3 replies to this topic

[medbg]

i want to know if the flow coefficient Cv has a relation with the response time of the valve.
because i can't make my choice between the volume booster and the quick exhaust vale. this in the target to improve the response time in both the opening and closing of the valve

[Art Montemayor]

medbg:

I've had to get involved with response times for control valves - especially Shutdown Valves (SDVs) and Blowdown valves (BDVs) - when developing P&IDs and Hazop action items.

The C_V, in my opinion, has no bearing on the response time. I have never found it to be a factor. The response time has, in my cases, always relied on the type and make of actuator employed on the subject SDV or BDV. The speed of the controller signal and its strength also have had a bearing - but I've never had to worry about the inherent C_V on the control valve, as long as I selected the correct size of valve. Granted, the larger the valve (& the C_V), the more difficult it is to make a control valve operate rapidly. Perhaps I am wrong, but that has been my experience to date.

[JoeWong]

Mr. Montemayor,

Please allow me to drop my supplementary comments...

medbg,
If the control valve associate with a ON-OFF control function e.g. in some drum handling low liquid loading with intermittent peak, response time may be required to minimize spurious HIGH-HIGH level trip.

Another occasion where response time may be associated with the opening of control valve is the compressor anti-surge control valve.

Above examples only relate the response time for full close to full open BUT still no relation between C_V and response time.

JoeWong

[Padmakar Katre]

Dear,
Addition to the comments by the Mr. Montemayer and Mr Joe,

Here is one link where we will find how to calculate the responce time of the control valve,

http://www.rosscontrols.com/vresp.htm