3-Bolt Flange Design 1

[alex2010]

Can someone pleae adise me on what ASME code to use for the design of a 3 bolt, class 150 flange.
I have looked into ASME Sec. VIII, Mandatory Appendix 2, but it does not ask for the number of bolts, which leads me to belive that you may not be able to design for a 3 bolt flange using this standard.
Thank you,
Alex

 

[MJCronin]

Alex...

There seems to be a fundamental problem in your understanding the scope and structure of the Codes and Standards.

When an ASME Class 150 flange is used as part of a piping system or pressure vessel, the designer is restricted to the dimensions, bolt configurations and pressure/ temperature limits given in the Standard.

When a designer wants a "unique", one of a kind flange for his particular application, he can use the complex rules of ASME VIII, Appendix 2.

I know of no previous case where a "three bolt" flange was used in either a piping system or as an ASME B16.5 flange.

-MJC

 

[alex2010]

I have looked into ASME Sec VIII, Appendix 2 and it does not mention bolt configuration. Does that mean that we are allowed to design 2 or 3 bolt flanges?

 

[pennpiper]

Alax2010,
Why would you possible want to design such an ODD flange?????

The other question how are you going to match up to four bolt flange configurations on Valves, Gaskets and Equipment.

If you really want or need such and ODD configuration, then you had better have a lot of money because you will need to create all the related connecting items in the same configuration. This means not only for the original installation but for replacement during the 25 to 30 year life of the plant.

This does not sound like a good idea to me.

 

[alex2010]

The reson why I want to design a 3 bolt flange is because the new flange has to match an existing flange that is currently installed in the system. I have spoken to the customer and he has agreed to pay for the costly design.

 

[pennpiper]

What did you do with the flange you took off of there?

 

[jte]

Folks-

I would guess that the reason to go to a 3 bolt flange is installation expense. Noting that alex's tag identifies him as "nuclear" there is a good likelyhood that the installation of this flange will be by robots in a "hot" environment. Ever wonder why nukes ar so expensive? In the process world that I'm used to we can inspect our pipes and equipment almost anytime and repair options are relatively plentiful. In the nuclear world, those options are severely limited. Different environment, different cost structure.

alex-

I'd suggest that you are not in VIII Div. 1 Appendix 2 territory, but in FEA land. Keep in mind that meeting the allowable stress will be relatively easy - its the deflections that will get you. I'd also poke around a bit at the offshore industry - they may have devices you can use or at least get inspiration from.

jt

 

[unclesyd]

In one of those long time ago stories we used a 3 bolt flange on polymer lines designed for 2200 psig @ 650F. These flanges came from Germany with all the required papers. Our flanges were of the slip-on type that required a stub end. These flanges were for polymer equipment that had an extended run life, more than a year. The unique aspect of these flanges were than you welded the edges of the two stub ends together eliminating the gasket and the required seating stress. All that was required of the 3 bolt flange was to handle the hydraulic end force and some minor moments.
If I recall correctly there were also some weldneck flanges in their brochure.

 

[ColonelSanders83]

Appendix 2 does not explicitly list the number of bolts. It instead calculates the required bolting area for the various load conditions the bolts will see. It approximates the bolt individual point loads as a line load at the bolt circle diameter.

This assumption is valid for even and close distribution of bolts. The further away from this assumption you get the less valid the underlying assumption.

In my opinion jte is correct in guiding you towards an FEA analysis. Stress is not likely to be the governing criteria; deflections and the associated loss of sealing in between the bolts are going to be your headache.

If it this was my project I would initially size the flange based on Section VIII app 2 (making damn sure I had planty of margin on the rigidity criteria), I would then perform an FEA analysis on 1/3 of the flanged joint (making use of symmetry) to evaluate deflection due to only having three bolts. I would then interface with a gasket vender to find out what would be acceptable and compare. This will be no easy feat and can easily take up a lot of time and energy. Especially if you don't have a good FEA person around

Just my two cents worth


Always remember, free advice is worth exactly what you pay for it!

 

[IFRs]

"The reason why I want to design a 3 bolt flange is because the new flange has to match an existing flange that is currently installed in the system."

Why not copy the existing flange?

 

[superdaigle]

Perhaps another option is to cut off the existing flange and weld on a standard 150# class?

 

[eadwine]

I've seen three bolt flanges before, in pneumatic conveying systems out of the E.U...?, this could possibly be one of the bizzare DIN standards. Don't reinvent the wheel, just cut it off and replace it with a standard off the shelf variety in the proper material and flg. class.

 

[sjrfc2]

The flange design might be to Mil-F-20670. This is a carbon steel flange spec used by the US Navy. I think it is intended to mate up with non-ferrous (bronze) flanges designed to Mil-F-20042. Both specs use three-bolt flange patterns for 1/4, 3/8, and 1/2 NPS sizes. Youshould be able to get a copy by googling the spec. You should at least be able to get the dimensions to verify that this is the design you're looking at.