ASME B16.5 Gaskets for Class 150 Flanged Joints 1

[GD_P]

Hello forum,

I apologies for posting this topic once again, since we were not able conclude by that time.

A) This is with reference to ASME B16.5 para 5.4.3 & ASME B31.3 Appendix F para F308.4. Is it prohibited to use of spiral wound gasket for class 150 slip on flanged joint?

B) Is it prohibited to use gaskets other than ASME B16.5 Non-mand appdx B, Table B-1, group no. I gaskets for class 150 slip on flanged joint?

I heard answers stating that these are only recommendation and hence not mandatory. But if it is recommendations and we dont want to follow them, we should have some sort of backup?

Please share your view.


GD_P

 

[XL83NL]

1) No. As per F300;

These are not Code requirements but should be taken into account as applicable in the engineering design.

The Code is silent here by the way on SWG's for Cl. 150 flanges, not sure where you got that from.

2) No

The Code is not a cookbook type document to go through step-by-step.The Code only has minimum provisions & requirements.

 

[GD_P]

Thank you XL83NL for response.

In para 5.4.3 of ASME B16.5 code states that "When the ring joint or spiral wound gasket
is selected, it is recommended that line flanges be of the welding neck or lapped joint type.".
Gasket to used as per cust. spec is Spiral Wound and we use slip on type of flanges generally. As per the B16.5 standard recommendation we can not use it. But as it is a recommendation we thought that the parent design code may give clarification that when this recommendation should be applied. But B31.3 F308 is also silent on this.
One more advise required "when should these recommendation should be considered and what basis?"
We will really appreciate your suggestions.

GD_P

 

[r6155]

GD_P, please try to understand.

"Recommendation" is like "good engineering practice".
"Recommendation" is not "requirement".

Engineering judgment shall be applied.

Regards

 

[TGS4]

You said "We use slip-on type of flanges generally". Why? What is your engineering judgement/justification for that choice?

 

[gasketguru]

Many users have spiral wound gaskets on class 150 flanges, though they are sometimes thought of as being too "hard" for lightweight flanges with limited bolting (remember that originally spirals had a "y" factor of 4500 psi which was later increased to 10,000 psi). Note that many manufcturers offer "low-loaded" or "low-stress" variants for class 150 when users expect to attain "full" compression to the guide ring. However also note the recent changes in the 2017 version of ASME 16.20 which give typical load-compression-leak info, so such gaskets no longer really conform to the standard.

I think your main problem will be related to using spirals with SOW flanges, particularly on the smaller bores (<1.5").Check tables SW-2.5-1 and 2.5-2 in the ASME 16.20 standard - on the small bores the sealing element comes too close to the bore of the SOW flange so you have the risk of the gasket collapsing / buckling inward as the inner ring is not being supported on the flange face. A spiral-wound element has a radial internal stress when compressed and the element must be fully supported and not overhanging. On the small bores the kammprofile gasket is a much better option if you want a semi-metallic gasket rather than a soft cut one.