Control Valve

<...what typical factors to be considered to give preference to linear, equal %, and quick opening valve...>

Control system stability at the full range of output signals.

By changing Positioner Cam we may be able to change the valve characteristics,although tight control will not able to achieve

For Selecting the Valve characteristics follow the guidelines , these guidelines may vary from due to change in company standtards,

a) linear flow characteristic

when the ratio of differential pressure across the control valve at minimum flow over the differential pressure across the control valve at maximum flow is equal to or less than 1.5

when the differential pressure conditions across the control valve under all specified flow conditions are more than (2/3) the differential pressure across the control valve in the closed condition

b) equal percentage flow characteristic

for all other modulating control applications, except for those

under a)

Regards

Jose John

If you want quick response on a linear valve, you can program (or adjust) dither on your controller, that'll keep your valve slightly oscilaling, thus giving faster response to a proportional position command.

Spirax Sarco and Bela Liptak's control book have some pretty decent explanations. When you have sized your valve and contact valve manufacturers, they will come back with a characteristic and you can quiz them on their choice at that time.

Betomachine

Hi there,

Download the fischer control valve handbook from www.emmerson.com

This will explain in a bit more detail what you are asking.

Regards,

Craig

sorry sir, I could not able to open the link what you gave. it is asing login name and password, please give some other link to help me in this issue

Hi there,

www.documentation.emersonprocess.com/groups/public/documents/book/cvh99.pdf -

Regards,

Craig