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DocLightning
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Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 1:19 am

I've heard stories about people coming in contact with hydraulic fluid ("SKYDROL") and being miserable because of it.

Why is the stuff so nasty? Can't they come up with something less toxic?
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notaxonrotax
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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 2:03 am

I´ve heard the same about alcohol……………very miserable they were, them poor sods!!!
WHY?


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EMBQA
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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 2:10 am

You're an MD.... go look up what it is and what it will do when it comes into contact with the skin.

As far as the rest of your question. Its the best chemical make up they can come up with that meets all the requirments.

[Edited 2011-03-23 19:11:55]
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ctempleton3
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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 2:11 am

Did some searching it appears that non-petroulium based hydraulic fluids are used in in high temp applications where the fluid needs flame resistance properties. See the article located at http://www.tpub.com/content/engine/14105/css/14105_39.htm

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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 2:41 am

Quoting EMBQA (Reply 2):
Its the best chemical make up they can come up with that meets all the requirments.


That is pretty much the deal. The -40F/C or lower temps pretty much leave out water based fluids and the high temps and flammability pretty much leave out mineral base so you get phosphate ester (Skydrol)

Skydrol falls under the old description of a "good performer but a bad actor". I would trust that as much of an irritant that Skyrol is plenty of research has been done looking for a better product.

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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 5:12 am

You ain't even seen miserable yet!!  


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wingscrubber
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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 6:40 am

Skydrol or Hyjet AS1241 phosphate ester hydraulic fluids are the nasty ones - early versions of the now-common fluids came to be after the war during the rapid technological development of civil transports.

Hydraulics was needed more and more for the ever larger and faster aircraft, with system pressures becoming higher and higher - traditional hydraulic fluids were always petroleum, diesel or mineral oil based, all highly flammable if they leak.

There were accidents caused by hydraulic leak fires, it became rapidly apparent that there was a need for flame retardent hydraulic fluid.

Skydrol 500B was created in 1952, nobody set out to deliberately engineer a horrible chemical which all mechanics would hate, it just happened to be a chemical combination which would meet a level of flame retardance, but then also meet viscosity and bulk modulus requirements across the required temperature and pressure range.

http://www.skydrol.com/pages/product.asp

The funny thing is, the US military never used skydrol, they had their own spec - MIL-H-5606 or 'red oil'.
For the longest time, civil airliners were being designed with skydrol systems while the military (the ones who get shot at, and most likely to catch fire...?) continued to use MIL-H-5606, which is easier on maintenance personnel but has a lower flash point(more flammable) and narrower operating temp range.

Subsequently skydrol has been regarded as the civil aviation gold standard in hydraulics for the longest time, with LD-4 systems being the most common. Now manufacturers are beginning to migrate to skydrol type 5, which is the latest and greatest 'formula'.

http://www.hydraulicspneumatics.com/200/Issue/Article/False/6528/Issue

Traditionally, smaller aircraft and business jets have opted for 'red oil' systems where they weren't so worried about flammability issues or had less harsh environmental requirements, but many OEMs have often rejected red oil systems as being too dangerous because 'they're much more flammable' and that perception remains, the reality is that MIL-H-5606 was superseded some time ago by MIL-H-87257 which is nearly equal to or greater than skydrol in many aspects. MIL-H-83282 is another.

Some of the things I dislike about skydrol are the following;
-Skydrol is not chemically stable at very high temperatures; the acid control additives break down and turns it into a highly corrosive soup which procedes to eat component internals. In comparison red oils are pretty stable at extreme temperatures, especially MIL-H-83282, but they can also turn into a corrosive soup if exposed to chlorine solvents.
-Skydrol cannot be reconditioned; when it reaches a certain 'stress level' it has to be drained and thrown away
-Skydrol cannot be recycled or disposed of in any kind of environmentally friendly manner, it has to be buried in landfills or incinerated producing some very toxic gasses.
-Skydrol has a high coefficient of thermal expansion compared to MIL-H-87257, meaning reservoirs have to be bigger.
-Skydrol has a higher specific density than MIL-H-87257 resulting in heavier wet-weights.

That said, there are a couple of places where skydrol is pretty good; it has good low temperature viscosity and it's an efficient heat transfer fluid.

If you can't tell, I am anti-skydrol, having heard stories of what it does to the people who work with it and having seen what it does to components when it breaks down, I have strong reason to recommend against it.
BUT, that said, OEMs and the FAA are sticks in the mud, and they like skydrol because they're comfortable with it, it's also just so damn common, so even if I present a trade study to an OEM for their new aircraft hydraulic system which categorically states that red oil is better, they'll still want to build a skydrol airplane! Grr.
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HAWK21M
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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 9:24 am

Skydrol serves the purpose under extreme temperatures so does the job intended.
If Mx uses adequate protection while handling it.There should not be a problem.
regds
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aviopic
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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 7:39 pm

Quoting DocLightning (Thread starter):
Can't they come up with something less toxic?

