Answer / someone

No...valve can only be used as on/off purpose..not for control without positioner.

A positioner is a device put into a valve to ensure that it is at a correct position of opening as per the control signal. An I/P converter only sends the opening/closing request to valve but can not confirm its position.
Positioner senses the valve opening through a position feedback link connected to valve stem which is its input signal. I/P converter output is its setpoint input. The difference between these two is the error signal based on which the positioner positions the valve to correct position to reduce error to zero. Hence positioner is nothing but a pneumatic feedback controller. Controlled external supply air to positioner provides power to positioner to position a valve. Also positioner is used in a valve when valve operating signal range is different from I/P converter output range.

In recent days software configurable digital positioner are being used in valves which do not require I/P converter and has many features like advanced valve diagnostics, partial stroke testing, remote communication etc.

Answer / jagan kumar

Positioner is used to give the feedback about the position of control value. ie: how much valve has been opened eg: 74%. Obiviously control value work with out positioner

Answer / jagan kumar

Positioner in control value is used to provide feedback about the position of the value. ie: How much value is opened eg: 74%. control value can be operated without the positioner.

why we use by pas on a positioner? When can a by pass be not used on a positioner ?

1 Answers  

---

What is Fieldbus?

3 Answers   NSL,

---

We have ZR22G-100-S-A-E-T-T--E-A/CV/F1 Model Zirconia Oxygen analyser which is Yokogawa make. I kept the analyser in Flue gas path at Air pre heater area. My plant is 7.5MW Biomass power plant. For a particular fuel, Coconut Husk which contains Sodium and Potassium chlorides iam not getting proper reading, Analyser output always Zero. I calibrated the analyser and it is OK. For Other fuels like Wood chips, Cholam waste, DOB, Groundnutshells, Ply wood waste and all iam getting actual percentage of Oxygen. What is the main reason behind this draw back?

2 Answers  

---

How to calibration of vibration probe

1 Answers   Mina Al Ahmadi Refinery,

---

What is Difference between PLC and CNC ?

2 Answers  

---

what is plc communication?

2 Answers   Siemens,

---

why we are not using the turbine flow meter in the steam service?

0 Answers   Jaypee,

---

what is the differnt between open loop and close loop ?

5 Answers   India Cements,

---

flow transmeter accuracy 0.075% of full scale & find ucertainty is 0.025 % so what is maximum limit band of uncertainty

0 Answers   ONGC,

---

What is the diffrence between ff tx and non ff tx

0 Answers   Jindal, Rosemount,

---

how to trim the pressure transmitter ?

2 Answers  

---

What pressure results for a flow transmitter of range 0- 180t/h in the dcs and 0-301mbar in the field using square root extraction. Kindly also suggest formulae for the percentages 0,25,50,75,100?

0 Answers   Kentz,

---