Can I use a control valve without positioner?

Dear Dana If you are asking generally, The answer is "NO", if you give me a specific scenario, I can decide more scientifically.
The positioner receives4 to20 mA DC signal through Analogue output card of the DCS in the marshaling cabinet and sends it to the control valve, the positioner correspondingly sends3 to15 psi in certain applications to control the opening and closing of the valve.
The On/Off valves do not have positioners, if you remove the positioner of a control valve, it becomes an NO/Off valve.
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to make it short , if it is for a continuous control valve with different opening percentages no you can't .
if it is for an open / close valve then you can but you'll have to use a solenoid valve and the4-20 mA signal from the controller will be connected to the solenoid valve installed on the instrument air entrance to the valve actuator.

The contlol valve works efficiently with posotioner assoon as signal comes from controller to the I/P converter,having the pneumatic supply in positioner it provide the3-15 psi air pressure thus valves takes action of open/close position as per controller signal ,but without positioner it works as on/off control with delay action ,further draw back is change in Set point and Increase in Dead band of controller .

Dear Dana, Mr.
Saud AlHarbi is right.
With a positioner, u can control the opening and closing of the valve like25% or50% or75% or100%, from DCS as u wish.
But if u remove the positioner, the control valve will act as an on/off switch that means100% open or100% close.

Control valve can be used without positioner only when its actuator is designed according to line pressure. and can also be used as on/off valve.

Dear Friend, Answer is "NO" Control Valves are used for controlling the pressure, temperature, Flow & Level.
U can think without positioner u are able to control this parameter from operating station.
u are not able to control.
thats y we are using the positioner.
For proper operation.

The output of the i/p converter is3 to15 psi. The positioner is used for accurately controlling the desired parameter. In this case if the spring range of the control valve is3 to15 psi and the valve is of small size, the positioner need not be connected and i/p converter output can be directly provided to control valve.

Of course you'll need an I/P converter but if its a small valve and the pressure is not too high the diaphram can probably actuate the valve without a positioner.   Changing fluid conditions will cause the position of the valve to change even with a constant pneumatic signal which may cause some disturbance in control.   I've had success without a positioner.   In most cases the control is fast enough and the hysterisis due to starting friction on the packing is mild.

Dear Friends Actually the positioner is uses in control valve to have accurate control, It means without Positioner you can control the process parameter but not so accurate.
If you want to remove the positioner or to neglect it , you must consider a simple I/P atleast.
I To P: Current to Pressure.
The current design of Positioner includes the I/P also.
Regards Jalal Ghotbi Instrumentation and Control Instructor

control valve0 -100% i can use without positioner feedback we can obtain from flow meter for example.