Fluid temps.?

   / Fluid temps.? #1  

NIXON

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Nov 26, 2002
Messages
1,281
Location
West Sunbury ,Pa.
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L3130 hst
Sorry if this has been beaten like a rented mule ,but I did search with no results :)
At what temps does hydraulic fluid start breaking down ( aw 32 and 46 ) ?
The reason I'm asking is that my splitter has a relatively large capacity pump vs the oil tank size . 16 gpm v 5 or so gallons . I'm going to switch over to schaeffers # 264 synthetic in aw 46 this spring to help things out ,but I'd to know at what temps things are getting dicey .
 
   / Fluid temps.? #2  
Sorry if this has been beaten like a rented mule ,but I did search with no results :)
At what temps does hydraulic fluid start breaking down ( aw 32 and 46 ) ?
The reason I'm asking is that my splitter has a relatively large capacity pump vs the oil tank size . 16 gpm v 5 or so gallons . I'm going to switch over to schaeffers # 264 synthetic in aw 46 this spring to help things out ,but I'd to know at what temps things are getting dicey .

Typically seals start to bad before the oil. Normal seals are good to around 250 F. Oil not sure but mobile hydraulic systems run 180 - 200F as normal operating temperature.

How hot does the oil get in engines?

Roy
 
   / Fluid temps.? #3  
There is no dirext comparison but just using a "rule of thumb", ISO 32 is very much like 10W fluid while ISO 46 compares to 20W. The common/genaric ISO fluids do have some amount of viscosity changers in them but are not full multi-viscosity fluids, but for a reference they are close to 5W-20 for ISO 32 and 10W-30 for the ISO 46.
These are not true absolute comparisons but close if trying to decide which weight to use. If all else fails, read the label on the container it should give you some temp ranges to work with.
 
   / Fluid temps.? #4  
I have quite a bit of research on this for work. As far as viscosity goes I have never seen any mention as long as you are dealing with common hydraulic fluids.
-----------------------------
Vickers Mobile Hydraulics Manual, page 372, section: Heat or thermal contamination.

Hydraulic fluids are typically not considered 'high temperature' fluids. Their useful life, as well as maintenance of viscosity, chemistry and the other attributes discussed in Chapter 16, is based upon continuous operation below a critical temperature. This critical temperature is 140°F. Every 18°F increment higher than 140°F effectively 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 176°F would reduce the useful life of the fluid by 75%.

Most fluid manufacturers specify optimum ranges of temperature for their products - typically 90-120°F or 100-130°F - even though many fluids are operated in excess of these temperature ranges. The effects of temperature on the fluid are the same, regardless of the source of heat.
------------------------------------
What is Oxidation in Lubricating Oil?, by Mark Barnes, NORIA

For most mineral oils, a general rule of thumb is that the rate of oxidation doubles for every 10°C (18°F) rise in temperature above 75°C (165°F). Because of this, synthetic oils are often required in high temperature applications to prevent rapid oil oxidation.
----------------------------------
Oil Hydraulic Systems, by S.R. Majumdar

2.11.3 Oxidation
A dominant factor which determines the service life of the oil is degradation through oxidation. Oxidation occurs when oxygen combines with the original hydrocarbon molecules angives a chain reaction. Traces (even a few PPM) of certain metals, particularly copper, iron, zinc, lead and water act as catalysts and markedly increase the rate of oxidation.

Temperature is another factor in accelerating the rate of oxidation. As a working rule oxidation rate is doubled for each 10°C/18°F rise in the temperature. An oxidation-inhibited high viscosity index (HVI) oil may give a useful life of ~100,000 hours at 40°C/104°F even under the condition of aeration and catalysis. When the oil temperature is raised to 60°C/140°F, life drops to as low as 10,000 hours.

Oxidation produces soluble as well as insoluble products and these may form sticky substances and may deposit as gum or sludge in oil passages, various pump parts, valve spools and ports, etc. blocking them and restricting oil flow and making the machine run sluggishly. As a result of oxidation, the oil becomes progressively darker and gets acidic properties which ultimately deteriorates the life of the oil.

2.11.4 Total Acidity Number
Total acidity number (TAN) or the neutralization number is the measure of acidity of oil. It is defined as the number of milligrams of potassium hydroxide required to neutralize one gram of oil (mg KOH/g). Oil enriched with anti-oxidant additives has a long induction period. Such an oil takes a longer period to reach the TAN value of 1, but after that the increase in TAN value is very sharp and it quickly reaches the value of 2. Though the permissible value of TAN is 2, a sharp increase in value is a better indicator for changing the oil. Once the sharp increase is noticed, it is a warning to the plant engineer to prepare the machine for shut down for changing the oil.
 
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   / Fluid temps.? #5  
Another area of concern is the additive package in the oil. Each supplier has their own recipe and that can have some affect the high temp resistance.

A third area of concern is seal and hose degradation. There is some variance in the numbers given depending on the exact formulation, but....

Buna/Buna N/NBR/XNBR: 212-250°F (very common)
Parker: Up to 100°C (212°F) with shorter life @ 121°C (250°F).

Hydrogenated Nitrile/HNBR: 285-300°F (higher grade parts, low cost upgrade)
Parker: short periods up to 450°F to 590°F depending on compound.

Buna EP/EPDM: 300-400°F

Viton/FPM/FKM: 350-400°F (to +600°F for short periods)
(high cost upgrade, I think it has a lower resistance to cutting/tearing)

Hydraulic hose tops out at 212°F to 300°F depending on the construction. It's oxidation rate increases at higher temps just like oil and seals.
Nitrile, neoprene, NBR, CPE

A fourth thing to consider is the oil viscosity and pump life. Oils viscosity is specified to minimize vacuum at the inlet when cold yet get the best performance when hot. If the oil is too thin you will decrease the efficiency and increase wear. (i.e. waste more energy)

In the end it depends on how long you want everything to live. The cooler you keep it the longer it will last.

ISZ
 
   / Fluid temps.? #6  
Thanks for posting, that was interesting.
 
   / Fluid temps.? #7  
Your standard 100R1 and 100R2 hose is good to 212°. Most cylinder seals are rated for the same temp. If your hydraulic oil is getting that hot, which I have only seen in a Blaw-Knox asphalt paver, you're in for a world of repair bills.
 

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