Reducation in MDMT for A106GR B

Not sure I what you mean! But piping is also about what is going through the pipes in the end!

Off hand, I doubt it. I suspect you will need A333-6, or maybe even stainless. However, I couldn't easily follow your notes, so you might be okay.

BTW, you should be saying down to -104°C, rather than up.

Thanks for your reply

Actually we want to use A106GrB for cold flare line having intermittent flow, with out impact test requirement by taking advantage of thickness using reduction in mdmt if minimum temperature is -104 deg C

Thanks for your reply

Actually we want to use A106GrB for cold flare line having intermittent flow, with out impact test requirement by taking advantage of thickness using reduction in mdmt if minimum temperature is -104 deg C

For A106 Gr B the curve is B (from Appendix B - B31.3) . whose minimum is -30 deg C (see 323.2.2A)

See the curve in 323.2.2B

if your stress ratio is 1 = temperature reduction is zero therefore the minimum temp is -30 deg C

if your stress ratio is 0.8 = temp reduction is 11 deg C therefore -30-11 = -41 degree C

if your stress ratio is 0.5 = temp red is 34 degrees therefore -30-34 = -64 deg C

if your stress ratio is 0.3 = temp red is 120 degrees therefore -30-120 = -150 deg C

it also depends upon thickness. the above example for curve B is only for minimum thickness as per 323.2.2A. the more the thickness the less will be MDMT in minus side.

Too bad you didn't mention all this in the first place; it appears that your question would already have been resolved.

For above mention problem A106 B and A333 6 all parameters eg

Dia of pipe (14'' od=355.6mm), internal pressure 50 Psig), allowable stress (same for A106B and A333 6 from table A1 20000 Psi), quality factor ( E from table A-1B) and coefficient Y remain same than stress ratio and reduction in MDMT will be same (as I supposed/understand that curve B is applicable for both materials). So both materials can be used although A106B is cheaper than A333 6. Plz suggest

For above mention problem A106 B and A333 6 all parameters eg

Dia of pipe (14'' od=355.6mm), internal pressure 50 Psig), allowable stress (same for A106B and A333 6 from table A1 20000 Psi), quality factor ( E from table A-1B) and coefficient Y remain same than stress ratio (less than 0.3) and reduction in MDMT will be 120 deg C for both materials for A106GRB -29-120=-149deg C and for A333 GR 6 -50-120=-170 deg C So both materials can be used if design minimum temperature for system is -107 deg C, although A106B is cheaper than A333 6. Plz suggest Tornado

Is this interpretation is true please suggest

The below statements are for weld deposits only. This means that parent metal will be impact tested (if required per Fig. 323.2.2A) but for welding, you may go for NO testing if the stress ratio is 0.3 and design min. temp between -29 and -104. Irrespective whether you do or not do the impact test for weld deposits, the base metal as well as filler metal (welding rod) has to be impact tested (if required by Fig. 323.2.2A) by manufacturer. The only advantage you are gaining is that field or shop weld can be avoided to be impacted tested if stress ratio is below 0.3 for Curve A & B and design min. temp between -29 and -104 deg. C.

So, answer to your question is WE CANNOT USE A106 Gr. B OR A333 Gr. 6 FOR -104 DEG. C. WE CAN AVOID IMPACT TESTING OF WELD DEPOSITS BETWEEN -29 AND -104 DEG. C FOR STRESS RATIO BELOW 0.3 FOR A SUITABLY SELECTED MATERIAL.

(All above is my own interpretation and discussion with a metallurgist, pl. consult with experts on this subject).