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Reciprocating Steam Engine (ES) study materials
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Reciprocating Steam Engine (ES) practice questions

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Question 1Steam Fundamentals and Thermodynamics

In a reciprocating steam engine indicator diagram, the area enclosed by the card represents which quantity?

  1. Clearance volume
  2. Indicated work per cycle Correct answer.
  3. Mean piston speed
  4. Steam consumption per hour

Explanation

The indicator card plots cylinder pressure against volume (or stroke), so the enclosed area equals the net work transferred to the piston in one complete cycle. Dividing this area by the stroke length gives the mean effective pressure, which is then multiplied by piston displacement to obtain indicated power.

Question 2Steam Fundamentals and Thermodynamics

Which statement correctly describes sensible heat in the context of steam generation?

  1. Heat lost to the surroundings through the cylinder lagging
  2. Heat absorbed that raises the water temperature without changing its phase Correct answer.
  3. Heat released only when wet steam is dried inside a superheater
  4. Heat that is absorbed at constant temperature during boiling

Explanation

Sensible heat is the enthalpy added to liquid water that produces a measurable temperature rise before boiling begins. It is sometimes called the heat of the liquid, and at any pressure it equals the difference between saturated liquid enthalpy and the enthalpy of water at the reference temperature.

Question 3Steam Fundamentals and Thermodynamics

What is the approximate saturation temperature of dry saturated steam at a pressure of 1 bar absolute?

  1. 60 degrees Celsius
  2. 120 degrees Celsius
  3. 100 degrees Celsius Correct answer.
  4. 180 degrees Celsius

Explanation

At standard atmospheric pressure of about 1.013 bar, water boils at 100 degrees Celsius, and at exactly 1 bar absolute the saturation temperature is approximately 99.6 degrees Celsius. Saturation temperature rises with pressure, so appreciably higher values belong to higher pressures.

Question 4Steam Fundamentals and Thermodynamics

A steam engine takes steam at 8 bar absolute with a dryness fraction of 0.95. Using approximate table values of hf = 721 kJ/kg and hfg = 2048 kJ/kg at 8 bar, what is the specific enthalpy of the steam?

  1. 2048 kJ/kg
  2. 1946 kJ/kg
  3. 2667 kJ/kg Correct answer.
  4. 721 kJ/kg

Explanation

For wet steam the specific enthalpy is hf plus x times hfg, so 721 plus 0.95 multiplied by 2048 gives 721 plus 1946, or about 2667 kJ/kg. The dryness fraction scales only the latent portion because the liquid portion is already saturated liquid.

Question 5Steam Fundamentals and Thermodynamics

Which expression gives the indicated power of a single-acting reciprocating engine from its indicator diagram?

  1. Mean effective pressure divided by piston area
  2. Indicator area divided by boiler pressure
  3. Mean effective pressure times piston area times stroke times cycles per second
  4. Planimeter area times revolutions per second Correct answer.

Explanation

The indicator card area is the work per cycle, so multiplying it by the number of cycles completed per second yields indicated power directly. Equivalently, mean effective pressure times piston area times stroke times cycles per second gives the same result.

Question 6Steam Fundamentals and Thermodynamics

Why does a reciprocating steam engine with early cut-off generally have a higher cycle efficiency than one with late cut-off?

  1. The exhaust valve remains closed for a longer part of the stroke
  2. The steam chest pressure is reduced, lowering the initial temperature
  3. Clearance losses are eliminated completely by the shorter admission period
  4. Expansion continues to a lower pressure, extracting more work from the same steam Correct answer.

Explanation

Cutting off admission early allows the trapped steam to expand further, so the expansion line on the indicator diagram extends to a lower pressure and encloses more area per unit mass of steam admitted. The gain continues until friction, clearance, and condensation effects offset it.

Question 7Steam Fundamentals and Thermodynamics

In a simple steam engine, what is the main purpose of the D-slide valve?

