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600# swing check valve - retest after trim change

600# swing check valve - retest after trim change

600# swing check valve - retest after trim change


I have a 600# FL RF swing check valve in high speed oxygen service which due to scheduling issues had to have its trim (disk, lever arm, seat) changed to solid monel. The valve vendor just gave us the test documentation and they only tested the shell to 200psi and the seat leak test to 200psi. Considering this is a 600# valve and that the original stainless seat was seal welded and was replaced with solid monel seat, I feel like they need to test it to full code required pressure in order to certify the valve. They claim the valve complies with ASME B16.34 and API598 but I don't feel safe using this valve in critical oxygen service.

Your thoughts on the matter and advise will be greatly appreciated. I went over the code and can't locate a section that will give me clear answer on a rebuilt valve.

Thank you,

RE: 600# swing check valve - retest after trim change

This is a double post. However this one is in the right forum

I suggest you delete the one in piping and keep this one.one

Sometimes its possible to do all the right things and still get bad results

RE: 600# swing check valve - retest after trim change

Hi KJ7,

Your information is not complete yet. Still missing the body material (this is related to the ASME B16.34 material selection), Is it Liquid oxygen or Gaseous Oxygen (this is related to the body material selection), what is the operating maximum temperature (related to Auto ignition and or impingement potential), what is the differential pressure and what design code and leakage rate that you've quoted?

In general, assuming the body used is also Monel400. Then you are correct it is not according to MAWP stated in ASME B16.34. at ambient temperature it should be 1,200 Psig. This is at least for the body test, Seat test might be performed at maximum DeltaP
However, also assuming that this modification done by some sort of service company (not the original manufacturer), kindly take into account two things: Oxygen (fire hazard) and Check valve leakage rate and cracking pressure. Check valve leakage rate is not necessarily Class B as per ISO 5208 and also since the trim is modified (let say Monel is heavier compare to the previous ones), then it will have some effect on cracking pressure as well among other parameter.

Slightly in detail about Oxygen application and valve:
- refer to EUROPEAN INDUSTRIAL GASES ASSOCIATION AISBL (which can be used also for Liquide application), the exempted (not prone for kindling or impingement effect shall its get ignited) material selection for Oxygen are but not limited to:
(L)iquid OX --> SS321 and or Monel for Body and trim.
(Gaseous)OX --> especially for High temperature to use Monel
and there are different chapter over cleanliness and soft goods

- NRV is not isolation valve but more for back flow preventer. If ones requires Check valve or NRV to be tight shut-off, then I can assure you that Swing type is not the right type. And some service company try to respond over this "commercial" requirement by applying smaller test pressure.

- For safety reason (even though possible), I never see testing company perform gas test with real pure Oxygen or even pure Hydrogen. So it must be either Nitrogen or Helium. And not all also can perform high temperature testing shall this is part of your requirement. If they can, some will choose to do it on lower pressure side.

I've dealing with similar situation several times. The manufacturer or service company is not sure over the check valve performance at high pressure and possibly high temperature. they maybe comfort at 200 Psig since it is again maybe tight seal at that pressure. Does it comply with ASME B16.34 and API 598? maybe partially in terms of valve general design code (ASME 16.34) and differential pressure and testing period (as per API 598).
Can you blame them for their hesitation to perform such test? Yes and No

Does it safe for your plant? having the new Monel trim is already exempted, it is perform ok at 200 Psig (differential pressure?) and its function is back-flow preventer (not isolation valve). Not to be generalized but IMHO it is safe

Good luck,

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected


RE: 600# swing check valve - retest after trim change

Thank you for the detailed and very helpful reply MR!
Below are answers to your question:
- Body material is SS A351 CF8M
- Service is Gaseous Oxygen
- Max operating temperature Ambient 30 degC
- Max operating pressure 860 psig
- Differential pressure across the valve 15 psi
- Leakage rate requirements None
- The valve is a flow preventer
- The valve modification is done by service company and they claim the valve is compliant with ASME B16.34 , API 598, API 594
My main concern is that the valve was machined in order to replace the seal welded seat with solid monel seat (the valve shell was affected by the grinding of the weld and rewilding). I don’t really feel comfortable with 200 psi hydro test. In my opinion the valve shall be retested to full pressure (as a new valve would). I was hoping to find a code reference that will back me up instead of just “feeling uncomfortable” but can’t seem to locate one.
Your opinion on the matter is appreciated.

