# How hot is too hot for hydraulic oil?



## Firewood Bandit (May 29, 2014)

When the ambient temp is in the 20's the splitter cylinder never gets real hot no matter how long it is run.  However now that it is in the 80s I never run in longer than say 90 minutes as the cylinder and reservoir tank are real hot.  The temp is unknown, just the palm of my hand.

So experts, what say Ye regarding hydro oil temps.  I have heard over 200 degrees is hard on the oil which is ATF.


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## TreePointer (May 29, 2014)

I'm no expert, but I was told that if you spit on the cylinder and it boils, then it's too hot.  I guess that coincides with what you heard about "over 200 degrees."


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## WiscWoody (May 29, 2014)

At 200 degrees F you'd burn your hand quickly by touching it. When I worked in maintenance the rule was if you touched something with the palm of your hand and it neither felt cool or warm it was at the same temp as your body or 100 degrees. I'd say your feeling 140-150. You can get a infrared thermometer pretty cheap nowadays. There range isn't as high as a more pricey Fluke brand but they are right on as far as accuracy at a fairly close distance.


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## mstoelton (May 29, 2014)

Flashpoint for hydraulic is about 400 f.


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## ewdudley (May 29, 2014)

Oil will do fine up to about 275 degF or more, but seals, hoses, pumps, and whatnot should not see anything above 180 degF for any amount of time.


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## Jags (May 29, 2014)

Yep - I have always heard the 180 number.  I don't have any reference to give, just the old noggin hopefully remembering things proper.


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## ewdudley (May 29, 2014)

Jags said:


> Yep - I have always heard the 180 number.  I don't have any reference to give, just the old noggin hopefully remembering things proper.


Same here, just repeating what I've read here and there.  Yet automatic transmissions must run well over 200 degF for a couple thousand hours, so there must be such a thing as a hydraulic system that can run hotter than 180 degF


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## Jags (May 29, 2014)

I was always told it is not the fluid that has problems, its the seals and such (on typical hydro systems).


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## Longstreet (May 29, 2014)

I have no idea if you can make this comparison, but see below for time to burn at different temps of water.

http://www.accuratebuilding.com/services/legal/charts/hot_water_burn_scalding_graph.html

200F water burns you immediately, so I doubt your oil is that hot given your statements.  Sure, the temp of the cylinder my not be the hottest part of the system, but even 180F (the number people are talking about here) burns you in a fraction of a second.

Edit:  Plus, look at the steepness of the curve from 212 to 155F.  It's still almost instantaneous at those temps.


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## Jags (May 29, 2014)

Not a 100% comparison.  That graph is for immersion which transfers heat energy MUCH faster than touching a surface.  The graph is good - it just isn't the same energy transfer that we get by touching a hydro cylinder or even a wood stove for that matter.


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## 1kzwoman (May 29, 2014)

100 degrees over ambient temp on well maintained equipment is common.
No guage on my splitter so I will allow a cool down  period every tank of fuel for both myself and equipment when it hits 70F air temp. I try not to split in hot weather.


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## Firewood Bandit (May 29, 2014)

Sounds like my 90 min rule and then let cool down isn't a bad idea.


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## Mt Bob (May 29, 2014)

175 is a good running temp for atf(in a transmission).The fluid really starts to break down above 225.Your book prob. reccomends changing it every season.If you use it a lot in hot weather switch to full syn. fluid.


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## mustash29 (May 29, 2014)

As far as ATF in a transmission, and installing external coolers, the general rule of thumb is a 20 deg drop in fluid temp will double the life of the fluid.


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## tsquini (May 29, 2014)

Seals and gaskets and the lack of lubrication is the real risk running to hot. The oil viscosity defines the runing temperature. If you are running a low viscosity oil you may be over heating at a lower temperature. I'm not familiar with hydraulic oil weights. I do know you can buy different grades that can handle heat and oxidation better.


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## triptester (May 29, 2014)

The optimum operating temp for hydraulic fluid is 130 degrees. The same temperature that is recommended for a domestic hot water heater. At 180 degrees the fluid starts to lose some of its anti-wear properties and the seals and 0-rings lose strenght.


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## Firewood Bandit (May 30, 2014)

Yesterday I ran it about 75 minutes and it was in the 80's, a nice day.  Since I had bib on long sleeves on so I couldn't get my arms scratched up, it was very warm.  After 75 min. I could hold my hand on the cylinder for the count of 4 and couldn't quite make it to 5.


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## Jags (May 30, 2014)

Firewood Bandit said:


> I could hold my hand on the cylinder for the count of 4 and couldn't quite make it to 5.



Sounds like you were well within acceptable limits.


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## D8Chumley (Jun 1, 2014)

1kzwoman said:


> 100 degrees over ambient temp on well maintained equipment is common.
> No guage on my splitter so I will allow a cool down  period every tank of fuel for both myself and equipment when it hits 70F air temp. I try not to split in hot weather.