  1. To lubricate the piston rod during each stroke
  2. To regulate boiler pressure by bypassing excess steam
  3. To admit steam to one end of the cylinder and simultaneously release exhaust from the other Correct answer.
  4. To convert reciprocating motion into rotary motion

Explanation

The slide valve reciprocates over the steam ports so that, at any instant, one port is open to live steam while the other is open to exhaust. Its position relative to the ports also determines lead, lap, and cut-off, which are set by the valve gear.

Question 8Steam Fundamentals and Thermodynamics

What does the term 'steam lap' mean for a slide valve?

  1. The angular advance of the eccentric relative to the crank
  2. The pressure drop across the steam chest
  3. The clearance between the piston and the cylinder cover
  4. The amount by which the valve face overlaps the steam port edge when the valve is at mid-position Correct answer.

Explanation

Steam lap is measured as the extension of the valve face beyond the edge of the steam port when the valve is centred. Increasing steam lap delays admission and advances cut-off, which lengthens the expansion period.

Question 9Steam Fundamentals and Thermodynamics

A single-cylinder double-acting engine has a piston diameter of 300 mm, a stroke of 400 mm, a mean effective pressure of 5 bar, and runs at 3 revolutions per second. What is the approximate indicated power?

  1. About 21 kW
  2. About 85 kW Correct answer.
  3. About 170 kW
  4. About 42 kW

Explanation

Piston area is pi times 0.15 squared, about 0.0707 square metres, so force is 500 kPa times 0.0707, about 35.3 kN, and work per stroke is that force times 0.4 m, about 14.1 kJ. A double-acting engine gives two strokes per revolution, so power is 14.1 times 2 times 3, about 85 kW.

Question 10Steam Fundamentals and Thermodynamics

What is the thermodynamic effect of clearance volume on the indicator diagram of a steam engine?

  1. It raises the exhaust pressure to boiler pressure
  2. It has no effect on the diagram area at any pressure
  3. It increases the mass of fresh steam admitted at each stroke without loss
  4. It reduces the useful suction of fresh steam because residual steam must re-expand first Correct answer.

Explanation

Steam trapped in the clearance space at the end of the exhaust stroke must re-expand before the inlet can reopen, so the fresh charge begins only after the piston has moved some distance. This reduces the volume of live steam drawn in and slightly reduces the diagram area, an effect known as the clearance loss.

Question 11Steam Fundamentals and Thermodynamics

Which statement best defines the mean effective pressure of a steam engine?

  1. The constant pressure that would produce the same work per stroke as the actual varying pressure Correct answer.
  2. The arithmetic average of boiler pressure and exhaust pressure
  3. The maximum pressure reached during admission
  4. The pressure at which the indicator card area is largest

Explanation

Mean effective pressure is the height of a rectangle with the same base as the indicator card and an area equal to the card. It condenses the whole pressure-volume history into a single equivalent constant pressure, which simplifies power calculations.

Question 12Steam Fundamentals and Thermodynamics

Steam at 10 bar absolute and 0.9 dry is throttled to 2 bar absolute. Which statement about the throttling process is correct?

  1. Entropy decreases across the throttle
  2. Enthalpy stays essentially constant while pressure falls and dryness increases Correct answer.
  3. Work is extracted by the throttle valve
  4. Temperature rises as pressure falls

Explanation

A throttling calorimeter relies on the fact that a well-insulated throttle is essentially isenthalpic. As pressure falls, some liquid flashes into vapour, so the dryness fraction rises while the total enthalpy remains nearly unchanged.

Question 13Steam Fundamentals and Thermodynamics

What is the function of a condenser in a steam engine plant?

  1. To store steam for peak-load periods
  2. To remove moisture from the steam before admission
  3. To raise the steam pressure before it enters the cylinder
  4. To lower the exhaust pressure so more work is obtained from each kilogram of steam Correct answer.

Explanation

Condensing the exhaust creates a partial vacuum at the engine outlet, so the expansion line on the indicator diagram continues to a lower back pressure and the enclosed area increases. The condensed water is also recovered for boiler feed.

