API 620 NOZZLE LOCATION

[THEMAZE41]

API620 SECTION 5.14.5 STATES THAT NOZZLES MUST BE LOCATED A MIN OF 6" FROM THE TANK BOTTOM. I HAVE A 15FT DIA. X 12 FT STRAIGHT SIDE OPEN TOP (WATER) TANK THAT REQUIRES A 1.5" NPT COUPLING APPROX. 4.5" FROM THE BOTTOM FOR A TANK DRAIN.
CAN I LOCATE NOZZLES BELOW THE 6" MIN. IF I FEEL THE DESIGN AND CONSTUCTION IS SAFE PER 5.1.1.

 

[MJCronin]

Thema,

Who, ultimately, will approve the design of this tank ? You ? or some other party ?

API-620, like several other codes and standards, permits modifications to some of it's rules under certain conditions.

You are using a 1.5 inch NPS dain on a tank this large ??!??!!??

How many months are you allowed to wait until the tank is drained ?

My thoughts only.....

MJC

 

[MrVessels]

First question to be asked is why are you using API 620 which is a Standard meant for pressurized tanks.

Secondly if this is new construction it would be more appropriate to use either ANSI/AWWA D100 standard or API 650 Appendix J, as its size certainly classifies it as shop built, assuming there are no transportation limitations of course.

AWWA does not define the minimum location of nozzles except in Section 14 which is for Alternative Design rules, which references API 650.

For API 650 you could use a low type connection for the drain and assuming that your wall thickness is less than or equal to 1/2" would only have to comply with the weld separation requirements of paragraph 3.7.3.2 which would dictate a 3" dimension.

MJC comments regarding drain nozzle size and time to empty the tank are to be noted.