4th Class Boiler Test 2

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| By Deno70

Deno70

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Quizzes Created: 3 | Total Attempts: 15,895

Questions: 50 | Attempts: 782 | Updated: Jul 21, 2024

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Questions and Answers

1.

In a recovery boiler:
- A.
  
  Waste heat is recovered from the baking operation
- B.
  
  Black liquor is burned to eliminate lignin
- C.
  
  Smelt is burnt to produce black liquor
- D.
  
  Lime is recovered for re-use
Correct Answer
B. Black liquor is burned to eliminate lignin

Explanation
In a recovery boiler, black liquor is burned to eliminate lignin. Black liquor is a byproduct of the pulp and paper industry, and it consists of lignin, chemicals, and water. By burning the black liquor, the lignin is eliminated, leaving behind the chemicals and water. This process allows for the recovery of chemicals and the production of steam, which can be used to generate electricity or heat in the pulp and paper mill.

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2.

The economizer in the steam cycle of an electricity generating plant is located between the:
- A.
  
  Radiant and convection superheaters
- B.
  
  Boiler drum and superheater
- C.
  
  Feedwater pump and the boiler drum
- D.
  
  Superheater and the turbine.
Correct Answer
C. Feedwater pump and the boiler drum

Explanation
The economizer in the steam cycle of an electricity generating plant is located between the feedwater pump and the boiler drum. The economizer is a heat exchanger that preheats the water before it enters the boiler drum. By utilizing the waste heat from the flue gases, the economizer increases the efficiency of the plant by reducing the amount of fuel needed to heat the water. Preheating the water also helps to prevent thermal shock to the boiler drum.

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3.

The purpose of the absorber in a natural gas plant is to:
- A.
  
  Remove condensates from the gas
- B.
  
  Absorb all the hydro-carbons from the gas
- C.
  
  Scrub the gas from amine
- D.
  
  Remove hydrogen sulphide and carbon dioxide from the gas
Correct Answer
D. Remove hydrogen sulpHide and carbon dioxide from the gas

Explanation
The purpose of the absorber in a natural gas plant is to remove hydrogen sulphide and carbon dioxide from the gas. This is an important step in the gas purification process as these impurities can be harmful and need to be removed before the gas can be used safely. The absorber works by using a solvent or absorbent material to selectively capture and remove these unwanted gases from the natural gas stream.

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4.

During an internal boiler inspection an engineer should check:
- A.
  
  That there is a proper air flow through the furnace.
- B.
  
  That all external parts of drums and equipment are positioned properly.
- C.
  
  For scale deposits, corrosion, erosion, cracks, leaks or other defects.
- D.
  
  That the moveable grates and ash system are functioning properly.
Correct Answer
C. For scale deposits, corrosion, erosion, cracks, leaks or other defects.

Explanation
During an internal boiler inspection, it is important for the engineer to check for scale deposits, corrosion, erosion, cracks, leaks, or any other defects. This is crucial to ensure the proper functioning and safety of the boiler. Scale deposits can reduce the efficiency of the boiler and cause overheating, while corrosion, erosion, cracks, and leaks can lead to structural damage and potential hazards. By inspecting and identifying these issues, the engineer can take appropriate measures to address them and prevent any further damage or accidents. Checking for proper air flow, positioning of external parts, and functionality of moveable grates and ash system are also important aspects of a boiler inspection, but they are not directly related to identifying defects.

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5.

Raising or lowering of heavy objects using ropes and cables is known as:
- A.
  
  Lifting
- B.
  
  Rigging
- C.
  
  Hoisting
- D.
  
  Elevating
Correct Answer
C. Hoisting

Explanation
Hoisting refers to the act of raising or lowering heavy objects using ropes and cables. It involves the use of mechanical devices such as cranes, pulleys, and winches to lift the objects off the ground or lower them to a desired level. This term is commonly used in industries such as construction, manufacturing, and transportation where the movement of heavy loads is required.

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6.

Natural ropes are made of:
- A.
  
  Nylon
- B.
  
  Polyethylene
- C.
  
  Dacron
- D.
  
  Manila
Correct Answer
D. Manila

Explanation
Manila is the correct answer because it is a type of natural rope made from the fibers of the abaca plant, which is native to the Philippines. It is known for its strength, durability, and resistance to rotting, making it a popular choice for various applications such as construction, agriculture, and marine use. Unlike nylon, polyethylene, and Dacron, which are synthetic materials, manila rope is derived from a natural source, giving it a distinct texture and appearance.

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7.

Prior to commencing boiler cleaning operations it is necessary to: 1. test the boiler water 2. close steam and water valves 3. tag all valves to indicate shut down 4. complete the boiler-room log book 5. check out the burners.
- A.
  
