instrument question (imp)

7/29/2019 Instrument Question (IMP)

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QUESTIONAIRE FOR INSTRUMENT MECHANICS

OBJECTIVE QUESTIONS

1. The two metal alloy elements in "K" type thermocouple is (B)

(a) Copper - Constantan(b) Chromel - Alumel

(c) Platinum - Rhodium

(d) Chromel - Constantan

2. The resistance of PT-100 RTD is (C)

(a) 100 ohms at ambient temp.

(b) 0 ohms at 100 c

(c) 100 ohms at 0 c

(d) None of the above

3. The gain of a PID controller is "1", Then proportional band is (B)

(a) 0%

(b) 100%

(c) 50%

(d) 1%

4. The square root output of a flow transmitter when the input is 25% of the

calibrated range is (D)

(a) 5%

(b) 25%

(c) 62.5%(d) 50%

5. In Honeywell TDC - 3000 DCS, the controller should be put in ----------mode

while configuration a data point. (B)

(a) Auto mode

(b) Manual mode

(c) Cascade mode

(d) Auto -cascade mode

6. If Pressure Transmitter is calibrated in the range 0-60 kg/cm2, what is the output

(in terms of 4-20 mA) when the input is 22.5 kg/cm2

(A)(a) 10 mA

(b) 12 mA

(c) 8 mA

(d) 16 mA0 - 60 kg4 20mA

22.5 kg0 >> 4

15 >> 822.5 >> 10

30 >> 12

45 >> 1660 >> 20


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7. The type of Thermocouple for "Iron-Constantan" element is (D)

(a) T Type

(b) K Type

(c) R Type(d) J Type

8. What is the unit of CV in control valves (D)

(a) Liters / Minute

(b) M3 / Hour

(c) Gallons / Hour


9. What is Beta Ratio on orifice flow calculation (A)

(a) Orifice dia / Pipe ID(b) Pipe ID / Pipe OD

(c) Orifice dia / Pipe Od

(d) Orifice dia / 2

10. The output of a Turbine flow meter is in (B)

(a) Milliamperes

(b) Pulses

(c) Ohms

(d) Millivolts

11. The drawback in Proportional only controller is (B)

(a) Dead band

(b) Offset

(c) Oscillatory response

(d) All of the above

12. The output of a two input AND gate when both of the inputs are 1 is (B)

(a) 0

(b) 1

(c) 10


13. The flow and the Differential Pressure across an Orifice Plate are (B)

(a) Inversely Proportional

(b) Directly Proportional

(c) Not related with each other

(d) Insufficient data

14. In a Reverse Action Controller, the controller output increases when process value

is ---------- set point (B)

(a) More than

(b) Less than(c) Equal to


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15. Zener Barrier is used for (A)

(a) To make the instruments intrinsically safe

(b) To make the instruments explosion proof

(c) To save energy(d) To make the instrument respond fast

1. What are the instruments connected to separators?

2. What are the continuos controls in CRU area?

3. Explain the plant shutdown logic with diagram.

4. Explain the controls in fuel gas system and HP system with controls.

5. Draw the logic and protection devices in CRU area.

6. When the pressurizing valve will open? Explain the logic.

7. What are the kind the control valves installed in GCs.

8. Name the parts of control valves?

9. What is the difference between seismic probe and proximity probe?

10. Explain the Foxboro DCS with drawing explaining the basic components.

11. Name the DCS components of Foxboro I/A.

12. Explain the process of Desalter unit?

13. Explain heater logic with protection devices.

14. Calibration procedure of flow transmitter, pressure transmitter and temperature

transmitter.

15. Explain the Vocab system followed in the KOC system? How the instruments are

classified?

16. What is a loop diagram?

17. What is meant by Cause and Effect Diagram?

18. Write the specification of DP Transmitter?

19. How the tapping point is taken for flow transmitter for Gases, Liquids?

20. Write the kinds of thermocouples and its range? Also what type of thermocouples

are used in KOC areas?

21. What are the minimum tools required for instrument technician?

22. What is the type of instrument used to measure level in tank and separator? What is

the difference?

