DN200 PN40 needle valve calulation

[llunydecasa]

Hi all,

I am adapting a needle valve design which was originally working with a servomotor, to work manually by means of a gearbox and a wheel.

The problem, is that I would like to calculate the axial loads on the shaft, due to hydraulic efforts, but I do not know how to do it. Does anyone knows the way to calculate this, or where to find this information (mainly a book). Luckily, I have a CAD drawing of the valve so I have all the geometrical dimensions.

Thanks a lot in advance!

 

[hsbcn]

Hi, llunydecasa! It might help to upload the drawing if the information is not propietary.

I work with valves in exotic alloys at alloy-valves.com. This is our blog, and this is me on Twitter and LinkedIn. Let's connect!

 

[gerhardl]

I assume your question concerns input dato for dimensioning your gear. If you have the original servomotor specifications available, for instance output power and gear ratio you will have a pretty good idea of necessary input force.

Another way is to select a handgear where you later may add a second topgear with additional ratio 1:2 or 1:3, if you find the operating force too high. (Available through AUMA and others)

A third test is to check allowable or recommenden opening and closing time (which ideally, because of waterhammer, should be as long as possible) which could give you an indication av max gear ratio.

A calculation of axial force based on hydraulic conditions depends highly/only on the valves technical details, and will be greatly influenced by piping layout before and after the valve. The factory only is able to answer this correctly through experience and test/measurement observations.

 

[SPDL310]

The hydraulic force on the shaft is equal to the cross sectional area of the shaft OD at the valve's packing multiplied by the pressure in the valve. While the valve should never be operated at test pressure the retention mechanism should be able to safely hold back test pressure. You should also contact the valve manufacturer in order to request the unseating torque of the choke/valve you are trying to adapt as that is likely to be the highest axial force you will need to generate.