Fwd: [MW:13723] Interpass timing

Dear sir,

Interpass means temperature (3" on either side of joint) inbtween two consecutive passes. And in this case if it is left after laying Root & Hotpass all through out the shit/night, then you tell me where is the essence of the word interpass.-Unless otherwise it has ben kept under the preheat you mentioned all through out the break.

 

As far as my knowledge goes, there is no code reference about this GEP(Good engineering practice). Basically this is a truely a welding-metallurgical aspect and if the joints are so critical, then your QC has right to say so.

Actually what happens: With only two passes laid on this XXS heavy wall thickness parent metal, the weld deposit thickness is not that much to withstand the contractional forces exerted by the parent metal from both side of the joint. Thereby resulting huge stress build up which leads to cracks. In heavy walled plates as well as pipes, longitudinal ( cold cracks / HIC ) on the bead laid yesterday are often seen in this partially welded items.

 

Way forward: May be at the best if you can put a deviation note and convince yourself as well the QC that it will be 100% NDT done before proceeding further. 100% LPI & 100% MPI on all such partially welded joints. And marking these joints with a distint identification no. and doing 100% RT of all these particular joints after final weld completion., even if the drg says % RT on all finished joints.

 

regards,

Debasish

Dubai. 

+971504349936 

 

 

On Wed, Feb 15, 2012 at 5:07 PM, jesti fer <jesti_fer@yahoo.com> wrote:

Dear experts,

I need your help, In our project (B.31.3) CS pipe joints ASTM A106 Gr.B 8" Sch XXS, our construction team kept the joints after root pass and hot pass welding, but our QC instructed to cut and and re-weld the joints. Really it is required and  it is mentioned any were in code? We are maintaining preheat at 150-Deg and inter pass temp 300-Deg

Please help me;;;;

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