Maximum service temperature of materials

[starfarooq]

We have a refectory lined transfer line installed between primary and secondary reformer at our plant. The material of the pipe is DIN 17155 (19Mn5). The design wall temperature of the pipe written over drawing is 343 Deg C. However when I searched the literature over internet, I found that the maximum service temperature for this material is 475 Deg. C. (this site ) So what exactly is the maximum allowable (tolerable) temperature for this material?

 

[JStephen]

For the ASME pressure vessel code, the allowable stress is reduced as the temperature goes up, so you don't have any way of knowing a maximum temperature for a material in place unless you know the design data for it. I assume other vessel and piping codes are similar in this respect. In some cases, maximum temperature may be further limited by corrosion issues, etc.

 

[starfarooq]

So you mean to say that the maximum allowable temperature depend upon the operating pressure?

 

[ivymike]

Yes, and/or other load conditions if applicable

 

[jtseng123]

I am not material engineer. However, the maximum service temp for each specific material has something to do with creep property, carbonization, phase change, sigma phase, martensite, bla bla bla. To be safe, limit the use to the temp set by code. Can you use beyond the code ? yes you can, on your own risk. In the old day, I saw regular carbon steel was used in 900-1000F. Nowadays, we don't use CS at that temp.