Cold bolt preloading of Hot design temperature flanges

[aldocigna]

When the equipment design temperature is very hot (e.p. > 350°C) is correct use, in the cold bolting operation, the same 50KSI standard preload value for B7 bolt type preview in ASME PCC-1?

When the equipment will be in temperature is correct think that the DL/L of bolt will remain the same value and the preload the same percent of RP0.2(t) at operation temperature?

For standard equipment with standard flanges and standard gasket (TEMA, ASME) can we be sure that is sufficent calculate the preload stress based on dimensions and material of bolt only or is always however necessary verify the gasket (seal and resistance) everytime?

tx Aldo Cigna

 

[CoryPad]

No, the standard preload value is not correct to use if joints will experience high temperatures that cause extra stresses due to thermal expansion.

The preload will not necessarily remain the same.

VDI 2230 covers temperature-dependent preload changes.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[aldocigna]

In the ipotesys that in operation the bolt temperature and flange temperature will be equal (e.p. heat insulated flanged joint) i think that the bolt stretch will be the same value in cold and in operation condition but in this last case the stress for the same stretch will be inferior than in previous case (the stress curve will be lower)
The temperature automaticaly will unload the initial bolt preload
Is this correct?