Insane Hydraulics
Bold and audacious blog about fluid power
The multitude of hydraulic hose standards makes my head hurt every time I think about it, and the fact that hose manufacturers use them "as please" to identify their product adds to the confusion. One quick example - I took these two shots an hour ago - a couple of random hoses from the same manufacturer - Parker:
As you can see, the first hose is marked as:
"NO SKIVE 301SN-10 WP 25.0 MPa (250BAR) and then also MSHA IC-272/1, and SAE100R2AT-10, and 16mm (5/8) X 2W, and EN853/2SN/16/DIN"
Why so many letters and numbers? 301SN sounds like 1SN, which would be an indicator of a single-braided hose but then the R2AT means two braided hose, doesn't it? Do I really need to know all this stuff? The short answer would be - no, you don't. But let's dive in just for the heck of it:
"NO SKIVE" is a no-brainer (and one of the few things making "human sense" here).
"301SN" is the reference that Parker engineers chose to identify this product. But why does it end with 1SN? Only God knows. Never try to make any sense out of naming decisions of large companies. This is a common two-braided hose, and we accept that its Parker's name is 301SN. Can you guess what its one-braided brother is called? 300SN maybe? Nope! It's 421SN! Very (not) intuitive! I imagine engineers gather around a large round table trying to deliberately invent the least obvious names for their products - like a language that only a selected few understand...
-10 is the size in sixteenth of an inch, and it determines the internal diameter of the hose. This, I mean the dash size of a hose, is the only thing that all hose manufacturers seem to agree on and respect. So, if you want to be able to identify a hose size with a vernier caliper you do need to know how to read it in inches. Just saying.
WP 25.0 MPa (250BAR) is another human-readable marking that means working pressure. No doubts here. And thank you for pointing out so clearly that 1 MPa equals 10 bar.
Now the rest of the stuff that they decided to put on the hose can be described as a "beautiful mess".
What the hell is this MSHA thing?
MSHA stands for Mine Safety and Health Administration, which is a US agency that develops and enforces safety rules for all US mines. The IC-272/1 is the acceptance number that was given to this hose by the MSHA when it was accepted "under interim fire criteria" (whatever this means).
SAE100R2AT-10 means that under the SAE (Society of Automotive Engineers) standard J517 (never mentioned on the marking), this hose is identified as 100R2AT with the dash size of 10. More on SAE hose standards below.
Then you have the metric plus imperial size of the hose (once again - referring to the internal diameter), 16mm equals 5/8 of an inch, and the 2W, I suppose, means two wires.
And in the end - a cherry on the top of our confusion cake:
EN853/2SN/16/DIN, which means that this hose is defined as a 2SN hose by the EN853 standard, where the EN means "Europäische Norm" (European Standard), and the DIN probably means either the "Deutsches Institut für Normung" (German Institute for Standardization) or simply Diameter Internal. Who knows what at this point?
Wow! So much useless information in such a short combination of meaningless characters and numbers!
Cool. But what about the second hose? It's marked as:
NO-SKIVE 731-16 WP38.0 Mpa (5500 PSI) 25mm (1) X 4S EN856-4SH/25
OK... Where is the SAE specification? And what about the MSHA? Just MPa and PSI, no bar this time? I am guessing 4S means four spirals, but why not say 4W, four-wire, the spirals are made of wire, aren't they? The EN856-4SH seems to be the name of another European standard this hose is compliant to. Once again, the only two things that seem to be making human sense are the working pressure and the dash size of the hose.
One thing is clear, though. There seems to be a number of organizations out there, that decided to elaborate a set of rules, or better standards, for industrial hydraulic hoses, to bring order to the chaos in the hose-producing industry.
Since the point of this blog is to bring clarity, I decided to shed some light on some of the existing hose standards, starting (today) with the SAE. And by the way - this standard is not freely available to the public, and if you really want to dig into the details, you will have to dish out a certain amount of cash in order to download the official document. I guess it's another of those "exclusive engineering club" things.
Before all - the full name of the SAE standard for the hydraulic hoses would be the J517, which in its most recent revision (2020) stands as J517:202007.
