PWHT Temperature

[metboss]

Hi All,

Please note that during PWHT (after cladding on Valve bore) monitoring process, it was observed that temperature was exceeded the required value i.e. Reqd. 600̊C whereas observed 780̊C. The soaking period was 4 Hrs.
This discrepancy is mainly due to faulty control instrument and negligence of technician. Eventually, valve body was tested for hardness and found to be (150-160 BHN) less than the minimum hardness value i.e. 197 BHN (contract specs).

Details: The reference standard - API 6A, Material- AISI 4130 with internal bore cladding with Inco 625 overlay.

Is there any additional mechanical testing required? Can we reject the valve? Can we go for an additional heat treatment to obtain required hardness (min 197 BHN)?

I would like to have your advice on way forward.

 

[0707]

You can do what you want. I will reject the valve.

luis

 

[weldstan]

You can and should reject the valve.

 

Scrap & replace

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[metboss]

Thank you all for your feedback.
Is there any code reference for such rejections. Our management may ask for justification.
As per latest updatws, our vendor is now proposing to carry out some mechanical test (tensile, charpy) on some sub-components of Valve. These sub-components are blind flange and exit adapters. But, same material grade AISI 4130 and received the same heat treatmwnt of main valve body (under same batch). Even if test is passed for these sacrificial sub-components, i have no clue how they will correlate results with main valve body. In fact, main valve body will not be mechanically tested.

Kindly advise.

 

[EdStainless]

It fails, reject it. You don't know what the structure is or what the real properties are.
What was the original HT condition?

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P.E. Metallurgy, consulting work welcomed

 

[metboss]

The original HT is Quenched and Tempered.
Material class is E (AISI 4130) of API 6A. MTC is in compliance with API 6A.

 

[weldstan]

The PWHT is above the lower critical temp and the hardness is below spec. That's all you need to reject.

 

[EdStainless]

Yes, this part has no hope. You undid the Q&T by going that hot.

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P.E. Metallurgy, consulting work welcomed

 

[metboss]

Thank you Weldstan & EdStainless.

Valid points. We can justify now. I'll keep you updated soon.