Hello, could you help me with this issue.
we need weld the piping designed to ASME B31.8 material ASTM A333Gr.6 it is required to qualify welding procedures per API 1104.
According to A333 Gr.6 material specification, minimum guaranteed yield strength is 35 000 psi (240 MPa) and, according to API 1104 Paragraph 5.4.2.2, this base material falls under the group:
a) SMYS less than or equal to that of the material specified as API 5L Grade X42;
However, one often encounters ASTM A333 Gr.6 materials with actual minimum yield strength 46 400 psi (320 MPa) specified in their certificate. In such case, according to API 1104 Paragraph 5.4.2.2, this base material falls under the group:
b) SMYS greater than that of the material specified as API 5L Grade X42 but less than that of the material specified
as API 5L Grade X65;
Question:
When selecting a welding procedure, shall we be guided by the lowest value of SMYS specified in material specification or the actual data specified in material certificate?
According to ASME IX, the listed materials have similar properties, such us composition, weldability and mechanical properties, and fall under the same group P-1.
Considering that, according to API 1104 the change of yield strength groups is regarded as a change of essential variable parameter, based on which minimum yield strength - item a) or b) - shall we re-qualify the welding procedures?
If I remember correctly, one would be better off selecting the base metal with the higher tensile strength to qualify the WPS for the reason that the higher tensile strength base metal also qualifies for the higher and lower tensile strength materials.
Selecting the material with the lower tensile strength only qualifies for the lower strength materials.
Al
Couple of things. Your in 5.3.2.2 which you've failed to mention, assuming 20th Ed. That then takes you to 5.4.2.2. Procedure MAY be grouped, but grouping is not required. Almost everyone does though - so that takes us to procedure qualification to the highest "specified" yield strength in that group. Not actual. So, to qualify a WPS for group (a) from 5.4.2.2. you would need to use material with a "specified" minimum yield of 42Ksi. If not, and you chose to qualify the WPS with the A333 Gr.6 material then your procedure would only be good for 35KSI materials. I have not verified the properties of A333 Gr.6, only going by numbers in your post.
By Sergey K
Date 05-04-2017 07:03
Edited 05-04-2017 10:43
thanks,
so, we have to be based on the actual yield strength specified in the material certificate, then WPS would be qualified for 35 KSI materials only, not cover 42 KSI group.
