Hot Tap Blind Flange ? 1

[rides426]

Hello,

Does anyone know if B31.3 or B16.5 will allow me to weld onto a blind flange for the purposes of hot tapping. I'd like to weld a 20" weldolet onto a 24" blind flange and then install a 20" valve and hot-tap the 24" blind. Shutting down the process will cost about $1,000,000 so that's out.

Any input would be appreciated.

 

[donf]

Don't have a definitive answer, but here are some things to check.

1. B16.5 has restrictions on maximum size connection for blind flanges without hubs. (This may apply to NPT connections only)

2. Will gasket and flange bolting handle the welding temperature?

3. Have you considered freezing the line?

Please keep us informed as to how you resolve this.

donf

 

[donf]

Check this option(s):

http://www.teaminc.com/literature_pdf/Hot_Tap_Brochure.pdf

donf

 

[rides426]

What I've come up with is that B31.3 paragraph 304.5 says for flat blinds with large openings fall under Boiler and Pressure Vessel code Section VIII Div 1, Appendix 2. There is a case for butt welding a flange to a nozzle, so I'm thinking at can be done and still be code compliant once the calcs are verified.

Any thoughts anyone ?

 

[TGS4]

Rides426, follow that path to VIII-1, App 2. That's the correct approach. A properly-designed hot tap connection should make it work.

 

[Krausen]

Looking at this from a high level, I'd think you'd have issues with the proximity of your stud bolts, nuts & gasket to the WOL weld. But where there's a will there's a way. All my work related to this has been for a client that strictly forbids tapping onto blind flanges, hot or cold.

 

[Kiwi2671]

rides426,
What about installing a Stopple valve on the 24" line just before the blind ?
Plug the line, remove the blind, install a 24" valve and you are ready to go.
Have no idea of the cost but we have used them previously while welding on a live methanol line and they were great.
Regards,
Kiwi

 

[MJCronin]

I agree with Kiwi..... why must you tap into a blind flange ?

Why not perform a more conventional tap just upstream of the flange ?

It looks like, based on you picture, that there adequate room for the tap....

 

[TD2K]

All the companies I done work involving hot taps have required flow past where you are welding, that could be difficult on a blind flange especially looking at the picture, you see to have a reasonable dead leg ahead of the blind flange.