SOPEEC 4th Class Power Engineer Exam Part 4B

What is the primary function of a lubricant in a mechanical system?

• ATo prevent any mechanical movement between parts
• BTo reduce friction and wear between moving surfaces
• CTo increase the operating temperature of the equipment
• DTo act as a catalyst for chemical reactions

Which property refers to a fluid's internal resistance to flow at a specific temperature?

• AViscosity
• BPour point
• CFlash point
• DSpecific gravity

What does a high Viscosity Index (VI) indicate about a lubricating oil?

• AThe oil's viscosity changes significantly with temperature changes.
• BThe oil has a very high flash point and is highly resistant to ignition.
• CThe oil's viscosity changes relatively little with temperature changes.
• DThe oil contains a high concentration of sodium soap thickeners.

The lowest temperature at which a lubricating oil will flow or pour is known as the:

• ACloud point
• BPour point
• CFreezing point
• DFlash point

Which of the following is classified as a solid lubricant?

• ASilicon oil
• BGraphite
• CLard oil
• DSodium soap grease

What type of lubrication occurs when the moving surfaces are separated by a continuous, complete film of liquid lubricant?

• ABoundary lubrication
• BSolid lubrication
• CHydrodynamic (fluid film) lubrication
• DExtreme pressure lubrication

What is the main function of babbitt metal when used as a lining for journal bearings?

• ATo increase the friction coefficient of the bearing
• BTo provide a soft, conformable surface that embeds wear particles
• CTo prevent the bearing from absorbing lubricating oil
• DTo withstand temperatures exceeding 800 degrees Celsius

Which bearing type is specifically designed to handle loads that act along the axis of a rotating shaft?

• AJournal bearing
• BRadial bearing
• CThrust bearing
• DSleeve bearing

What is the purpose of oil grooves in a plain sleeve or journal bearing?

• ATo reduce the overall weight of the bearing shell
• BTo facilitate the escape of wear particles from the bearing assembly
• CTo distribute lubricating oil evenly across the load-bearing area
• DTo increase the running clearance of the shaft

A Kingsbury thrust bearing utilizes pivoting shoes to support axial loads. How does it maintain a lubricating oil film?

• ABy using high-pressure external oil pumps to inject oil directly under the shoes
• BBy allowing the pivoting shoes to tilt slightly and create a wedge-shaped oil film
• CBy operating completely dry with self-lubricating Teflon coatings
• DBy trapping a static pool of oil between the shoes that does not circulate

Which of the following is classified as a rolling contact (antifriction) bearing?

• ASleeve bearing
• BTapered roller bearing
• CBabbitt journal bearing
• DKingsbury thrust bearing

Which type of rolling contact bearing is best suited to handle combined heavy radial and heavy axial (thrust) loads?

• AStandard cylindrical roller bearing
• BTapered roller bearing
• CNeedle roller bearing
• DLight-duty ball bearing

What is the primary cause of 'spalling' in rolling element bearings?

• AUsing a lubricant with a viscosity that is too high
• BMetal fatigue resulting in flaking off of the race or rolling element surfaces
• COperating the bearing at speeds below its minimum design speed
• DMinor shaft misalignment that is corrected by babbitt compression

Grease is defined as a semi-solid lubricant consisting of a liquid lubricant and a:

• AThickener (usually soap-based)
• BHigh-pressure volatile solvent
• CSolid abrasive compound
• DGaseous suspension agent

Which type of grease thickener is highly resistant to water washout and is suitable for moist environments?

• ASodium-based grease
• BCalcium-based (lime) grease
• CGraphite-based grease
• DSulfur-based grease

What is the purpose of the 'dropping point' specification of a grease?

• AThe temperature at which the grease begins to separate into soap and liquid oil
• BThe density of the grease compared to water
• CThe maximum height from which the grease can be dropped without splashing
• DThe minimum speed at which the grease begins to flow under gravity

In a force-feed lubrication system, what device is used to clean the lubricating oil continuously by spinning it to separate water and solids?

• AA coalescer filter
• BAn oil centrifuge
• CA magnetic strainer
• DA plate-and-frame heat exchanger

What is the typical consequence of over-lubricating a high-speed rolling element bearing with grease?

