Hello Stressers,
Just want to get your opinion on the subject above.
Actually my dillema is I found out that there are two approach that EPC company uses and both approach appears in the code and for me is both valid as per my interpretation. For ASME B31.3 Code Committee members please help me in interpreting this section of the code.The approach I will describe below:
1. Approach 1--->The conservative approach of using the stress ratio of 0.3 regardless if it's above or below -48^C application. I think this approach is based from Table 323.2.2 Requirements for Low Temperature Toughness Tests for Metals Note 3 of ASME B31.3 2012 page 48 which states " Impact testing is not required if the design minimum temperature is below −29°C (−20°F) but at or above −104°C (−155°F) and the stress ratio defined in Fig. 323.2.2B does not exceed 0.3." Please note that the range of temperature here is -29^C to -104^C.
2. Approach 2 is divided into two temperatures that other EPC company adopts:
---->Temperature 1 ranges from -29^C to -48^C. This can be found in ASME B31.3 2012 section 323.2.2.d.(1) Lower Temperature Limits, Listed Materials page 46 which states: "For design minimum temperatures of −48°C (−55°F) and above, the minimum design metal temperature
without impact testing determined in para. 323.2.2(b), for the given material and thickness,may be reduced by the amount of the temperature reduction provided in Fig. 323.2.2B for the applicable stress
ratio. If the resulting temperature is lower than the minimum
design metal temperature, impact testing of the material is not required.". I can see that in this approach we can use the values from Fig. 323.2.2B say for a 10^C temperature drop (0.8 stress ratio and below is allowed) as long as the temperature is not colder than -48^C.
---->Temperature 2 ranges from -48^C to -104^C. This can be found in ASME B31.3 2012 section 323.2.2.d.(2) Lower Temperature Limits, Listed Materials page 46 which states: "For design minimum temperatures lower than −48°C (−55°F), impact testing is required for all materials,
except as provided by Note (3) of Table 323.2.2." This basically goes back to approach 1 of using 0.3 stress ratio as stress limit to be exempted for impact testing. The only difference is that this approach uses temperature range from -48^C to -104^C.
Please clarify more if I have missed some statements that links between the the three section of the codes mentioned above especially to the Code Committee members who is part of this section of the Code.
Many Thanks in advance...
Cheers!!!!
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