Thank you.That looks like the kind of damage you'd expect in a plant that has been in service a few decades. Just replace it and make sure, that the tubing layout is designed for maintenance to take things apart without damaging them. Take alook at
Thanks for the photo! It does, indeed, help a lot.
When I see damaged tubing like this (and I think some part of this homemade "fitting"--a nut--is missing), most often I find it is caused because a backing wrench was not used when loosening or tightening the "fitting." It's amazing how few people know to use--and do use--backing wrenches on tubing fittings and devices when loosening and tightening them. A backing wrench can save a lot of trouble!
Also, when I see damage like this it is quite often caused by poor support of the devices on either side of the "fitting" (the solenoid-operated valve, SOV, and the control valve), allowing one or both of them to vibrate and wobble. Sometimes on device on one end of a piece such as in the photo is properly secured but the other side is not and it is free to "shake, rattle, and roll" and vibrate.
Alignment of the two devices a "fitting" like this connects is also often found to be a problem. And, it's very difficult to make a short piece of rigid tubing with any kind of bends in it to make up for misalignment. Sometimes, a braided hose, in a circle, is a great idea in such cases.
Combine this with not using a backing wrench to loosen--or tighten--the fittings' nuts and that's a recipe for premature failure.
The "corrosion" on the right side of the fitting also suggest that nut on the right was not properly tightened... It looks like the "fitting" is actually a piece of tubing with compression fittings on either side of it, and that one of the nuts used to set and tighten the compression rings (on the left side of the photo) was not in place for the photograph, probably to better show the damage to the tubing.
One last thing as I review the photo one more time. The tubing in the picture is "thin-wall" tubing; you could probably use a thicker-walled tubing for more strength. One of the things that often happens with thin wall tubing is that when the nut is tightened to set the compression rings it is over-tightened and that can weaken and even crack the thin-wall tubing. Many sites, and maintenance personnel, don't use go-no-go gauges for setting compression fittings the first time, or don't know how many flats to turn the fitting from hand-tight to initially turn the nut if a go-no-go gauge is not used.
There's a lot of possibilties for why the tubing might be damaged. Incorrect material--for dry, instrument air--is probably not one of them. Thicker-walled tubing, properly set fittings--done using a backing wrench, alignment of the two devices the tubing is connecting, and secure mounting of the two devices are probably one or more of the reasons for the failure.
Hope this helps!
Another thing about "fittings" like the one in the picture, usually they are made very quickly, sometimes using bits or pieces of tubing found laying around in the instrument shop--new and used.... Usually, they are not always cut to proper length (or if the as-found piece is used to determine the length, the as-found piece was not cut to the proper length when it was installed).
So, there's a few things to consider. Only you can know if the material you are considering using is right for the application/service. If it's just dry instrument air, it is probably okay--as long as it's at least as strong as the piece it is replacing. But, again--it would be interesting to see the two pieces of equipment the "fitting" is connecting--the solenoid-operated valve and the control valve, and the gap between them, and to know if both pieces of equipment (the SOV and the control valve) are mounted such that they are properly aligned, and one, or the other, or both aren't free to "shake, rattle and roll."
Thank You CSA.Nikhil vaghela,
I believe you said this was for dry, instrument air service. I'm not a metallurgist, so I can't comment on what material might be best or even better.
If you don't have a need for high flow-rates (such as for opening or shut-off or control valve position changes), I would suggest using thicker-walled tubing of the same material. It's readily available (or should be in most plants/instrument shops/pipefitter's shops) and if the compression fittings are set properly initially (not overtightened) using a backing wrench everything should be fine. Again, this presumes proper alignment of the two devices being connected, and secure mounting of the two devices being connected, and the proper length of tubing. Using such a short piece of tubing means that installation and disassembly (proper installation and disassembly) of the length of tubing will require that one device or the other (probably the SOV) will have to be loosened from its secure mounting to allow for insertion of the tubing during assembly and removal of the tubing during disassembly. And, of course the loosened device will have to be re-secured after assembly or re-assembly.... And the fittings will have to be properly tightened using a backing wrench.
I can't stress enough the use of backing wrenches--it's so often overlooked, and it's so simple and logical and intuitive--once the need is understood. If you don't have a go-no-go- gauge for proper initial tightening of the compression fittings on initial assembly, then use the "flat count" method; after the fitting nut is screwed hand tight and using a backing wrench tighten the fitting nut 8 total flats (1-1/3 turn on a six flat nut). That should be sufficient to set the compression fittings ferrules without causing damage--presuming there is not angular misalignment between the two pieces of equipment (the SOV and control valve). Do this on both ends--using a backing wrench when tightening--and you will be fine. Subsequent re-tightening of the fitting--using a backing wrench after reassembly--should turn the nut no more than half a flat, if that.
Many people mistakenly believe that over-tightening compression fittings to account for misalignment and/or loose devices will "solve the problem" of misalignment or loose devices. NOT TRUE. Over-tightening only serves to increase the probability of premature tubing failure. And, again, I cannot over-stress how important--and simple--using a backing wrench is on tightening (and even loosening!) tubing fittings, especially when initially tightening a compression tubing fitting.
Best of luck!
|Thread starter||Similar threads||Forum||Replies||Date|
|H||Reason for Load spike when system frequency is disturbed||Power Generation||3|
|C||Reason for looping input connections of circuit breaker||Power Generation||1|
|H||Mark-V trip on a non clear reason||General Automation Chat||4|
|U||History behind Sizes of Valve||General Automation Chat||4|
|M||Temperature measurement of object behind glass||Instrumentation & Measurement||0|
by Seth Price