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Impact Test & Material Choice

Impact Test & Material Choice

Impact Test & Material Choice

(OP)
HI,

I have just taken up a project where the CLIENT SUPPLY is API-5L-x70 at 15.01mm wall thick with a Design Temp of -25 Deg C.
and to be used for a Gas Pipeline.
The Code is B31.8 but referencing the B31.3 for Impact Chart Figure and the corresponding Table for interpolation, the thickness just falls outside the "Curve B".(FOR X70)
The client is wanting to use this pipe (job lot).
Is a new Impact Test at -25 Deg C OR -46 Deg C acceptable (Originally the API-5L-x70 was Impact Tested at 0 Deg C.)and what would be the acceptable Joule Values.

Thanks in anticipation

pipestan

RE: Impact Test & Material Choice

Depending on the diameter and %SMYS design, you will need to calculate impact absorbed energy required for ductile fracture arrest. With the new lower temp design, you will need to retest the pipe at -25 C unless the lower temperature is based on Joules-Thompson cooling with depressurization. You need to discuss with your Client, the pipeline operator. It's the Operator's responsibility.

RE: Impact Test & Material Choice

(OP)
Hi,

The pipe size is 10" and the %SMYS is 0.4. Am i right in assuming that these fall outside the need for fracture arrest ? If i am wrong, where would i find the formula for Impact absorbed Energy ?
What would be the test temp seeing that the temp is based on Joule Thompsoncooling with depressurisation ?

Many thanks for the help
cheers
Pipestan

( normally it would be the operator responsibility but this job isn,t as clean cut as that - sadly )

RE: Impact Test & Material Choice

You will not need to calculate for ductile fracture arrest.
Battelle's simplified formula is 2/3 Cv = 2.382.10 to the -5 power x hoop stress squred (Radius x thickness) to the 1/3 power.

Review Fig.323.2.2B in B31.3 for permitted temperature reduction without impact testing.

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