Interested to Buy Any Domain ? << Click Here >> for more details...
Answer Posted / welcome4ujd
Summary - Positioners
1. A positioner ensures that there is a linear relationship
between the signal input pressure from the control system
and the position of the control valve. This means that for
a given input signal, the valve will always attempt to
maintain the same position regardless of changes in valve
differential pressure, stem friction, diaphragm hysteresis
and so on.
2. A positioner may be used as a signal amplifier or
booster. It accepts a low pressure air control signal and,
by using its own higher pressure input, multiplies this to
provide a higher pressure output air signal to the actuator
diaphragm, if required, to ensure that the valve reaches
the desired position.
3. Some positioners incorporate an electropneumatic
converter so that an electrical input (typically 4 - 20 mA)
can be used to control a pneumatic valve.
4. Some positioners can also act as basic controllers,
accepting input from sensors.
A frequently asked question is, ‘When should a positioner
be fitted?’
A positioner should be considered in the following
circumstances:
1. When accurate valve positioning is required.
2. To speed up the valve response. The positioner uses
higher pressure and greater air flow to adjust the valve
position.
3. To increase the pressure that a particular actuator and
valve can close against. (To act as an amplifier).
4. Where friction in the valve (especially the packing)
would cause unacceptable hysteresis.
5. To linearise a non-linear actuator.
6. Where varying differential pressures within the fluid
would cause the plug position to vary.
To ensure that the full valve differential pressure can be
accepted, it is important to adjust the positioner zero
setting so that no air pressure opposes the spring force
when the valve is seating.
| Is This Answer Correct ? | 10 Yes | 0 No |
Post New Answer View All Answers
Can any body tell me about SAP MAINTINANCE MODULE. WHAT IS its function and application. And study material Source about it. I shall be very thankful.
Why not come out analog output in ABB EL3020 when display show correct value
What are the materials available to prepare individually for competetive exams in Instrumentation field? Plz reply...
Why the ammonia and Nitric Acid level indicators is with millimeter ? and What is the conversion form millimeters that level indicator indicate to weight ?
How many interlocks at turbine? Plz explain briefly
how to calibrate corollaries (Mass flow meter)?
How many types of sensor
Difference between ultra sonic flow meter
What is difference of fanuc alpha series 16i and 18i controller.also what is differnce betn TC and MC controller
why we take %i0.0 as input for twido plc
What is furnace draft control?
How is PH sensor works ?
What are the type of bonnets in the control valves?
Dear Sir/Madam,im going to attend Hpcl written exams on feb 17th in instrumentation stream..can anyone send me the HPCL model papers and pattern of HPCL ....i ve not yet attended anything in HPCL...so i dont know how it comes...so just i need some model test papers and pattern ..pls help me friends...
why I need valve guard and whats different between guard and positioner ??