• AThe bearing will run cooler due to the excess lubricant.
• BChurning of the grease will occur, leading to high operating temperatures and seal damage.
• CThe bearing will seize instantly due to lack of clearance.
• DThe grease will immediately turn into a solid block of soap.

What type of seal consists of a series of ridges and chambers that create a tortuous path to prevent lubricant leakage and restrict entry of dirt?

• ALip seal
• BLabyrinth seal
• CMechanical seal
• DO-ring seal

In a ring-oiled journal bearing, how does the oil ring deliver oil to the top of the rotating shaft?

• AThe ring is keyed to the shaft and rotates at high speed, throwing oil upward.
• BThe ring is larger in diameter than the shaft and hangs loosely on it, rotating slowly to…
• CThe ring acts as a piston pump to force oil through small capillary channels.
• DThe ring is stationary and uses surface tension to draw oil up from the reservoir.

What is the function of a wear ring in a centrifugal pump?

• ATo increase the friction between the impeller and casing to prevent slip
• BTo provide a replaceable seal that minimizes recirculation of liquid from the discharge t…
• CTo hold the pump packing firmly in the stuffing box
• DTo support the pump shaft and absorb radial thrust loads

What is the purpose of a lantern ring (seal cage) in the stuffing box of a centrifugal pump?

• ATo prevent the shaft sleeve from sliding axially
• BTo distribute sealing liquid or cooling water to the packing to prevent air leakage and c…
• CTo lock the packing gland bolts in place
• DTo balance the axial thrust of a multi-stage impeller

What must be done before starting a centrifugal pump that is located above the liquid supply level?

• AThe discharge valve must be fully opened to reduce startup head.
• BThe pump casing and suction line must be primed with liquid and air vented.
• CThe packing gland must be tightened until no liquid can drip out.
• DThe pump must be run dry for 5 minutes to warm up the bearings.

What is the primary cause of cavitation in a centrifugal pump?

• AThe pump is running at a speed below its design threshold.
• BThe liquid pressure drops below its vapor pressure at the pump inlet, forming vapor bubbl…
• CThe packing gland is adjusted too loosely, allowing air to enter.
• DThe discharge valve is closed while the pump is running.

Which type of pump is classified as a rotary positive displacement pump?

• ACentrifugal pump
• BGear pump
• CPiston pump
• DTurbine pump

Why must a positive displacement pump (such as a gear or piston pump) always have a pressure relief valve installed on its discharge line?

• ATo prevent the pump from losing its prime when stopped
• BTo prevent excessive pressure buildup and mechanical damage if the discharge line is bloc…
• CTo regulate the flow rate by bypassing excess fluid back to the suction line
• DTo separate air from the liquid before it reaches the system

What is 'pump slip' in positive displacement pumps?

• AThe physical slipping of the drive belt on the pump pulley
• BThe leakage of fluid backward from the high-pressure discharge side to the low-pressure s…
• CThe failure of the pump coupling to engage with the shaft
• DThe cavitation effect caused by air bubbles in the impeller

What is the main advantage of a double-acting reciprocating pump compared to a single-acting one?

• AIt requires no suction valves.
• BIt discharges liquid on both the forward and backward strokes, providing a steadier flow.
• CIt can run at double the speed without cavitation.
• DIt uses centrifugal force to prime itself.

What type of compressor compresses air using two intermeshing helical rotors?

• AReciprocating compressor
• BRotary lobe compressor
• CRotary screw compressor
• DCentrifugal compressor

In a multi-stage air compressor, what is the primary purpose of an intercooler?

• ATo heat the air between stages to prevent condensation
• BTo cool the air between stages to reduce the power required for compression and increase…
• CTo lubricate the second stage cylinder walls
• DTo dry the compressed air completely before it enters the receiver

What is the function of an air compressor receiver (air tank)?

• ATo increase the pressure of the air after it leaves the compressor
• BTo store compressed air, dampen pressure pulsations, and allow moisture to settle out
• CTo vaporize water so that it flows easily to tools
• DTo separate oil from the compressor coolant loop

What device is used to unload an air compressor during startup?

• AAn unloader
• BA safety valve
• CA check valve
• DA governor

What is the purpose of an aftercooler in an air compressor system?