  1 and 3
- B.
  
  2 and 3
- C.
  
  3 and 5
- D.
  
  1 and 5
Correct Answer
B. 2 and 3

Explanation
Before starting boiler cleaning operations, it is necessary to close steam and water valves to ensure that no steam or water enters the boiler during the cleaning process. This is important for the safety of the cleaning personnel and to prevent any damage to the boiler. Additionally, tagging all valves to indicate shut down is important to communicate to others that the boiler is not in operation and should not be tampered with. Therefore, the correct answer is 2 and 3.

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8.

The boiler boiling out procedure:
- A.
  
  Should be done at operating pressure
- B.
  
  Should be done before the dry out procedure
- C.
  
  Should be done at one-half the operating pressure
- D.
  
  Should be done once a year
Correct Answer
C. Should be done at one-half the operating pressure

Explanation
The correct answer is "should be done at one-half the operating pressure." This means that the boiler boiling out procedure should be conducted at half of the normal operating pressure. This is important to ensure that any impurities or contaminants in the boiler are effectively removed without causing any damage or excessive stress to the boiler system. Conducting the procedure at a lower pressure helps to minimize the risk of any potential issues or accidents during the process.

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9.

The purpose of boiling out a boiler is:
- A.
  
  To test the material of the boiler
- B.
  
  To find the boiling point of the water in the boiler
- C.
  
  To remove any grease and oil from the heating surface
- D.
  
  To check if there are any leaks
Correct Answer
C. To remove any grease and oil from the heating surface

Explanation
Boiling out a boiler is done to remove any grease and oil from the heating surface. Over time, grease and oil can accumulate on the surfaces of the boiler, reducing its efficiency and potentially causing damage. Boiling out involves filling the boiler with water and raising the temperature to its boiling point, causing the grease and oil to loosen and be flushed out. This process helps to ensure that the boiler operates at its optimal performance and prolongs its lifespan. It is not done to test the material of the boiler, find the boiling point of the water, or check for leaks.

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10.

The best type of filter for the removal of fine dust, smoke and fumes is the:
- A.
  
  Viscous impingement filter
- B.
  
  Dry filter
- C.
  
  Bag type filter
- D.
  
  Electrostatic filter
Correct Answer
D. Electrostatic filter

Explanation
An electrostatic filter is the best type of filter for the removal of fine dust, smoke, and fumes. Electrostatic filters use an electric charge to attract and trap particles, making them highly effective in capturing even the smallest particles. They are particularly efficient in removing smoke and fumes, which are often composed of tiny particles that can be harmful to breathe. Additionally, electrostatic filters can be easily cleaned and reused, making them a cost-effective and environmentally friendly option.

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11.

A Runaround air conditioning heat recovery system consists of two finned tube heat exchangers, the preconditioning coil and the recovery coil. Where is the preconditioning coil of this system usually located?
- A.
  
  On the suction side of the pump
- B.
  
  On the discharge side of the 3-way mixing valve
- C.
  
  In the duct work handling the ventilation into the process
- D.
  
  At the end of the charging unit
Correct Answer
C. In the duct work handling the ventilation into the process

Explanation
The preconditioning coil of a Runaround air conditioning heat recovery system is usually located in the duct work handling the ventilation into the process. This means that it is positioned within the duct system where fresh air is being brought into the process. The purpose of the preconditioning coil is to preheat or precool the incoming fresh air before it enters the process, improving energy efficiency and reducing the load on the main heating or cooling system.

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12.

Three common sensing elements used on humidistat are the: 1. Human hair element 3. Wood element 2. hygroscopic element 4. Metal element.
- A.
  
  1, 2 and 3
- B.
  
  1, 2 and 4
- C.
  
  1, 3 and 4
- D.
  
  2, 3 and 4
Correct Answer
A. 1, 2 and 3

Explanation
The correct answer is 1, 2 and 3. This is because the three common sensing elements used on a humidistat are the human hair element, hygroscopic element, and wood element. These elements are used to detect humidity levels and trigger the appropriate response or action based on the desired humidity range. The metal element is not commonly used as a sensing element on a humidistat.

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13.

Which of the following is a primary function of a boiler's safety valve?
- A.
  
  To maintain the boiler's water level
- B.
  
  To provide a means for manual operation of the boiler
- C.
  
  To release pressure and prevent explosions
- D.
  
  To regulate the temperature of the boiler
Correct Answer
C. To release pressure and prevent explosions

Explanation
The safety valve is a critical component of a boiler system. Its primary function is to release excess pressure from the boiler to prevent potential explosions. When the pressure within the boiler exceeds a predetermined safe level, the safety valve opens to allow the excess steam to escape, thereby protecting the boiler from over-pressurization and potential damage.

