A106 Gr.B & A105 LT15
A106 Gr.B & A105 LT15
(OP)
I was reviewing a vessel drawing the other day and noticed that the nozzle necks and flanges were to A106-B LT15 and A105 LT15 respectively. As per table A1-M of ASME B31.3 the standard A106-B and A105 are suitable down to -29degC. My query is why have these been specified as LT15? Is it simply that they have been impact tested as part of the material requisition?





RE: A106 Gr.B & A105 LT15
RE: A106 Gr.B & A105 LT15
The design code is technically PD 5500 as it is a pressure vessel, however I am a piping engineer and given these are piping components I figured this may be the best place to get an answer.
I am currently undertaking a PD 5500 Annex D assessment on an existing vessel and don't have access to material certs for this particular vessel. I know that from ASME B31.3, these materials are suitable, however I have never seen A106-B and A105 labelled as LT15 before. When looking at older BS material specifications they are labelled LTXX when they have been impact tested at -XXdegC. I was just wondering if this was the same methodology??
RE: A106 Gr.B & A105 LT15
Thanks,
Ehzin
RE: A106 Gr.B & A105 LT15
RE: A106 Gr.B & A105 LT15
Just a possibility, and with what weldstan has posted, it could be your answer.
RE: A106 Gr.B & A105 LT15
There are couple of things to look at why the impact testing was done:
1. -29C is good only upto a pipe wall thk up to 12.5mm for A106 gr B pipe. As WT increases. Minimum temp will increase too. For example.if the pipe WT is 25mm. Minimum temp for the pipe will be 0C (zero C).
2. A105 is good upto -29C. It is not dependent on thickness.
3. Even if these two materials can stand upto -29C, impact testing is not required by the material manufacturing standard.
4. Now.this minimum temp set by the code is different than MDMT(Minimum Design Metal Temp). MDMT is set by the process design conditions.
5. For a given WT. If the MDMT is above the min temp.impact testing of the base metal (pipe) is not required.If MDMT is below the minimum temp, impact testing is required.
6. The first part of the rule (MDMT>or= min temp. Donot limit the Owners to do a impact testing. It gives the Owners a more confidence level.
To find the reason why the designer chose to impact test the materials, you need to find out the following data:
A) The MDMT
B) the pipe WT
You said while 'reviewing vessel drawings...'. Is your vessel made of a pipe? Usually. Vessels are made out of plate material.A106 is a pipe designation.A105 is a forged material and widely used for flange.
Ganga D. Deka, P. Eng
Canada