Probably not because Skydrol is only slightly toxic at best.
It doesn't feel nice on your skin and certainly not in your eyes but even ingested it hasn't harmed people for as far as I know.
Unlike the Fluid 41 which feels nice but isn't.

Could not find an official hazard report in English but a Dutch version can be found here:
https://team.solutia.com/sites/msds/Skydrol%20MSDS%20Documents/181ENL.pdf
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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 8:36 pm

Quoting Aviopic (Reply 8):
Could not find an official hazard report in English

https://team.solutia.com/sites/msds/Skydrol%20MSDS%20documents/181AEN.pdf
here it is
 
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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 9:43 pm

It's actually fairly safe.
It will irritate and BURN the crap out of your (my) eyes (a few times in the past few years), and it doesn't feel good on skin, either.
I also have a friend who was exposed to a wheel well full of skydrol mist, and his liver shut down for a period of time.

But as far as fluids go, it won't kill you nearly as fast as jet fuel or Royco LGF or CPCP or any number of other, truly toxic fluids we use on and around aircraft on a daily basis.
 
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RE: Why Is Hydraulic Fluid So Awful?

Thu Mar 24, 2011 10:01 pm

Quoting Wingscrubber (Reply 6):
Some of the things I dislike about skydrol are the following;
-Skydrol is not chemically stable at very high temperatures; the acid control additives break down and turns it into a highly corrosive soup which procedes to eat component internals. In comparison red oils are pretty stable at extreme temperatures, especially MIL-H-83282, but they can also turn into a corrosive soup if exposed to chlorine solvents.
-Skydrol cannot be reconditioned; when it reaches a certain 'stress level' it has to be drained and thrown away
-Skydrol cannot be recycled or disposed of in any kind of environmentally friendly manner, it has to be buried in landfills or incinerated producing some very toxic gasses.
-Skydrol has a high coefficient of thermal expansion compared to MIL-H-87257, meaning reservoirs have to be bigger.
-Skydrol has a higher specific density than MIL-H-87257 resulting in heavier wet-weights.

I hate:
In the cold weather, it freezes any skin contact.
In the heat, it feels like it has raised the temperature of the contact are by 20 deg.
It tastes like crap.
It smells like crap.
It burns the eyes.
It stains the clothes.
It's slippery as snot on the hangar floor.

Redeeming quality? If you're working in it, you can be assured the flight crew won't be bugging you.
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DocLightning
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RE: Why Is Hydraulic Fluid So Awful?

Fri Mar 25, 2011 6:43 am

Quoting EMBQA (Reply 2):
You're an MD.... go look up what it is and what it will do when it comes into contact with the skin.

They say it's phosphate-based and non-flammable. I don't understand why it is such an irritant. I guess that it's the best they can do given the specs. I wonder if anyone's considered a silicone-based solution. Would that work?
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RE: Why Is Hydraulic Fluid So Awful?

Fri Mar 25, 2011 1:43 pm

Quoting fr8mech (Reply 11):
I hate:
In the cold weather, it freezes any skin contact.
In the heat, it feels like it has raised the temperature of the contact are by 20 deg.
It tastes like crap.
It smells like crap.
It burns the eyes.
It stains the clothes.


Good point:

I have found it cauterizes small cuts. They heal much faster after being in contact with Skydrol.
 
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kanban
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RE: Why Is Hydraulic Fluid So Awful?

Fri Mar 25, 2011 4:38 pm

seems to me TWA tried Mil-H in their first 747's... which created a problem since little things like O-ring and gasket materials were different ... and using the wrong one ended up in either a leaker or the material swelled...
 
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RE: Why Is Hydraulic Fluid So Awful?

Sat Mar 26, 2011 1:47 pm

Quoting DocLightning (Reply 12):
I don't understand why it is such an irritant.

It's actually Phosphate Ester... It causes chemical burns and rashes with longer exposures. Some people are more resistant then others. I do ok with Skydrol.. but don't really like it. Now jet fuel turns my skin white..
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RE: Why Is Hydraulic Fluid So Awful?

Sat Mar 26, 2011 9:51 pm

So who has a story with skydrol that they'll always remember to wash their hands before a leak  
Quoting EMBQA (Reply 15):

It's actually Phosphate Ester... It causes chemical burns and rashes with longer exposures

The Skin starts to peel in layers after long exposure.I made a mistake of wearing cotton gloves while working 8hrs on hydraulics.The gloves were soaked with skydrol.When I got them off the skin had started to flake on my palms at places.Oddly the back of the hand seemed normal.
Took a forthnight to normalize.

