What is the API 650 Nozzle Size?

Written by duncan s. anderson
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API is the acronym for American Petroleum Institute. API 650 is the latest standard for welded steel tanks for oil storage.

Appendix P

The method for the definitive allowed external loads on tank shell opening is solved with Appendix P of the API 650 Appendix P is from two papers written by Hagstrom and Billimoria in 1997, paper number 77-PVP-19 and another by Billimoria and Tam in 1980 paper number 80-C2/PVP-5. The industry has put Appendix P in use for several years now even though it is not a mandatory appendix. Any tank that is less than 33.6 meters or 120 feet in diameter is not covered in Appendix P.

General Standards

Size nozzles starts from 1 ½ NPS in the flanged fittings category. This does not mean smaller flanged fittings are not allowed, just that smaller than 1 ½ flanged fittings are not covered in API 650. Rules for the nozzle reinforcement in API 620 may in fact be used in designing nozzle reinforcements for a stainless steel API 650 tank. Nozzle penetrations also require full penetration welds where the shell and the nozzle neck meet.

The Specifics

Unless it is stated otherwise, minimum nozzle size is 40 NB. The minimum nozzle size, column is 50 NB. All specific nozzle flanges up to 600NB conform to ASME/ANSI B16.5 and for those nozzle flanges above 600NB ASME/ANSI B 16.47. For all nozzles 100 NB and below only a weld neck flange is required. And in Class 150 rating nozzles above 100NB can be slip-on flanges.

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