23. Explain each working functions.


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24. A pressure Transmitter is calibrated for 600-psig range. We want change its range

to 150 psig how can this be done and what are instruments required for calibration?

25. What is orifice Plate? Make a drawing of orifice palate? Where are orifice plates

installed in our plants?

26. What is the difference between reciprocating compressor and centrifugal

compressor?

27. Explain the logic and protection devices used in Ruston Turbine?

28. Name the instruments installed in pump area and explain the logic?

29. What is UV / IR detector? What is Gas Detectors? Explain.

30. Explain the process of CRU by diagram.

31. When pump trips why CRU also trips after sometime? Explain the reason.

32. Explain the Rosemount DCS system with diagram?

33. What is barrier? Where is it installed in our plants? What are classification of Zones

in our plants?

34. What is PLC Explain its working?


5/27

Lead Instrument Technician

1. What are the advantages of PLC over conventional relay logic?

A) PLC is a) Compact

b) Easy to change the logic

c) Quick action (Fast scan rate)

d) No moving parts

e) Minimum failure

e) Can be interfaced with DCS and other control devices

f) Can perform complex functions

2. Draw the Architectural diagram of a DCS

3. Which thermocouple is best suited for a range of 0-1200-deg C.

A) K-type (Chromel allumel)

4. Name some of the commonly used pressure measuring devices in process

industry

A) Bourdon tube, Diaphragm, capsule, bellows

5. Draw a simple automatic control loop.

6. If the flow transmitter o/p is 6 psi what is the actual flow in %.

A) 50%

7. Describe briefly the calibration procedure of an inter-face Level Transmitter?

A) On an interface level there are two liquids of different Densities.

Adjust zero level with the chamber filled with lighter liquid

PL note zero level = H*D H = ht of the displacer

D = sq.gr of the lighter liquid

Adjust span with the chamber filled with heavier liquid

8. Draw a block diagram of a Gas Turbine?


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9. What is the difference b/w centrifugal and reciprocating compressor?

9) A) In a reciprocating compressor, a quantity of gas is drawn into a cylinder and

compressed by positive displacement where the mechanical energy is converted

to pressure energy.

In a centrifugal compressor compression is achieveded by applying inertial

forces to the Gas velocity energy is then converted to pressure Energy by

decelerating the gas through the diffuser

10. What is LEL with reference to Gas detection?

A) LEL stands for lower explosive limit

OBJECTIVE TYPE QUESTIONS

1) The resistance of PT -100 RTD is (C)

a) 100 Ohms at ambient temp

b) 0 Ohms at 100 deg c.

c) 100 Ohms at 0 deg c.

d) none of the above.

2) How do you zero check a flow transmitter?

A) a) Open equalizing valve

b) Close impulse line valves

c) Open drain valves

3) Name the essential parts of a typical DCS system?

A) a) I/O Modules

b) Signal Processor

c) History Module

d) Application Module

e) Work station (Including, Pheri-Pherals)

f) Removable media drives

g) Power Supply

4) Give the most commonly used engineering units for the following?

a) Very low Pressure (Inches of H2O)

b) Flow of Oil (BPD or Barrels per day) and (GPM or Gallons per Minute)

c) Temperature (Deg. C, Deg. F)

e ) Density (kg/cu.m and gm/c.c)


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5) Define proportional, integral, & derivative actions?

6) What are the advantages of PLC over conventional relay logic?

A) a) Compact

b) reliablec) performs complex functions

d) Logic can be changed easily

e) Can force the out put

7) Name two methods detecting ignition?

A) U. V. Detector

Flame Rod

Thermocouple

8) What is the procedure of installing Bentley Nevada vibration probes?

A) a) Check linearity of probe using TK -3

b) Confirm length of the extension cable

c) Clean probe mounting area

d) Install vibration probe and adjust gap voltage accordingly

e) Tighten all connections

f) Check & note gap voltage

9) Why are bleed valves used in gas turbines?