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RE: Why Is Hydraulic Fluid So Awful?

Mon Mar 28, 2011 9:41 am

Skydrol exposure, IMO anyway, isn't as bad as some make it out to be. Just don't go swimming in it or inhale it and you'll be all right.

Some info from Solutia:


Q: What chemicals in Skydrol fluids cause irritation?
A: The phosphate ester base stock is the cause of irritation. Phosphate esters are good solvents, and can dry the skin. They contain mild organic acids that give a slight burning sensation on sensitive skin areas, and in the eyes they are quite painful. In all cases of exposure, however, as soon as the phosphate ester is removed, by washing, the pain subsides. Skydrol fluids are not known to cause allergic skin rashes, although repeated or prolonged exposure may dry the skin. If left unattended, this could result in complications such as dermatitis or even secondary infection from bacteria.


Q: What can I use to protect my hands?
A:

To avoid exposure, a worker should wear gloves that are impervious to Skydrol hydraulic fluids. Solutia has tested several different glove materials and has published guidelines in the publication titled "Glove Facts." Contact Skydrol Technical Service to obtain a copy.

Solutia does not recommend the use of barrier creams in place of gloves. Barrier creams are not a reliable method of protection.


Q: What is the proper first aid treatment for eye exposure to Skydrol fluid?
A: Solutia is not aware of any case of eye damage from exposure to Skydrol fluid. When the fluid gets into the eyes, it can cause severe pain, but the pain will subside as soon as the fluid is removed. First aid is washing with tap water, or a standard eye irrigation solution. 15 minutes of washing with water will usually be enough to remove the Skydrol and cause the pain to cease. Secondary treatment, such as with sterile mineral oil, should only be given under the care of a medical professional, as it goes beyond recommended first aid. Milk is not recommended as an eye wash, because it is not sterile and can cause infections in the eye. Always remember to wear safety glasses or chemical goggles to prevent eye exposure when working around Skydrol.


Q: What happens if I breathe in Skydrol fluids?
A:

Upper respiratory irritation, including nose and throat irritation and tracheitis and/or bronchitis, can occur from inhalation of a mist. People with asthma may have a more marked reaction.

If through some accident liquid Skydrol fluid is aspirated directly into the lungs, such as by swallowing a large amount and breathing in at the same time or by breathing in while vomiting, it is quite possible that chemical pneumonitis could occur. This occurs following deep aspiration of any foreign material into the lungs. We have never heard of this happening with the Skydrol fluids. The possibility of it happening under normal industrial conditions does not appear likely.

When mist or vapor is possible because of high pressure leaks or any leak hitting a hot surface, a respirator capable of removing organic vapors and mists should be worn.


Q: What is the best first aid treatment if Skydrol fluid is ingested?
A: Immediate first aid is not likely to be required. Consult a physician or a Poison Control Center.
 
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bikerthai
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RE: Why Is Hydraulic Fluid So Awful?

Mon Mar 28, 2011 7:04 pm

Quoting Wingscrubber (Reply 6):

Some of the things I dislike about skydrol are the following;

There's also a quirt about skydrol that is not widely known.

Titanium (specifically 6AL-4v) in general resist most corrosion except when exposed to dripping skydrol at a specific temperature range. Can't recall what the temperature range was but it was something to think about when designing titanium parts in areas around the engines.

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RE: Why Is Hydraulic Fluid So Awful?

Wed Mar 30, 2011 7:22 pm

Quoting kanban (Reply 14):
seems to me TWA tried Mil-H in their first 747's... which created a problem since little things like O-ring and gasket materials were different ... and using the wrong one ended up in either a leaker or the material swelled...

Skydrol and Red oils do require different o-ring rubber compounds due to the way they react to the fluid.
A lot of that kind of thing was discovered back in the 60s, and that's when many of the now-trusted industry standard Mil-specs for hydraulics were written!

Quoting bikerthai (Reply 18):
Titanium (specifically 6AL-4v) in general resist most corrosion except when exposed to dripping skydrol at a specific temperature range. Can't recall what the temperature range was but it was something to think about when designing titanium parts in areas around the engines.

Did not know that... thanks for the info. Additionally, there are some anti-vibration clamps which if they get too hot can sweat acid onto hydraulic tubes. MS21919DF clamps, the yellow ones, they also break down when they come into contact with skydrol.

