Cutting permanent door sheet in API 650 Tank that is no longer in service

[mechengr12]

My site has an existing tank that is no longer used and the HAZMAT team would like a small door sheet like cut out for training purposes. This would allow the HAZMAT responders to perform rescue attempts in confined spaces with supplied air. The question I have is how do I determine the allowable size for the cutout with proper documentation? API 653 has a section for door sheets but they are considered temporary openings. Any suggestions for calculations would be greatly appreciated. (i.e. reinforcement calculations for cutouts like you would do in ASME Sect VIII for nozzles?)

 

[JStephen]

That's an odd question. If the tank isn't in service, and isn't ever going to be in service again, you can cut a pretty huge hole in the shell and still have everything stable. And there isn't any standard that limits size or detailing for non-functioning tanks.

If you want it to be typical of door sheets used in actual tanks, those door sheets are variable in size, depending on the equipment that needs to pass through. If you want the opening typical of manways or flush manways in tanks, see API-650 for dimensions.

 

[mechengr12]

I guess my concern is that if the tank was to remain outside in an area that can be prone to high wind speeds from hurricanes and the diameter of the tank is only 12' ID, 24' Tall, and 3/8" SA-283-C Plate would there be any long term concerns if a 6' tall by 3.5' wide "door sheet" was cut out.

 

[IFRs]

The tank won't care. It probably already has anchors ( or perhaps should have them ), this can be checked using API 650 wind overturning calculations. Does it have a fixed roof? But, perhaps for practice you should cut two 24" diameter holes, representing shell manways ( assuming they are not there ) - that would be better practice !!

 

[chicopee]

Since the tank is going to be used as a training stage in which workers inside the tank need to be evacuated, then make the opening as realistic as possible, that is have it round perhaps 24" in diameter with flange that would allow entry on personnel. Also within the tank have internals that you would find in process tanks in order to make the conditions more realistic. API 653 covers such openings.