Calculation of Allowable Piping Reactions at a Head Nozzle?

[KernOily]

Guys I have a couple questions for you:

(1) Do any of you know a method to calculate the allowable piping reaction loads (forces and moments) on a head nozzle for a cylindrical vessel? Megyesy's book has a method based on WRC 107 but it only covers shell nozzles.

(2) Megyesy's method does not cover all six possible applied loads at a nozzle. His method only covers a radial force and a longitudinal and circumferential moment. So - what about the other three loads? E.g., the force and moment in the plane of the nozzle?

Any help would be greatly appreciated. I have not looked in Section VII yet, so I'm guilty of not doing my homework first... OK, I'm HEADing to the library now... ;-) Thanks!
Pete
P. J. (Pete) Chandler, PE
Principal Engineer
Mechanical, Piping, Thermal, Hydraulics
Processes Unlimited International, Inc.
Bakersfield, California USA
pjchandl@prou.com

 

[Tankman650]

Pete,

Megyesy uses an abreviated method. I assume the forces he considers are the most common.

WRC107 determines all directions of forces. There are limitations to the vessel geometry however, and a newer WRC297 was produced to handle some additional geometry and expand on the existing values. WRC297 considers only cylinder shapes since WRC107 handles Spheres just fine.

I might add that determing allowable loads from a given geometry will require some iterations. The method of WRC107 is to take the loads and determine the stresses that are produced from each load and sum these and compare to the allowable.

Taking an allowable and working backward will require some work.

HTH

 

Pete,

Try looking at this reference book:

Pressure Vessel Design Handbook
Second Edition, By Henry H. Bednar

Section 7.3 covers Spherical Shells or Heads with Attachments and Section 7.4 covers Cylindrical Shells
with attachments.

I think, the choice of forces to consider in calculation procedures depend on the designer doing the design. In my opinion, a good and experienced designer will neglect in his design calculations, forces that have minimal effect
on the magnitude of the maximum stress.

Take a look also at the procedure used by the APV
Pressure Vessel Design software (WRC 107).

 

[matclarke]

You could also use
· BS 5500 Appendix G
· The theory and design of pressure vessels by John F Harvey section 6.16 pp 474 in edition 2 or
· The pressure vessel design manual by Dennis R Moss section 5 pp 159
· Mechanical design of heat exchangers and pressure vessel components K.P Singh & A.I Soler section 20 pp 947 in edition 1.
· Pressure vessel design concepts and principals J.Spence and A.S Tooth section 5 pp 125 in edition 1. This basically narrates the BS 5500 method.
Once again determining allowable loads from a given geometry will require some iterations.

 

Hello,

Check out the same question on the Piping board.

Regards, John

 

[kstaylor]

As Tankman650 said, use WRC-107. It covers all loading configurations on attachments on both cylindrical and spherical shells, including the center ~spherical portion of dished or semi-elliptical heads.

Note that WRC-107 will NOT give you the allowable forces and moments for a given nozzle/shell configuration but rather will tell you if the stated loads create stresses that exceed the allowable stresses.

You may have some trouble determining the allowable stresses to compare against your calculated values. ASME VIII-1 gives no rules for these stresses. I have always used the ASME VIII-2 methods but used the ASME VIII-1, VIII-2, B31.1, or B31.3 stresses as applicable for the equipment or component being analyzed. I know others always use the ASME VIII-2 stress intensities regardless of the governing Code for the equipment or component under consideration. This subject might be fodder for a separate thread.

Good luck.

 

walther j. stikvoort who used to head the mech'l eng section for kellogg continental (netherland)has written an article titled "piping reactions on pressure vessel nozzles". his procedure is almost as good as the bijlaard method. example included.

 

[rkchalla]

I have used BS5500 methodology in calculating the stresses in the past. IMHO, BS5500 is probably the easiest to use.

 

[DavidCR]

I´d say that all comments above are very helpful, but the easiest way is to have a software.

A pair of references:
PVElite from Coade.inc (

http://www.coade.com)

Pauling Research Group (

http://www.pauling.com)

There are others.

WRC methods are the most accepted but the "tricky point" is to understand what is defined as the allowable stresses considering ASME VIII 1 and 2, and how to compare the different stresses obtained with the WRC with the allowables. There are special considerations for the different kind of loads (thermal, pressure, bending, etc.) in order to compare them with the allowables. (It´s not just to add the vectors, calculate the stresses and compare with the allowable from table A1 of asme VIII 1, it´s quite more tricky than that).

I´ve have unserstand it a litlle from using this software PVElite and the manual and somebody told me some tricks. So I don´t have a good written material to understand this to help you.

I´ve not used BS5500, but I´ve heard that the comparison with the allowables is less complicated.

Good luck.

 

[GeraldG]

We caclulate allowable loads on nozzles fairly regularly and use Paulin Research,

http://www.paulin.com,

program FEPipe and Nozzlepro(which is a simplified version). It often takes a few iterations between these programs and the pipe stress program to come up with a resonable solution when the piping is tight due to space constraints and high temperatures.