Quoting DocLightning (Reply 12):
They say it's phosphate-based and non-flammable. I don't understand why it is such an irritant. I guess that it's the best they can do given the specs. I wonder if anyone's considered a silicone-based solution. Would that work?

Concorde had a silicon ester based fluid, Chevron M2V Silicate Ester. I believe it had problems with water contamination inducing corrosion. There's a story about it here in another old post.
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HAWK21M
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RE: Why Is Hydraulic Fluid So Awful?

Fri Apr 01, 2011 5:28 pm

Quoting bikerthai (Reply 18):
Titanium (specifically 6AL-4v) in general resist most corrosion except when exposed to dripping skydrol at a specific temperature range. Can't recall what the temperature range was but it was something to think about when designing titanium parts in areas around the engines.

Ducts near the Pack ceilings on a B737 are suseptible to such events hence are coated to reduce the effect.
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RE: Why Is Hydraulic Fluid So Awful?

Sun Apr 03, 2011 5:23 pm

Quoting EMBQA (Reply 15):
It's actually Phosphate Ester... It causes chemical burns and rashes with longer exposures. Some people are more resistant then others.


I always wear gloves when working around it. Could never understand why some guys don't take that extra step and let it get all over their hands.

Quoting EMBQA (Reply 15):
Now jet fuel turns my skin white..


It does'net do that to me. But then I never volunteer for fuel tank work either.
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HAWK21M
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RE: Why Is Hydraulic Fluid So Awful?

Sun Apr 03, 2011 9:09 pm

Quoting LMP737 (Reply 21):

I always wear gloves when working around it. Could never understand why some guys don't take that extra step and let it get all over their hands.

Depends on the type of gloves used......Out here in case of Hydraulic system work out comes the Gloves & Goggles.

Quoting LMP737 (Reply 21):

It does'net do that to me. But then I never volunteer for fuel tank work either.

Only small framed persons can fit through these Access panels .......

regds
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MD11Engineer
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RE: Why Is Hydraulic Fluid So Awful?

Mon Apr 04, 2011 2:12 am

Skydrol and relatives consist mainly of tributylphosphate plus additives. From what I understand tributylphosphate reacts with water and decomposes into butanol and phosphoric acid.
The acid then causes the pain and attacks titanium.
As an organophosphate ester it has also come under suspicion of causing neurological problems (it is also a component of many gas turbine engine oils, like Mobil Jet 2). Doc might have more information about the toxicity of tributylphosphate.

BTW fuel can cause bad rashes as well. I had the experience of having laid for several hours in a fuel puddle inside a wing without noticing it. My overalls were thoroughly soaked with fuel. After a few hours I felt an itchy and burning sensation in the affacted areas. Even though i left the tank, took of my overalls and washed with water and soap my skin turned very red and started to peel off like a bad sunburn.

Jan

[Edited 2011-04-03 19:13:54]
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tdscanuck
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RE: Why Is Hydraulic Fluid So Awful?

Mon Apr 04, 2011 4:07 am

Quoting MD11Engineer (Reply 23):
Even though i left the tank, took of my overalls and washed with water and soap my skin turned very red and started to peel off like a bad sunburn.

Fat is soluble in fuel...the problem is that the fuel disolves fat right out through your skin. We had this happen to a guy at work several years ago and his skin cracked so badly that his whole leg got deeply infected and he darn near lost the whole thing.

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RE: Why Is Hydraulic Fluid So Awful?

Mon Apr 04, 2011 8:03 am

Quoting tdscanuck (Reply 24):
Fat is soluble in fuel...the problem is that the fuel disolves fat right out through your skin.

So does the tributylphosphate. It is an excellent solvent for body fats.

Jan
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HAWK21M
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RE: Why Is Hydraulic Fluid So Awful?

Mon Apr 04, 2011 10:06 am

Quoting MD11Engineer (Reply 23):
Even though i left the tank, took of my overalls and washed with water and soap my skin turned very red and started to peel off like a bad sunburn.

True.ATF if in contact with skin for a longer duration tends to peel the top layer off.

Best is to wash off with Soap & Water as soon as possible.

regds
MEL.
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RE: Why Is Hydraulic Fluid So Awful?

Mon Apr 04, 2011 10:53 am

Quoting HAWK21M (Reply 26):
Quoting MD11Engineer (Reply 23):
Even though i left the tank, took of my overalls and washed with water and soap my skin turned very red and started to peel off like a bad sunburn.

True.ATF if in contact with skin for a longer duration tends to peel the top layer off.

Best is to wash off with Soap & Water as soon as possible.

regds
MEL.

If I notice that I got contaminated with larger amounts of fuel, I usually wash at work and later at home I nick some of my fiancee´s skin lotion to re-grease the skin.

Jan
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