Lowest Documented Temperature for SA 350 LF2

[skulcak]

We have a situation with a customer which we have built an instrument (probe) for connecting to a cryogenic pipeline (LNG). We have built this probe from SA 350 LF2 and our customer is now demanding we verify the SA 350 LF2 will be sufficient to handle temperatures as low as 150F. I have attached an email from a flange manufacture indicating the SA 350 LF2 is acceptable in this range but I been unable to support his comments with any documentation.

Any help you might be able to give will be much appreciated.

 

[metengr]

skulcak;
Your customer is absolutely correct in asking for CVN impact verification. If you review ASME SA 350, for Grade LF2 impact testing assuming Class 2, is required at -50 deg and at O deg F for Class 1.

 

[skulcak]

metengr,

I do not disagree with you as I have read the material specification thoroughly due to using these materials and other materials / specifications for the PED. We have consulted with many pipeline companies such as El Paso in determining what materials for flanges they use in LNG service which at times may see below -100F and their engineers tell us SA 350 LF2 which confuses me when I see the CVN impact temperature for LF3 being -150F.

 

[metengr]

skulcak;
The CVN testing of this material is mandatory to assure complinace with the CVN notch toughness requirements at the required service temperature.

Lower than -50 deg F service would require Grade LF3 material as specified in SA 350, not Grade LF2. I don't know what is so confusing about this????????

 

[stanweld]

If the probe is in LNG service, the pipe carrying the LNG to storage or from storage to gassification will be 304 or 304L stainless steel. Your probe should be manufactured from stainless steel. If I were the Owner of the LNG facility, I would not permit LF2 or LF3 in that service. If this pipe system is in the USA, it is governed by NFPA 59A and ASME B31.3; neither of which would permit 350 LF2 or LF3; I believe the temperature of LNG is -259 F and normal design is -320 F unless the LNG is at high pressure.