I was thinking this also, as far as 10 or 30W hyd oil in heavy equiptment. Not sure about ATF however, and heavy equiptment isn't the same as a personal use log splitter. I try not to split in warm temps. I try to get all my c/s/s done in fall through early spring but sometimes it is necessary. In that case I have done the same- split until my log haulin' wagon is full then shut off the splitter and go stack the splits.
EDIT: I wonder in the case of not having a gauge, would the stack temp from my stove be better than nothing at all? I might have to try that next time I split, stick it to the cylinder or tank and see what it reads. I don't have an IR temp gun


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## kennyp2339 (Jun 1, 2014)

Not to beat a topic to death but, I run ISO 46 hydro oil in my splitter. My manual specifically said not to run tractor ATF for hydro. So I went to tractor supply and asked an employee what they use in there splitters, right off the bat the guy said the ISO 46, when I asked why; he said that it handled the heat better. I took his word and bought the 10gal I needed. Let me tell you guys, there is a difference.  I use to borrow my friends splitter (iron and oak 20ton fast cycle) and when the fluid got real hot, the expanded fluid would squirt out the relief cap on top of the tank, At the time I though that's just what it does, no big deal. I bought the same splitter this spring (brand new) put the ISO46 as my oil and so far hadn't had a drop of oil come through the relief hole in the cap. I ran the splitter yesterday at my mom and dads for about 5 hours, (1 & 1/2 tanks of gas) The cylinder got pretty hot (hand on it for 3-4 seconds) Oil did not leak, weather was sunny & warm (mid 70's).  Anyway I don't really know anything about oil viscosities, or the difference between ATF, tractor ATF, or what I'm using, but all I can say is I like what I'm using doesn't expand as much.


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## Mt Bob (Jun 1, 2014)

kennyp2339 said:


> Not to beat a topic to death but, I run ISO 46 hydro oil in my splitter. My manual specifically said not to run tractor ATF for hydro. So I went to tractor supply and asked an employee what they use in there splitters, right off the bat the guy said the ISO 46, when I asked why; he said that it handled the heat better. I took his word and bought the 10gal I needed. Let me tell you guys, there is a difference.  I use to borrow my friends splitter (iron and oak 20ton fast cycle) and when the fluid got real hot, the expanded fluid would squirt out the relief cap on top of the tank, At the time I though that's just what it does, no big deal. I bought the same splitter this spring (brand new) put the ISO46 as my oil and so far hadn't had a drop of oil come through the relief hole in the cap. I ran the splitter yesterday at my mom and dads for about 5 hours, (1 & 1/2 tanks of gas) The cylinder got pretty hot (hand on it for 3-4 seconds) Oil did not leak, weather was sunny & warm (mid 70's).  Anyway I don't really know anything about oil viscosities, or the difference between ATF, tractor ATF, or what I'm using, but all I can say is I like what I'm using doesn't expand as much.


 Some hyd. valves do not do well with atf.As hydraulic oils do not use same weight number systems,here is a little help,most non synthetic atf is equivilent to 10w motor oil.Your iso 46 is closer to 15,and a better choice in my opinion.Alot of tractors/equipment use transdraulic in the hydros and shuttle shift,has clutch additives,but not ness. in a splitter,but if it is on sale I would use it.In extream cold a synthetic or specialty fluid would be better,such as meyer(or other) low temp fluid.But who wants to split when it is -30?


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## Firewood Bandit (Jun 1, 2014)

Well today I tried an experiment in order to get some data regarding how hot the splitter is running.
I took a sponge and soaked it with as much water as it would hold and wedged it between the cylinder and hard metal hydro line.  Then I stuck an accurate meat thermometer in the sponge.  The water was to transmit the heat more effectively.  After an hour of running the cylinder to the palm of my hand felt the same as it did in the first post.  (temp outside was about 80).
The thermometer ran up to 140 degrees, (medium well) and hung there and was not going up much but I had to quit to go play golf.  I had wet the sponge several times and each time the temp would drop when water was added then quickly climb again.  An amazing thing was that in less than 5 min of the splitter being off, the temp of the cylinder had dropped to 120 degrees.


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## WiscWoody (Jun 1, 2014)

It might drop fast due to the water evaporating on the sponge. Anytime a liquid evaporates it cools. Thats why pool water, even above ground ones are always cooler than ambient air. Inground pools get some cooling effect from the ground surrounding them also. And evaporation is how A/Cworks. The liquid refrigerant goes from a pressurized liquid into a section (the evaporator) that's on the suction side of the compressor making the refrigent flash to gas and having it's cooling effect.

I never run my splitter long enough for it heat up much. Since I'm limited on room here I pile up my rounds in a area where the splitter is and I have to use a wheel barrel to take the splits 30 feet over to the racks and stack them. I do a few wheel barrels here and there and the dogs just sit there watching me all the time waiting to go on another walk so that gets worked into my schedule often.


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## Kevin* (Jun 2, 2014)

180 F for buna seals/O-rings. Viton can safely run into the high 300's F. Pumps can take heat but the viscosity of the oil starts to degrade to the point where is can damage the pump and loose performance. In general you want to keep oil between 60-150 F for gear pumps.


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## missedbass (Jun 2, 2014)

Firewood Bandit said:


> Sounds like my 90 min rule and then let cool down isn't a bad idea.


 60 min- beer brake-60min- beer brake, never had a problem


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## Highbeam (Jun 2, 2014)

A 200 degree dry surface is not hand burning hot, easy touch but don't leave your ice cream on it. Dipping your hand in 200 degree liquid is bad mojo and can be a serious burn. My rule for hydro equipment including my tractor is that I can hold my hand on the filter and count three seconds. Any hotter and I give it a break, clean the chaffe. 

Of course, my hands might be tougher or weaker than yours.

I like the simplicity of the spit boil rule but to burn spit off, the surface temp would have to be quite hot and the tank temp would be much hotter. That's too hot for the equipment.

On the splitter. Easy to touch, but not leave your hand there forever is fine.


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## Joey (Jun 12, 2014)

missedbass said:


> 60 min- beer brake-60min- beer brake, never had a problem


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