ASME B31.8 Pars. 812 & 841.1.2 Concerning Circum. Butt Welds and HAZs

[jweld81]

ASME B31.8-2022 Ed. Par. 812, (2nd Par.), indicates that a fracture control program shall be established for minimum design temperatures below -20°F and the program shall address circumferential butt welds and HAZs among other welds and materials. The next paragraph in Par. 812 indicates to see Par. 841.1.2 for additional requirements relative to fracture control of pipe. This paragraph provides additional requirements based on stress for different sizes of pipe (Par. 841.1.2(a)(1) & (2)). Therefore, if either (a)(1) or (a)(2) applies, then the pipe needs to meet the requirements of (b) and (c) or (d) of this paragraph, even if the minimum design temperature is above -20°F. Will the CVN requirements specified in (b) apply to the circumferential butt welds and HAZs, even if the minimum design temperature is above -20°F, and the pipeline is designed to meet either (a)(1) or (a)(2)?

 

[GD2]

OP,
Fracture toughness of material is dependent on material strength, stress/press and temperature.
Para 814.1.2 provides the criteria for impact testing. Only one condition (not all three (a)(1)(2)(3)) need to be met to kick off the impact testing. For example, if the pipe diameter is equal or >NPS 16 (814.1.2(a)(1)) and a pipeline is designed to operate either at a hoop stress over 40% through 80% of SMYS, impact testing is required regardless of Minimum Design Temp (MDMT).
To find out where and how to collect the CVN test specimen, read Para 10.2.3.3 of API 5L. Test procedure is given in Annex G of API 5L. CVN test temperature shall be at or below the MDMT.
What's the Minimum Design Temp or MDMT for your service?

 

[jweld81]

+23F

 

[SJones]

The referenced paragraphs are related to long running fracture along the pipeline, and are not applicable to the girth welds. API Std 1104 isn’t much help for testing of girth welds as it leaves it to “the company” to specify Charpy criteria, although it does offer some guidance in Annex A that is along the same lines as . EPRG https://www.eprg.net/fileadmin/EPRG_Dokumente/EPRG_Weld_Defect_guidelines.pdf requiring a minimum of 40 Joules average.

 

[GD2]

OP,
SJones is right. Sorry, I directed you the wrong way.
Unfortunately, there is no guidance so far in Pipeline Codes on girth weld including notch toughness requirement. API 1104 provides WPS qualification for general welding but don't provide any guidance on notch toughness.

The only place, I find as a reference guidance is ASME B31.3 in Chapter III - Materials. However, pipeline girth welds are different. Process piping uses low strength materials compared to pipelines that uses high strength.

At this point, it is worthy to highlight that there had been several failures at pipeline girth welds that had been welded using API 1104 during hydrotest or after taken into service. It has become a subject of study and research to find out why these failures are happening. Most of failures are with API 5L X70 pipelines.

If you are new in this area, I suggest you take help of experts who are onto this subject.

To date, there is no any Standard/Code that defines and goes into depth on pipeline girth welding.

 

[jweld81]

Thank you for your explanations. It is intended to contact experts for further discussion.