API 650 Appendix P - Nozzle Loads 1

[xema77]

I have a few questions regarding API 650 Section P. Any assitance is appreciated.

1) Section P.1 indicates that the appendix shall be used for tanks greater than 36m diameter and tanks less than 36m diameter only when specified by the purchaser. Are there any issues with using the appendix for tanks < 36m diameter? Are there alternate methods better suited for tanks < 36m?

2) Can section P.2 be used to calculate radial growth, and stiffness coefficients for nozzles above the lower half of the bottom shell course? If not, how are these factors determined in order to calculate the nozzle loads?

3) If using P.3 to calculate local stress due to nozzle loads, can the stiffness coefficients in P.2 be used to calculate the nozzle loads?

Thanks

 

[hcjulien]

I have the same question in 1) above (see xema 77 question)! Does somebody can answer this important question?

 

[richay]

1) See PVP (Pressure Vessel and Piping) paper 1279 - Stiffness Coefficients for Nozzles in API-650 Tanks, by Lengsfeld, Bardia, Taagepera, Hathaitham, LaBounty, and Lengsfeld.


Richard Ay
COADE, Inc.

 

[IFRs]

There are significant errors in sample problem 2 in method P.3 that need to be corrected and are being addresses by API.

 

[JStephen]

As I recall from several years ago, one of the approximations made to simplify the nozzle analysis was to assume that shell thickness is proportional to pressure in the tank. For tanks governed by minimum shell thickness, this is not the case. I believe that is the reasoning behind the 100' limitation. Refer to the technical papers referenced for that section.

Radial growth can be calculated by finding stress at the point in question, then finding strain, and then strain times the radius is radial growth. Away from the bottom, the standard 2.6HD-type equations should be reasonably accurate, or you can work out the elastic analysis if you don't have enough to do.