We are using PROCEQ Equotip 2 hardness meter which measures the hardness by REBOUND method. Heater is being fired with 90% pure hydrogen gas.

Hello Ashfaq,

Referring to your point # 4, we have experienced that high hardness is on the surface only because when the hardness reaches around 350 to 400 BHN, flakes/scale starts falling from external surface. When we take readings from new surface, it records around 200 BHN.

Pls. let me know ...

Yes, we carried out replica of one of the tubes with maximum hardness 420 BHN (Material A 335 P9) and the results also showed carburization. But the question still remains, WHAT SHOULD BE THE LIMIT? HOW MUCH CARBURIZATION / HARDNESS WILL BE THE LIMIT FOR REPLACEMENT??


For A-161 carbon steel tubes ...

@ashfaqanwer. API 530 is meant for calculating design thickness of heater tubes. I wish to find out the retiring thickness of heater tubes i.e. when they are placed in service and corrodes with time, so what should be the minimum thickness after which they should be replaced??

@ben. I think the ...

Inspection procedure of heater tubes of our 40,000 BPSD Crude Refinery consists of the visual inspection, O.D measurement, Ultrasonic thickness measurement and Hardness Testing. I want to know the maximum permissible hardness of tubes (which should become the replacement criteria). There are four ...