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Need ANSI B16.5 1973 Flange pressure ratings

Need ANSI B16.5 1973 Flange pressure ratings

Need ANSI B16.5 1973 Flange pressure ratings

Can anyone provide me with rated ceiling values from the 1973 ANSI B16.5? Specifically, the max working pressure for class 150 and 300 up to 700ºF.

Thanks in advance.

RE: Need ANSI B16.5 1973 Flange pressure ratings

What material are your flanges?

I don't have the 1973 edition, but in 1968 all steels were at 110 psi at 700° for 150 lb. For 300 lb. there is some variation, 470 psi for carbon steel, a bit higher for the low alloys up to 9 Cr, and quite a bit lower for some flavors of stainless.

By 1977, the 150 lb etc designations had become Class 150  etc designations. For CL-150 the steels and low alloys are still at 110 psi at 700°F while the CL-300 series are at 535 psi for material group 1.1 (A105). Carbon steels in material group 1.2 and the low alloys are at 570 psi.


RE: Need ANSI B16.5 1973 Flange pressure ratings

Thanks for the fast response jt.

The mat'l is A105.
I have the 1981 standard and as I suspected, the pressure ratings did not change between '73 and '81.


RE: Need ANSI B16.5 1973 Flange pressure ratings

I think that the time between 1973 and 1981 was a major change.

RE: Need ANSI B16.5 1973 Flange pressure ratings

Here is my situation:
Exhaust piping on a 450 to 150 psi reducing turbine.
Designed & built in 1978 using B31.1-73, B16.5-73, B16.9-71, B16.34-73
Inlet design press. 450 psig @ 750 ºF
Outlet design press. 150 psig @ 750 ºF
(I did mention 700F in my earlier post)
The turbine exhaust has a 300# flange.
The relief valve on the outlet piping has a 300# flange.
All other outlet piping flanges, valves and expansion joints have 150# flanges (A105).  The exhaust expansion joint needs to be replaced.

My dilemma is that by today's standards, class 150 flanges are only rated for 95 psig and the system would operate out of compliance with the local regulatory authority. We would have to change all the fittings and valves to class 300# That is, unless the original design code allowed for the use of 150# fittings at that design temperature. I would suspect that that back in 1973, 150# flanges did not have a higher pressure rating than either the current rating or the 1968 rating.  However, if there was a major change between '73 and '81 as JLSeagull suspects, these fittings may have been OK.  This would save a lot of time and expence of replacing the components.

Can anyone offer the info I need?

RE: Need ANSI B16.5 1973 Flange pressure ratings

I doubt there were any major change during this period for carbon steel. I can't see '68 rated at 95#/750F with '73 showing a 60% increase and then '77 going back to 95#/750F.

While your turbine outlet has design conditions of 150 psig @ 750F, does the outlet line have these conditions? While the vendor has assigned design conditions to his machine, it's possible the outlet line has different design conditions due to the way it operates and that the 150# flange class is acceptable at these outlet line conditions.

Have you checked the original project line list and vendor data files for the expansion joint. I'd be surprized that a expansion joint vendor would supply a joint with flanges that don't meet the design conditions.

What is your relief valve set pressure on the outlet line? Your design pressure should be the same.

Houston, Texas

RE: Need ANSI B16.5 1973 Flange pressure ratings

I stand corrected on the pressures & temperatures in question.  The drawings have conflicting information.
After much digging I managed to determine that the exhaust piping is sectioned into two different design conditions.

From the tubine exhaust to a de-superheater (approx 30 Ft.) the piping is designed to 160 psig and 600ºF.
After the desuperheater: 160 psig and 450ºF.
Inlet piping: 450 psig and 750ºF.

By today's standard, I see that the max pressure for class 150 is 140 psig at 600ºF and 185 psi @ 450ºF.

I suspect that the section of higher design temperature may have been overlooked by the designer when class 150 flanges were specified.  What's got me wondering is how it could have been overlooked by the local authority when the system was registered with them.

It therefore could be possible that B16.5-73 allowed for 160 psig @ 600ºF, and I am still trying to find printed proof.

RE: Need ANSI B16.5 1973 Flange pressure ratings


What is the piping design code which the system was designed to? If it is B31.3 then using paragraph 301.3.2(b)(2) the flanges are good for 158 psi using a 540°F flange design temp to correspond to 90% of the piping system's 600°F design temp.

Although I'd typically not use this allowance for new design and would round down for new design, for an existing installation with a history of satisfactory flange service and low consequence for a flange leak, I could see rounding the 158 psi up to 160 and calling it good. How much of the work that we do is really good to more than two significant figures anyway?


RE: Need ANSI B16.5 1973 Flange pressure ratings

While of course I cannot judge whether any existing piping is "ok", I believe that when you eventually lay your hands on some "printed proof" it will show that per ANSI B16.5-1973 "Materials: Group 1.1" (incl A105) Class 150 steel flanges then showed "Working Pressures" of 210 psi at 600 degree F.  

RE: Need ANSI B16.5 1973 Flange pressure ratings

jt: B31.1-73

Thanks for your reply.  Sounds like you have access to the ratings table.
I'm using other resources to obtain the document. In the meantime, would I be asking too much if you could provide me with the ratings of Class 150 (A105) at all the listed temperatures?  Or better yet, a PDF scan of the table? (will that infringe on any copyright or forum rules?)

RE: Need ANSI B16.5 1973 Flange pressure ratings

As best I read from the 1973 standard table you are interested in: -20 to 100 degrees F. - 285 psi, 200F-260 psi, 300F-250 psi, 400F-245 psi, 500F-230 psi, 600F-210 psi, 650F-205 psi, 700F-205 psi, 750F-195 psi, 800F-160 psi, 850F-105 psi, 900F-65 psi, 950F- 40 psi, and 1000F- 20 psi.

RE: Need ANSI B16.5 1973 Flange pressure ratings

Thank you very much.

RE: Need ANSI B16.5 1973 Flange pressure ratings

By the way, I do hope you eventually get your copy of the obsolete standard (as in addition to these sort of tabulated ratings e.g. I suspect it also contains further information/commentary on other joining components such as bolting and maybe also on possibility of very high temperature application or temperature gradient leakage etc. of particularly minimum class flanges etc.)

RE: Need ANSI B16.5 1973 Flange pressure ratings

I also hope we find a copy.  There was a copy here at one point but it "disappeared".  We are supposed to have a copy on hand because we have a lot of piping designed and installed using this standard (and B31.1-73)

Thanks for everyone's help.

RE: Need ANSI B16.5 1973 Flange pressure ratings

I am not sure where you will find the rating you seek.  However, I am aware the old Crane handbook, "Valves Fittings Pipe Fabricated Piping" for many years published pressure temperature ratings for 150# carbon steel "Welding Neck Flanges" (that I suspect in many cases followed some applicable piping codes from the day).  I don't believe there were any changes from 1949-1952 in these ratings, but unfortunately I do not have "Catalog 48" of the Crane handbook series (that I suspect was specifically applicable to the year 1948).  Maybe you could get lucky and pick up that edition/year on E-bay or somewhere else for a reasonable price, though I couldn't guarantee it would have exactly what you need!    

RE: Need ANSI B16.5 1973 Flange pressure ratings

i would get ahold of someone at Texas Flange

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