How to calculate the thikness of reduced bore ball valve example 6''X 4'' class 600 RB used asme B16

[ismail06]

HI EVERY ONE
i have some difficulties to understand good how to calculate the thickness of reduced bore ball valve example 6''X 4'' class 600 RB used asme B16.34 article 6.1.2
6.1.2 Inside Diameter. For the purpose of determining ð17Þ wall thickness, tm, using Table 3A or Table 3B, or the equations
in Mandatory Appendix VI, the inside diameter, d, shall be in accordance with the following requirements:
(a) The inside diameter, d, shall be the minimum diameter of the flow passage but not less than 90% of the basic inside diameter at the valve end subject to the considerations listed in (b) through (f).
(b) For socket welding- and threaded-end valves, the socket or thread diameters and associated counterbores
or threaded bores need not be considered in establishing the value of d (see paras. 6.2.3 and 6.2.4).
(c) For multipiece valve construction, where the body consists of a central core to which are affixed two end pieces, the inside diameter, d, is determined by only one of the following methods:
(1) in accordance with (a).
(2) for the end pieces, the value of d shall be in accordance with (a), and for the central core piece the value of d shall be the inside diameter of the core piece. For a core piece with axial holes, whether through- or partial threaded, the inner and outer ligaments shall also meet the requirements of dimensions f and g in Figure

Could someone guide me on wich inside diameter i can use for the calculation thikness of reduced bore ball valve example 6''X 4'' class 600 RB

Thank you in advance for your help

Regards

Djamel

 

[bcd]

Ok. Start at the end and work toward the beginning. If you have a 3-piece ball valve body construction (example, API 6D ball valve with forged construction), part c) gives you 2 options. Wall thickness of the center section can be determined in 2 possible ways. The designer can select which option they want to use. Using part a) will end up with less wall thickness and a lighter valve. Other than making the valve heavier and more expensive, there is no need to base the wall thickness of the center section. Use part a).

For part a), wall thickness is determined by the minimum bore diameter in the valve.....unless this is small than 90% of the end connection diameter. In your case, assuming the basic valve size is the bore diameter for simplicity in explanation, 4 is less than 90% of 6. So you use 90% of 6 (5.4) to determine the required minimum wall thickness per B16.34.

 

[ismail06]

Dear Bcd (Mechanical)
Thank you for your reply now you put me on the right way
90% of the end connection diameter will be used tor calculation of the minimum wall thickness required by ASME 16.34
but the manufacturer have to calculate the real thickness according to real parameters of operation it means he will the design pressure and others, could give more about this with formulate i can used to determine the actual thickness of RB ball valve and is there any margin to be add to the thickness calculated

What about the ASME VIII div 1 or 2 for the thickness calculation of RB / FB ball valve
could you share with me this standard

thank you in advance for your help

Salutations

Djamel

 

[bcd]

You do not need to us the ASME boiler and pressure vessel code to calculate wall thickness. Extra thickness may be needed for things like ability to pour a casting, extra material for a threaded hole, etc.

You can use the ASME boiler and pressure vessel code to calculate the thickness of a body joint flange, but this is not required by ASME B16.34.

There is no formula in an ASME or any other code that is going to give you the formula to determine the actual thickness of a reduced bore valve.

Note that valve bodies are designed to stay below the creep strength of the body material. This is what the minimum wall thickness formula in B16.34 is doing.

Do not try to calculate a thickness and trust in that alone. There are stress concentrations wherever the valve geometry changes. There is a stress concentration where the stem or shaft exits the body. Extra reinforcement is needed in this area. Design the valve body so it can be made, then either do FEA analysis or make a prototype and do burst testing to verify the design is strong enough. Better yet, do both to ensure your FEA analysis is accurate.