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14.

The expansion valve in a refrigeration system is:
- A.
  
  Between the condenser and the receiver
- B.
  
  Between the evaporator and the compressor
- C.
  
  Between the receiver and the evaporator
- D.
  
  Between the compressor and the condenser
Correct Answer
C. Between the receiver and the evaporator

Explanation
The expansion valve in a refrigeration system is located between the receiver and the evaporator. This valve is responsible for regulating the flow of refrigerant into the evaporator, where it undergoes a phase change from a high-pressure liquid to a low-pressure gas. By controlling the flow of refrigerant, the expansion valve helps to maintain the desired temperature and pressure levels in the evaporator, ensuring efficient cooling of the system.

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15.

Safety valves on a refrigeration system:
- A.
  
  Should be fitted on the receiver
- B.
  
  Should be tested by hand lever regularly
- C.
  
  Should be equipped with a leather seat
- D.
  
  Should discharge to sewer
Correct Answer
A. Should be fitted on the receiver

Explanation
Safety valves on a refrigeration system should be fitted on the receiver. The receiver is a container that stores the refrigerant in a liquid state, and fitting the safety valves on it ensures that any excess pressure in the system can be released safely. Placing the safety valves on the receiver allows for efficient and effective pressure relief, protecting the system from potential damage or failure.

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16.

In the vapour compression type of refrigeration system, the liquid refrigerant is changed to a gas in the:
- A.
  
  Condenser
- B.
  
  Evaporator
- C.
  
  Receiver
- D.
  
  Compressor
Correct Answer
B. Evaporator

Explanation
In the vapour compression type of refrigeration system, the liquid refrigerant is changed to a gas in the evaporator. The evaporator is responsible for absorbing heat from the surroundings, causing the liquid refrigerant to evaporate and turn into a gas. This gas is then compressed in the compressor, condensed in the condenser, and returned to the evaporator to repeat the cycle. The evaporator plays a crucial role in the cooling process by extracting heat and allowing the refrigerant to change state from a liquid to a gas.

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17.

In some installations in order to guarantee a supply of clear hot water and prolong the life of a hot water heater the:
- A.
  
  Temperature differential of the temperature control is increased,
- B.
  
  Temperature differential of the temperature control is decreased,
- C.
  
  Operating temperature is raised,
- D.
  
  Inner shell of the heater is lined with cement,
Correct Answer
D. Inner shell of the heater is lined with cement,

Explanation
Lining the inner shell of the heater with cement helps to prolong the life of the hot water heater and ensure a supply of clear hot water. The cement lining provides an extra layer of protection against corrosion and rust, which can occur due to the constant exposure to water and heat. This helps to prevent leaks and damage to the inner components of the heater, ultimately extending its lifespan and maintaining the quality of the hot water supply.

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18.

One advantage of the electric probe type of low water fuel cut-off is:
- A.
  
  It contains no moving parts or the possibility of mechanical failure is eliminated,
- B.
  
  They operate at a higher water level than the float type,
- C.
  
  That the probes give an indication of the dissolved solids in the boiler water,
- D.
  
  It gives a quicker response to the feedwater regulator,
Correct Answer
A. It contains no moving parts or the possibility of mechanical failure is eliminated,

Explanation
The advantage of the electric probe type of low water fuel cut-off is that it contains no moving parts or the possibility of mechanical failure. This means that there is less chance of the device malfunctioning or breaking down, leading to more reliable and consistent operation.

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19.

Two element feedwater control:
- A.
  
  Measures water level and steam flow
- B.
  
  Measures water flow and steam flow
- C.
  
  Measures water level and steam level
- D.
  
  Measures oil flow and steam flow
Correct Answer
A. Measures water level and steam flow

Explanation
The correct answer is "measures water level and steam flow." In a two element feedwater control system, it is important to measure both the water level and steam flow. This allows for accurate control and regulation of the feedwater flow into the steam generator. By monitoring the water level, the system can ensure that there is enough water to maintain safe operation, while measuring the steam flow helps to determine the demand for steam and adjust the feedwater accordingly. This combination of measurements ensures efficient and reliable operation of the steam generation process.

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20.

Steam is prevented from leaking out around the valve stem of a packless radiator valve with the use of:
- A.
  
  A seat
- B.
  
  A diaphragm
- C.
  
  A spring
- D.
  
  An outside screw
Correct Answer
B. A diapHragm

Explanation
A diaphragm is used to prevent steam from leaking out around the valve stem of a packless radiator. The diaphragm acts as a barrier between the steam and the valve stem, ensuring that no steam escapes through any gaps or openings. It provides a tight seal and helps maintain the efficiency and effectiveness of the radiator by preventing any loss of steam.

