Meg cold diving - QC4 leak

jdicediver

I think the part is a Tomco product, not "Genuine Swagelok", however cannot confirm without seeing the old male QC4 part I removed which is at home in a spares box. There are slight design deviations which IMHO are operationally sounder and physically more durable on the Swagelok item. Explanation later.

Insturmentation Process Control Series.

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Regards;

"Alterations performed under controlled conditions, on a closed course by a qualified Closed Circuit Diver"

"Some people shouldn't dive...others shouldn't even get wet".

tibby

I wonder what the cost savings are for ISC, I hope it's worth it. This might be just the proper fix - getting the proper part. What a novel idea!
Thanks John.
Tibby

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Does the voice of reason change when you add helium to the mix?...hmm

jdicediver

To the credit of ISC, I maintain they are one of the most "proactive" Companies I have dealt with, and most likely have NOT had a great deal of issue with the other compatable part. I also anticipate that they monitor these threads and have already made arrangements to investigate and correct this very issue.

__________________
Regards;

"Alterations performed under controlled conditions, on a closed course by a qualified Closed Circuit Diver"

"Some people shouldn't dive...others shouldn't even get wet".

Stephane

Excuse me but we are talking about a $8000 machine and a $35 connector!
This is not a washing-machine or a television set build at thousands of units a year, but few hundred units.
Trust me, if ISC put a Swagelok instead of a Tomco connector, that's the end user that will pay the difference.

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Stéphane
Hammer-rEvo powered!

sensor330

Be careful with the Swag item as I don't think they have gone through the passivation process. That's probably why ISC went with the QC4 they currently provide.

Scott

6Gill

Ok guys, the history is originally we used Swagelock, Scott is correct that they did not passivate the knob so there were issues with discoloration. Swage did not want to passivate so we switched to Hylock. These worked well but they were not able to deliver the parts (5 month backlog!!) we recently developed our own passivation process and switched back to swagelock. The parts that Tibby is having issues with are Hylock.

Jerry

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"It's a shame ignorance isn't painful!"

tibby

Thanks Jerry, I apreciate the post and clarification on the part's history. I am now confident ISC will look into this issue and soon fix it. I promised I will try to duplicate and document the behaviour but failed to do it properly. All I can tell so far with confidence is that my connector leaks when exposed to temperatures between 15 to 8 deg F but I don't know when (what temp) it actually starts or stops leaking.
I really don't think the brand is that important (although I come across that way in my previous post) as long as it doesn't leak. I should know better than commenting about things before having all the facts.
Tibby

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Does the voice of reason change when you add helium to the mix?...hmm

jdicediver

Tomco/Hylock I was unsure. Thanks for the clarification Jerry. The part I had trouble with was the male "quill" which leaked upon disassembly from new on my COPIS meg. The change from Hylock to Swagelok seemed to correct the problem, and the Swagelok part appears more durable and better engineered internally.

Forgive me, but based on my background information (QA and materials process related) the passivation process utilized is only in place to eliminate post processing impurities on the stainless componentry, thereby possibly assisting in the prevention of oxidation (rust). Unless I misread his post, Jerry stated that the knob on the Swagelok part has not been passivated in the past. What concerns would the elimination of this process cause on the internal components where the leakage must occur? Tibby, have you pinpointed the location of leakage encountered? Was it male or female part, or internally after assembly? Pressurized or unpressurized? There are many variables to consider here.

__________________
Regards;

"Alterations performed under controlled conditions, on a closed course by a qualified Closed Circuit Diver"

"Some people shouldn't dive...others shouldn't even get wet".

jdicediver

To explain the reasons behind my opinion in regards to this matter:

The fitting on the left (Swagelok) has a larger internal pin which is integral to the collet (trishape inside quill) and the one on the right (Hylock) has a smaller internal pin that moves independantly within the collet. In my observations, the Swagelok Male p/n QC4-D-400 and Female p/n QC4-B-400 are otherwise operationally and dimensionally similar and compatable with the Hylock item originally supplied with the Meg. I do apologize for the poor quality photo.

Attached Images

DSC02118a.JPG (204.8 KB, 63 views)

__________________
Regards;

"Alterations performed under controlled conditions, on a closed course by a qualified Closed Circuit Diver"

"Some people shouldn't dive...others shouldn't even get wet".

tibby

In my opinion, the source of the leak is the o-ring housed in the female part which seals onto the shaft of the male side when connected (under pressure of course). I think what happens is that this o-ring gets stiff from the cold and if the male part has room to move inside the o-ring (excessive tolerance) then a leak occurs. The connector did not leak until I moved the male connector but then it got worse and worse.
Tibby

__________________
Does the voice of reason change when you add helium to the mix?...hmm