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[ SEATING FORCE FOR CONTROL VALVES ]

[ SEATING FORCE FOR CONTROL VALVES ]

[ SEATING FORCE FOR CONTROL VALVES ]

(OP)
Dear All,
I am completely new to the control valves and currently studying the control valve actuator sizing. May be my question is basic but i have found the following thing very suspicious.
The book says:
the direction of the seat load is in upward if the valve is push down to close. What I think is the opposite. Can someone clarify me on that point?
Regards,

RE: [ SEATING FORCE FOR CONTROL VALVES ]

Qulu Quliyev (Industrial),
Please do not be hurt by my comments, My intent is to help you.
1: What does "Industrial" mean in your world?
2: What does "I am completely new to the control valves" mean?
3: What does "currently studying the control valve actuator sizing." mean?
4: What does "I have found the following thing very suspicious." mean?
5: What Book?
6: Why do you question the flow direction through a "Globe type Control Valve?

You will need to do more study on the many different types of valves that are used to "Control" fluids and gases. Just to name a few, there are; Globe Type Control Valves, Gate Type Control Valves, Butterfly Type Control Valves, Plug Type Control Valves, Ball Type Control Valves, Needle Type Control Valves, Pinch Type Control Valves, and so on and so on. They all tend to have the same function but they will each have unique, specific needs
Then there are the many different types of actuators. It goes on and on.

Go here for a place to start:
https://www.google.com/search?q=Images+of+differen...

Sometimes its possible to do all the right things and still get bad results

RE: [ SEATING FORCE FOR CONTROL VALVES ]

QQ,

pennpiper makes some very good points.

For many types of relatively simple control valves the flow is vertically up into the body where either a cone or cylinder or a flat plate moves vertically up and down to change the flow characteristics of the valve.

This means that there is a vertical force upwards on the moving item which needs to be taken care of by the actuator.

some types of valve have different actions and don't have this effect.

The most simple example is a normal tap.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: [ SEATING FORCE FOR CONTROL VALVES ]

(OP)
LittleInch
I am talking about the sliding stem control valves..
the thing which u are saying is called static unbalance force. I am talking about the seating force. why it is in upward direction while it has to be in downward?

RE: [ SEATING FORCE FOR CONTROL VALVES ]

Please post a drawing or sketch and also it is much better to say what you just posted in your original post.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: [ SEATING FORCE FOR CONTROL VALVES ]

(OP)
Little Inch
I didn't post anything actually.
i am talking about the unbalanced control valve where the inlet pressure is applied to the bottom of the plug while the outlet pressure is around the plug.
here the seating force (force applied by the actuator in order to achieve the required shutoff class) has to be directed downward, in where training books says upward :/

RE: [ SEATING FORCE FOR CONTROL VALVES ]

QQ

You appear to have answered your own question "where the inlet pressure is applied to the bottom of the plug"

This will create a force which you need to counter if the plug is to close.

I know you didn't post anything, but I asked you to add a drawing or sketch to show better what it is you are talking about.

Also next time just write your title without the [ ] and don't use all CAPITALS. It is interpreted as shouting.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

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