Hydraulic seals

[J_J]

I saw this in a hyd article. Would you consider it a valid statement.

Excerpt:

Seals must be compatible with the specific type of hydraulic fluid used in the pump. Specifically, seal material for carbon based fluids and synthetic fluids are different.

I know that some hyd fluids are synthetic, and some motor oils are synthetic.

I know of people that have switched fluids between 10W-40 motor oil, used in hyd system, and 10W40 synthetic motor oils and not noticed any difference except the heat tolerance is better.

Do they actually make a different seal kit based on the fluid used , say in tractor hyd cyl?

Seems that most people are never asked which fluid they are using.

Are people really qualified as seal experts.

Can't say that I have had this conservation, but maybe something like this.

I am looking to improve the seals on this cyl, what would you recommend for high heat, 6 hrs a day utilization, synthetic hyd fluid will be used, just what changes could a hyd technician make to a cyl seal kit to make it better. Would they even change the piston to meet the criteria for a more harsh environment .

What say you.

 

[oldnslo]

Yes different seals are required different fluid types and operating temperatures. Synthetic fluids is a touchy subject because the oil manufacturers typically don't perform seal compatibility tests. Now look at a seal manufacturers recommendations for seal compatibility for hydraulic fluids with synthetic base and they rate Buna-N as fair with Viton being preferred. This is from Parker O-Ring handbook.

Example: ExxonMobil isn't going to tell you that using Mobil 1 may cause your seals to leak. NO I am NOT stating Mobil will cause seal failure.

Phosphate esther fire resistant fluids will dissolve standard Buna-N/nitrile seals which are the most common seal around. This type of fluid requires Viton seals.

Freon will destroy both Viton an Buna-N.

Buna-N has a temperature range of -30 to 250 degrees F

Viton has a temperature range of -15 to 400 degrees F

A vast majority of industrial and mobil hydraulic OEM's are switching to Viton as there standard seal material because in most cases it provides a greater range of fluid compatibility than Buna-N.

Roy

 

[BotaBigot]

My dino/syn experience is w/engine oils. Only "negative" I've experienced w/syn is slightly greater propensity for gasket seepage...which I unscientifically "assume" to be possible lower surface tension of some ingredients. Syn has been around a while and if there were material compatibility problems, it would be common knowledge by now...like that of ethanol and older fuel system materials. Syn motor oils are built on a dino base.

Edit: Composing this when Roy posted. I defer to his post...bottom line...always use most advanced sealing material available, especially with extreme temp/pressure

 

[murphy1244]

When I worked at VanDorn we used Parker cylinders Viton seals and Mobil hydraulic fluid. These plastic injection machines run 24-7. I use what they use.

 

[J_J]

This article seems to suggest that mineral oil based fluid, mineral based motor oil, mineral based synthetic, and full synthetic fluid, with no mentioned of changing out seals. Most of us do not even know what kind of seals are used in any cyl, unless you have ordered the kit and they explained what seal are being used.

http://hydraulics.eaton.com/products/pdfs/03-401-2010.pdf

I have one of the Power-Tracs , and had considered the swap out of the fluid in my hyd tank, which is now 10W-40, about 20 gal.

Even Eaton recommends motor oils as hyd fluid, and synthetics also, with no mentioned of seals.

My idea was to switch out to a full synthetic with no detergents, and therefore decrease the water problem that so many tractors have, and give extended heat range, and extended fluid changes.

I can not think of a single Power-Trac that has ever had a water problem.

The excerpt posted above , post 1, sort of suggested that if switching type fluid, you need to change the seals, or select a particular fluid that is good with both types.

 

[oldnslo]

Take a look at Eatons model codes for their pumps or motors. if memory serves me correctly they specify different RPM's, pressure capability and seal material depending on fluid type.

probably 95% or more of the industry just uses what there is and in most cases it is either Buna-N or Viton or a combination of the above.

If you are really concerned look at some O-ring or seal manufacturers site. They should have pages of documentation on seal compatibility.

Attached is small sampling of products Vs recommended seal material.

 

[MHarryE]

Back in the early 90's we switched all of our hydrostatic transmission stuff to Viton for improved temperature capability and bio-hydraulic fluid capability. Our hydro suppliers at the time were Sauer-Sundstrand and Mennesman-Rexroth. When I retired the companies had changed hands so they were Sauer-Danfoss and Bosch-Rexroth but they both still said Viton due to heat in the Hydrostatics and the steering units. I can't remember if we did anything special about steer cylinder seals. Now you have me wondering if that is why the warranty on steer cylinders was higher than I cared to see.

 

[Wayne County Hose]

JJ, did they state why one seal could not handle both types of fluids? I would ask what seal for dino oil, what for synthetic? Most hydraulic hoses use a nitrile inner liner and I have never heard of a compatibility issue. I would check the Hercules- Bulldog seal catalog. There is a very good seal/fluid compatibility chart.

 

[J_J]

No, and I believe that excerpt was from Eaton.

Here is some more good reading about mixing fluids.

Managing the Risk of Mixing Lubricating Oils

When I first picked up my Case trencher, it was low on fluid, and the label said 10W-40 or ATF. So I put some ATF in the system. Don't know what was in there, and don't know if they will mix well. I plan to rebuild the radiator and add ATF.

Now my Case 1845c says to use 10W-40 with a quart of Case additives, or Hy-Trans. I guess that either one is acceptable, but not to mix.

Hy-Trans, is more expensive, but is it any better?

 

[oldnslo]

No, and I believe that excerpt was from Eaton.

Here is some more good reading about mixing fluids.

Managing the Risk of Mixing Lubricating Oils

When I first picked up my Case trencher, it was low on fluid, and the label said 10W-40 or ATF. So I put some ATF in the system. Don't know what was in there, and don't know if they will mix well. I plan to rebuild the radiator and add ATF.

Now my Case 1845c says to use 10W-40 with a quart of Case additives, or Hy-Trans. I guess that either one is acceptable, but not to mix.

Hy-Trans, is more expensive, but is it any better?

My two cents..

Hy-tran is meant for high pressure hydraulics & transmission use and has the anti-foam, anti-wear, etc. additives. Normal 10W-40 does not, that is why they require the additives. I used to have a viscosity curve on Hy-Tran but can't find it now. From memory I think it was similar to a 10W-30.

ATF does have some of the required additives and was the fluid of choice for some equipment. if memory serves me Sundstrand recommended ATF for their HST's in the 70's & 80's.

I think today most hydraulic equipment OEM's like Sauer-Danfoss, Bosch Rexroth, Eaton-Vickers, Parker Hannifan just specify a viscosity range with petroleum based fluids and seal types, operating RPM & pressure depending on the fluid type. Example: Water emulsions usually have a lower operating pressure and RPM Vs petroleum fluids.

Agree with mixing fluid types should be avoided if possible.

Part of the dual label for fluids might stem from the availability if ATF or 10W-40 Vs Hy-tran. Almost any convenience store has ATF or 10W-40.

Roy