Suitability of SA106B?

[SBlowers]

Friends,

We are using 1500# SA106B (xxs grade) material for 6" well flowline, which may possibly go to temp as low as below -5deg C. Is the impact testing required? Should we require to normalize SA106B? Or is it better to opt for low temp CS material? We do not prefer this due to high cost of LTCS material. Note the temp will not fall below -29deg C.

SB

 

[metengr]

SBlowers;
If you use ASME B&PV Code, Section II, Part D as a guide, this material is exempt from impact testing down to -29 deg C. So, I would say impact testing for your service conditions is not required.

 

[rneill]

I think this one depends a little on the design code in use. If your design code were ASME B31.3 then I would refer to the rules for ASTM A106 Grade B material (since SA materials aren't listed in B31.3) and in that case, it lists curve B for the minimum temperature value.

From Curve B of Figure 323.2.2A, I pick off a minimum temperature value of approximately -4.4 C. Any colder than that and ASME B31.3 would require impact testing in which case I would normally just default to material standard that included impact testing (e.g., ASTM A333 Grade 6).

If this is a well flowline it may well be under some other design code such as ASME B31.4, B31.8, CSA Z662, etc and you would be best to consult the applicable code as the rules can vary between them. For example, under CSA Z662, if this pipe were in gas service then it would be permitted to -30 C without impact testing.

 

[rneill]

I guess I should probably also mention that just last week I had a client consult me after using some ASTM A106 Grade B 3" pipe for wellsite piping that was supposed to have a stated minimum design temperature of -29 C. The design code was Z662, which did not require any impact testing, but the client had testing completed (using full size longitudinal samples) and the pipe failed miserably. The toughness values were far below what we would normally consider acceptable. He's now in a bit of a pickle since the code didn't require the tests but he did them and got poor results so can the pipe be used or not?

I only mention this to highlight that for A106-B or SA106-B pipe greater than 0.5" thick, I would not assume that it would have acceptable toughness values. Since I almost always apply a design minimum temperature of at least -29 C to the work I do, I would normally default to A333-6 pipe for anything over 0.5" wall.