WHAT IS THE USE OF HYDRAULIC OIL IN EXCAVATORS?

[Robert_in_NY]

Water is just as incompressible as oil. But, water does not lubricate and causes rust.

And freezes

 

[radioman]

thanks for correction dave, but I failed to also mention that water heats up faster under compression so it becomes spongy push which is why I say it doesnt compress as well. Oil can be heated to a point and still work well.

 

[BXpanded]

Water has been a relatively common hydraulic fluid in some industrial applications like rubber compression molding for years. Obvious advantages are: cost, no hazards if some leaks or spills, non-flammable, no urgency to repair slight leaks. It's almost always set up as a central system that might run dozens of presses and might contain thousands of gallons.

It's not unusual for large rubber presses to have six 24" diameter cylinders or a 48" diameter cylinder so fluid is a real cost and disposal of old fluid is a problem.

Newer fitting, seal and hose technology has made it easier to control leakage so most newer stuff has a self-contained oil system.

 

[BXpanded]

Boy, did I get off the OP's original topic! My apologies, just thought it might be of interest to some.

 

[MHarryE]

I assume you are asking which oil to use. Depends on your excavator. My Cat mini-excavator uses Cat HYDO Advanced 10 in temps up to 40ｰC, and 15W-40 engine oil when temperatures are above 40ｰC. There are a lot of other options shown in the book but those are the 2 basics. Most of the other options are good only under 40ｰC and cost more than straight HYDO Advanced 10. Other makers will probably be similar but many will probably use a universal fluid.

 

[john4153]

With regard to hydraulics, there is no substitute for referring to the owner's or shop manuals. There are many differences and conditions to account for. My Komatsu PC30MRx lists 4 different engine oil viscosities (API CD or CE, which are obsolete, see: API Oil Service Categories) plus Komatsu's own branded hydraulic fluid for the hydraulics. Other brands may have fewer choices.

John

 

[Kevin M]

I borrowed a friends Komatsu PC 55 , It was low on hydraulic oil , I called the dealer and they wanted the serial and model # first. Even the same machines us different oil depending on the year. This one required a 10w motor oil. Bizarre !

 

[J_J]

What is so bizarre about the use of motor oil. Apparently they did test on their hyd system and found that 12W motor work the best for a certain situation.

All the Power-Tracs, use 10W-30 or 40 ,motor oil as the hyd fluid. Has been that way for about 30 years.

 

[sae8425]

Oh boy!

Irrespective of what is written in any of their manuals, Komatsu's hydraulic fluid recommendation is not for just any 10W motor oil. It is only for a NON-DETERGENT 10W motor oil. This, as far as I know, rules out ANY multi-grade oil in existence because EVERY multi-grade oil is a detergent oil.

And the selection and availability of non-detergent motor oils is more restricted today than it was even 5 years ago. Handwriting & wall (or something to that effect).

And while I know that Power Tracs use 10W-30/40 motor oil (I have a 1430), I wouldn't run any typical multi-grade motor oil any hydraulic system of that vintage no matter what the 'end use assembler' recommended.

Detergent additives are (or at least were) widely known to lead to foaming issues. I would rather not hasten the demise of any of my hydraulic systems.

And while the additive packages in more recent hydraulic fluids and motor oils has overcome at least some of the foaming issues, their main downside is their water emulsifying ability. Evidently, especially with higher pressure hydraulic systems, it can be difficult to insure that the water content is kept to below the 0.1% level, which is needed to combat cavitation & corrosion issues in hydraulic systems.

So, out of the frying pan and into the fire!

Another example. Shell says that the anti-wear technology used in their Tellus T oils (which, like the vast majority of lubricants, is based on zinc) should not be used in older hydraulic pumps. Seems many of these contained silver plated parts and the zinc attacks the silver plating. Ever seen this mentioned in any owners manual?

Today, every major lubricant company is researching high VI (200 CentiStokes min) hydraulic fluids. And while these are being touted as delivering 5% or more improvements in fuel economy and productivity, they are all being developed for the latest generation of excavators and such (many with 5000 psi hydraulic systems, and all having pilot controls). And while the applicability such fluids have for older equipment is highly debatable, as they become the most utilized hydraulic fluids, the availability of suitable fluids for older equipment will most certainly diminish (just you try to find a diesel engine oil that doesn't comply with the latest API standards. I only know of one currently being offered and it's a synthetic by Amsoil).

Also the ZDDP levels in the latest diesel engine oils has been decreased (evidently hastens the demise of certain components in the pollution control systems installed on late model trucks). And while such lubricants might be good for the environment, their certainly not good for using in most hydraulic systems. But you try prying ZDDP level information for oils and hydraulic fluids out of the oil companies. Talk about something that's proven nearly as difficult (but not quite as costly) as locating one particular 6 ft 10 Arab turned out to be!

I'd certainly want to know the ZDDP level of any hydraulic fluid before I used it. If it was too low, but I still wanted to use said fluid, I would look for an additive to raise the ZDDP level, and I would then do at least twice yearly fluid analysis checks to monitor the breakdown/loss of ZDDP.

Hydraulic lubricant selection seems to become more of a minefield with each passing year (or fluid change interval).

And simply because it's written in an owners or shop manual doesn't make the information correct either.

Once you spend time talking to hydraulic pump manufacturers, or going through their installation design manuals, you will soon realize that many 'end use assemblers' (ie. Case/JD/Komatsu/etc) often chose to not follow the guidelines of the manufacturers actually making the hydraulic components they utilize! Go figure.

 

[aroberts10]

Kevin I have heard about this too. A friend of mine had a excavator that had ran out of hydraulic oil. He also was told that even though he had the same model as someone who he worked with it didnt mean he would use the same oil - Does anyone know the reason for this?