Thank you,

RE: 600# swing check valve - retest after trim change

Hi KJ,

Thanks for the additional information. Your service company is just being conservative with respect to EIGA or any other empirical data. In Europe we have EIGA, in US they have WHA International, not sure about other countries. And there is no single standard to cover your concern. Oxygen clean have their own standard ASTM G127-15; mechanical impact test and aging test resistance ISO 21010; ASTM G114, etc.
And once all of those standards complied, there is no assurance that it will not be ignited or even during its lifetime will ever be ignited. For that purpose you need to do what Oxygen people name OHFRA (Oxygen Hazard & Fire Risk Analysis), and even this is subjective assessment. And of course there will be price and design consequences.
OHFRA consist of 4 step:
Step 1: Use condition (Pressure and temp)
Step 2: Material flammability. Consist of Materials HNBP, AIT (Auto Ignitition temperature), etc
Step 3: Ignition Probability. consist of particle impact, compression heat, mechanical impact, flow induced heat, promoted ignition.
And Step 4: Ignition Constanta >> Fire propagation, Reaction effect and consequence

Why did your service company only dare to do up to 200 degC. Basically two things:
a. Your operating paramater is 30 degC, so it will never reach 200 degC
b EIGA summary over promoted ignition. Courtesy of EIGA and not to be generalized

In summary your Monel trim is more or less ideal for this application. But your body material have a possibility to be (promoted) ignited shall operated at 200 Psig and 200 degC (see bottom note). But even this is 1 out of several promoted ignition attempted in the lab. So the likelihood is small but possible.

In regards with API quality, maybe others can correct me, I understand that there is Q1 or sort of monogram certification for manufacturer. And for testing company it can be also API598 certified, meaning that their test bench including booster pump is audited. But I am not quite certain that service company can claim that they are 16.34 compliance.

My personal comment (I am Level 4 Oxygen Inspector and have a Plant that is running at 83 barg and 400 degC most of them full Monel) are:
a. Having "not so clean" hydro test as final test is not convenient. Oxygen application shall be clean, so I would recommend to do re-cleaning and further finalized with Helium either high or low pressure testing
b. To do body test at 860 Psig or higher (1,43 MAWP??) to ensure that it is still comply with PED. This can be performed with or without valve internal. This shall be done with Helium or Nitrogen (what could go wrong bigsmile
c. Seat test can be perform at 15 Psig as per your DP or even 200 Psig

If for some reason you loose the debate, is it ok to accept it as current? Do final check yourself using black light and check the leakage rate at 200 Psig (if leakage rate acceptable process wise). If it is clean and relatively tight. Yes, I would say it is ok.

Again, good luck. This is always a challenge for even the best service company or manufacturer.

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected


RE: 600# swing check valve - retest after trim change

B 16.34 refers in the scope to a new valves only.

Therefore their claim for it to comply with this code is incorrect.

I agree with you and would continue to reject the valve until they comply with B 16.34 as though it were a new valve, given the amount of work which has been done on it.

If it wasn't explicit it in the scope of works, quotation or work order then you might need to pay for it, but I would agree with you that it should be done.

This is an instance where the code is not designed for these items, but is up to you to specify up front to the company what you want done in a clear scope of works or specification. you can't just say B 16.34 unless you say " all aspects of B 16.34 as though this was a new valve".

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: 600# swing check valve - retest after trim change

Thank you MR and LittleInch!

I really appreciate your input. We ended up on the phone with their technical department and convinced them to retest the valve at higher pressure.


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