TEMA / ASME Backing Ring

[alanw7272]

Hi,
TEMA RCB-5.14 has 4 different configurations for a backing ring, type S. The TEMA equations suggest that for Styles A, C and D you can use the bolt load 'W' and for Style B you must use the bolt load '2W'.
I understand the 2W as Style B is split, but then so is Style A and D. I am using Style A so I will relate my questions to this Style.

1. Does anyone understand why TEMA only uses W (and not 2W) for the bolt load as this flange is split? Is it their intention that there is limited bending due to the close tolerences and if so why is this not referenced or explained?

2. TEMA definition of W refers the user to the ASME Code Appendix 2 wherein this Code uses 200% of the flange moment for a split flange/ring design. As the ASME Code is used to determine W, I am inclined to use 2W for my Style A design to keep within Code Requirements!

ASME does not address backing ring designs (As far as I know) but this ring must still meet Code Requirements!
Any feedback would be appreciated.
Thanks

 

[DG72]

Rotation of the back up ring is limited by the floating head for the styles you mentioned--this is addressed in the TEMA interpretations.

The back up ring is not designed according to App. 2. Pressure does not directly act on the back up ring.

 

[alanw7272]

Thanks for your reply DG72,

I have reviewed the interpretation in TEMA and understand their thinking. However I think PD5500 uses double the moment for flange stress! Guess its a bit open to interpretation!
I just would have expected TEMA to be a bit more precise with their calculation or at least definitions!

 

[eolivares]

Hi, anyone out there who has or know how to get the ASME Div. I Code? I have try the rapid share with no luck.

 

[doberdorks]

Hi, anyone out there who has or know how to get the ASME Div. I Code? I have try the rapid share with no luck.

Material is copywrite, so I'd suggest ASME, IHS, or if it's a reference only thing, local university library may have it, not always the current version however.

SLH