valve sizing

I'm sure it does. There's a vast amount of valve information here:

http://www.namfg.com/

By geometry you mean position of the valve? If there is a full flow of liquid through the valve, the position will not make any differance in the sizing. The Cv of the valve is to be considered in the application. The feet of head, the viscosity of the fluid, the temperature all play critcal roles.

There are some tools on the DOE website; look for PSAT. Download it and learn to use it. There is a valve tool in the suite for Cv's and sizing. Maxozone@comcast.net

No, I don't think.

Sometimes the NPS of control valve is selected to be less than the NPS of the manifold itself. Sometimes we use a reduced opening (reduced diameter) valve. Please refer to ISA RP75.06 "Control Valve Manifold Designs".

All valve manufacturers take into account the design of the valve, seat, and stem to determine the flow characteristics through the valve.

A universal way in which to compare valve capacity is through Cv (or Kv if you're not in the USA).

First you'll need to calculate your required Cv.

There are several things that need to be taken into consideration when sizing a control valve:

1. specific gravity of fluid

2. viscosity of fluid

3. fluid temperature

4. fluid flow rate (GPM, lb/hr, l/min, etc)

5. Type of service: on/off, flow control, pressure reducing, temperature control

6. Inlet pressure of the fluid

7. Maximum pressure drop accross the valve when fully open.

8. Valve action: fail open, fail closed, fail in place

9. Do you need flow over the seat or under the seat?

10. Do you need a valve that has a linear, equal %, quick opening (etc) flow characteristic?

Some great resources that go over control principle are:

http://www.spiraxsarco.com/resources/steam-engineering-tutorials/basic-control-theory/basic-control-theory.asp

http://www.spiraxsarco.com/resources/steam-engineering-tutorials/basic-control-theory/choice-and-selection-of-controls.asp

I hope the above helps point you in the right direction.

If you can share more specific information on your application I am glad to provide you with specific information.

A short answer to your question: No, it is the valve trim that affects the control. You have been refered to to some good reference on the subject.

Best reference for all technical aspects of control valves that I know of is the Fisher Control Valve Handbook.

http://www.documentation.emersonprocess.com/

In this handbook you will find answers to almost anything concerning control valves: design, materials, calculations, failure modes, applications, ratings, etc. Plus an excellent technical annex with information about pipes, flanges, physical properties of materials, conversions and more.

I have used this handbook since I started my project engineer career 27 years ago. They are now in their fourth edition.