Answer / sbt, gmm, ypp

YES, ABSOLUTELYU. WE CAN USE CONTROL VALVE W/O POSSITIONER.
BASICALLY POSSITIONER IS USED FOR QUICK OPERATION OF
CONTROL VALVE. FOR AN EXAMPLE: IF CONTROL VALVE OPERATING
RANGE IS 0.6 TO 2.6 KG/CM2, AT THAT TIME POSSIOTIONER IS
USED FOR AMPLIFICATION FOR THE HIGH PRESSURE CONTROL VALVE
EVEN IF INPUT PRESSURE IS 0.2 TO 1.0 KG/CM2.

ANS. GIVEN BY: SBT, GMM, YPP (NFIL STAFF)

Answer / baban

Yes we can use a control valve without positioner.

We can use electro-pneumatic transducer.The transducer
receives a direct current input signal and uses a torque
motor, nozzle-flapper,and pneumatic relay to convert the
electric signal to a proportional pneumatic output signal.

Answer / sudalai muthusamy

Control valve can not be without positioner. The purpose of
the positioner is to control the control valve stroke so as
to keep the valve in desired position. The positioner
receives signal from the controller, and send the boosted
signal to the actuator to reach the desired position as and
when the valve reaches the desired position the positioner
cuts the boosted signal to the actuator and keeps the
position.

Answer / harsh zala

Yes, We can use control valve without a positioner. The
basic purpose of positioner is to supply required punemetic
air w.r.t 4-20 mA standard signal, you can say for example
3.2 kg/cm2 to 4 kg/cm2. and it also checks for the
appropriate vavle opening(feedback) and stops air supply
going to valve actuator.

Without Positiner we can use control valve,but we must have
i/p converter, which generally converts 4-20 mA signal to
0.2 -1 kg/cm2, so in that case valve will not opearate
fully . but it will opearate upto certain level.

So when positoner got fail and we dont have new one, and if
we require valve to be controlled upto certain level, we
can use i/p converter,

Answer / santosh nanavati

Yes, it can be used without positioner with the following
condition.

(1) Spring operating range should be 0.2 to 1.0 Kg/Cm2.
(2) If the application of the control valve for the
relevant process parameter control is not critical, the
valve can work without positioner i.e. it will give less
accurate output & control of parameter.

Answer / m.v.ramesh

There are yes and no answers of this query.
correct answer is Yes. Most of the answers are Yes but
Explanation is a bit not clear. Yes offcource valve
positioner has lot of usages and advantages in controling
the valve position.

Answer no 8 is some what clear.
Here is the straight right answer.

"Yes we can use a control valve with out positioner when
bench set of the control valve is matching with the
standard bench set of the valves." ie, valve spring range
is 0.2 kg - 1 kg. where the process fluid is clean, and for
the valve sizes below 1 inch usually.
Where these valves need regular preventive maintanence
(lubricating and changing the packings promptly or else
these valse will give erratic positions).

Answer / kuntal nayek

Yes we can use control valves without positioner.

But it will be risky as we would not able to know the
feedback that valve is working properly or not.
Normally position feedback is used to get the actual
position of the valves it is not used to control the valves.
To control a control valves we needed the process value that
usually called PV..that may be pressure, flow etc which we
could get from the transmitters or any other instruments.
According to PV controller generate corrected signal (ie.
Setpoint - Process value = error)in terms of 4-20mA.

Answer / ahmed rashed

yes you can as evry body said the control valve with out
positinor can use as on/off controller

and this the apllication to use valve with positinor:
1-split range cntrol action.
2-reverse acting actuator.
3-valve size large than 3"(8cm)
4-actuator power requirment in excess of controller out put.
5-valve design inhrent of flow chractristics change.
6-line pressure above 20bar or delta pressure more than 14
bar
7-quick response actuator.
8-elminated the hystersis.
while the valve without positinor the stem fraction can
cause a control valve to exhibit hystersis

Answer / vbp

Yes We Can Use The Control Valve Without Positioner But only
for the range between 0.2 to 1 kg.but it must have the I to
P for it.

Answer / warren holden

Yes, a control valve can be used without a positioner.
Some of the previous responses contain correct information
about certain elements of what a positioner actually does
however they do not address the fundamental issue from a
control perspective.
The positioner on control valve is essentially a cascade
(inner) loop acting as a high gain proportional controller
within the external (outer or master) loop (Shinskey, G.F.
1988). The positioner will be beneficial if its response
time constant is faster than the master loop element(s)
i.e. in the case of a temperature control (master) loop the
control valve positioner dynamics will undoubtedly be
faster than the temperature measurement change dynamics
(this being a fundamental requirement of cascade control).
However, the control valve positioner is of no use, and
actually a hindrance, on fast acting master loops i.e. flow
control with fast change dynamics. Hence control valve
positioners are often not used on flow control loops where
the outer (master) loop flow measurement and associated
controller can handle the control valve positioning quite
well themselves.

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