Impact Test Exemption

The best thing to do is to discuss the matter with the Client.

Yes.

You misinterpret/ don't understand the requirements of the spec.

Both -50°C and -60°C are colder than -48°C, so testing is required.

Dear Sir,

Thanks for your reply.

Is that mean impact test is mandatory below than -48 deg C even the MDMT of the material after reduction being made using Fig. UCS-66 and Fig. UCS-66.1? let say we are not considering condition in UCS-66(b)(3) and UCS-68(c).

What is the full wording of the UCS-66 sections? (The client won't necessarily know the needed info.)

Dear Sir,

Do you mean full wording in UCS-66 or UCS-66(b)(2) ?

Both sections, as mentioned.

Quoted as stating; 'Let say i get -60 degree C. The material right now is colder than client's MDMT, then no impact test require. However, based on UCS-66(b)(2), should i impact test this material?'

The answer to your question is clear and obvious. The MINIMUM requirement is -48C. If you only obtain -47C the product clearly failed the impact test. However, if you have a sucessful impact at -60C and the vessel surives, the vessel complies to the requirement quite well, and meets the minimum requirement for use.

The client may write whatever he wishes on a data sheet and the -50C may be the minimum the client requires or an actual test result he obtained previously. Therefore he may use this data and back it up with test reports or compliance reports.

I assume this is vessels for cryogenics.

Dear Sir,

Thanks for your reply.

I do understand that the vessel will not fail if i manage to do impact test until -60 deg C. However, in the UCS-66(b)(2), it says like -48 deg C is the maximum temperature for impact test exemption even i manage to reduce the MDMT of the material until -60 deg C. Let say condition of UCS-66(b)(3) and UCS-68(c) are not considered.

All these things make me more confuse after i read report from Compress.

ASME Impact Test Requirement - Inspection The Industrialwww.inspection-for-industry.com/asme-impact-test-requirement.html Ucs 66 - Free PDF downloadsfreepdfdb.com/pdf/ucs-66‎ I assume you may have checked these documents. The ASME document explains how to obtain exemption.Hope it helps you.‎

There are two cases, when dealing with UCS-66(b)

1. The design temperature shall NOT be colder than -48Degree Cecius. Materials shall be mentioned in part UCS of ASME B&PV Sec VIII Div-1.This condition is applicable when coincident ratio is less than 1(You have to find the coincident ratio). Then refer the diagram UCS-66.1 to find the extra temperature can be added to design temperature to get exemption. However, no exemption below -48C by this method.

2. -48Degree Celcius to -105 Degree Celcius .Materials shall be mentioned in part UCS of ASME B&PV Sec VIII Div-1.When MDMT is colder than -48C and not colder than -105 Degree Celcius and the coincident ratio is less than or equal to 0.35 (You have to find the coincident ratio),then impact testing is not required.

The logic is simple, Ferritic steels (BCC structure) will become more and more brittle (cleavage) when service temperature approaches cryogenic range. The crack initiation and propagation can be avoided if the load is reduced.

Thanks a lot for your reply. This what im looking for....