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21.

The purpose of fins on a convector tube is to:
- A.
  
  Strengthen the tube
- B.
  
  Prevent rupture
- C.
  
  Increase heat transfer
- D.
  
  Accumulate warm air
Correct Answer
C. Increase heat transfer

Explanation
The purpose of fins on a convector tube is to increase heat transfer. Fins provide a larger surface area for heat exchange between the tube and the surrounding air, allowing for more efficient transfer of thermal energy. This increased surface area enhances convection, enabling the convector tube to transfer heat more effectively. By maximizing heat transfer, the fins help to improve the overall efficiency and performance of the convector tube.

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22.

The purpose of a cushion tank is to:
- A.
  
  Store heat while the boiler is firing
- B.
  
  Allow for the expansion of water in the system
- C.
  
  Prevent the system from overflowing
- D.
  
  To prevent the water in the system from freezing
Correct Answer
B. Allow for the expansion of water in the system

Explanation
A cushion tank is used to allow for the expansion of water in the system. As water heats up, it expands in volume. Without a cushion tank, this expansion could cause excessive pressure buildup in the system, leading to potential damage or failure. The cushion tank provides a space for the expanded water to be stored temporarily, preventing pressure spikes and maintaining the system's stability.

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23.

The blow down valve of a steam heating boiler must:
- A.
  
  Be installed in series with the safety valve,
- B.
  
  Be installed in the steam space,
- C.
  
  Regulate the feedwater,
- D.
  
  Be installed at the lowest point of the boiler,
Correct Answer
D. Be installed at the lowest point of the boiler,

Explanation
The blow down valve of a steam heating boiler must be installed at the lowest point of the boiler. This is because the blow down valve is used to remove impurities and sediment that accumulate in the boiler. By installing it at the lowest point, it ensures that all the impurities and sediment can be effectively drained out of the boiler. Installing it at any other point may result in incomplete removal of impurities, which can lead to decreased efficiency and potential damage to the boiler.

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24.

Your boiler is operated with automatic water feeders. If the boiler suddenly requires an increase in water treatment, what should you look for?
- A.
  
  See if the chemical pump has stopped
- B.
  
  Check for a loss of water
- C.
  
  Check to see if the chemical supplier has sent the wrong chemicals
- D.
  
  Nothing. Simply increase the pump stroke to put more chemicals into the
Correct Answer
B. Check for a loss of water

Explanation
If the boiler suddenly requires an increase in water treatment, checking for a loss of water would be the appropriate action. This is because a loss of water in the boiler can lead to an imbalance in the water treatment chemicals, causing the need for additional treatment. By checking for a loss of water, any potential issues can be identified and addressed to maintain the proper water treatment levels in the boiler.

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25.

A hot water boiler is protected from over pressure by means of:
- A.
  
  A safety pop valve
- B.
  
  A safety relief valve
- C.
  
  An expansion valve
- D.
  
  An air release valve
Correct Answer
B. A safety relief valve

Explanation
A hot water boiler is protected from over pressure by a safety relief valve. This valve is designed to automatically open and release excess pressure in the boiler, preventing it from reaching dangerous levels. It is an essential safety feature that ensures the boiler operates within safe limits and prevents potential explosions or damage to the system. The safety relief valve is specifically designed for this purpose and is a critical component in maintaining the safety of the boiler.

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26.

The low water cut off can be tested by:
- A.
  
  Raising steam pressure
- B.
  
  Shutting off the fire
- C.
  
  Shutting off the feedwater
- D.
  
  Opening the safety valve
Correct Answer
C. Shutting off the feedwater

Explanation
The low water cut off is a safety device that shuts off the fuel supply to the boiler when the water level in the boiler drops below a certain point. By shutting off the feedwater, the water level in the boiler will gradually decrease. This simulates a low water condition and allows the low water cut off to activate and shut off the fuel supply. Testing the low water cut off in this way ensures that it is functioning properly and will prevent the boiler from operating without sufficient water.

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27.

In a variable area flow meter the differential pressure:
- A.
  
  Is constant
- B.
  
  Changes directly as the area changes
- C.
  
  Changes inversely as the area changes
- D.
  
  Changes to the square root of the area changes
Correct Answer
A. Is constant

Explanation
In a variable area flow meter, the differential pressure is constant. This means that regardless of any changes in the area, the difference in pressure between the inlet and outlet of the meter remains the same. This is a key characteristic of variable area flow meters, as it allows for accurate measurement of flow rates by observing the position of a float or piston within the meter.

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28.

