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Split Range Controller

A split range control loop directs the output of a controller to multiple control valves, typically adjusting one valve for 0-50% output and another for 50-100%. In a specific application, pressure control is managed by two valves: PV-B closes to reduce fuel gas when pressure increases, while PV-A opens to allow flaring. This method is also used when a single valve cannot manage the entire operating range, necessitating two valves with different operational ranges.

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75 views2 pages

Split Range Controller

A split range control loop directs the output of a controller to multiple control valves, typically adjusting one valve for 0-50% output and another for 50-100%. In a specific application, pressure control is managed by two valves: PV-B closes to reduce fuel gas when pressure increases, while PV-A opens to allow flaring. This method is also used when a single valve cannot manage the entire operating range, necessitating two valves with different operational ranges.

Uploaded by

shivigit2154
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Split Range Controller

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%.

In figure1, PIC-01 controls the pressure of the separator for liquid-vapor


hydrocarbons, by mean of a split range controller with the output signal split and
sent to two pressure control valves PV-A and PV-B. When pressure increases, the
fluid shall be discharged to flare. When the pressure decreases, Fuel gas is
introduced to compensate the pressure of the separator
The fuel gas valve (PV-B) needs to close in response to increasing of pressure of
the separator, while the flare valve (PV-A) will need to open when the pressure
increases beyond setpoint.
- When the pressure increases beyond setpoint in range of with 0-50% controller
output, PV-B shall close from fully open to fully close.
- When the pressure increases beyond setpoint in range of with 50-100%
controller output, PV-A shall open from fully close to fully open.

In summary, valve actions by PIC-01 is as follow: Case:1

Case2:
In this case, the service of both control valves is different, with respect to use of
fuel gas and flaring for pressure control. Another case of use of split range
control loop is when one control valve cannot be suitably designed to cover the
complete operating range of the controller. In that case, valve with a smaller Cv
operated between 0-50% range and the other operates for 50-100% range. For
example, a pressure controller for accumulator drum in overhead of a stabilizer
column splits range to open 2 control valves. In the low range (0-50 % range in
response to high pressure of the stabilizer), the off gas is routed to a gas plant
downstream, in the high range (50-100% range in response to high high
pressure of the stabilizer) the off gas goes to flare by opening of valve B. The
control valve actions is as follows:

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