Hello all,

We are designing a vessel to PD5500 and we would like to use a105 150lb flanges. As the minimum design temp is -10 deg C we are unsure to the suitability of a105 for the flanges. According to PD5500 if you plan to use a105 below 0 deg C impact test are required (unless an agreement is reached between customer, inspecting authority and manufacturer). However am I correct in saying that ASME VIII allows the use of a105 down to a temperature of -29 deg C without impact tests?

Can anyone clarify or comment on this apparent inconsistancy regarding PD5500 and ASME VIII material selection criteria?

Thanks in advance.

Andy Potts.

I am not familiar with PD5500, so I will just answer your question below.

[quote]However am I correct in saying that ASME VIII allows the use of a105 down to a temperature of -29 deg C without impact tests?[/quote]

ASME VIII-1 does not require impact testing on ASME B16.5/B16.47 flanges that are made of ASME SA-105 (not ASTM A 105) when used at MDMT's no colder than -29 deg. C

Please refer to ASME Sec II, Part A: It is mentioned that SA 105 is identical to A 105 and therefore either of this do not require impact testing as per ASME Sec VIII if MDMT is warmer than -29 Deg C.

Regards

Andy,

I am sorry to say that you got to follow your Construction Code, PD5500 in this case. PD requires Impacts, so you have to order the flanges with impact tests.

It is not acceptable to go "cherry picking" nice exemptions from Section VIII while designing to PD.

An alternative could be purchasing SA-350 LF2 flanges, they come impact tested already.

DK