This standard provides the specs for the 100R-series hoses (hoses used in hydraulic systems). Why are they called 100R? Who knows? I am accepting this as a given. So, let's get started:
SAE 100R1 - currently only has one type - R1AT. This is a one steel wire braid reinforced, rubber-covered hydraulic hose. There used to be type A (R1A), which had a thick cover that required skiving, but it was removed from the standard due to lack of demand. This is a medium pressure hose, for return lines or places where the weight of the hose matters, but, of course, you know this.
SAE 100R2 - the same thing about the A-type (R2A) - it's done with. Only 100R2AT now. Two steel braids in this one. The most used hose type in the world.
By the way - both the R1 and R2 used to have a special "S" type that defined hoses for higher (super) pressures, but both of the standards employ the "S" type max. pressure now.
SAE 100R3 - one would think that number three in the standard would identify a three-braided hose, but this is not the case. This one is a two-braided hose with fiber(non-metallic) braids. Another option for low-pressure lines (lubrication, etc).
SAE 100R4 - a common mistake is to interpret the digit 4 in the standard name as the number of reinforcement plies. I sometimes hear mechanics call high-pressure hoses R4 hoses. This is very far from the truth. R4 hose is for suction lines only. Well, return lines maybe. It has the reinforcement consisting of plies of woven or braided textile fibers and a spiral made of steel wire, which makes it harder to collapse - hence- good for suction lines. It also comes in very large sizes. Up to -64.
SAE 100R5 - another single wire braided hose, only this one has a fiber braided cover. This hose is suitable for hydraulic fluids and compressed air, so it can be used in air brakes, etc... Very often manufacturers place another textile braid around the inner tube to anchor the synthetic rubber to the wire. Goes up to dash-48 size. I don't think I ever used this type of hose.
SAE 100R6 - medium pressure hose with one or several layers of non-metallic fiber reinforcement, that comes in sizes from the tiny -3 up to -12. An option for lighter pilot lines, I guess. Never used this one as well.
SAE 100R7 - the famous thermoplastic hose, both on the inside and the outside. Uses synthetic fiber reinforcement. Non-conductive, obviously. Can come in orange. Medium and low pressure only. Recommended for places where high voltage "may happen", but I see manufacturers stick this type everywhere because it's quite compact.
SAE 100R8 - once again, thermoplastic, but with a higher pressure rating. "Higher pressure" is pretty relative because for larger dash sizes it goes down substantially. I never used one larger than -08 though.
SAE 100R9, 100R10, and 100R11 - you can forget about these standards altogether - they were dropped for lack of demand. All high pressure, heavy-duty, four and six-spiral hoses, if you need to know.
SAE 100R12 - This is a hydraulic hose reinforced with four spiral plies of steel wire wrapped in alternating directions. Note - even though this is a hose with four plies, the pressure specs are quite low, much lower than the most common 4SH hose. But the specs also state that it is good for a temperature of up to 121 C.
SAE 100R13 - another hose for temps up to 121 C, but with more wires, that comes in sizes from -12 to -32, and is specified for 350 bar for all sizes (!). Heavy duty. Sometimes referred to as "constant pressure hose".
SAE 100R14 - high-temperature hose (up to 204 C) that uses an inner tube made of PTFE and is reinforced with a single braid of stainless steel wire. There are two types of this hose - A and B, with B having the inner surface conductive. Despite having only one braid, this hose (especially in smaller sizes) is very high-pressure capable. Obviously, it is anti-corrosive as well.
SAE 100R15 - another heavy-duty multiple spiral ply hose. I would call it 4SH on steroids because it is supposed to have the max working pressure of 420 bar in all sizes - from -6 up to -24! Very heavy and physically challenging to work with.
SAE 100R16 - a more compact and lighter alternative to the 100R2 hose, that also offers the benefit of a tighter bend radius. Can have one or two steel wire braids, and has the same working pressure as the 100R2.
SAE100R17 - another compact hose with one or two steel braids. Unlike the R16 this one states the working pressure of 210 bar for all sizes (from -3 to -16).
SAE 100R18 - another version of thermoplastic hose. This standard implies that all the sizes (from -2 to -16) withstand 210 bar.
SAE 100R19 - Ever used castor oil or ester-based hydraulic fluid? I hope you never have to. But if you do - this is the hose to use. 280 bar across all sizes - from -3 to -16.
So, now you are an expert in the SAE hydraulic hose standard. I hope you learned something new here!