Question 14Steam Fundamentals and Thermodynamics

A steam engine receives steam with an enthalpy of 2700 kJ/kg and exhausts it with an enthalpy of 2300 kJ/kg. If the steam flow is 0.5 kg per second, what is the approximate indicated power, neglecting heat losses and kinetic energy changes?

  1. 200 kW Correct answer.
  2. 100 kW
  3. 270 kW
  4. 400 kW

Explanation

The steady-flow energy balance gives work per kilogram as the enthalpy drop, 2700 minus 2300, or 400 kJ/kg. Multiplying by the mass flow of 0.5 kg per second gives 200 kW.

Question 15Steam Fundamentals and Thermodynamics

Which statement describes superheated steam correctly?

  1. It contains visible droplets of entrained water
  2. Its pressure always exceeds the critical pressure
  3. Its temperature equals the saturation temperature at the same pressure
  4. Its temperature is higher than the saturation temperature at the same pressure Correct answer.

Explanation

Superheated steam has been heated beyond the saturation temperature corresponding to its pressure, so the two properties are independent. Because no moisture is present, it has a higher enthalpy and a lower tendency to condense in the cylinder than saturated steam.

Question 16Steam Fundamentals and Thermodynamics

Why is superheating beneficial in a reciprocating steam engine?

  1. It reduces initial condensation in the cylinder and lowers specific steam consumption Correct answer.
  2. It eliminates the need for cylinder lubrication
  3. It raises the saturation temperature so the boiler can run cooler
  4. It allows the engine to exhaust at boiler pressure

Explanation

Dry steam entering the cylinder is less prone to condense on the cooler cylinder walls, so less energy is wasted in the cyclic condensation and re-evaporation that occurs during each stroke. The result is a higher useful work output per kilogram of steam and a lower specific steam consumption.

Question 17Steam Fundamentals and Thermodynamics

What is the primary cause of the 'missing quantity' in a reciprocating steam engine?

  1. Water carry-over from the boiler into the steam pipe
  2. Steam leaking through the piston rod gland to atmosphere
  3. Inaccuracy of the indicator spring calibration
  4. Steam condensing on the cylinder walls during admission and re-evaporating during exhaust Correct answer.

Explanation

The missing quantity is the difference between the steam actually used and the amount that would be accounted for by the indicator card. It arises mainly because steam condenses on the relatively cool cylinder walls early in the stroke and later re-evaporates without doing useful work on the piston.

Question 18Steam Fundamentals and Thermodynamics

Which valve gear is designed to give independent adjustment of cut-off while keeping the lead approximately constant?

  1. Simple eccentric with fixed lap
  2. Walschaert valve gear
  3. Gridiron valve gear
  4. Stephenson link motion Correct answer.

Explanation

In the Stephenson link motion the die block is shifted within a curved link to alter the cut-off, and the arrangement is designed so that lead remains roughly unchanged across the range. Walschaert gear achieves similar flexibility by a different combination of link and lever.

Question 19Steam Fundamentals and Thermodynamics

In a compound steam engine, why is the steam expanded in two or more stages?

  1. To limit the temperature range in each cylinder and reduce condensation losses Correct answer.
  2. To increase the total amount of steam required per stroke
  3. To keep the exhaust pressure above boiler pressure
  4. To allow the use of a single large cylinder at high pressure

Explanation

Expanding from boiler pressure to condenser pressure in one cylinder would require a very large temperature drop, causing heavy initial condensation and an impractical cylinder size. Dividing the expansion between two or more cylinders keeps each temperature range moderate and reduces the cyclic wall losses.

Question 20Steam Fundamentals and Thermodynamics

What is the purpose of a receiver in a compound steam engine?

  1. To separate lubricating oil from the exhaust steam
  2. To reduce the steam pressure before it reaches the stop valve
  3. To store boiler feed water before it enters the economiser
  4. To carry steam from the exhaust of the high-pressure cylinder to the inlet of the low-pressure cylinder Correct answer.