A) Bleed Valves are provided to avoid surge in the air compressor during

start-up

10) The O/P impedance of an ideal op-amp is (B)

a) infinity b) zero c) unity

d )1000Ohms

LEAD INSTRUMENT TECHNICIANS

1 When the operator puts a controller in automatic mode he has direct control

over (A)

a) Set point b) Process variable c) Output

2 Describe briefly the calibration procedure of K type temperature indicator

using a milli volt source?

A) I) Note milli volts for ambient temp. from the table - X mV.


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ii) Note milli volts for Zero - A mV and span - B mV.

iii) Apply (A-X) mV from the source and adjust zero.

iv) Apply (B-X) mV from the source and adjust span.

v) Repeat III & IV till no adjustment is required.

vi) Check meter for 25%, 50% and 75%.

3 Draw a simple block diagram of PLC?

4 What is the difference between EPROM and EEPROM which is better

suited for re-programming?

A) EPROM -Erasable Programmable Read Only Memory

EEPROM -Electrically Erasable Programmable Read Only Memory

5 What are most commonly used tap locations in orifice plate and why and for

what application bleed hole is provided?

A) Flange Taps, Pipe Taps

6 What is ratio control?

A) Ratio Control maintains the magnitude of a controlled variable at a fixed ratio toanother variable.

7 What are the various protection systems in a Gas Turbine?

A) a) Over Temperatureb) Over Speed

c) Under Speedd) Surge

e) Vibration

f) Diff EGT (Exhaust Gas Temperature)

g) Lube Oil Temp. & Pr.

h) Fire and Gas

i) Low Fuel Gas

8 What is the principle of proximity type vibration probes?

A) Proximity probe works on the principle of Eddy current losses in the proximity of

conducting Material.

9 Name three types of pressure measuring elements?

A) Bourdon tube, Diaphragm & Bellows

10 What is surge in a compressor?

A) Momentary reversal of flow is called surge in a compressor.


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Objective Questions:-

Q.1 Zener Barrier is used for (A)

a) To make the instrument intrinsically safe.

b) To make the instrument explosion Prof.

c) To save energy.

d) To make the instrument respond fast.

Q. 2 The two metal alloy elements in "K" type thermocouple is (B)

a) Copper - Constantan

b) Chromel - Alumel

c) Platinum - Rohmium

d) Chromel - Constantan

Q. 3 The type of T/C for "Iron - Constantan" element is (D)

a) "T" Typeb) "K" Type

c) "R" Type

d) "J" Type

Q. 4 What are commonly used unit of pressure? (C)

a) Meter

b) Feet.

c) PSI

d) Pound

Q. 5 In Honeywell TDC - 3000 DCS, the controller should be put in ----------- Mode

while configuration of data point. (B)

a) Auto mode

b) Manual mode

c) Cascade mode

d) Auto - Cascade mode

Q. 6 What is the difference between "Absolute and Gauge pressure"? (A)

a) Absolute pressure > Gauge pressure

b) Gauge pressure > Absolute pressure + 14.667


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c) Absolute pressure = Gauge pressure + 14.667

d) Gauge pressure = Absolute pressure + 14.667

Q.7 The output of a two input AND gate when both of the inputs are 1 is: (B)

a) 0b) 1

c) 10

d) None of the above.

Q.8 What are 5 commonly used units of flow rate measurement?

A) 1) M3 /Hrs.

2) GPM

3) BBL/DAY

4) SCFD5) Litters per minute

Q. 9 How do you identify upstream side of an orifice plate from outside?

A) Marking on orifice tab is always on the up stream side.

GIVE THE FLOW DIRECTION FOR THE GIVEN ORIFICE PLATE

Q.10 Give three most commonly used methods for level measurements?

A) 1) Manometer

2) Level transmitter with a sealed diaphragm sensing the head.3) Displace type transmitters.

4) Differential pressure transmitter

5) Capacitive probes.

Q.11 Identify the symbols given below.


11/27

NPN Transistor PNP Transistor Diode Zenor Diode SCR

Nand Gate Not Gate Exclusive OR Gate Op. Amp.

Q This question itself is wrong

S1

-

1 +

+ - 2

a) With switch SI connected to battery No.1 what is the status of the lamp ON

or OFF---------------why?

b) If the switch is operated to connect the battery No.2 what will be the status

of the lamp?

