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O-Ring Face Seal and Loc-tite

03/10/2021 10:41 AM

I've been using O-Ring Face Seals (ORFS) on hydraulic hoses and tubes for a while, then I started this job, where the ole 37deg. JIC fitting was the standard. Well, the company (the design engineering guys) wanted to change over to the more reliable ORFS, but they didn't change the designs to allow for the torque wrenches, so they (the design engineering guys) decided to just forego torqueing hoses all together. It wasn't too long before the field reports started coming in on leaks at the hose fittings and they (the design engineering guys) are thinking the operators on the floor are not tightening the fittings, or they are coming lose after tightening. So, they (the design engineering guys) asked us (the manufacturing engineering guys) to come up with a solution that didn't include a torque wrench. So, we, (the manufacturing engineering guys) came up with a dot or just more than a dot of loc-tite on the threads of the fittings. The idea works better than nothing, but until we can convince the design guys to move hoses, this is what we're doing.

The question comes around from rework or leaks found in the factory. Once the fitting is covered with oil, how can we get the loc-tite to work? We can never get the oil completely off the fitting.

Thanks

Laby

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#1

Re: O-Ring Face Seal and Loc-tite

03/10/2021 2:12 PM

Try some Teflon pipe thread compound on the hose fitting threads. It may seem counterintuitive to make the fitting easier to turn to keep it from loosening, but the compound will make the fitting tighter for a given amount of torque.

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#2
In reply to #1

Re: O-Ring Face Seal and Loc-tite

03/10/2021 2:32 PM

Teflon tape is used in applications where the thread is the seal, normally called pipe threads. In this application, it's the O-Ring that forms the seal. The hydraulic fluid would assist in making the seal as it would lubricate the O-ring and make it less likely to cut during the install. I don't see how the teflon tape would do the same as the loc-tite to hold the fitting from becoming loose during operation. if we were able to get a torque wrench on the fitting, then the loc-tite wouldn't be needed.

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#4
In reply to #2

Re: O-Ring Face Seal and Loc-tite

03/11/2021 3:17 AM
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#6
In reply to #4

Re: O-Ring Face Seal and Loc-tite

03/11/2021 5:37 AM

A crow foot wrench would work but you should consider getting the flare nut style if there is room. (Less likely to round the fitting).

Also, try using brake cleaner on the fittings before putting any o-rings or Lok-Tite on. This will remove the oil very quickly.

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#9
In reply to #4

Re: O-Ring Face Seal and Loc-tite

03/11/2021 7:48 AM

We have crows feet, and use them where we can.

Thanks for the answer thou

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#12
In reply to #4

Re: O-Ring Face Seal and Loc-tite

03/11/2021 10:28 AM

we had Parker Tube come into our plant, observe and test....thats why we now use the Hyd Loctite on the threads....

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#3

Re: O-Ring Face Seal and Loc-tite

03/10/2021 10:47 PM

I have come across this issue many times over my working life and find that the design details are critical.

Static Face seals absolutely require -

Correct O-ring / Square ring / X-ring / Backup washer selection appropriate for the fluid pressure and fluid type.

Correct Groove diameter OD (for a hose application).

Correct Groove depth dimension to achieve a suitable o-ring crush on assembly.

These issues are well addressed in literature from manufacturers such as Parker Hannifin.

If you do the design right, then bolt tightening torque becomes far less critical.

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#5

Re: O-Ring Face Seal and Loc-tite

03/11/2021 5:35 AM

I know you won't believe this, but try it just to humour me. Wrap some insulation tape around the outside of the joint.

I had a problem with a chuck that kept loosening when I was trying to drill a hole; in desperation I tried insulating tape, and did 6 off half inch by six inch holes into the wall with no more problems. I can't understand how it worked, but it did.

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#8
In reply to #5

Re: O-Ring Face Seal and Loc-tite

03/11/2021 7:47 AM

I like the idea, but marketing may frown on tape around a fitting, I can almost hear our competition, "Ha, Ha, Ha, they use duct tape to hold their hoses in place!" yea, might result is less sales...

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#7

Re: O-Ring Face Seal and Loc-tite

03/11/2021 5:59 AM

There are grades of threadlocker that are more tolerant to oil.

Loctite 278 is an example.

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#10
In reply to #7

Re: O-Ring Face Seal and Loc-tite

03/11/2021 7:52 AM

Thanks, we'll get some and to do some testing, I hope this is it !!

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#11

Re: O-Ring Face Seal and Loc-tite

03/11/2021 10:26 AM

I had to read this twice as this is exactly my current co for the last 13 years. We too were using ORFS and on our high speed equipment the hoses came loose. we now use Hydraulic Loctite on ALL nuts on the rotating heads. holds but is removable.

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#13
In reply to #11

Re: O-Ring Face Seal and Loc-tite

03/11/2021 10:32 AM

That one is new to me. We'll try that and test it also !!

Thanks

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#14

Re: O-Ring Face Seal and Loc-tite

03/12/2021 9:22 AM

We use flats method for JIC fittings with great success. Face seal supposed to be torqued.

http://blog.parker.com/turn-vs-torque-how-making-the-right-choice-keeps-your-hydraulic-fitting-connections-leak-free

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#15
In reply to #14

Re: O-Ring Face Seal and Loc-tite

03/12/2021 9:25 AM

Yes, I know. thanks for the comment.

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#16

Re: O-Ring Face Seal and Loc-tite

03/12/2021 9:32 AM

Rather than using a torque wrench to measure how tight the nuts are, mark them and specify an angle of rotation that will provide the proper torque.

Each facet of the nut corresponds to 60°.

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#17
In reply to #16

Re: O-Ring Face Seal and Loc-tite

03/13/2021 7:49 AM

Interesting: is that angle from first engagement or from "finger" tight?

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#18
In reply to #16

Re: O-Ring Face Seal and Loc-tite

03/15/2021 8:09 AM

I'm stunned that you got 2 "Good Answer" votes. There are so many factors that go into a proper torque, to just say 60deg will satisfy and replace a torque wrench is beyond my comprehension. A burr on the thread will make you think your "hand tight" when you only 1/2 way there or less for matter.

A quality engineer I worked with did a study on torque and repeatability of a torque wrench and he found there was no repeatability as to the relation of the flats to the torque values. He also found that the proper torque value was met at various positions dependent on condition of the threads. Meaning that the nut went further onto the bolt the more times you removed and replaced the nut. Elongation of the treads and the smoothness of the threads all had an impact on the nut location at full torque.

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#19
In reply to #18

Re: O-Ring Face Seal and Loc-tite

03/15/2021 8:33 AM

Unfortunately the repeatability of torqueing when compared with the desired consistency of bolt tension is also very poor.

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