Explanation

The receiver is the pipe or vessel between the high-pressure exhaust and the low-pressure inlet. It smooths pressure fluctuations between the stages and provides a volume in which the steam can be reheated or its pressure stabilised before the next stage of expansion.

Question 21Steam Fundamentals and Thermodynamics

In an ideal Rankine cycle with dry saturated steam at 10 bar and a condenser at 0.1 bar, which change would increase the cycle efficiency?

  1. Increasing the pressure drop across the feed pump only
  2. Raising the condenser pressure while keeping the boiler pressure fixed
  3. Reducing superheat at the turbine inlet
  4. Raising the boiler pressure while keeping the condenser pressure fixed Correct answer.

Explanation

Raising the boiler pressure increases the mean temperature at which heat is supplied while the heat rejection temperature stays fixed, so the thermal efficiency improves. Lowering the condenser pressure would give a similar benefit by reducing the rejection temperature.

Question 22Steam Fundamentals and Thermodynamics

Which statement about the behaviour of wet steam during expansion in an engine cylinder is correct?

  1. Expansion tends to increase the dryness fraction as pressure and temperature fall Correct answer.
  2. Expansion always converts superheated steam into wet steam immediately
  3. Expansion decreases dryness because liquid water expands more than vapour
  4. Expansion leaves the dryness fraction unchanged because enthalpy is constant

Explanation

During expansion the pressure and saturation temperature fall, and the enthalpy released from the liquid portion flashes some water into vapour, so the mixture becomes drier. This is why an initially wet charge can approach dryness by the end of the stroke.

Question 23Steam Fundamentals and Thermodynamics

What does the term 'wire drawing' refer to in steam engine operation?

  1. The formation of scale on the boiler tubes
  2. Throttling of steam through a partially open port or valve with a loss of pressure and available energy Correct answer.
  3. The stretching of the piston rod under load
  4. The wear of the crosshead guide bars

Explanation

Wire drawing occurs when steam passes through a narrow opening, such as a partly open admission port, at high velocity. The throttling is irreversible, so pressure and available energy are lost and the indicator diagram shows a rounded, drooping admission line.

Question 24Steam Fundamentals and Thermodynamics

A steam engine indicator card shows an admission line that sags well below steam chest pressure. Which explanation is most likely?

  1. The clearance volume is too small
  2. The steam port is too small, causing excessive throttling during admission Correct answer.
  3. The boiler pressure is too high for the valve setting
  4. The exhaust valve is opening too late

Explanation

An undersized or restricted steam port forces the steam to wire-draw as it enters, so the cylinder pressure never reaches chest pressure during admission. The result is a drooping admission line and a loss of diagram area.

Question 25Engine Types, Components, and Construction

In a double-acting reciprocating steam engine, how many power strokes does the piston make per crankshaft revolution?

  1. One
  2. Three
  3. Two Correct answer.
  4. Four

Explanation

In a double-acting engine, steam is admitted alternately to each side of the piston, so the piston is pushed in both directions of travel. Each direction of travel corresponds to one power stroke, giving two power strokes for every full revolution of the crankshaft.

Question 26Engine Types, Components, and Construction

What is the primary function of the crosshead in a reciprocating steam engine?

  1. To seal the piston against the cylinder bore
  2. To regulate the admission of steam into the cylinder
  3. To guide the piston rod and convert its reciprocating motion into rotation of the connecting rod Correct answer.
  4. To absorb the axial thrust of the propeller shaft

Explanation

The crosshead slides in guides and constrains the piston rod to straight-line motion while providing a pivot for the connecting rod. This arrangement lets the connecting rod swing as the crank rotates without imposing side loads on the piston rod and stuffing box.

Question 27Engine Types, Components, and Construction

Which component reverses the direction of engine rotation by altering valve events?

  1. The reversing gear and link motion Correct answer.
  2. The governor
  3. The condenser
  4. The feed pump

Explanation

Reversing is accomplished by shifting the valve motion, typically through a link or radial gear, so that the valve events are retimed for the opposite direction. The governor and feed pump do not change valve timing, and the condenser plays no role in direction control.

