API 5L grade B pipe can be used in continius high temp equipment 1

[franciscogilberto]

ok guys lets see if someone give me any idea

I have a phthalic anhydride reactor with a salt bath agitator. The structure of this agitator was made with pipes of ASTM 201 quality for high temp work. (400 Celcius). It is a 1,20 mt lenght pipe 8 inches diameter and half inch thick. What i have available only at the plant is the same pipe size but is API 5L grade B seamless . So can I use this pipe to replace the damaged while we import the wright material.
I couldnt find any web page that says the maximum working temperature for this pipe, some one told me 500 Celcius is that ok???

 

[JohnBreen]

Hello Francisco

In recent years, pipe manufacturers have been making one pipe material that complies to the rather non-exclusive specifications for ASTM A-53, Gr. B, ASTM A-106, Gr. B and API 5L, Gr. B. These grade designations are usually imprinted on the OD of the pipe in the longitudinal direction.

These grades of carbon steel pipe are susceptible to "graphitization" when used at temperature above 750 degrees F. for long periods of time. This phenomenon causes carbon to "migrate" from the metal grains into the boundary layers between the grains. This results in pipe that becomes embrittled over a period of time. Your application is right on the edge of the temperature range where you should expect grapitization. The real question is how long will the "stop-gap" repair be in service before it is replaced. This is a question that only the owner should address.

Best regards, John.

 

[JohnBreen]

Back again Francisco,

Your reference should be to the B31.3 Code, Appendix "A", Table A-1. You should look at note 57 on page 154 of the 2002 edition of B31.3. The Code tells you the conversion of carbons to graphite begins at 800 degree F. (427 degree C.). Actually, the carbon conversion temperature will vary from heat to heat of the manufactured metal. I won't use these carbon steels for design of new piping systems that will be used above 700 degrees F. Again, these decisions should include the owner.

Regards, John.