Answer / chowdary

The controller name is Split Range controller.

Answer / divyang

There can be many reasons to provide two CV-
1. Case where flow controllability is extremly important.
Hence to get better control at lower load 2" CV will be
operated & once plant reaches cerain load higher size
control valve comes into picture.

2. Higher size CV is kept on certain value of manual
opening, and fine control is done by smaller valve. eg if
flow requried is 10000 kg/hr and controlling limits are +/-
200 kg, smaller CV will give fine control.

3. During revamp of the plant capacity instead of
increasing the existing CV, if a samller size CV is
available in spare same can be installed in parallel

Answer / guest

any technical reason. please clarify. With Regards-Kittu

Answer / ajith294

above answer is split range controller. what is a split
range control? two control valves are controled by a
controller is split range. for eg: 50% of controller out
put both of the valve will be close condition , see below
table.

% input Valve A opening %, Valve B opening&
0 0 100
25 0 50
50 0 0
75 50 0
100 100 0

but in your question on 2" valve is connected parrallel
with 6" Control valve. means for the bypassing 6" control
valve, they are using 2" valve.

for technically it is very very improtant. becasue at the
time of maintance of the control valve, there will be no
disturbance in process.

Answer / girishkumar

It is called split range control and split a big CV into two
parts as 1:4 for fine control.ie:- in 0% both valves keep in
close. In 25% the 2" valve keeps fully open and 6" keeps
fully close. In 50% the 2" keeps fully open and 6"keeps in
25%open. In 75% the 2" keeps fully open and 6"keep 50% open
and in 100% both keeps fully open.These two valves
controlled by same controller with two AO.

How Honeywell FSC is functioning and what is its purpose? Can we bypasa it and only use DCS instead of that.

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