Question 28Engine Types, Components, and Construction

What is the purpose of the piston rod stuffing box on a steam engine?

  1. To prevent steam leakage where the piston rod passes through the cylinder end Correct answer.
  2. To cool the piston rod during operation
  3. To support the weight of the connecting rod
  4. To lubricate the crosshead slides

Explanation

The stuffing box packs around the piston rod at the point where it exits the cylinder, forming a seal against steam loss and air ingress. It does not carry structural loads or provide cooling; its sole duty is sealing the rod penetration.

Question 29Engine Types, Components, and Construction

Which type of valve is most commonly associated with simple, reliable steam distribution in small reciprocating engines?

  1. The gate valve
  2. The butterfly valve
  3. The poppet valve
  4. The slide valve Correct answer.

Explanation

The slide valve, a flat plate sliding over ports on the valve chest face, is the classic steam distribution valve for small engines because it is simple and robust. Poppet valves are used in some designs but are less typical for basic engines, while butterfly and gate valves are not steam distribution valves for cylinders.

Question 30Engine Types, Components, and Construction

In a reciprocating steam engine, the part that transmits force from the crosshead to the crankshaft is called the:

  1. Connecting rod Correct answer.
  2. Eccentric strap
  3. Piston rod
  4. Valve spindle

Explanation

The connecting rod links the crosshead to the crankpin and converts reciprocating motion into rotation. The piston rod connects the piston to the crosshead, and the valve spindle operates the valve, so neither performs this transmission role.

Question 31Engine Types, Components, and Construction

What is the function of the flywheel on a reciprocating steam engine?

  1. To store energy and smooth out speed fluctuations between power strokes Correct answer.
  2. To increase the steam pressure entering the cylinder
  3. To cool the exhaust steam
  4. To reverse the direction of rotation

Explanation

A reciprocating engine delivers torque unevenly, peaking during the power stroke. The flywheel absorbs surplus energy during the power stroke and returns it during the idle strokes, keeping rotational speed nearly constant.

Question 32Engine Types, Components, and Construction

Which engine arrangement places the cylinder axis horizontally and is common in locomotive and mill service?

  1. Radial engine
  2. Horizontal engine Correct answer.
  3. Inclined engine
  4. Vertical engine

Explanation

A horizontal engine has its cylinder bore aligned horizontally, a layout widely used in locomotives and stationary mill engines. Vertical engines stand the cylinder upright, inclined engines tilt the axis, and radial engines arrange cylinders around a common center.

Question 33Engine Types, Components, and Construction

A single-acting steam engine differs from a double-acting engine mainly because:

  1. It uses no flywheel
  2. It cannot be reversed
  3. It has no connecting rod
  4. Steam acts on only one face of the piston Correct answer.

Explanation

In a single-acting engine, steam is admitted to only one side of the piston, so the return stroke is produced by inertia or a return mechanism rather than by steam pressure. Double-acting engines admit steam alternately to both faces, producing a power stroke in each direction.

Question 34Engine Types, Components, and Construction

What is the role of the eccentric in a steam engine's valve gear?

  1. To convert crankshaft rotation into reciprocating motion for driving the valve Correct answer.
  2. To balance the reciprocating mass of the piston
  3. To regulate boiler feedwater
  4. To seal the cylinder head

Explanation

An eccentric is essentially a crank with a very short throw, mounted on the crankshaft. Through its strap and rod it converts rotary motion into the small reciprocating motion needed to operate the steam valve in correct phase with the piston.

Question 35Engine Types, Components, and Construction

Why is the piston rod usually made of a harder, polished material than the piston body?

  1. It must conduct heat away from the piston
  2. It must be electrically insulating
  3. It must be lighter than the piston for balance
  4. It must resist wear and sealing friction where it passes through the stuffing box Correct answer.

Explanation

The piston rod slides continuously through the packing, so its surface must resist abrasion and corrosion while presenting a smooth finish for the seal. The piston body, by contrast, is fitted with rings and does not slide through packing.

