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ELECTRO PNEUMATIC POSITIONER
As a unit which can be used for positioning of pneumatic rotary actuator of pneumatic cylinder or diaphram type control valve the final control element can be moved to precise position by means of high pressure air supply providing necessary power and speed of operation.
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Salient Features
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• Adaptable for double acting & single acting actuator / cylinders.
• Easily convertible form DIRECT to REVERSE function.
• No effect on performance due to vibration.
• Most convenient for converting ELECTRONIC SIGNAL TO PNEUMATIC in low cost.
• Unique design feature where instrument can be calibrated to give 100% stroke at 40% input signal or VICE VERSA.
• ACCURATE feedback without linkage facilities precision control on movement of final control element.
• Under the balance condition unit DOES NOT consume any air similar power consumption is negligible hence
saving on energy.
• Control unit is SAME for all types of actuating devices however only feedback element is changing depending upon
application.
• Control unit can be converted for use with electrical actuator. |
Function
Modern automated process installation demand use of electronic signal to position final control element in proportional manner depending on demand. In a close loop system positioner is located between controller & final control element which is normally pneumatic control valve this unit meets this gap of converting signal from electric to pneumatic & monitor position.
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PRINCIPLE OF OPERATION :
The electro pneumatic positioner receives an electrical signal from the electronic controller. The unit can accept it in 4 different forms. This position control unit operates on the pulse width modulation principle. The input signal is conditioned & given to a precision instrument amplifier, also the signal from the feedback element is conditioned & given to a precision instrument amplifier. Depending upon the difference of these Values. (Desired position & actual position) The relays are driven by pulse width modulations to operate the solenoid valves. This inturn changes the position of final control element till the desired position is achieved.
The Unit can be arranged to give either linear or logarithmic relationship between the control signal & actuator position, the actuator position, the actuator can be arranged so that increase in the electrical signal moves the actuator in either direction. The direction of movement in relation to the control signal can be easily reversed on site by changing the connections.
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TECHNICAL SPECIFICATION :
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01] Input Signal
a) 10-20 MADC b) 4-20 MADC c) 0-1 VDC d) 0-10 VDC
02] Pneumatic input signal 0-10 Bar max
03] Electrical power input 230VAC 50c/s
04] I/P impedance 750 OHMS
05] Supply Variation effect-NIL
06] Supply stroke as per demand calibrated.
07] Air Supply connection 1/4" NPT
08] Mounting can be mounted in any position
09] Repeatability 1% of span (Travel)
10] Linearity 1% of span (Travel)
11] Hystersis 1% span (Travel)
12] Deadband 2% of input span can be adjusted to 1%
13] Temperature 5 celcious to 60 celcious
14] Response time depends on size & air consumption of final control element.
* UNLESS SPECIFIED UNIT IS NORMAL CALIBRATED FOR 4-20 MADC INPUT SIGNAL
* PHYSICAL DIMENSION - L 230mm X W195mm X H95mm |
COMPARISON WITH PNEUMATIC POSITIONER |
I/P Converter not required |
I/P Converter is required |
Saving in cost |
Additional Cost of I/P Converter |
No mechanical Linkage |
Mechanical Linkage required |
Potentiometer is used for feedback |
Potentiometer is not required |
No transmission error |
Due to mechanical linkage transmission error is involved. |
Fast Response |
Slow Response |
Can handle any stroke length |
Requires clumsy linkage for stroke |
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UNIQUE APPLICATION
1] Pneumatic Cylinders.
2] Pneumatic Slide Gate.
3] Diaphragm Control Valve.
4] Pneumatic Rotary Actuators.
5] Pneumatic Butterfly or Ball Valves.
6] Pneumatic Linear or Ball Valves.
7] Electrical Actuators. |
