Follow Our FB Page << >> for Daily Laughter. We Post Funny, Viral, Comedy Videos, Memes, Vines...

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

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

Answer / carl_ellis

Pneumatic positioners equipped with a bypass option can be removed for maintenance without interrupting the valve service.

A position bypass is/was a common optional feature on pneumatic positioners that receive a pneumatic control signal (typically 3-15 psi, 20-100 kPa, or 0.2 - 1.0 bar) from a controller or I/P.

The bypass option is a pneumatic switch. The inlet is the control signal. The valve's outlet is either the positioner (normal mode) or the actuator (bypass mode).

If the positioner needs servicing, the bypass switch is changed from normal mode to bypass mode and the control signal will drive the valve actuator directly. The bypass assembly can typically be removed from the positioner with a couple bolts so that the bypass assembly remains connected to the process, while the positioner is removed for service.

Positioner Bypass operation does not work
- on valves with actuators whose input signal range does not match control signal range (a 1:1 output:input signal ratio). A valve actuator that requires 40-60 psi to actuate will not be actuated by a 3-15psi control signal.
- for split range valves
- for valves with control action (direct or reverse) the opposite of the control signal action.
- Electropneumatic positioners that use a 4-20mA input signal have no bypass option because there's no pneumatic signal to bypass to the actuator.

Carl Ellis
Measure First

Is This Answer Correct ?    1 Yes 0 No

Post New Answer

More Instrumentation Interview Questions

What is three element in drum level?

0 Answers  

kindly sent some demo question and answer

0 Answers   HPCL,

sir i m preparing for BARC but i am not getting any papers to prepare for this exam so please send me some sample papers to my i.d for the preparation of barc.

0 Answers  

what is the basic principal of vertax flow meter

3 Answers   Balrampur Chini Mill, Saba,

Why hunting will occour in control valve?

6 Answers  

How can I zero check of wet leg type DP Tx ?

6 Answers   ONGC,

how many types of preheaters are in cement industry & what r they can any body explain?

0 Answers  

Can we use PLC in Hazardous Area?

2 Answers   MNHG,

whey we conect ammeter in series and voltmeter in parallel in circuit

1 Answers  

please tel me the calibration of pneumatic controler.

0 Answers  

there are two candidates p and q in an election.During the campaign,40% of the voters promised to vote for P ,and rest for Q.however, on the day of election 15% of the voter went back on their promise to vote for P and instead voted for Q. 25% of the voters went back on their promise to vote for Q and instead voted for P.suppose,P lost by two votes,then what was the total no. of voters.

4 Answers   GATE,

whats the working of principal thermocouple

6 Answers  

  • Civil Engineering Interview Questions Civil Engineering (5082)
  • Mechanical Engineering Interview Questions Mechanical Engineering (4449)
  • Electrical Engineering Interview Questions Electrical Engineering (16624)
  • Electronics Communications Interview Questions Electronics Communications (3916)
  • Chemical Engineering Interview Questions Chemical Engineering (1094)
  • Aeronautical Engineering Interview Questions Aeronautical Engineering (214)
  • Bio Engineering Interview Questions Bio Engineering (96)
  • Metallurgy Interview Questions Metallurgy (361)
  • Industrial Engineering Interview Questions Industrial Engineering (259)
  • Instrumentation Interview Questions Instrumentation (3008)
  • Automobile Engineering Interview Questions Automobile Engineering (332)
  • Mechatronics Engineering Interview Questions Mechatronics Engineering (97)
  • Marine Engineering Interview Questions Marine Engineering (124)
  • Power Plant Engineering Interview Questions Power Plant Engineering (171)
  • Textile Engineering Interview Questions Textile Engineering (575)
  • Production Engineering Interview Questions Production Engineering (0)
  • Satellite Systems Engineering Interview Questions Satellite Systems Engineering (106)
  • Engineering AllOther Interview Questions Engineering AllOther (1379)