definition,Loop and discription

1. 1

2. i. INDEX
ii. Introduction.
iii. Definition.
iv. Block diagram.
v. Description of loop.
vi. Advantage.
vii. Disadvantage.
2

3. Introduction.
 In a split range control loop, output of
the controller is split and sent to two or
more control valves. The splitter
defines how each valve is sequenced
as the controller output changes from
0 to 100%. In most split range
applications, the controller adjusts the
opening of one of the valves when its
output is in the range of 0 to 50% and
the other valve when its output is in
the range of 50% to 100%.
3

4.  Unlike the cascade and selective control
scheme the split range control has one
measured and more then one
manipulated variable. Since there is only
one controlled output , we have only
one controlled signal which is thus spilt in
to several parts each affecting one of
the final control element which are
available in the system . In other words
we can say that we have one output
from controller and split in to no of signal
depends upon how many final control
elements are there. So finally we control
the process by one output and many
final control element.
4

5. 5
PV
FT
LT
CEP
PID
PV
Fig-1
TO DEAERATOR CV
SV 50%
ATC
ATO
TO HOTWELL
RECIRCULATION CV
SUCTION
HOTWELL
50-100%
0-50%
HOTWELL LEVEL CONTROL

6. An “Split range control ” control strategy involves a controller
and many final control elements depends upon the various
process. In fig-1 we are going to control the hotwell level
control for steam turbine . we consist some equipments and
some instruments for control the process. We have a motive
to control the hotwell level at 50% desired level . When level
goes down below 50% then controller generate the
command on the basis of error and open the recirculation
valve to maintain the level at 50%.Now when the level goes
greater then 50% then the same command open the
deaerator FCV to dump the excess water to deaerator to
control the level . So in this process we are controlling two
CV with single output in such a manner that when level are
increasing then deaerator CV will open and When level
gose down then Hotwell recirculation CV will open and
control the desired level.Deaerator CV will work from 0 to
50% and Hotwell recirculation will work from 50 to 100%.So
finaly split control are using in the given process to control
the hotwell level accurately.
6

7.  SYMBOLS
 FT, Flow transmitters.
 PV, Process variables.
 SV, Set variables.
 LIC, Level controller.
 LT, Level transmitter.
 CV, Control valves.
7

8.  Advantages:
 We have more then one final control element so we
can control the process effectively.
 We are using single controller for many final control
element, so the control system will be cheap and
loading will be educed .
 We can use the split range control effectively where we
have many source of one physical quantity to control
as single output.
 Disadvantages
 More then one Physical quantity source are required.
 We are using single controller output to control all the
manipulated variables so if there will be some fault in
controller all the system will be unbalance and device
will be damaged.
8