ASME B16.5 Hub Outside Diameter at Bevel End - Upper Tolerance Limit

[mitulmech]

Dear Group Members,

I have following query related to subject post

Design Code : ASME Sec.VIII Div.2
Design Pre : 320 bar
Design Temp : 85 Deg C
Inside Diameter (ID) : 187.3 mm
Cylinder Required Thickness is : 24 mm
Material of cylinder : SA 350 LF2 CL1
Material of attached flange : SA 350 LF2 CL1
Pressure rating : 2500#, ASME B 16.5
Equipment : Pig Launcher

Due to specific inside diameter (ID) requirement cylinder outside diameter (OD) is coming = 187.3+24+24 = 235.3 mm
But B 16.5 STD. hub outside diameter at bevel end shall be not larger than the 219.08.

Query :

If we increase hub outside diameter at bevel end to 235.3 mm to match the same with cylinder OD keeping all other dimension as per B 16.5.

Still can we qualify this flange standard flange as per B 16.5 or it will be custom design flange and need to be perform thickness calculations?

What is tolerance limit of deviating from STD. OD of 219.08?


Static Equipment Engineer

 

[Gilmiril]

If you deviate beyond the limits specified by B16.5, then you absolutely cannot stamp it as B16.5. The limits on that dimension ('A') are given in para 7.5.1, which for NPS 6 and larger is +2.0/-1.0 mm.

But unless you have some kind of high external loading condition that's driving your OD that large, I would think your design calcs can refer back to B16.5 as the design basis without need for further calculations. That would be an engineering judgement, I would think.

 

[SnTMan]

mitulmech, assumming your B16.5 flange is rated for the conditions, why not just blend the mismatch with weld metal?

Regards,

Mike