Closure and Stem Calculation

[neroverdi41]

Hello.

I want to calculate the wall thickness for the lid of a pressurized vessel, but I am not sure if I am using the right formula. I used the UG-34 formula in ASME BPVC Div. 8. Do you have any suggestions?
How can I calculate the minimum wall thickness of the stem of a valve?

 

[goutam_freelance]

Check the joint configuration. It should be similar to (m), or (o) of figure UG-34.

Stems of valves are circular in cross-section. What is stem wall thickness?

 

[neroverdi41]

Check the joint configuration. It should be similar to (m), or (o) of figure UG-34.

Stems of valves are circular in cross-section. What is stem wall thickness?

I made the stem diameter of an 8” C600 control valve 40 mm. According to the flat heads calculation, the minimum wall thickness value is 7.4 mm with 1,5 mm corrosion allowance. I am not sure, should I also consider the act. torque when calculating the stem minimum wall thickness?

 

[goutam_freelance]

Could you provide a sketch of the equipment you are designing?

 

[neroverdi41]

Consider a straight stainless steel rod with a diameter of 40 mm. i want to calculate whether its wall thickness is sufficient. how to calculate the minimum wall thickness of a solid stem?

Could you provide a sketch of the equipment you are designing?

 

[SPDL310]

There are multiple forces to consider when designing a valve stem, and there are no codified formulations for doing so. To answer your latest question, yes you should consider actuation forces when designing your stem, as well as any intentional or unintentional load that can be applied to the stem. Given what you have stated there is not enough information here to answer your question. What type of movement is your stem going to provide; linear or rotational? What are the seating/unseating forces you expect? How is it operated? Is there any type of anti-extrusion method? What is expected temperature range of the valve? As stated above a sketch/free body diagram would be very helpful.

Generally speaking a stem does not have a wall thickness. Wall thickness refers to hollow elements that undergo differential pressure between an interior and exterior element. The 40mm you mentioned above would be considered a stem diameter. it would need to resist any tensile/compressive/torsional load it is subjected to by the design margins of the code/standard you are designing to.

 

[neroverdi41]

There are multiple forces to consider when designing a valve stem, and there are no codified formulations for doing so. To answer your latest question, yes you should consider actuation forces when designing your stem, as well as any intentional or unintentional load that can be applied to the stem. Given what you have stated there is not enough information here to answer your question. What type of movement is your stem going to provide; linear or rotational? What are the seating/unseating forces you expect? How is it operated? Is there any type of anti-extrusion method? What is expected temperature range of the valve? As stated above a sketch/free body diagram would be very helpful.

Generally speaking a stem does not have a wall thickness. Wall thickness refers to hollow elements that undergo differential pressure between an interior and exterior element. The 40mm you mentioned above would be considered a stem diameter. it would need to resist any tensile/compressive/torsional load it is subjected to by the design margins of the code/standard you are designing to.

First of all, the valve will move linearly (rising stem). I think what I need to take into account here is that the shear force resulting from the torque to be applied to the valve is smaller than the shear force of the material I use. I made calculations accordingly. While the shear strength of AISI 316 material is about 290 MPa, the shear force to be applied to the stem is about 56 MPa and quite low. Therefore, it will work safely even when multiplied by the safety factor (even if the safety factor is 5). Thank you for your answer.

 

[neroverdi41]

Thank you guys for your help. See you on another subject.