ON or OFF ------------why?

Q. What is the output logic?

1

1

0 OUT PUT? Zero

0

LampC

E

R1B

-

+

YA

BA Y A

B

Y Vin

- V

+ V

- V

Volt


12/27

OUTPUT ?

Q.11 What is "Off Delay" and "On Delay" timer? Draw them symbolically.

Q.12 Define following terms used in digital system?

CPU:-------------- HiwaY:----------------

ALU:-------------- DCS:--------------------

EPROM:------------ SCADA:----------------

RAM:---------------- PLC:---------------------

FLOPPY DISK:---- HARD DISK:--------

MODEM:--------------

Q.13 Convert the following quantities:

Quantity Convert to

1200 mm H2O ------------------- psig

180 0 F ------------------- 0C

75 M -------------------- Feet

Q.14 What safety devices used in instrument air compressor?

Q.15 Write the truth table of "AND" gate.

Q,16 What are standard signals used for electronic and pneumatic transmitters?

a) Electronic -----------------------------------

b) Pneumatic ------------------------------------

Q.17 Give most commonly used Engineering units for the following in imperial systemTemperature ---------------- Density ------------------------


13/27

Gas Flow ------------------- Pressure -----------------------

Oil Flow --------------------- Vibration -----------------------

Tank Level ------------------

Q.18 What is meant by "Fail Close" and "Fail Open" in control valves?

What is importance?

Q.19 What is "Configuration" in a distributed control system?

Q. 20 Write 3 important sensors of temperature measurement?

Q. What is voltage logic levels of TTL and Ohms Ics Draw a TTLAND gate.A. TTL operates normally at 12 V DC and 0V ohms ICS operate on 5v DC

and 0V.

Ye

A

B

Y

Q. Draw half wave. Full wave and bridge rectifier. How a bridge rectifier is more

efficient than full wave rectifier.

+

-

Half Wave

Full Wave


14/27

+

-

A. Bridge rectifier is more efficient than ordinary full wave rectifier because it requires

small transformer due to full use of its secondary.

Q. Draw a failsafe relay diagram with reset push button to give a contact for shutdown

if either pressure rises above 100psi or temp. goes below 50c.

Reset ps

TS PS

R1

150'c 100 Psi

Q. What is Off delay and On delay timer. Draw them symbolically.

A. OFF DELAY - The timer relay whose contact change after the set delay after it is

de-energized. The contact however change immediately. It is energized again..

B. ON DELAY - The timer relay whose contact change after the set delay after it is

energized. The contact however immediately it de-energizes.

ON DELAY OFF DELAY

Q. briefly explain the relay logic given below

A. At 50 psi (R) pressure timer operates if timer remain operated for set time

and it Rx is closed, the relay "R" energized. Relay "R" contact 1 energizes

SOV and relay "R" contact 2 gives lamp indication.

RxT1

Bridge

R

1

TR

TDR

TRTDR

T

R


15/27

R1

R2

Q. Draw a typical motor start/stop push button with "AUTO" contract from inst.

Interlocks.

START STOP

M

psi

A

R1

Q Draw a flow control loop showing flow of signals in DCS.

IS

s

So

v

Lamp

R1

DCS

DATA

H-WAY

HTD

ISB SLOT A/D 3 CPUO/P

CARD

I/P ISB


16/27

Fy

Q. What will be the reading on an uncompensated mV temp. indicator in two cases

shown below.

