Boiler Super heater and Re heater

[ANKA RAO]

thread794-339070
What is the allowable sag for Super heater and Re-heater coils of fired boiler and HRSG ?

 

[Dhurjati Sen]

Dear ANKA RAO,

There is no code for this. You have to ask the boiler manufacturer. Different manufacturers would give different limits for various pressure parts. A reputed Indian manufacturer gave a limit of 4 x diameter of the tube for water walls and evaporator tubes a decade back.

Basically this boils down to the fact that how far you can use the plasticity of the tubes before the onset of necking at the service temperature taking into account the creep also.

Regards.

DHURJATI SEN
Kolkata, India