Cap Screw

[marchieV]

Hello, everyone.
I'd like to ask a question about the cap screw that will be utilized on both faces of a lug type butterfly valve. How can I calculate the length of the cap screw? Do I need to provide a space between the two (2) cap screws on both sides of the butterfly valve? Do we have any standards to follow?

Thank you, and hopefully you can help me with this.

Regards,

marchieV

 

[GBTorpenhow]

The valve manufacturer will typically have a recommended length listed in their IOM, but you can calculate the length required yourself. Draw a sketch of the joint cross section and the length calculation should be fairly self evident. Face to face lengths for the valves should be per API 609 but cap screw length selection is left up to the user as far as I know. Yes you should provide a space between the ends of the two screws.

 

[TugboatEng]

The cap screws MUST NOT touch. The math is simple, the bolt needs to engage at least its diameter in the threads of the valve. It must not be so long as to bottom against the opposing bolt.

Or, you can look it up in the chart if your valve is built to standard dimensions.

https://www.povbutterflyvalve.com/how-to-use-and-interpret-a-butterfly-valve-bolt-chart/

 

[marchieV]

Hi GBTorpenhow,

Thank you for your response.

Do you know what the recommended gap between the ends of the two screws is? or a reference that specifies a recommended gap?

 

[marchieV]

Hi TugboatEng,

Thank you for or insight.

Do you know what the recommended gap between the ends of the two screws is? or a reference that specifies a recommended gap?

 

[TugboatEng]

The links we have provided give you enough information to calculate a nominal gap. You have not provided us with anything to give you a more specific answer. If you follow the guidelines above you do not need to concern yourself with a nominal gap.

 

[KernOily]

Just contact the valve manufacturer or the vendor. They have that information right at hand.