O-Ring Boss, JIC Hydraulic Fittings.

[George7941]

The place I work at just bought an old Toyota ForkLift and I replace a leaking hydraulic hose.

For proper access, I had to remove a couple of O-ring Boss fittings. I screwed them back in with their existing O-rings. Should I have replaced the fittings? I am concerned about the old o-rings leaking.

The new JIC fittings on the ends of the new hose tightened up nicely with a satisfying "crush". What about the old JIC fittings I had unscrewed for access purposes and rescrewed back on? Can JIC fittings be repeatedly disassembled and still seal up well? I did not use any pipe dope on the 37 degree sealing faces, I left the faces bare.

 

[HM12460]

37 degree JIC fittings by Parker is a quality product. If the crown isn't scored or dinged up it should seal up just fine.

 

[abycat]

Jic does not need any sealant. You can also use them many times. There are torque specs by the way so dont over due it. The o-ring boss fittings which by the way are the exact same thread and diameter as jic. Just for a little tidbit for you. But you should replace the oring each time on the boss fittings. Since they are the part that seals the connection.

Oh and they have a torque spec as well. If you need to know any more just ask i was a shop supervisor at a large hyd and industrial shop. I know anything aboit that stuff. I also made a book with all the info you could imagine.

Let me know if you need to know the specs. Also there are a few fittings that are almost identical to jic but not interchangable. Like komatsu, sae, and some weird chinese metric jic type one.

 

[AVB]

Hey abycat, what is the difference in boss o-rings and regular o-rings? When I worked on hydraulics I was always told not to use a regular o-ring on boss fittings, but no one could tell me why.

 

[abycat]

Well they are a certain size but you should use 90 durometer ones not 70. You can use viton ones if heat is a concern but they are 10-12 times more.

 

[George7941]

Couple of issues you can resolve for me, abycat.

I have never seen the o-rings for the boss fittings for sale separately (not as part of the complete fitting). Would a hydraulic shop have the o-rings for sale?

I was not able to tighten the boss fittings as much as I would have liked to because of orientation. I got them a little tighter than finger-tight.I don't it will cause leaks because it is the o-ring that does the sealing. However I was wondering about vibration and flexing of the joints. I hope the O-rings can handle the (small)vibration and flexing. A new boss fitting I purchased had a back-up washer behind the o-ring. Is the purpose of the washer to provide a little crush so that mechanical tightness of the joints can be achieved even when the final position of the fitting is dictated by orientation requirement?

 

[AVB]

Normally there is a washer and a nut. You screw the fitting in most of the way, clock them in what ever position they need to be. Then tighten the nut to lock them in place while holding the fitting in position.

 

[abycat]

Avb you are right but those are for 45 or 90 degree fittings so you can position them. Straight ones dont have the nut. As for you george they will leak and loosen on you. The shop i worked in had 40 ish orings for each boss fitting in stock at any given time. I will have to give you the dimensions so you can locate some. Do you have a princess auto? They should have some or know were to get some. Im out of town so i dont have my book with me but ill get the info for u tomorrow.

 

[bmod305]

Napa has two sources for the correct orings:

Weatherhead(Eaton) or Gates. Most stores carry one of the two but not both. Our store group uses Gates. Bring the old fitting in so it can be matched up.

Dave

 

[George7941]

Originally Posted By: abycat
Avb you are right but those are for 45 or 90 degree fittings so you can position them. Straight ones dont have the nut. As for you george they will leak and loosen on you.


Now you have me concerned. The fitting is a 90* elbow 1/2 in boss by 3/8 JIC.It is #S3649-68 on this page http://www.fairviewfittings.com/techdata.html?id=62446
I tightened the fitting by wrenching on the flats of the body and was not paying attention to the nut. The fitting was in a very awkward place with little access and I had to remove a number of fittings and hoses to access this fitting. I will have to do some disassembly again and tighten that nut.

Thanks for pointing it out. It is better I tighten the nut now rather than have the fitting leak later. And now that I am going to be taking the fittings apart again, I will get new o-rings and replace the old ones.