Re: [MW:8306] PWHT and RT

Hi Mr.Sagar

This case always depends on application.

The election between PWHT + NDT or NDT+PWHT+NDT is a decision to take according to the criticality of service, the specific experience of welding workshop, welders skill, time schedule, costs, etc.

About PWHT:

• PWHT does not always have a positive effect and can cause distortion and degradation of the microstructure.
• PWHT can "open up" indications (due to heat cycle) that might not show by NDT before PWHT.
• There is a chance for delayed cracking or post heat treatment cracking may happen in or adjacent to welds after PWHT.

Considering the above reasons NDT is preferable after PWHT to make sure the weld quality.

NDT + PWHT + NDT:

"RT before PWHT" would be an optional additional examination. Some folks do this do make sure the joint will pass RT prior to doing the PWHT. In some cases, if "RT before PWHT " is a requirement, it may be included in purchase order/specification.

If you noticed repair after PWHT, then you need repair and  re-PWHT required;to minimise/avoid this situation, preferable choice is NDT+PWHT+NDT. Repair work with re-PWHT may affect time schedule and cost impact also.

Customers always interested in NDT acceptance after PWHT.

PWHT + NDT:

However, have found that some contractors will tend to pay more attention to detail if they only shoot one RT after PWHT. Nobody wants to have to repair and perform a second PWHT.

 

Rgds/Shankar

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From: Sagar QC <sagarqcwelding80@gmail.com>
To: materials-welding@googlegroups.com
Sent: Mon, 15 November, 2010 2:20:45 PM
Subject: [MW:8267] PWHT and RT

Hi,

I have a doubt regarding PWHT and RT. We are welding P1 Material Pipes which has thickness more than 19mm so we are performing PWHT for the same. But my question is regarding when to take RT? Can we accept the joints which is radiographed before PWHT and  MPI after PWHT. Or will we have to perform the RT only after PWHT of the joints? Please advice me regarding this and provide the supporting clause.

Thanks and Regards,

Sagar.

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