why we use by pas on a positioner? When can a by pass be
not used on a positioner ?
Answer Posted / 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 View All Answers
what is the calibration procedure for transweigh make weigh feeder?
A DP transmitter is used to measure the level of an open tank. The drain line of the tank is connected to a control valve, and is configured as, if the level of the tank is 90% the valve should get open 10%. And if the tank level is 10%, the valve should get open 90%. Draw wiring diagram and explain how to configure DP transmitter and control valve using HART communicator. If the span error at output is 1%, what will be the %opening of the control valve at 60% level of the tank?
i want to find out iffco get test paper
how do u calibrate the vacuum transmitter if it shows more reading
What are the error values can accepted in flow transmitter calibration?could u give any formula for this?
why we use impulse line of flow transmitter at 45 deg. angle both side of orifice plate.
any questions on motor and energy conversions machines?
Define the difference between a stable versus an unstable controlled system and some of the tools you might use to be able to detect when this is happening and assumptions used for control system application design that could contribute to instability
how to measure oxygen which methods are using?
how is work pressure switch& level switch?what is the principle of this?
what is effect of specific gravity in differential level transmitter , explain formula related with this .
Hi i am aneesh, done btech in applied electronics & instrumentatiin. And then i took mba in finance & marketing.After that i got placement in finance co and worked there for 3.5 yrs.Now i wanted to come back to engineering job.But without engg experience, i may not able to find an opening.i have done a course related to flow meters and ite calibrations. Kindly suggest where should i try to get a job?
what are the diff. in servo and regulatory control?
Linear amplifier.
What are primary elements of measuring pressure? Which type of pressure can be measured by these elements?