How hot should Hydraulic cylinder get?

[oldnslo]

"Heat" is a very relative term!! Cold too!!
"Heat" is a strong term, and usually not a god word to use for describing increased temperature, because it is RELATIVE....

Actually, straight physically, there is nothing like cold, according to William Thomson, 1st baron kelvin, that discovered the absolut temperature scale.

Thomson found out that at a certain lowest material temperture, there is a theoretical absence of all thermal energy. No molecular activity. That temperature is about minus 273 C, or minus 460F...He gave that lowest temperature Zero, on his own scale called KELVIN, which is also the official international system scale for temperature......plus 273K=0C=32F....

Hammering metal or stretching rubberbands etc, is molecular stress or molecular movement, that causes friction. So is pouring fluid out of a bottle. And from friction we get "heat", or better, INCREASED TEMPERATURE.

So by forcing material to deform, pour, flow, change volume, etc, we transfer some work energy into increased temperature ("heat") in that piece of material....That happens around everything that moves....

Pressureize oil in a hose, wont create any "heat", maybe some 0.1 or 0.01 of a degree temperature raise. But if we force that oil to move, there will be friction, and that will be a "heat"-factor of importance....the more we restrict flow, the higher pressure is needed to maintain flow, and the higher temperature increase we get.....Broken piston seal, leaking relief valve, worned out pump, clogged return filter, elbow fittings, undersized hoses etc etc.

+ 1 on this. A good functioning cylinders does NOT create heat when doing work. In almost all case a componet doing work is not creating heat. The Inefficiency of that component is what creates the heat. I.e. pump slippage, valve pressure drop etc.

Largest heat generator on most log splitters is the pump itself, second is the valves and plumbing.

A good hi-lo gear pump is probably around 85% effecient and when the low section unloads this gets worse since a portion of the same fluid is being recirculated in the pump itself.

Roy

 

[SPYDERLK]

I'd like someone to expand on this concept. How is the cylinder doing (absorbing) work and making heat, other that if it is bypassing oil through a leaking seal. The cylinder is doing no work, it is a balance of forces, psi*area and rod reaction. The pump does the work (dP*gpm) and the system absorbs the work as heat (pressure losses*gpm) and splits wood (force*distance).

I just don"t get the heat of compression concept in the cylinder, being that it is a solid fluid system.

Dont worry about it. It was wrong.
larry
Ahh .... - Good, I see AKKAMAAN explained it - including ack of slight heat of oil compression and hose expansion. :thumbsup:

 

[gpflepsen]

What the heck is a "solid fluid system"???????

A solid fluid system is... devoid of gases. Entrain air into the system then it is not solid. The compression of the air will generate heat, but then the expansion of the air will absorb heat.

I think any heat created by the compression of the almost incompressible oil would be carried out of the cylinder by the working fluid. This effect would be absolutely negligible in the application of a log splitter, IMHO.

Anyway, if the cylinder is hotter than the system as a whole, fix on fixin' some seals!

 

[SPYDERLK]

Most home water heaters are set below 140 degrees and you cannot hold your hand under the water. My guess is your cylinder's temperature was far below 140 degrees. That said, my car regularly gets up to 140 degrees inside during the summer while sitting in the sun with the windows up. 140 degrees for a hydraulic system is a "walk in the park."

Touching dry 140 is a lot different than emersing in 140 liquid. Its a heat transfer thing. A great deal of difference in coupling the heat.
larry

 

[Coyote machine]

Hydraulic systems regularly run at 100* above ambient temperature, 140* for your splitter while it's working hard is good.

For clarification, I believe your statement above is incorrect. Ambient temp on a given day for example may be 70 degrees F. At 100 degrees above that ambient temp the hydraulic system you refer to would be at 170 degrees F. Is that what you meant to say?
Wouldn't there be a range that hydraulic fluid should run at based on a given ambient temp- for instance at 70 degrees F the hyd. temp should not be more then 140 degrees F?

 

[kennyd]

For clarification, I believe your statement above is incorrect. Ambient temp on a given day for example may be 70 degrees F. At 100 degrees above that ambient temp the hydraulic system you refer to would be at 170 degrees F. Is that what you meant to say?
Wouldn't there be a range that hydraulic fluid should run at based on a given ambient temp- for instance at 70 degrees F the hyd. temp should not be more then 140 degrees F?

Yup, that is what I meant to say...I never brought up the 140* number. I stand behind my statement.

 

[Coyote machine]

Yup, that is what I meat to say...I never brought up the 140* number. I stand behind my statement.

Ok, So you're saying whatever the outside (ambient temp) is, the hydraulic fluid should be 100 degrees more? So at 32degrees F the hydraulic system fluid should be around 132 degrees F?

 

[kennyd]

Ok, So you're saying whatever the outside (ambient temp) is, the hydraulic fluid should be 100 degrees more? So at 32degrees F the hydraulic system fluid should be around 132 degrees F?

I never said/wrote "should" be.

I wrote:

Hydraulic systems regularly run at 100* above ambient temperature, 140* for your splitter while it's working hard is good. 04-16-2010 12:29 AM

 

[wdchyd]

Ken,

years ago I was taught you should be able to hold a count of five on any reservoir or component to be safe (right around 150 deg)...anything hotter should be questioned...Seals and hoses start being affected around 185+

 

[Coyote machine]

I never said/wrote "should" be.

I wrote:

Point taken on my wording- I was not trying to misquote you - just trying to understanding the intent of what you said. So if I'm getting this right, stating it another way in my own words: 100 degrees above ambient is considered a normal operating temp when the equipment is being worked hard.
Would that be accurate?
thx