Temperature Limit for Flanged Connection as per ASME B31.3

[nikolastrojman]

Hi

I would like to know if there is a temperature limit for using flanged connections (i.e. bolted connections) stated in B31.3 or B31.1. Or should I ask my question in this way...can I use flanged connection at temperatures greater than 500°C.

Best regards
Nikola

 

[moltenmetal]

Yes to your first question- you can find the limits in ASME B16.5. And yes, to your 2nd question- there are many materials which have flange ratings well beyond 500 C- in fact to about 815 C.

 

[XL83NL]

As an addition to MM's reply, custom designed flanges to ASME VIII-1 app 2 (could theoretically) be used to even higher temperatures; but you may end up with non standard dimensions for bolt holes etc. Keep in mind though that ASME II-D (as per note G5) may put restrictions on the use of materials for higher temperatures, since slight deformations or distortions can cause leakage.

 

[MJCronin]

According to the best of my recollection, because of high costs, flanged joints were strongly discouraged in high temperature, high pressure piping systems.

This was the policy of large AE firms such as Bechtel and Stone & Webster in the 1970s ....

I have rarely encountered a flanged joint on boiler Main Steam, HRH and CRH systems.

I would like to hear Pennpiper and other senior piping engineers on this issue

MJCronin
Sr. Process Engineer

 

[nikolastrojman]

Thanks for the help.

Yes I'm aware that ASME B16.5 defines the pressure-temperature rating for different flange materials but I heard form one of my colleagues that ASME B31.3 (and maybe even B31.1) specifically states not to use flange connections over temperature of 470°C and that only welded connections are allowed.

I have a situation where I have to install an expansion joint at the end of the safety discharge line of the main steam line in a power plant. This discharge line will be connected through this expansion joint to the vent silencer on the roof of a boiler house building. We want to use flange connections for this expansion joint because we would like to be able to replace the joint if necessary.

 

[moltenmetal]

I can't comment on B31.1, but am unaware of any restriction in B31.3 on the use of B16.5 flanges anywhere within their limits, which as I've already said are available for use all the way to 815 C. And while flange use can definitely be problematic at high temperatures, and requires care in design to minimize, the problems associated with having to cut and re-weld pipe when disassembly is required on a frequent basis for process reasons is obviously far greater.