Comparison ANSI/ASME B31.3 AND B31.8 1

[carthago]

We have new piping materials (including fittings)
all with correct material certificates , WPS and PQR and all according to ASME / ANSI B31.3.
Design pressure under 100 barg , design temperature between Zero and 80 Degr. Celsius

Is it possible to use the obove for a part under ASME/ANSI B31. 8 ( eight !!)

If THE answer is NO , how can we make this possible ? I mean which steps , recirtification , extra calculation, re-qualification, etc,.. have to be done to get a system approved for B1.3 also approved for B31.8

 

[SJones]

I don't think that there will be a problem as the design factor in 31.3 is lower than B31.8. However, B31.3 may not address Charpy toughness testing in the same manner as 31.8 (in the sense that 31.8 demands the designer to assess the need for it and a lot of people overlook running ductile fracture in rich gas lines for example). Personally, I don't subscribe to the B31.3 approach of allowing A106 Gr B to go to -29 deg C without Charpy testing (in line with a lot of upstream oil companies). In addition, if you have any fittings or pipeline parts that have girth welds, 31.8 demands that they be made in accordance with API 1104 which may not hold with the standard used to manufacture the fittings.

Steve Jones
Petroleum Development Oman LLC
Muscat
Sultanate Of Oman

 

[dcasto]

The big difference is in 31.8 you cannot weld onto the pipe. In 31.8 you must perform a strenght test and in 31.3 it's only a leak check, the differnce really being the lenght of time required. I've co-qualified pipe before by doing this. Do the calcs. interpert the x-rays to the more stringent; poristy , high/lows, excetera are a little different, then test for 4 hours.

Don't get too concerned on temperature since your design is above the lower limits.