LEVEL MEASUREMENTS

Question 1

the height or depth of a liquid in a particular level

Answer 1

LEVEL

Question 2

determination of the position of an existing interface bet. two media

Answer 2

Measurement of Level

Question 3

probably the first of the process variable to be measured and controlled

Answer 3

Liquid Level

Question 4

Reasons for Level Measurement

Answer 4

• Safety
• Economy
• Monitoring

Question 5

importance of monitoring of level in bulk storage tanks

Answer 5

• Plant efficiency may be assessed and optimized
• Stock records may be kept
• Cost may be correctly allocated

Question 6

In the OIL and GAS industries, level measurement is necessary to achieve the ff. objectives

Answer 6

1. Compute the tank inventories of hydrocarbon liquid and utility liquid
2. Protect Equipment such as columns, compressors, turbines and pumps from damage
3. Protect operating and maintenance personnel against injury resulting from hydrocarbon, corrosive or toxic spillage
4. Protect the environment from the release of objectionable liquids into the rivers and seas
5. Control phase separation processes and product loading operations

Question 7

Methods of level mesurements

Answer 7

1. Direct method

2. Indirect method

Question 8

Direct methods of level measurement

Answer 8

1. Dip sticks and Lead Lines
2. Sight Glass
3. Chain or Float Gauge

Question 9

simple, almost straightforward and economical

Answer 9

Direct Method

Question 10

types of sight glass

Answer 10

1. Magnetic
2. Reflex
3. Transparent
4. Bi-color

Question 11

it provides a continuous visual indication of liquid level in a process vessel or a small tank and more convenient than dip stick, dip rod and manual gauging tapes

Answer 11

Sight Glass

Question 12

used in corrosive or hazardous chemical

Answer 12

Magnetic sight glass

Question 13

Used in pressurized vessel (condenser, evaporator)

Answer 13

Reflex sight glass

Question 14

most common in process wave, it can be changed (viscous and uncolored fluid)

Answer 14

Transparent sight glass

Question 15

used in high pressure boiler steam drum, steam boiler

Answer 15

Bi-color sight glass

Question 16

uses the principle of buoyant element that floats on the surface of the liquid and changes position as the liquid level varies

Answer 16

Chain or Float Gauge

Question 17

connected by a chain or flexible cable and the rotating member of the pulley is in turn connected to and indicating device w/ measurement graduation

Answer 17

Float

Question 18

depend on the material having a physical property which can be measured and related to level

Answer 18

Indirect or Inferred Methods

Question 19

Indirect methods

Answer 19

1. Buoyancy
2. Hydrostatic head
3. Sonar or ultrasonic
4. Microwave
5. Conductance
6. Capacitance
7. Radiation
8. Weight
9. Resistance
10. Micro-impulse

Question 20

the force produced by a submerged body which is equal to the weight of the fluid it displaces

Answer 20

Buoyancy

Question 21

the force or weight produced by the height of the liquid

Answer 21

Hydrostatic head

Question 22

materials to be measured reflect or afflect in a detectable manner high frequency sound signals generated at appropriate locations near the measured material

Answer 22

Sonar or ultrasonic

Question 23

similar to ultrasonic but uses microwave instead of ultrasonic beam

Answer 23

Microwave

Question 24

at desired points of level detection, the material to be measured ( or ceases to conduct) electricity between two fixed locations or between a probe and vessel wall

Answer 24

Conductance

Question 25

the material to be measured serves as a variable dielectric bet. two fixed capacitor plates.

Answer 25

Capacitance

Question 26

the material measured absorbs radiant energy

Answer 26

Radiation

Question 27

the force due to weight can be related very closely to level when it’s density is constant

Answer 27

Weight

Question 28

pressure of the measured material squeezes two narrowly separated conductor together; reducing overall circuit resistance in an amount proportional to level

Answer 28

Resistance

Question 29

“time of flight”, electrical impulses launch and travels back in frequency directly proportional to the level of the liquid

Answer 29

Micro-Impulse

Question 30

the force produced when a body is submerged into a liquid with a constany density is equal to the fluid displaced

Answer 30

Archimedes Principle

Question 31

a special type of spring that acts in an upward direction in opposition to the weight of the displacer (Twist Force)

Answer 31

Torque Tube

Question 32

this method relies on the pressure of the measured liquid head to provide level indication

Answer 32

Hydrostatic Head or Differential Method

Question 33

One of the oldest and simplest methods of level measurement is called the ________________

Answer 33

Air bubbler, air purge or dip tube

Question 34

provide the bubbles

Answer 34

Totameter

Question 35

empty space that remains

Answer 35

Ulage

Question 36

Yung may laman

Answer 36

Fillage

Question 37

the air pressure is nearly linear to the water pressure and therefore water depth

Answer 37

Bubbler Systems

Question 38

used when contact is not desirable

Answer 38

sonar or ultrasonic device (normally referred to as “radar”)

Question 39

measuring liquid level in vessel by bouncing a travelling wave off the surface of the liquid

Answer 39

Echo Based Level Measuring Device

Question 40

designed for continuous, non-contact level measurement of liquids, pastes and slurries.

Answer 40

Microwave (Radar)

Question 41

travel in speed of light of 2.9979x10^8 m/s in perfect vacuum

Answer 41

Radiowaves

Question 42

operate on the principle of electrical conductivity

Answer 42

conductivity level switches

Question 43

the property of a circuit that stores electrons and thus opposes a change in voltage in the circuit

Answer 43

Capacitance

Question 44

an electrical component that consists of two conductors separated by a dielectric or insulator

Answer 44

Capacitor

Question 45

Capacitance value is determined by:

Answer 45

- area of the conductors (plates) - distance between the plates - dielectric constant of the insulator between the plates

Question 46

the material in the vessel which will determine the capacitance value when it rises and falls

Answer 46

Dielectric

Question 47

advantages of capacitance level devices

Answer 47

- they contain no moving parts - simple and rugged design is possible - design for corrosive application is possible - easy to clean - sanitary design is available for food processing industry - extreme temperature and pressure requirements are possible by careful design - can be designed for explosion proof service

Question 48

Limitations of Capacitance level devices

Answer 48

- measurement is subject to error caused by temperature changes affecting the dielectric constant of the material to be measured - coating of the probe by conductive material causes error in measurement - usually empirical calibration techniques are used - in solids measurement, variations in particle size affect the dielectric constant

Question 49

variations in particle size

Answer 49

- alpha particles | - beta particles

Question 50

were first used in instrumentation and related industries in the early 1950’s

Answer 50

Nuclear Radiation

Question 51

can be used for either point or continuous applications

Answer 51

Nuclear Radiation Measurement

Question 52

In point measurement, there are two basic components:

Answer 52

1. radiation source | 2. detector with associated amplifier

Question 53

the detector is usually a ________________ with a solid-state amplifier and associated power supplies

Answer 53

Geiger-Mueller tube

Question 54

it use a weighing machine attached to the tank to weigh the liquid

Answer 54

Weight Method

Question 55

A device that has gained performance in level applications consist of a tape type resistance-sensing element (called “METRITAPE) used when feasible

Answer 55

Resistance Devices