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RE: [MW:32404] LAS P11 minimum required hardness for operation

By Materials & Welding

Dear Devang,

This P11 material is already affected by creep, the microstructures reveal it.

It has accumulation of microstructural damages due to prolong operation (10 years) decreasing their load bearing capacity, with formation of Cr carbides at the grain boundaries and carbon dissolution in the matrix.

You have to notify the plant of the need to change that section of pipe affected by creep, due to the risk of sudden cracking, with operational consequences.

On the other hand, under normal conditions, the welding of P11 material (1 ¼ Cr - ½ Mo) should has maximum hardness of 225 HBN for service at high temperature operating.

A good solution is use the material P22 (2 ¼ Cr-1/2 Mo). Propose it.

 

Regards,

Ramon Briceno

http://www.linkedin.com/in/ramonbriceno-metalengineer

 

Sent from Mail for Windows 10

 

From: Devang Majithia
Sent: Friday, May 28, 2021 1:27 AM
To: materials-welding@googlegroups.com
Subject: [MW:32392] LAS P11 minimum required hardness for operation

 

Dear All,

Hope all are safe and doing good in this tough time.

 

36" LAS P11 steel is used in FCC Reactor O/H line with operating temperature of 500-530 Deg. C. Design temp. is 569 Deg. C. Creep temperature starts from 427 Deg. C as per API 571. Line in service for 10 yrs.

 

Insitu metallography is taken and noted to be with pearlitic structure disintegration and dissolved carbides in matrix (at 500X). Refer pic.

 

We noted hardness in the range of 105-120 BHN which appears to be quite low against generally noted 160-180 BHN. Baseline reading is not available. Hardness measurement done with a portable machine having angle compensation.

 

Request to kindly guide me on how much minimum hardness is acceptable for P11 material for such critical service?

 

Regards,
Devang Majithia

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