The Bourdon tube is often shaped in the form of a "C", having an arc span of about:
- A.
  
  200 degrees
- B.
  
  360 degrees
- C.
  
  270 degrees
- D.
  
  200 degrees
Correct Answer
C. 270 degrees

Explanation
The Bourdon tube is often shaped in the form of a "C" with an arc span of 270 degrees. This shape allows for better sensitivity and accuracy in measuring pressure. The tube is designed to flex and move in response to pressure changes, and the 270-degree arc provides a wider range of motion for the tube to respond to different pressure levels. This design ensures that the Bourdon tube can accurately measure a wide range of pressures, making it a popular choice in pressure measurement devices.

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29.

A commutator would be found in:
- A.
  
  An AC generator
- B.
  
  An induction motor
- C.
  
  A DC generator
- D.
  
  A wound rotor motor
Correct Answer
C. A DC generator

Explanation
A commutator is a device that is used to convert alternating current (AC) to direct current (DC) in a generator. In an AC generator, the output current is already AC and does not need to be converted. Similarly, an induction motor does not require a commutator as it operates on AC power. A wound rotor motor also does not have a commutator as it is a type of AC motor. Therefore, the only option left is a DC generator, where the commutator is necessary to convert the generated AC current into DC current.

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30.

The rotating field of an AC alternator is obtained by exciting the windings on the rotor with:
- A.
  
  AC power
- B.
  
  Stator current
- C.
  
  Magnetic particles
- D.
  
  DC power
Correct Answer
D. DC power

Explanation
The rotating field of an AC alternator is obtained by exciting the windings on the rotor with DC power. This is because the rotor windings create a magnetic field when DC power is applied to them, which then interacts with the stator windings to generate the rotating magnetic field necessary for AC power generation. AC power alone cannot create the rotating magnetic field, so DC power is required to energize the rotor windings and initiate the generation process.

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31.

Regarding alternating current systems, starting from zero and rising to a maximum positive or negative value and returning to zero, is known as:
- A.
  
  A cycle
- B.
  
  The frequency
- C.
  
  One half cycle
- D.
  
  An open circuit
Correct Answer
C. One half cycle

Explanation
One half cycle refers to the movement of an alternating current from zero to its maximum positive or negative value and then returning back to zero. It represents half of a complete cycle, which includes both the positive and negative phases of the current.

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32.

10 metres of wire of uniform cross sectional area has a resistance of 20 ohms. If the length of the wire is increased to 500 metres the resistance will be:
- A.
  
  1 000 ohms
- B.
  
  0.4 ohms
- C.
  
  25 ohms
- D.
  
  250 ohms
Correct Answer
A. 1 000 ohms

Explanation
When the length of a wire is increased, its resistance also increases. This is because resistance is directly proportional to the length of the wire. In this case, the length of the wire is increased from 10 metres to 500 metres, which is a 50-fold increase. Therefore, the resistance will also increase 50-fold. Since the initial resistance is 20 ohms, multiplying it by 50 gives us a final resistance of 1,000 ohms. Thus, the correct answer is 1,000 ohms.

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33.

Isolated electrical power lines:
- A.
  
  Are always closed
- B.
  
  Are always visible
- C.
  
  Require double insulation
- D.
  
  May have an induced or static electrical charge
Correct Answer
D. May have an induced or static electrical charge

Explanation
Isolated electrical power lines may have an induced or static electrical charge because they are not connected to a grounded system. When power lines are isolated, they are not in contact with any other conductive material or earth ground, which can lead to the accumulation of electrical charges. These charges can be induced by nearby electromagnetic fields or static charges that build up due to friction. Therefore, it is possible for isolated electrical power lines to have an induced or static electrical charge.

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34.

The voltmeter is placed:
- A.
  
  In series with the ammeter
- B.
  
  In parallel with the circuit
- C.
  
  Across the synchroscope
- D.
  
  In series with the circuit
Correct Answer
B. In parallel with the circuit

Explanation
A voltmeter is used to measure the voltage across a circuit or component. To obtain an accurate reading, the voltmeter should be connected in parallel with the circuit. This means that the voltmeter's positive terminal should be connected to the point in the circuit where the voltage is to be measured, and the negative terminal should be connected to the reference point (usually the ground). Connecting the voltmeter in series with the circuit would disrupt the flow of current and give incorrect readings.

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35.

The value of the current flow in an electric circuit, where the voltage is 12 volts and the resistance is 3 ohms is:
- A.
  
  4 watts
- B.
  
  36 amperes
- C.
  
  36 amperes
- D.
  
