VALVE BODY SHELL STRENGTH CALCULATIONS 3

[Pegasus2]

I have not had any luck finding any specific formula for finding shell strength calculations for valve body design. The type of valve I am looking at is similar to the 2" Fisher D Body. I would like to know how to calculate the wall thicknesses, shell strength and valve working pressure. If anyone has access to formulae and can pass them on, it would be greatly appreciated.

 

[unclesyd]

Back when there was really no way to correctly calculate the MAWP of a valve body there was a lot of approximations of the required wall thickness based on empirical data derived from actual proof tests. The company I worked for had tables of thickness for certain areas on each valve that had to be met. Production valves were periodically pulled and proof tested.
I never saw anyting but tables up to fifteen years ago.


I imagine most any FEA program will quickly derive data for curves that a formula could be worked out for a particular valve body.

 

[edmonton]

Hello,
For walll thickness you can use ASME B.16.34, which will give you direction for material to chose. For End to end-Face to face dimension, you can use ASME B.16.10. I have some proven formulas for wall thickness, but on language you probably can not read. Alco useful information you can find at Fisher Valve Handbook, which is downlodable on fisher web-site. If you have any question, please contact me: mirko@dynaflo.com

 

[ANBALAJI]

Hi
You can refer to DIN 3840 Sep 1982 for strength calculation of valve bodies.
Thanks

 

[manian]

i would suggest,

i) Use the ASME Section VIII Division 1 UG27 + Appendix 1 methods

ii) Use ASME B16.34 - One of the appendices provides the method for wall thickness calculation.

iii) Use Din 3840

i have been predominantly using ii) and supplemented with iii) and i).

Hope this helps

Bye

 

[howkers]

1. ASME B16.34
2. Euronorm standard that came out last year
3. Book 82 on this list (1950s technology):

http://www.processassociates.com/bookshelf/equipment/valves_2.htm

4. Finite element theory

 

[cranekiran]

Hi,

The Shell strength as per Pr-En-12516 is as follows:-

1)First determine the Body shell thickness as per:-

Ec=di x p / (2xf-p)xkc (x means multiply)

where,Ec=shell thickness in mm
di=Body Bore in mm
p =Pressure in Mpa =(0.1 x bars)
f=Allowable stress in Mpa
kc=Joint Coeeficient

For Example if the material is astm a216 gr wcb,

Then,As per Pr-en-12516-2,

1/1.9 of yield,or 1/3 of tensile
i.e 1/1.9 of 250,1/3 of 655
i.e 132Mpa,218.33Mpa
the lower of two is 132Mpa
Therefore for wcb material f=132 mpa

Kc=1 (if no joint in case of casting)

if di=55mm (I am assuming but you have to see from your drawing)
If p=20.2bars then in Mpa it is 2.02

Therefore,Ec=55 x 2.02/(2x132-2.02)x1
=0.424mm is the shell thickness for the given above parameters.

You will have to add some manufacturer's allowance & Corrosion allowance to the thickness as per the standard:-

therefore,0.424+3=3.424mm (See the standard for the allowances)

Now compare the calculated thickeness(3.424)with your actual thickness and check the %age of safety.

Another way is simply by tabulation method as per Pr-En-12516-1 which gives the thickness alongside the Bodybore and size.

The valve working pressure depends on the Pn rating of your valve also known as Pressure class rating,See Asme-b-16.34 or Pr-en-12516-1 for the class vs Pressure rating.

Hope this Helps,

Cranekiran