DPDT SWITCH

Bath Temp reading -(100-25 =75* C

Freezer reading - (-10-25) = 35*C Ambient Temp. 25*C

Ans; A dP transmitter is to be calibrated for Crude (Density=0.85) tank level measurement

as shown below;(Pneu-3 to 15 psi and electronics-4 to 20mA)

_

50' h _

output

Q. Describe briefly how a displacer type level transmitter works

Filter

Volts

BATH -100 0 C

- 10 0 C

FREEZER

mV

2.50c

Crude

DP


17/27

Out pout

Q. Draw a simple sketch to show mounting of a dP cell for the following:

Ans. Gas flow measurement

output

Crude Flow Measurement:

output

RLY

Air Supply

DP

Cell

Gas Flow Gas Flow

Crude Crude

DP

Cell


18/27

Q Draw a simple dP cell installed for measurement. Name the parts and write

steps to perform on line zero check.

a) Open equalizer valve.

b) Isolate downstream and upstream isolation valve.

c) Opoen both drain valve.

d) Check zero and adjust if necessary.

e) Close drain valves.

f) Open upstream valve and check if any shift on zero.

g) Open downstream valve.

h) Close equalizing valve.

out

-put

Q. Three orifice are shown below. Write down the typical application for each of

them .

Ans. A) Liquid flow (eccentric) B) Gas flow (concentric) C) Slurry (segmental)

Orifice Plate Orifice Plate

DPCell


19/27

Q. Draw a simple sketch of a pneumatic relay and explain.

Ans. When a back pressure from flapper nozzle changes pressure on the diaphragm, the

control ball attached to it changes it's positions whether more or less air supply to pass

through it thereby changing the output.

Filter Diaphragm

Nozzle

Q. Draw a 'AND' gate and a 'OR' gate for two inputs using pneumatic relays.

Ans. A) AND gate B) OR gate

C A C A C A

Y

B B B B

Note:-

A) No pressure on diaphragm A to C

B) Pressure on diaphragm B to C

C) Y = A * B

output

A

C


20/27

Q. Explain 3 most commonly used valve plugs with characteristic curves.

Ans.

100% 100% Flow 100% Flow

0% 0% 0%

open open open

A) Linear B) Equal or Quadratic C) Quick opening

Or Parabolic

Q. Draw a simple flow control loop with square root extractor and a recorder to control

crude flow.

3-15 psi

FCV

P/P

FR


21/27

4-20 mA

A-20MA

Q. What is a cascade control? Why is cascading of controllers required in a certain

applications?

Ans. A) A cascade control is a control involving two or more controllers connected in

such a way that the output of one controller called the master of primary controller goes as

a remote set point to the other controllers called the slave or secondary controller.

B) A cascade control is used when the process control requirements for the master or

primary controlled process variable dictates a high degree of accuracy for the slave or

secondary controlled process variable.

A/s

P.T.

Dp cell

xmitter

FC I/P

A/S

T/C

P/C

I/P

TT

4 -20 m

3 - 15 Psi


22/27

Q. Draw a flow control loop showing flow of signals in DCS.

Fev

4-20mA

Other PIVS or Com.

4-20 mA

Data

Hiway

P

I

PIV

ProcessInterface

Unit

OperatorStation

Traffic

Committee

P

_

O.P.

Stations


23/27

A) ADP tranmitter is to be calibrated for Crude (Density 0.85 ) Tank level

measurement as shown below-

2.5" wc Vapour Pressure

50'

CRUDE Output

3

Drain

B) Describe briefly how a displacer type level transmitter works.

DPCell

A.S.

Relay


24/27

Q) Draw simple sketch to show mounting of a DP cell for

I) Gas measurement II) Crude Flow measurement.

GAS

CRUDE

Q) Draw a simple DP cell installed for flow measurement name the parts and write

steps to perform on line zero check.

Secondary isolation Equalizer

Primary Isolation

Up strain

Process line Orifice

DPCell

DP

Cell

DPCell

Drain Valve

Drain


25/27

Q) What is a CASCADE Control, why is casecading of controllers required in certain

applications.

M.V.1MVL

O/P Remo---

Set Point

Lower set point

Q) Draw a bridge circuit using resistance thermometer for measurement indication?

+

RTA

Q) Draw simple sketch to show mounting of a DP Cell and Orifice for Gas

measurement.

Slave

Controller

R/2selection

Master

Controller

DP

Cell


26/27

Q) Draw a relay circuit with manual reset push button to give indication whenever

either temperature goes high or pressure goes low?

MASTER

To actuator

O/P

GAS

S.P. M.V.

Shave

S.P. M.V.


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instrument question (imp)

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