Gadrock]

That I believe to be a good choice on many view points. Our world should be rejoicing with the availability of Earth Friendly hydraulic fluid.

david G


carry on