  4 amperes
Correct Answer
D. 4 amperes

Explanation
The value of current flow in an electric circuit can be calculated using Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R). In this case, the voltage is given as 12 volts and the resistance is given as 3 ohms. Therefore, the current can be calculated as 12 volts divided by 3 ohms, which equals 4 amperes.

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36.

A basic law of electricity is, unlike charges attract each other and like charges:
- A.
  
  Repel each other
- B.
  
  Hold each other
- C.
  
  Attract each other
- D.
  
  Impact each other
Correct Answer
A. Repel each other

Explanation
Unlike charges attract each other because they have opposite electrical charges and therefore exert an attractive force on each other. On the other hand, like charges repel each other because they have the same electrical charge and therefore exert a repulsive force on each other. This is a fundamental principle in electricity known as the law of electric charges.

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37.

The pour point of an oil is:
- A.
  
  The lowest pressure at which the oil will flow
- B.
  
  The lowest neutralization number of the oil
- C.
  
  The lowest temperature at which oil will flow
- D.
  
  The lowest pressure at which oil will stop to flow
Correct Answer
C. The lowest temperature at which oil will flow

Explanation
The pour point of an oil refers to the lowest temperature at which the oil will flow. It is an important property to consider as it determines the oil's ability to flow and be pumped in cold conditions. If the temperature drops below the pour point, the oil becomes more viscous and may solidify, impeding its flow. Therefore, knowing the pour point is crucial for industries that deal with oil, such as transportation and oil refining, to ensure the smooth operation of equipment and prevent any potential blockages or damage.

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38.

Causes of anti-friction bearing failures are: 1. improper fitting 3. high operating temperature 2. false brinelling 4. poor quality lubricant
- A.
  
  1, 3, 4
- B.
  
  2, 3, 4
- C.
  
  1, 2, 3
- D.
  
  1, 2, 3, 4
Correct Answer
D. 1, 2, 3, 4

Explanation
The correct answer is 1, 2, 3, 4. All of these factors can contribute to anti-friction bearing failures. Improper fitting can cause misalignment and excessive load, leading to premature failure. High operating temperature can cause the lubricant to break down, resulting in inadequate lubrication and increased friction. False brinelling refers to the formation of wear grooves on the bearing raceways due to vibration or inadequate lubrication. Poor quality lubricant can also lead to inadequate lubrication and increased friction, causing premature failure.

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39.

Greases are commonly a mixture of mineral oil and:
- A.
  
  Carbon powder
- B.
  
  Soap
- C.
  
  Graphite
- D.
  
  Synthetic oils
Correct Answer
B. Soap

Explanation
Greases are commonly a mixture of mineral oil and soap. Soap is added to the mixture to provide lubrication and enhance the performance of the grease. Soap acts as a thickening agent, allowing the grease to stay in place and adhere to surfaces for a longer period of time. It also helps to reduce friction and wear between moving parts. Soap-based greases are widely used in various applications, including automotive, industrial, and household purposes, due to their excellent lubricating properties.

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40.

A sliding vane pump is termed:
- A.
  
  A reciprocating pump
- B.
  
  A centrifugal pump
- C.
  
  A rotary pump
- D.
  
  A double acting pump
Correct Answer
C. A rotary pump

Explanation
A sliding vane pump is classified as a rotary pump because it utilizes a rotating mechanism to create suction and move fluid. In a sliding vane pump, vanes slide in and out of slots in a rotor, creating chambers that trap and transport fluid. This rotary motion allows the pump to generate continuous flow and pressure, making it an efficient choice for various applications. Reciprocating pumps, on the other hand, use a back-and-forth motion, while centrifugal pumps rely on centrifugal force to move fluid. Double acting pumps are a type of reciprocating pump that have two suction and discharge strokes per rotation.

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41.

What size of packing should be used to repack a pump gland having an 8.6 cm stuffing box bore and 6.7 cm pump shaft diameter?
- A.
  
  0.5 cm
- B.
  
  0.95 cm
- C.
  
  1.9 cm
- D.
  
  2.0 cm
Correct Answer
B. 0.95 cm

Explanation
The correct answer is 0.95 cm because it is the closest size to the difference between the stuffing box bore and the pump shaft diameter. Using a packing size that is slightly larger than the difference ensures a tight and secure fit, which is important for preventing leakage and maintaining the efficiency of the pump gland.

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42.

Priming a water pump means:
- A.
  
  Raising the suction line to the level of the water
- B.
  
  Removing the foot valve to allow the water to flow through
- C.
  
  Closing the discharge valve before starting the motor
- D.
  
