API 6A material query

[metboss]

Good day,

We require API 6A material(material class EE) with temperature class U (i.e. temp range -18 deg centi to + 121 deg centi) whereas vendor supplied with material having temperature class K (i.e. temp range -60 deg centi to + 82 deg centi).
Upon our comments, vendor proposed us that this material can be upgraded to class U by doing lab tests.
Can we accept this proposal? If so, then what are the lab tests required?
Note: As far as charpy test concerned, it is noted from material test certificate that test temperature is -60 deg centi and impact values are meeting API 6A requirements.

Regards

Metboss

 

[metboss]

Good day,

Now manufacturer submitted revised MTC where charpy test conducted at -18 deg centigrade and temperature class mentioned as "U". Can we accept this or ask them to privide us the proof about this tests they carried out?
As mentioned earlier, our concern was on upper temperature value and I am confused; how can they simply change the temperature class in MTC. Your feedback is anticipated.

Regards

 

[ricklts]

I don't have a copy of 6A in front of me, but if the strength properties are similar in the classes, perhaps the vendor had additional test coupons and re-ran the tests at the 'EE' temp range. He can certify the material to that class as well.

 

[yudhichen]

All,

this is what i understood so far. when we specify material class EE according to API6A (i assume its for body, bonnet, end outlet connection),
the minimum material requirement is low alloy steel. while low alloy steel can withstand to max working temp 350°F.

the temperature demand is U [0°F to 250°F] but vendor supplied with K [-75°F to 180°F],
if they use low alloy steel (eg: 4130), then material can be re-certified to spec U.
I think impact test in 'U' is not necessary unless you specify those stuff to be PSL3 or PSL4 parts.

to be honest, i'm still looking from which clause that explain the max temp for low alloy steel is 350°F.
i believe this temp constraint came from NACE, as i saw one OTC16394 paper mention this max temp for low alloy steel taken from NACE MR0175-2003.
but i couldnt found those max temp statement on 2009 version that i have.

anybody could explain to me from which section in NACE mention this 350°F for low alloy steel?

 

[jbeckhou]

See Annex G, API-6A 20th Ed, should answer all your questions about high temperatures.

Your material class would be K+U.

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