Flange Design B16.5 vs App 2 for non-recognised gaskets

[JJCist]

Background:
According to ASME VIII Div 1 UG-44, ASME B16.5 flanges is acceptable under Division 1 in accordance with requirements of UG-11 .
According to ASME VIII Div 2 AD-711 , ASME B16.5 flanges is acceptable. In accordance with AM-105,1,such flanges and flanged fittings with exception of threaded and socket welding types, may be used at the pressure-temperature ratings specified in AM-105.1(b).

As per ASME B16.5 para. 5.4,
The user is responsible for selection
of gasket materials which will withstand the
expected bolt loading without injurious crushing, and
which are suitable for the service conditions. Particular
attention should be given to gasket selection if a system
hydrostatic test approaches or exceeds the test pressure
specified in para. 2.6.

Now, I have a 1500# flange group 2.2 (316 SS) @ 520 °C & 9800 kPa (g).
According to B16.5, the flange is suitable (125.5 bar allowed @ 538°C).
If this flange is designed in accordance with Appendix 2 (custom made forgings), the flange thickness is inadequate.

I intend to use a Helicoflex Seal (Garlock) with m value of 6.83, y value of 1700, and a effective gasket width of 1 mm.

Question:
Do I need to increase the flange to 2500#, or are a 1500# flange acceptable to B16.5.

 

[JJCist]

Do I accept a flange to B16.5 where a groove is machined in the raised face portion of the flange, not exceeding the depth of the raised face, or is it compulsary to design the flange to either ASME VIII Div 1 or 2.

The groove is there to ensure that the seal is not crushed, but the mentioned seal is not listed in the table at the back as part of B16.5.

I have done the calculations to Div 1, but still feel that it is unnecessary to increase the flange thickness (pound rating) if a 1500# flange is more that suitable for the job according to B16.5.

I would like to have a
Yes - B16.5 flanges are suitable, or
NO - Calculations is required thus flanges will have to be custom made forging

 

[unclesyd]

Helicoflex did have a work sheet, hopefully now computerized, that outlined the procedure to evaluate their gaskets according to ASME.

We used gaskets supplied by Helicoflex on both standard 16.5 and non standard flanges with very good success based on their recommendations based on our operating data supplied. We also used there gaskets on some very offbeat flanges using there calculation sheet.

I haven't had much contact with Helicoflex since they were purchased by Garlock, but at one time they had a very good technical staff.

 

[doct9960]

JJCist,

Does the Helicoflex meet the requirements of ASME B16.20?ASME VIII-1 lists the acceptable gasket standard in UG-44 and ASME VIII-2 list them in Table AG-150.1.

Is this the catalog for this Helicoflex?...

http://www.helicoflex.com/assets/pdfs/HelicoflexMasterCatalog.pdf

 

[JJCist]

Doct9960

Helicoflex does not fall within B16.20, or any ASME code as far as I could gather. I have been in contact with Garlock's(manufacturer)technical staff, but they were only able to assist me in computing m and y factors for these seals, and not the flange calculations. They mentioned that it was previously used with B16.5 flanges, but pressure and temperature play a role, and no specific example could be gained.

Helicoflex is a type of spring energising seal with a (in my case) Nimonic 90 spring, covered with an inner layer of 316 SS and an outer layer of Nickel for high temperature applications(type is HND-229)that give me the high seating stress.

The catalog you refered to, contain the correct information.

I hope this can give you more insight.

 

[SnTMan]

JJCist, I think you would be justified in what you propose.
First, grooving the raised face only is acceptable, it has no effect on flange dimensions.
Second, forget flange moments and bending, just see if you have enough bolting to seat the gasket at the manufacturer's m & y values. I believe you do.
Third, compare those m & y values to gaskets in ASME B 16.20, my guess is that they fall within the ranges for gaskets in that spec, although m appears a little higher than other gaskets may use.
Fourth, any given ASME B16.5 flange is presumably suitable for any gasket from soft rubber to solid metal rings, the only difference is the facing.
Fifth, ask yourself "Have I satisfied B16.5 para 5.4?"

As an aside, in my experience, ASME B16.5 flanges do not appear thick enough when analyzed per Appendix 2 because they usually have far more bolting than Appendix 2 would require. I realize this is not really a "reason", but the rating basis between the two types of flanges is completely different.

Regards,

Mike

 

[doct9960]

JJCist,

I have been in contact with Garlock's(manufacturer)technical staff, but they were only able to assist me in computing m and y factors for these seals, and not the flange calculations. They mentioned that it was previously used with B16.5 flanges

Did Garlock mention if this B16.5 flange was used on a ASME Code vessel? And at what temperature and pressure? Was it proven successful in actual high temp-high pressure ASME Code Vessel service? I would still prefer to use Spiral-Wound gaskets especially at the temperature and pressure (520°C & 9800 kPag) you mentioned.

316 SS may??? be used for B16.5 flange at 520°C & 9800 kPag; but if the flange is custom designed to Appendix 2, you need to meet the material requirements of ASME Section II Part D. I don't think 316 SS is allowed by Section II Part D for the temperature & pressure you mentioned. I hope some of the material experts in this forum could clarify this. I am no material expert myself.

Also consider if there would be severe external loads or thermal gradients. ASME B16.5 paragraph 2.5.2 says...
"Application at temperatures in the creep range will result in decreasing bolt loads as relaxation of flanges, bolts, and gaskets takes place. Flanged joints subjected to thermal gradients may likewise be subject to decreasing bolt loads. Decreased bolt loads diminish the capacity of the flanged joint to sustain loads effectively without leakage. At temperatures above 200°C (400°F) for Class 150 and above 400°C (750°F) for other class designations, flanged joints may develop leakage problems unless care is taken to avoid imposing severe external loads, severe thermal gradients, or both."

 

[tothepoint]

Why are you going to all of this trouble to use a Helicoflex gasket when a FG filled SW or camprofile gasket would work just as well and are designed/accepted for use in 16.5 flanges?

 

[JJCist]

Mike,

Thanks for your useful contribution. I also feel (gut) that B16.5 flanges will do the job, but will do the checks suggested.

tothepoint,
Helium is used as a product in a nuclear plant still in concept.

doct9960,
316 SS is acceptable if designed to ASME VIII Div 1 or ASME 3 (section NH special) for 520°C. ASME VIII Div 2 have a limit, and are not suitable for these high temperatures.

I have spoken to a few other engineers, and we feel that it is on the safer side to go the design route to code, sticking as far as possible to the dimensions of B16.5. Nozzle loads and bolt seating & operational loads will thus be taken into account. I appreciate your inputs, thanks.

 

[doct9960]

JJCist,

Finally got a hold of ASME Section II. You are right. 316 SS is good up to 815 [°]C (1500 [°]F). I was thinking of 316L SS, the low carbon version of 316. 316L is good up to 454 [°]C (850 [°]F) . We normally specify 316L especially if the welded parts are thick (over 6 mm). 316L is more resistant to carbide precipitation.