  Filling the pumps casing and suction line with water
Correct Answer
D. Filling the pumps casing and suction line with water

Explanation
Priming a water pump involves filling the pump's casing and suction line with water. This is necessary to create a vacuum and remove any air from the system, allowing the pump to effectively draw water and start pumping. By ensuring that the casing and suction line are filled with water, the pump can operate efficiently and effectively.

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43.

When starting-up a reciprocating pump:
- A.
  
  The discharge valve should be closed
- B.
  
  The discharge valve should be open
- C.
  
  The pump should be filled with air
- D.
  
  The pump should be at the correct temperature
Correct Answer
B. The discharge valve should be open

Explanation
When starting up a reciprocating pump, the discharge valve should be open. This is because when the pump starts, it needs a clear path for the pumped fluid to flow out. If the discharge valve is closed, the fluid will have nowhere to go and can cause damage to the pump. By keeping the discharge valve open, the fluid can flow freely, allowing the pump to operate smoothly and effectively.

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44.

The purpose of a regenerator on a gas turbine is to:
- A.
  
  Regenerate the fuel
- B.
  
  Cool the combustion air
- C.
  
  Improve the cycle efficiency
- D.
  
  Start the compressor
Correct Answer
C. Improve the cycle efficiency

Explanation
A regenerator on a gas turbine is designed to improve the cycle efficiency. It does so by recovering waste heat from the exhaust gases and transferring it to the incoming compressed air before it enters the combustion chamber. This preheating of the air reduces the fuel consumption required for combustion, thus improving the overall efficiency of the turbine cycle.

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45.

Generally, steam turbine blades are made of:
- A.
  
  Cast iron
- B.
  
  Stainless steel
- C.
  
  Carbon steel
- D.
  
  Brass
Correct Answer
B. Stainless steel

Explanation
Steam turbine blades are generally made of stainless steel because it offers excellent corrosion resistance, high strength, and good heat resistance. Stainless steel can withstand the high temperatures and pressures experienced in a steam turbine, as well as the corrosive effects of steam and other impurities. It also has good mechanical properties, allowing the blades to withstand the high rotational speeds and stresses involved in turbine operation. Overall, stainless steel is a durable and reliable material choice for steam turbine blades.

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46.

Cooling towers: 1. remove the heat from the condensate 2. should use water treatment 3. prevent thermal pollution of rivers and lakes 4. cannot be used during winter periods 5. remove the sensible heat of the steam in the condenser
- A.
  
  2, 3
- B.
  
  1, 3, 4, 5
- C.
  
  1, 3, 4
- D.
  
  2, 3, 4
Correct Answer
A. 2, 3

Explanation
The correct answer is 2, 3. This is because cooling towers should use water treatment to prevent the buildup of minerals and other impurities in the water. Additionally, cooling towers help prevent thermal pollution of rivers and lakes by removing heat from the condensate before it is released into the environment.

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47.

Dummy pistons: 1. are usually installed on reaction turbines only 2. are used to increase the turbine horsepower 3. are usually installed on the high pressure end of the turbine 4. balance out the thrust on the rotor
- A.
  
  1, 2
- B.
  
  1, 2, 3
- C.
  
  1, 3, 4
- D.
  
  1, 2, 4
Correct Answer
C. 1, 3, 4
48.

Impulse turbines:
- A.
  
  Have a velocity drop through the nozzle
- B.
  
  Have no pressure drop through the moving blades
- C.
  
  Use low pressure steam only
- D.
  
  Are of the single stage design only
Correct Answer
B. Have no pressure drop through the moving blades

Explanation
Impulse turbines have no pressure drop through the moving blades because they operate on the principle of converting the kinetic energy of a high-velocity jet of steam into mechanical energy. The steam passes through a nozzle, which increases its velocity, and then impacts the moving blades of the turbine. The blades are designed to redirect the steam flow, causing a change in momentum and generating rotational motion. Unlike reaction turbines, which have both pressure and velocity drops through the moving blades, impulse turbines rely solely on the velocity of the steam for power generation.

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49.

Impulse turbines: 1. have a velocity increase through the nozzles 2. blades have the angle of inlet the same as the outlet 3. could have more than one set of blades 4. are used for low pressure steam only 5. may not require a thrust bearing
- A.
  
  1, 2, 3, 4
- B.
  
  2, 3
- C.
  
  1, 3, 4, 5
- D.
  
  1, 2, 3, 5
Correct Answer
D. 1, 2, 3, 5

Explanation
Impulse turbines have a velocity increase through the nozzles (statement 1), which is a characteristic of these types of turbines. The blades of impulse turbines have the angle of inlet the same as the outlet (statement 2), ensuring efficient energy transfer. Impulse turbines could have more than one set of blades (statement 3), allowing for increased power output. Additionally, impulse turbines may not require a thrust bearing (statement 5), as the design of the turbine allows for the elimination of axial thrust. Therefore, the correct answer is 1, 2, 3, 5.

