Ring Joint Gaskets Using Appendix 2 Calculations

[wsmith22]

How do I determine the minimum width of a ring joint gasket to be used in a ASME Section VIII, Div.1 flange calculation? Typically, I would match the ring size to the pressure/temperature rating of a B16.5 flange. However, in this case, the pressure and temperature exceeds the 2500# flange rating. The gap between flanges after assembly will be 3/16". I assume FEA would be an option.

Thank you.

 

[KevinNZ]

Would API flanges be an option for you?

 

[jmec87]

I would try to stick with either a standard ASME or API 6A ring gasket (the smallest you can get away with that will still have sufficient corrosion allowance between the ring groove and the bore) to avoid ordering a custom one. If allowed, an API 6A flange (as suggested by KevinNZ) would likely be your simplest solution, but they are not allowed in some applications/jurisdictions.

 

[wsmith22]

Does anyone have any background designing an ASME Section VIII, Div.1 Appendix 2 flange using a metal C-ring or a Helicoflex type gasket? Per the following thread, Garlock gave user JJCist a m and y value for a Helicoflex gasket.

https://www.eng-tips.com/viewthread.cfm?qid=183863

However, the Pressure Design Manual by Dennis Moss, shows Helicoflex and metal C ring gaskets as self energizing gaskets (self sealing). Therefore, per Appendix 2-Table 2-5.1, the m and y values should be zero and the flange can be designed similarly to a flange using a elastomer o-ring.

 

[SnTMan]

wsmith22 I've not designed for a Helicoflex gasket, but I'd follow Garlock's recommendations for the gasket properties. Better to have "excess" bolting than insufficient.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[wsmith22]

I am having difficulty getting the m and y values. Technetics gives equivalent formulas for the operating load (Wm2 = Fj = π* Dj * Y2 = π * Dj * Y2) and minimum service load (Hp = Fm = 2* b* π * G * m * P = Ym2 = Y2 * (P/Puθ). For a Codeware Compress calculation, does it make sense to choose a value for the gasket width (N)that makes sense for the flange geometry and back calculate the values for m and y using the Technetics Helicoflex operating load and minimum service loads? I would also verify using a spreadsheet calculation.

 

[KevinNZ]

Are you sure this the correct type of seal for a ring joint groove

https://technetics.com/resource_library/helicoflex-spring-energized-metal-seals/

Seems to me, this type seal relies on limited compression and not suitable or the compression loads from a ring joint flange.

 

[XL83NL]

I concur with Kevin. It seems highly unlikely that C seals, like the Helicoflex, are suited for the high compression loads of RTJ flanges. I’m currently doing a project with C seals and the required compressive load is very small.

Huub
- You never get what you expect, you only get what you inspect.

 

[wsmith22]

No, it is an Appendix 2 flange with an o-ring style groove. The seal compression is approx. 0.6 mm nominal.

 

[SnTMan]

Wow, Tecnetics, that is one sucky website

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[wsmith22]

Ok, I'm not getting much help from the gasket manufacturer. They will give a total seating load for the c ring gasket. It looks like I should be able to replace Hp with this value in the calculation of Wm1. Does this make sense? For gasket seating, Wm2 will not govern so the minimum design seating stress does not matter.

Also, my company has always used Appendix 2 flanges and with no old timers around I cannot determine why the Appendix Y flange was never considered. Is there a disadvantage to using Appendix Y for design of a flange using an o-ring seal? The only thing I can determine is that welding could distort the flatness of the flange face.

Thank you

 

[BJI]

To answer your first question, per code the width is given in Table 2-5.2.

The RTJ version of these gaskets has a compression stop, so is not too dissimilar to using an RTJ gasket. You still have a metal faced sealing element, so I would be inclined to use the same properties as that for a standard RTJ gasket, unless suitable data can be provided otherwise. Do you trust these gaskets if the manufacturer can't provide you with basic data about their products?

So is it an o-ring style groove or an RTJ groove? If an o-ring style groove you will have metal to metal contact so should be designing to Appendix Y or similar. There is disadvantage to using Appendix 2 for o-ring grooves. However, you have stated there is a gap between flanges, so not an o-ring style groove?

What is wrong with using a more conventional style gasket? The API Type 6BX has already been suggested. You would still have to design the flange (unless a code break could be included), but at least you know the pressure energised ring gaskets have been proven to seal at high pressures.

Do you have a drawing of what has worked in the past?

 

[SnTMan]

A disadvantage with O-ring type flanges whether Apx 2 or Apx Y is the absolute necessity of both dimensional accuracy and proper surface finish. They won't seal without both being met. Tightening the bolts further is generally useless. Especially true of Apx Y flanges...


The problem with sloppy work is that the supply FAR EXCEEDS the demand