Connecting 300# and 600# RF? 4

[phamgiatoanbk]

Hi experts,

Do you think I could connect 2 RF flange with different class (300# and 600#) together?
They have the same number of bolts and dimensions, and we'll take the lowest rating as the rating of the assembly.
Is it allowed to do so?

Thanks alot,

Toan,

 

[moltenmetal]

At 3" and below, the bolt circle, stud size and count match between 300# and 600# class. As long as you know that the assembly has a rating no higher than 300#, I don't see the problem with bolting one to another.

 

[jte]

To add a bit of backup to moltenmetal's reply...

From B16.5:
2.3.2 Mixed Flanged Joints. If the two flanges in a
flanged joint do not have the same pressure–temperature
rating, the rating of the joint at any temperature is the
lower of the two flange ratings at that temperature.

Further, B16.5 Interpretation 2-20 from 1991 specifically addresses the issue of bolting flanges of different classes together. The response supports the approach proposed by phamgiatoanbk.

So, it is perfectly in compliance with B16.5 to do so. But engineering judgement has to apply as well, and the caveat would be that it needs to make physical sense. In your case, with the same quantity of bolts and matching dimensions, it seems pretty clear that this is an acceptable approach.

 

[SnTMan]

Due to the 1/4" raised face on the 600#, if I were pulling bolt lengths off a chart I'd pull 'em of the 600# chart.

Regards,

Mike