How hot is too hot??

[Chuck K.]

While doing a fair amount of digging for a customer I exited the backhoe and place my hand on the boom cylinder and was surprised how hot it was. It did not burn my hand but you would not want to leave your hand on the cylinder for mor than a few seconds...

I dont deadhead the hydraulics when digging and when hearing the engine load up or see the bucket quit moving I lighten up. To me this was too hot, I will try and have my temp. gun with me next time to check various temps..

 

[DieselPower]

How hot is too hot for a hydraulic system? It depends mainly on the viscosity and viscosity index (rate of change in viscosity with temperature) of the oil, and the type of hydraulic components in the system. As the oil’s temperature increases, its viscosity decreases. Therefore, a hydraulic system is operating too hot when it reaches the temperature at which oil viscosity falls below that required for adequate lubrication.

A vane pump requires a higher minimum viscosity than a piston pump, for example. This is why the type of components used in the system also influences its safe maximum operating temperature. Apart from the issue of adequate lubrication, the importance of which cannot be overstated, operating temperatures above 180 degrees Fahrenheit damage most seal and hose compounds and accelerate degradation of the oil. But for the reasons already explained, a hydraulic system can be running too hot well below this temperature.

 

[jinman]

Hot water in your house is probably 130-150 degrees and feels very hot to the touch. I'd bet you'll find your boom cylinder is not as hot as you think when you measure the actual temperature.

 

[Duffster]

I would say that if you could keep your hands on it for even a few seconds it wasn't "to hot"

 

[Bird]

This topic comes up periodically and generally speaking, the simple answer is that hydraulic temperature may be about 100 degrees Farenheit above ambient temperature. I did a little checking with a temperature probe into the reservoir on my tractor once, after talking to a dealer about it. It was definitely too hot to keep you hand on the valves for the FEL and Top 'N Tilt, but within a "normal" range.

 

[Redbug]

Just thinking about this subject a little bit more, (and I am no expert), wouldn't the hydro oil be about the same temp as the antifreeze in the radiator? I know both systems are separate, (in terms of fluids being separate), but the main engine parts are shared by both fluids. If the hydro oil gets hot, the heat would be absorbed by the engine parts and shared with both the regular radiator and the smaller hydro radiator in front of it. If this thinking is correct, then both fluids, (and engine oil, too), would all be around the same temperature most all the time. Is this right? Opinions?

 

[BrentD]

Ever put your hand on the roof of a car and burned it just from the car sitting in the sun? There's a lot of factors that contribute to temps. If the tractor is sitting out in the sun, working or not, on a bright day, the cylinders are going to be hot. I wouldn't start to worry unless they were significantly hotter than the surrounding metal, like the actual boom.

 

[kennyd]

Just thinking about this subject a little bit more, (and I am no expert), wouldn't the hydro oil be about the same temp as the antifreeze in the radiator? I know both systems are separate, (in terms of fluids being separate), but the main engine parts are shared by both fluids. If the hydro oil gets hot, the heat would be absorbed by the engine parts and shared with both the regular radiator and the smaller hydro radiator in front of it. If this thinking is correct, then both fluids, (and engine oil, too), would all be around the same temperature most all the time. Is this right? Opinions?

I agree.

 

[Chuck K.]

Thanks for the input guys... there is a little more to the story, I could smell a faint odor of hydr. fluid and the main boom has a problem the tractor is back in the shop.
The boom wont retract the last few inches so I can apply the boom lock. A new boom cylinder has been ordered, I will see how hot it gets compared to ambient with a temp gun..

 

[Bird]

Chuck, a faint odor of hydraulic fluid is another of those things that several of us have experienced and something that has been discussed several times on TBN. It's usually coming from the vent rather than a problem. Naturally, I don't know that's the case with your tractor, but would guess it's most likely.

 

[Opti-Mist]

Bird has it right as to 100 degrees + ambient. As for oil too hot - really overheated oil has a distinct "burnt" smell to it that most anyone will recognize despite never having smelled it before. It will definitely be different from the odor of working temperature hydraulic oil.

 

[patrick_g]

I think that I recall that tissue damage begins at temps above about 115F with prolonged contact. Metal that you can contact for several seconds without getting first degree burns is not likely to be hotter than that. I use a non-contact IR thermometer to get a fair idea of the temp of things.

Pat

 

[IceStationZebra]

As far as the oil is concerned I have research this several times for my employers (off-road OEM's). Every 18°F increment higher doubles the oxidation rate of the hydraulic fluid (petroleum based) thus cutting its useful life in half, e.g. running a system at a consistent 201°F vs. 165°F would reduce the useful life of the fluid by 75%.
I have found two different numbers for the start of oxidation...140°F and 165°F. I'm not sure which is correct but the data I have leans towards 140.

Most rubber components are good to at least 200°F.

As far as the IR temp gun goes, don't expect acurate readings of shiny surfaces like chrome rods or of plastics. Painted surfaces work great.

ISZ

 

[J_J]

Some more data to consider.

Note that fluid temperatures above 82 C (180 F) damage seals, reduce the service life of the hydraulic fluid and in most cases, will cause the viscosity limits of the fluid to be exceeded. This means that the operation of any hydraulic system at temperatures above 82 C (180 F) is detrimental and should be avoided.

http://www.plantengineering.com/art..._Fluid_is_a_hydraulic_system_s_lifeblood_.php