Instrumentation Inspection and Quality Control CBT 2021 Questioner - Part-02

Instrumentation Inspection and Quality Control CBT 2021 Questioner - Part-02

Q. How will you work/remove on a control valve which is in line?

Inlet and outlet discharge manual valve to be

closed by the operator and tagged.

The valve No. 1 to be closed first. Control valve

should be in fully open condition. Valve No. 2

closed. Secondly the line has to be drained and

depressurized before removing.

Q. What are the standard nozzles orientations for process control systems?

Q. What is different between Open Loop and Close Loop?

Open Loop : A Loop System which operates direct without any feedback and

generates the output in response to an input signal.

Close Loop : A loop system which uses a measurement of the output signal through

feedback and a companion with the desired output to generate an error

signal that is applied to the actuator.

Q. What is feedforward and feedbackward control system?

Feed‐forward control is a system in which corrective action is based on measurement of

disturbance inputs into the process.

Feed backward control involves the detection of the controlled variable & counter acting of

changes in its value relative to setpoint by adjustment of the manipulated variable.

Q. What is Logic Gate?

A Digital logic circuit with one or more input voltage but only one output voltage.

Q. What does a transmitter O/P signal start from 315 or 420 m.a.?

Linear and can check up weather its “live zero” or “dead zero”

Q. Why is M.A. signal preferred for signal transmission?

Noise reduction and no current drop for long transmission lines.

Q. Explain Cascade control (To prevent outside dist.

Cascade means two controllers in series, one of them is a matter of primary & the second is the

secondary or slave. The O/P of the slave controller operates the final control.

Q. Explain three element feed water control system.

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