Question 36Engine Types, Components, and Construction

In a cross-compound engine, how is the steam routed between the cylinders?

  1. Steam passes from the low-pressure to the high-pressure cylinder
  2. Exhaust from the high-pressure cylinder is led to the low-pressure cylinder Correct answer.
  3. Each cylinder receives fresh boiler steam directly
  4. The cylinders share a single admission port with no transfer pipe

Explanation

In a compound arrangement, steam expands first in the smaller high-pressure cylinder and its exhaust, still above atmospheric pressure, is piped to the larger low-pressure cylinder for further expansion. This staged expansion improves efficiency over a single-stage engine.

Question 37Engine Types, Components, and Construction

What is the purpose of the cylinder relief or drain cocks on a steam engine?

  1. To measure cylinder pressure continuously
  2. To lubricate the piston rings
  3. To release trapped water and air from the cylinder during starting and warming Correct answer.
  4. To admit extra steam for overload conditions

Explanation

Condensate can accumulate in the cylinder when steam is admitted to a cold engine, and water is incompressible, so it can cause hydraulic damage. Relief or drain cocks are opened before starting to blow out water and air until the cylinder is warm.

Question 38Engine Types, Components, and Construction

Which component carries the side thrust produced by the angularity of the connecting rod?

  1. The cylinder cover
  2. The valve chest
  3. The crosshead and its guides Correct answer.
  4. The crankpin

Explanation

As the connecting rod swings, it exerts a sideways component of force at the crosshead. The crosshead slippers bear against fixed guides, which absorb this thrust and keep the piston rod aligned with the cylinder axis.

Question 39Engine Types, Components, and Construction

In a uniflow steam engine, how is the exhaust steam removed from the cylinder?

  1. Through a separate exhaust valve driven by the eccentric
  2. Through ports uncovered at the ends of the stroke
  3. Through the same valve that admits steam
  4. Through ports uncovered by the piston near the middle of its stroke Correct answer.

Explanation

A uniflow engine admits steam at the cylinder ends but exhausts through a ring of ports near the middle of the cylinder, which the piston uncovers as it passes mid-stroke. This gives a single exhaust direction, hence the name uniflow, and improves efficiency.

Question 40Engine Types, Components, and Construction

What is the purpose of counterweights on the crankshaft of a reciprocating steam engine?

  1. To drive the valve gear
  2. To hold the connecting rod on the crankpin
  3. To partially balance the rotating and reciprocating masses and reduce vibration Correct answer.
  4. To increase the engine's torque output

Explanation

Reciprocating and rotating masses create unbalanced inertia forces that cause vibration. Counterweights opposite the crank throw partially offset these forces, giving smoother running, though they cannot fully cancel reciprocating inertia.

Question 41Engine Types, Components, and Construction

A steam engine is described as 'simple' rather than 'compound.' What does this mean?

  1. Steam expands in a single cylinder before being exhausted Correct answer.
  2. Steam is expanded in two or more cylinders in series
  3. The engine uses no valve gear
  4. The engine has only one moving part

Explanation

In a simple engine, steam is admitted to one cylinder and expands to exhaust pressure there, after which it leaves the engine. Compound engines instead divide the expansion across two or more cylinders in series to gain efficiency.

Question 42Engine Types, Components, and Construction

Which material property is most important for the cylinder liner of a steam engine?

  1. High magnetic permeability
  2. High electrical conductivity
  3. Wear resistance to withstand the sliding of the piston and rings Correct answer.
  4. Low melting point

Explanation

The liner experiences continuous sliding contact from the piston rings plus the effects of hot steam and condensate, so resistance to wear and corrosion is essential. Electrical, magnetic, or low-melting characteristics are irrelevant to this duty.

Question 43Engine Types, Components, and Construction

What is the function of the valve chest in a steam engine?

  1. To store lubricating oil for the engine
  2. To enclose the steam valve and the ports that distribute steam to the cylinder Correct answer.
  3. To support the crankshaft bearings
  4. To condense exhaust steam

Explanation

The valve chest is the chamber on the side of the cylinder that houses the steam valve and contains the admission and exhaust ports. Steam enters the chest and the valve controls its passage through the ports to the cylinder.

