Cryogenic Test Bench for Valves 1

[NGiLuzzu]

Dear All,
I work in the industrial valves business, were cryogenic testing is more and more required, in addition to standard room temperature tests (hydraulic shell strength of valve bodies, pneumatic and hydraulic tightness of valve seats, etc. as per API 598 and similar standards) wich are usually performed on dedicated test benches.

Dealing with butt-weld end valves to be cryo-tested (using liquid nitrogen as coolant and helium gas as test medium, according to BS 6364 standard or Shell MESC SPE 77/306 specification) and the relevant problems in applying test "caps" to enclose them, I was wondering about... a possible "Cryogenic Test Bench", i.e. a bench for valve testing which uses liquid nitrogen (or another cryogenic fluid) instead of air and water.

Does such an animal exist? ;-)

Thanks and Regards, 'NGL

 

[asukid99]

I seriously doubt it. You will probably have to design your own.

 

[VentilTestEquipment]

Maybe a bit late...
We are a manufacturer of valve test equipment and can provide you with a test unit for cryogenic testing your valves. Please feel free to contact us at +31 70 3209327, email: abaars@ventil.nl or have a look at

http://www.ventil.nl

 

[NGiLuzzu]

VentilTestEquipment,
sorry for the late reply!!
;-)
May I ask if you have ever realized "such an animal"?
In that case, what valve sizes could be tested on it?

Many thanks, 'NGL

 

[Burdy]

NGL, lets get back to your specifications BS6364 and Shell Mesc 77/306.
These only allow you to immerse the valve so that the LIN is on the outside. I believe one reason for this is safety, plus testing valves using the LIN on the inside is not good bacause a cryogenic pump is required, possible split phase flow would also be an issue. The leak rate - would it be a liquid or the expanded gas from the liquid?; which could not be measured in the same way as helium, No low temp rotameters(to measure BS6364 leak rates) exist(to measure cryo liquid flow).The expansion rate of the liquid to gas in itself would cause significant problems in monitoring the leak rate.
If you presented this test rig to British Standards and Shell I do not believe you would have an acceptable test.
Br
Bernard

 

[NGiLuzzu]

Burdy,
I appreciate your points.
Of course, a lot of practical (and economical) problems would arise, when trying to realize the approach I was wondering about.
But I think that one merit must be recognized to that approach: it would better represent actual service conditions (cold fluid inside, instead of outside...).

Standards and specifications often fix on the paper the state of the art (and/or the market trends, the operative habits, etc...) at a certain moment and sometimes remain retarded respect to the industry actuality.

BS6364 is the only international standard I know about cryogenic testing of valves (Shell MESC SPE 77/306 is a supplement to that, as well as all the other Engineerings' Specifications) and its edition dates back to 1982 (at least), with minor changes in the Appendixes (amendment 1998).
Considering the strong growth of this market and the relevant technical developments in the last years, I believe that a new standard would be useful!

Sorry if I went a little off-topic...! ;-)

Thanks and Regards, 'NGL

 

[Burdy]

NGL, I totally agree with what your saying. I always get the question when showing people aroung the cryo test facility - Why are you testing with the cold media on the outside when surely it is the inside which is being used.Plus the fact that ALL tests are done with Helium gas, where the valve will in fact see liquid (Most of which are Hydrocarbons).Realistic, I don't think so...
Be careful of your terms, the Shell MESC essentially 'adopts' BS6364 it most certianly is not a supplement as it is a users specification not an international standard. Shell 77/306 didn't originally use BS6364 until a little time into its life, late eighties early ninties I think.
But going back to 'a Standard'. This has to be based on the technology available to all and the price to test. Cryogenic testing is expensive now, N2 prices will climb relative to the increases in the recent and forthcoming cost of energy.
Anyone taking this unique challenge of yours will certianly have a niche market and no doubt be the sole supplier for some time.

Br
Berni

 

[NGiLuzzu]

Berni,
it is interesting to discuss with you!

I think the topic about cryo-testing standards updating is worth of another thread, so I opened one in the Valve Engineering Forum: see thread408-148535.

About Shell MESC SPE 77/306, I usually adopt 14-10-2002 revision, which in clause 1.1.3 says: "This specification is a supplement to BS 6364 and EN 1626"
(Just for information: EN 1626 is not applicable to LNG applications and over DN150...!).

Let me add just one more example...
Helium gas? After using that for years for external leakage tests (at both cryogenic and ambient or high temperatures), I found that graphite and PTFE, as well as many other materials used for sealing, are higly permeable to that gas!! So you do not know if what you see is real "leakage" or just "normal" helium flow through the sealing bulk material...

Once again the commonly accepted test method has nothing to do with the actual working conditions (on the contrary, it is even misleading...!).


Thanks and Regards, 'NGL