1000F temperature limit on flanged valves per ASME B16.34

[msmedesign]

I was wondering why there is 1000 F temperature limit on ASME B16.34 for flanged end-connections, but ASME B16.5 does not have 1000F temperature limitation. (Please see foot note on the material tables. Example material group 1.16)

Thanks

 

[GeoSmith]

It is really a very high temperature, can you tell me the real application in such high temperature?

 

[msmedesign]

Refinary cracker unit.

 

[davefitz]

I am not sure the rationale used by the B16.34 committee, but creep relief of the yiled stresses built into the threaded bolts that hold the flange together will tend to allow loosening of the flange. Thermal cycling of the valve will tend to loosen the nuts after the yield stresses are relieved .

 

[msmedesign]

dave but ASME B16.5 does not have the same limitation for the same material group.I think thermal cycling would have the same affect on any equipment.

 

[abscott]

You will find this note at the bottom of all the standard class rating tables in ANSI B16.34 and there are two reasons that I know of:

First,the iron based (steel) materials above 1000F become plastic and the designer has to design valves based on "stress time to rupture" and not a fixed tensile/yield stress. While the exact transition from elastic-to-plastic varies by material the arbitrary limit of 1000F has been fixed as a boundary.

Second,the standard bolting for carbon steel systems is ASTM A193, GR B7 (chrome-moly)which has a minimum tempering temperature of 1100F. The standard bolting for stainless steel systems is ASTM A193, 300 Series, Class 2 which is strain-hardened. These 300 Series fasteners have a lower annealing point of 1100F. Therefore, standard bolting materials exposed to temperature above 1000F will changes mechanical properties over time.

Since both the basic body materials and the standard bolting materials will change mechanical properties over time, the 1000F limit was put in place.

It should be noted that even though "Flanged ends terminate at 1000F" most valves designed for services above 1000F will still have some type of "body-to-bonnet" flange and this must be designed based the use of alloys specifically formulate for high temperature applications.

Hope this helps,

 

[NozzleTwister]

msmedesign,

I don't know what version of B16.34 you have, but I checked my 1998 version and there is no Material Group 1.16 in mine.

I checked several other materials that should be suitable above 1000 deg. F. and the Note 1, For welding end only. Flanged end ratings terminate at 1000 deg. F. applies only to CL150 valves, not CL300 and up.

Also note that in the past B16.5 and B16.34 were issued in parallel so that the flange ratings agree. A 2003 B16.5 has been issued with ratings for some materials that differ from the latest B16.34, which is B16.34a-1998 unless the new edition has just been released. Hopefully the next B16.34 will match the current ratings in B16.5. For now if you have a system with both flanges and flanged valves, you're limited to the lower rating of the two.

You gave me a scare. We just installed a bunch of Flanged Valves in an FCC unit with service from 1200 to 1400 deg. F.

Bolting for chromium steels in high teperature servicee is typically A193, Gr. 16 studs with A194, Gr. 4 heavy hex nuts.


NozzleTwister
Houston, Texas

 

[NozzleTwister]

Let me update my own post:

I just logged into our standards service and found that ASME B16.34-2004 has been finally issued with an issue date of Sept. 2, 2005.

In the new edition, there is a Material Gr. 1.16. In reading the forward, it looks like some materials got moved to a different group than they were before. That should keep the Pipe Spec folks on their toes.

It also looks like U.S. Customary Units is losing another battle against the world of Metric. These tables have been placed in Mandatory Appendix VII instead of the main Pressure-Temperature Table section which is now only in Metric.

In the U.S. Customary Unit section the note limiting flanged valves to 1000 deg. F. does not tag any particular flange class. I have to assume this omission is in error, in the Metric tables, this same note (538 deg. C.) does tag CL150 flanges only as it did in previous editions.


NozzleTwister
Houston, Texas

 

[msmedesign]

Nozzle Twister
I have talked some of the ASME B16 members and they believe 1000F limitation on some flanged materials are a editorial mistake. This limitation only applies to Class 150 flanges. (As you stated).

I think you should review your 1200 F to 1400 F FCC unit valves.
1)If the valves are higher than Class 150 there is no temp limit other than ASME B16.34 regular material limitation.
2) You need to use very special high temperature packing and gaskets for at this temperatures. ( especially if the enviroment is oxidizing). For flange gasket you may want to use thetmoclite material . (most likely i spelled it wrong)
3) I do not think B16 / 4 bolting is good for above 1100F depending on the code that you are using. Most likely you need to change your flange bolting.
4) If you used bolted bonnet type of valve, please also check the body bonnet gasket and BOLTING as well.
5)Let me know if you need my help .

 

[NozzleTwister]

msmedesign,

Our 1400 deg. F. valves were in hot wall FCC Flue Gas Service and CL300 flanged ball valves, 347H bodies with bolting, gaskets and packing suitable for the service.

The B16 / 4 bolting we normally use in our Chrome-Moly piping systems which is what I thought you were talking about. Our applications for the Chrome-Moly's generally don't exceed 1050 deg. F.

The limitation of 1000 deg. F. in B15.34-2004 is only an editorial mistake in the U.S. Customary Units Tables. In the Metric Tables only the CL150 vavles are noted.


NozzleTwister
Houston, Texas

 

[abscott]

Msmedesign & Nozzle Twister,

Comments from the prospective of a valve manufacturer (globe valves):

1.ANSI B16.5 is an old national standard and history has proven that the 150 Class flanges are susceptible to creep at elevated temperatures and this has resulted in loss of gasket loading. (ANSI B16.5, para.2.4.2 & ANSI B16.34, para. 2.3.1)
2.The 1000F limitation should be on the Standard Class tables and for the 150 Class Flanges.
3.Most manufacturers offer valves with either 150 Class or 300 Class flanges at the same price, therefore most customers immediately opt for the 300 Class flanges even though the process is 150 Class.
4.Agree, ASTM A193, B16 fasteners are limited to 1100F.
5.ANSI B16.34, Table 1, Bolting Materials lists ASTM A453, Grades 651 & 660 as the high temperature bolting that is compatible with stainless steel valves, however, stress rupture testing is required for applications above 800F.

In the temperature range 1000F-1200F standard steel based materials can be applied, but as the temperature increases the use of specialty alloys or the ASTM A193, Class 1 bolting and the de-rating of valves becomes more common. The de-rating of valve flanges and bolting is very similar to that required by NACE for flanges subject to the H2S environment.
Hope this helps,
ABScott