• ATo cool the compressed air immediately after discharge, condensing oil and water vapor fo…
• BTo heat the air before it enters pneumatic tools
• CTo cool the compressor crankcase oil
• DTo prevent the safety valve from opening

If an air compressor runs continuously but the system pressure fails to rise, what is the most likely cause?

• AThe receiver drain valve is closed.
• BThe compressor valves are leaking or the unloading mechanism is stuck in the unloaded pos…
• CThe intercooler cooling water flow is too high.
• DThe safety valve has its setting adjusted too high.

Why is it necessary to regularly drain the condensate from an air receiver?

• ATo prevent water from filling the tank and reducing air storage volume, and to prevent in…
• BTo ensure the air remains moist for tools
• CTo keep the air pressure from dropping too low
• DTo prevent the compressor from running at constant speed

A centrifugal pump is vibrating excessively and making a metallic rattling noise. The suction pressure is normal, but discharge flow is fluctuating. What is the most likely cause?

• AThe discharge check valve is stuck open.
• BThe pump is misaligned or has a damaged bearing/impeller.
• CThe packing gland is dripping too much water.
• DThe motor is running backward.

What is the main operating difference between dynamic compressors and positive displacement compressors?

• ADynamic compressors trap a specific volume of air, whereas positive displacement compress…
• BPositive displacement compressors trap a volume of air and reduce its physical volume, wh…
• CDynamic compressors are only used for liquids, while positive displacement compressors ar…
• DPositive displacement compressors cannot handle air temperatures above 0 degrees Celsius.

What is the function of the pump casing in a volute-type centrifugal pump?

• ATo increase the speed of the liquid leaving the impeller
• BTo house the drive motor and its electrical windings
• CTo collect the liquid discharged from the impeller and convert its velocity energy into p…
• DTo act as a secondary filter for large solids

Which type of compressor control is most economical when air demand is highly intermittent and the compressor can be stopped frequently?

• AConstant-speed control
• BStart-stop control
• CModulating inlet valve control
• DVariable displacement pocket control

What hazard is associated with using carbon-based lubricating oil in an air compressor cylinder?

• AThe oil will dissolve the metal cylinder walls.
• BOil carryover can form carbon deposits in the discharge piping and receiver, which can ig…
• CThe oil will prevent the air from being compressed.
• DThe oil will freeze at standard operating temperatures.

In an impulse steam turbine, where does the expansion of steam and drop in pressure occur?

• AOnly in the stationary nozzles
• BOnly in the moving blades
• CEqually in both the stationary nozzles and the moving blades
• DIn the exhaust piping only

How does a reaction steam turbine differ from an impulse steam turbine regarding steam expansion?

• AA reaction turbine does not use stationary nozzles or blades.
• BA reaction turbine experiences steam expansion and pressure drop in both the stationary b…
• CA reaction turbine operates only on wet steam.
• DA reaction turbine does not require a shaft seal.

What is the purpose of carbon rings used as shaft seals on small steam turbines?

• ATo lubricate the shaft bearings
• BTo prevent steam from leaking out of the turbine casing along the shaft, or air from leak…
• CTo absorb axial thrust loads from the turbine rotor
• DTo balance the rotor dynamically at high speeds

At what speed does a steam turbine's emergency overspeed trip typically activate?

• A5% below rated operating speed
• B10% to 15% above rated operating speed
• C50% above rated operating speed
• DExactly at double the critical speed

What is 'critical speed' in relation to a steam turbine rotor?

• AThe maximum speed the turbine can achieve before the blades fly off
• BThe rotational speed at which natural vibration frequency matches rotor rotation, causing…
• CThe minimum speed required to establish a hydrodynamic oil film in the bearings
• DThe speed at which steam flow changes from laminar to turbulent inside the casing

During the startup of a steam turbine, why must the steam casing and piping be thoroughly warmed up and drained of condensate?

• ATo prevent water hammer and thermal shock/uneven expansion of the casing and rotor
• BTo ensure the steam pressure is reduced before entering the blades
• CTo allow the carbon rings to expand and lock onto the shaft
• DTo prevent the governor from operating too quickly

What is the function of a sentinel valve on a steam turbine casing?

• ATo shut off steam flow automatically when speed is exceeded
• BTo act as a warning alarm by releasing steam to the atmosphere if casing exhaust pressure…
• CTo regulate steam flow during fluctuating loads
• DTo drain condensate from the casing automatically