Rerating ASME Section IV Boiler

[procyonlotor]

I currently work for a Mechanical contractor that has our ASME U, S, H stamps and NB R stamp and I am trying to rerate a 15PSI steam boiler. The boiler has a tubesheet that is unstayed made of .5" thick SA-285C. When I attempt to find pressure using the equation from HG-307.2 t=d*sqrt(CP/S) I am getting results smaller than the max allowable working pressure. The boiler diameter is 60" and the shell is made of SA-36 that is 5/16" thick. Any help would be greatly appreciated

 

[goutam_freelance]

A 60-inch unstayed tube sheet is very uncommon. Please check whether it is actually with 'Fire tubes used as stays'.

 

[procyonlotor]

A 60-inch unstayed tube sheet is very uncommon. Please check whether it is actually with 'Fire tubes used as stays'.

It is unstayed. We have it open in our yard. The H-2 also lists it as Stays or braces: None & Staybolts: No. None

 

[goutam_freelance]

The thickness appears to be lower than the code requirement. Please again check all the parameters, including the C value.