API vs D1.1

Date 04-03-2012 00:10 Edited 04-03-2012 19:19

Because they are three different codes issued by three different institutions.
ASME IX has been issued by the American Society of Mechanical Engineers and applies to boilers, unfired pressure vessels, storage tanks and piping other than oil and gas pipelines.
API 1104 has been issued by the American Petroleum Intitute and applies to oil and gas pipelines.
AWS D1.1 has been issued by the American Welding Society and applies to structural steel.

Three different codes issued by three different institutions and for three different applications. So, the fact that one discontinuity is accepted by one code does not mean that it is automatically accepted by the others; or one variable that is non essential in one code can be essential in the others.

Giovanni S. Crisi
Sao Paulo - Brazil

By MILLSCALE (*)

Date 04-03-2012 05:05

Sorry a typho, it should be LOF (lack of fusion) and not LOP.

By ozniek

Date 04-03-2012 11:06

Hi

A couple of points here:

1) ASME IX does not give acceptance criteria for production welds, only for procedure and performance qualification. The acceptance criteria for production welding needs to be found in the referencing code. In the case of ASME IX that could be B31.3 for piping, or ASME VIII for PV's or B31.8 for pipelines. Interestingly, the acceptance criteria for NDT to B31.8 is API1104! Given that API1104 and B31.8 both deal with pipelines, the fact that they have the same acceptance criteria is probably not so crazy.
2) Because different codes have different assumptions built in, and also have different levels of engineering, (e.g. pipeline codes often require ECA's) it is not that surprising that they have different acceptance criteria for defects.
3) LOF is permitted by B31.3 in certain circumstances. (Mostly not.)

What we need to remember is that the principle job of the welding / fabrication team is to ensure that the design intent of the designer (and by implication the design code) is implemented during fabrication. Different design codes = different design intent.

Regards
Niekie

By 803056

Date 04-03-2012 20:14

Different codes and welding standards use different terminology for similar discontinuities. Different service conditions, different allowable stresses, different design assumptions result in different acceptance criteria for different applications.

Best regards - Al

By dbigkahunna (****)

Date 04-04-2012 00:21

LOF is a discontunity that is really hard to do with process, heat and travel speed when welding on pipelines. When you are in third gear and 70 LOF is not going to happen.

By ozniek

Date 04-04-2012 12:34

Hi

Got to disagree with you on this one. A lot of automated pipeline welding is done with narrow gap GMAW. (downhill) For this situation, the main defect that is found is LOF. The automated UT procedures (Or Real time radiography - RTR) need to be specially qualified to make sure that they can detect this.

Regards
Niekie

By dbigkahunna (****)

Date 04-05-2012 02:22

Sorry
LOF is a discontunity that is really hard to do with the SMAW process, heat and travel speed when welding on pipelines. When you are in third gear and 70 LOF is not going to happen. The SMAW process is used in the overwhelming majority of cross country pipelines.