Effect of drilling though compensating pad??
Effect of drilling though compensating pad??
(OP)
We have a refractory lined cylindrical pressure vessel which is exhibiting some hot spots due to gas tracking through fine cracks. The vessel ID is too small to repair from the inside so I wanted to weld some 1/4"- 1/2" nozzles onto the vessel and inject liquid refractory from the outside. The nozzles would be plugged after use.
One of the hotspots is in the junction of the vessel and a nozzle, incorporating a compensating pad. Am I able to weld a nozzle to the compensating pad, drill though the pad and underlying material and inject refractory through the hole? How would drilling through the com pad affect vessel strength?
The vessel OD is 28" and the attached nozzle is 20" OD. Materials is carbon steel.
Thanks for any help.
One of the hotspots is in the junction of the vessel and a nozzle, incorporating a compensating pad. Am I able to weld a nozzle to the compensating pad, drill though the pad and underlying material and inject refractory through the hole? How would drilling through the com pad affect vessel strength?
The vessel OD is 28" and the attached nozzle is 20" OD. Materials is carbon steel.
Thanks for any help.





RE: Effect of drilling though compensating pad??
RE: Effect of drilling though compensating pad??
To answer the specific question, putting a hole in a compensation pad reduces the metal available for reinforcement (reduces its strength).
The nozzles that you are adding should be designed per the code rules for nozzles. If they are closely spaced, they should follow the rules for closely spaced nozzles.
RE: Effect of drilling though compensating pad??
-a larger hole in the pad could be acceptable, especially if it is not on the same longitudinal line as the manhole; you'll need to revise the compensation calculations accordingly
-it is likely that the new opening and the manhole will have their limits of reinforcement overlapping, and this also will require additional calculations: however pad compensated openings have often more added metal than the minimum required, so I think you have quite a few chances
-of course additional welding onto the vessel need be checked against any other requirement per code (PWHT, NDT,...).
prex
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RE: Effect of drilling though compensating pad??
The only thing I would recommend is that you have someone well versed in the art kill the "stingers".
Describe the problem area a little better and can you access the area of refractory in question while the refractory is still hot.
RE: Effect of drilling though compensating pad??
RE: Effect of drilling though compensating pad??
A word of advice is to get someone to make the refractory repairs who has experience, as this is no place for the low bidder or someone learning. If the designer or the refractory people recommend that the refractory be replaced, take this suggestion seriously.
Another trick is when you go back is put a heat sensitive paint on the header. This will give you a little extra time the next time the refractory starts to fail.
Good luck with your repair.
RE: Effect of drilling though compensating pad??
would have to groove-weld the nozzles all the way to the vessel isntead just a fillet to the pad. If this is an ASME stamped, your inspector has the last word.
ER