Trim 8 in lieu of trim 12 1

[jskernahan]

Hi there,

I'm wondering if trim 8 can be used in lieu of trim 12 for an A105-N check valve in a sour hydrocarbon service with a design temp of 294 deg C and pressure of 7832 kPA. From what I've read the only difference seems to be trim 8 uses 410SS, while trim 12 uses 316SS

Thanks

 

[hsbcn]

hi jskernahan:

yes, the only difference betweeen API trim 8 and trim 12 is the grade of steel;

you've probably had a look at the API 600 trim chart, where seat, disc, backseat and stem materials are defined: [URL unfurl="true"]http://alloy-valves.com/Alloy-Valves-Product-Range/API-600-trim-chart.htm[/url]

316 is molybdenum-bearing and gives better corrosion resistance than 410, whilst 410 is a basic martenistic steel with 11.5% chromium which gives basic/sufficient corrosion coverage.

Commercially speaking, there's barely much price-difference depending on size/quantities involved.

My focus is on valve stockists in the us and uk who supply duplex and super duplex valves, and inconel and hastelloy valves, plus titanium, alloy 20 and 904L valves.

 

[jskernahan]

Ok thanks hsbcn!

Yes I've seen the trim chart, I just don't know much about metallurgy so didn't know if 410 could be used in lieu of 316. From what you're saying it seems like 316 is the better choice but 410 can be used, correct? The specs I'm using calls for 316 but my valve vendor only has 410 in stock.

 

[hsbcn]

Well, "better" can really only be defined in the context of the process itself; someone better versed in that area might be able to assess and advise far better.

My focus is on valve stockists in the us and uk who supply duplex and super duplex valves, and inconel and hastelloy valves, plus titanium, alloy 20 and 904L valves.

 

[SNORGY]

In sour HC service, most of my clients would want to spend the extra money on Trim 12 and 316 SS. A NACE valve with 410 SS might perform satisfactorily and might even be a superior choice if there is significant free water with moderate to high concentrations of chlorides present, but otherwise its general corrosion resistance would likely not be as good as would that for 316 SS.

 

[jskernahan]

OK, thanks for the input guys.

 

[jimenezjf]

To sum up, it is a good engineering practice use trim 12 in lieu of trim 8, but not the reverse.

 

[kpm21443]

jskernahan (Mechanical),

From my experience, trim 8 cannot be used inplace of trim 12. But you can offer trim 8 to your client & see his reply.

 

[jskernahan]

Thanks for the input guys. Here was the resolution:

I tried to get a spec waiver approved for trim 8, with my justification being that trim 8 is certified under NACE if the PH is greater than 3.5 and the process fluid is produced vapour at a temp above 60 deg C with chlorides present (trim 8 has better resistance to chloride stress corrosion cracking). The client said it would be acceptable if the PH was proven to be greater than 3.5 but suggested the use of trim 5, 10, or 16 as better alternatives. In the end my vendor found some trim 16 valves.