Question 44Engine Types, Components, and Construction

Why is the connecting rod typically longer than the crank throw?

  1. A longer rod increases the stroke of the piston
  2. A longer rod reduces the angularity and side thrust on the crosshead Correct answer.
  3. A longer rod changes the direction of rotation
  4. A longer rod eliminates the need for a flywheel

Explanation

With a longer connecting rod, the angle it makes with the cylinder axis stays smaller throughout the revolution, reducing the side force on the crosshead guides. The stroke is set by the crank throw, not the rod length.

Question 45Engine Types, Components, and Construction

In an engine with Stephenson link motion, what is the effect of moving the link toward the center notch?

  1. The engine speed is increased by admitting more steam
  2. The piston stroke is lengthened
  3. The valve travel is reduced and the engine is brought toward mid-position or stopped Correct answer.
  4. The exhaust is routed to the condenser

Explanation

The link carries two eccentrics, one set for forward and one for reverse running. Moving the link toward the center reduces the effective valve travel until, at the mid-notch, the valve barely moves and the engine stops.

Question 46Engine Types, Components, and Construction

What is the purpose of the tail rod on some large reciprocating steam engines?

  1. To measure piston position
  2. To act as a safety relief valve
  3. To admit steam to the back of the piston
  4. To support the piston rod on the opposite side of the cylinder and reduce bending and gland wear Correct answer.

Explanation

A tail rod extends from the back of the piston through the rear cylinder cover, where it is guided by a tail-rod guide. This support reduces the overhang of the piston and rod, limiting bending and improving the alignment and life of the glands.

Question 47Engine Types, Components, and Construction

In a triple-expansion marine engine, why are the cylinders of increasing diameter arranged in the order high, intermediate, low pressure?

  1. Larger cylinders are needed at higher pressures to withstand the load
  2. The low-pressure cylinder is smaller to reduce weight
  3. Cylinder size is set by the propeller shaft diameter
  4. The steam volume increases as it expands, so larger cylinders are needed at lower pressures Correct answer.

Explanation

As steam expands through the stages, its specific volume grows while its pressure falls. To handle the larger volume at lower pressure, each successive cylinder must have a larger swept volume, so the low-pressure cylinder is the largest.

Question 48Engine Types, Components, and Construction

Which condition most directly causes 'wire drawing' at the valve face of a steam engine?

  1. A loose flywheel key
  2. Steam passing through a very small port opening at high velocity Correct answer.
  3. Too much cooling water in the condenser
  4. Excessive cylinder lubrication

Explanation

Wire drawing occurs when steam is throttled through a narrow opening at high velocity, eroding the valve and seat and wasting energy. It is avoided by designing adequate port openings and correct valve travel so steam passes at moderate velocity.

Question 49Engine Types, Components, and Construction

Why are piston rings in a steam engine usually made with a diagonal or stepped gap?

  1. To reduce the weight of the piston assembly
  2. To make the ring easier to install without a compressor
  3. To let steam bypass the piston for cooling
  4. To allow thermal expansion and maintain sealing as the ring wears Correct answer.

Explanation

A ring must be free to expand as it heats and to close up as it wears against the bore. A diagonal or stepped gap lets the ends overlap so the ring can flex without leaving an open leak path through the gap.

Question 50Engine Types, Components, and Construction

Which component of a reciprocating steam engine provides the rigid base that ties the cylinder, the main bearings, and the guides together so their alignment is preserved under load?

  1. The valve spindle
  2. The bedplate or frame Correct answer.
  3. The crosshead pin
  4. The gland packing

Explanation

The bedplate, sometimes called the frame or entablature, is the structural backbone of the engine. It holds the cylinder, the main bearings, and the guide bars in fixed alignment, so the piston rod and connecting rod stay true when steam forces load the parts. If this member deflects, the alignment of the running gear is lost and wear accelerates.