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50.

IN GRAVITY SYSTEM, CONDENSATION IS RETURNED ON ISTS OWN FREE WILL AND BOILER WILL BE LOWER THAN ANY OF THE RADIATORS?
- A.
  
  TRUE
- B.
  
  FALSE
Correct Answer
A. TRUE

Explanation
In a gravity system, condensation from the radiators is returned to the boiler on its own without the need for a pump. This is because the condensation is heavier than steam and naturally flows back to the boiler due to gravity. As a result, the water level in the boiler will be lower than any of the radiators. Therefore, the statement "CONDENSATION IS RETURNED ON ITS OWN FREE WILL AND BOILER WILL BE LOWER THAN ANY OF THE RADIATORS" is true.

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Feb 17, 2012

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4th Class Boiler Test 2

In a recovery boiler:

The economizer in the steam cycle of an electricity generating plant is located between the:

The purpose of the absorber in a natural gas plant is to:

During an internal boiler inspection an engineer should check:

Raising or lowering of heavy objects using ropes and cables is known as:

Natural ropes are made of:

Prior to commencing boiler cleaning operations it is necessary to: 1. test the boiler water 2. close steam and water valves 3. tag all valves to indicate shut down 4. complete the boiler-room log book 5. check out the burners.

The boiler boiling out procedure:

The purpose of boiling out a boiler is:

The best type of filter for the removal of fine dust, smoke and fumes is the:

A Runaround air conditioning heat recovery system consists of two finned tube heat exchangers, the preconditioning coil and the recovery coil. Where is the preconditioning coil of this system usually located?

Three common sensing elements used on humidistat are the: 1. Human hair element 3. Wood element 2. hygroscopic element 4. Metal element.

Which of the following is a primary function of a boiler's safety valve?

The expansion valve in a refrigeration system is:

Safety valves on a refrigeration system:

In the vapour compression type of refrigeration system, the liquid refrigerant is changed to a gas in the:

In some installations in order to guarantee a supply of clear hot water and prolong the life of a hot water heater the:

One advantage of the electric probe type of low water fuel cut-off is:

Two element feedwater control:

Steam is prevented from leaking out around the valve stem of a packless radiator valve with the use of:

The purpose of fins on a convector tube is to:

The purpose of a cushion tank is to:

The blow down valve of a steam heating boiler must:

Your boiler is operated with automatic water feeders. If the boiler suddenly requires an increase in water treatment, what should you look for?

A hot water boiler is protected from over pressure by means of:

The low water cut off can be tested by:

In a variable area flow meter the differential pressure:

The Bourdon tube is often shaped in the form of a "C", having an arc span of about:

A commutator would be found in:

The rotating field of an AC alternator is obtained by exciting the windings on the rotor with:

Regarding alternating current systems, starting from zero and rising to a maximum positive or negative value and returning to zero, is known as:

10 metres of wire of uniform cross sectional area has a resistance of 20 ohms. If the length of the wire is increased to 500 metres the resistance will be:

Isolated electrical power lines:

The voltmeter is placed:

The value of the current flow in an electric circuit, where the voltage is 12 volts and the resistance is 3 ohms is:

A basic law of electricity is, unlike charges attract each other and like charges:

The pour point of an oil is:

Causes of anti-friction bearing failures are: 1. improper fitting 3. high operating temperature 2. false brinelling 4. poor quality lubricant

Greases are commonly a mixture of mineral oil and:

A sliding vane pump is termed:

What size of packing should be used to repack a pump gland having an 8.6 cm stuffing box bore and 6.7 cm pump shaft diameter?

Priming a water pump means:

When starting-up a reciprocating pump:

The purpose of a regenerator on a gas turbine is to:

Generally, steam turbine blades are made of:

Cooling towers: 1. remove the heat from the condensate 2. should use water treatment 3. prevent thermal pollution of rivers and lakes 4. cannot be used during winter periods 5. remove the sensible heat of the steam in the condenser

Dummy pistons: 1. are usually installed on reaction turbines only 2. are used to increase the turbine horsepower 3. are usually installed on the high pressure end of the turbine 4. balance out the thrust on the rotor

Impulse turbines:

Impulse turbines: 1. have a velocity increase through the nozzles 2. blades have the angle of inlet the same as the outlet 3. could have more than one set of blades 4. are used for low pressure steam only 5. may not require a thrust bearing

IN GRAVITY SYSTEM, CONDENSATION IS RETURNED ON ISTS OWN FREE WILL AND BOILER WILL BE LOWER THAN ANY OF THE RADIATORS?