Pumps and Compressors Quiz
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Questions and Answers

What is the main characteristic of a centrifugal pump?

  • It operates at low volumes.
  • It can only be used in the engine room.
  • It requires a complex mechanical design.
  • It is typically used for high volume discharges. (correct)

Which type of air compressor is classified as a positive displacement pump?

  • Reciprocating compressor (correct)
  • Diffuser compressor
  • Centrifugal compressor
  • Rotary compressor

What is the typical storage pressure for the air receiver for engine starting purposes?

  • 20 – 25 bar
  • 30 – 40 bar (correct)
  • 50 – 60 bar
  • 10 – 15 bar

Why is 30 bar used for engine start instead of a lower pressure?

<p>It reduces the size of the air receivers needed. (D)</p> Signup and view all the answers

Which pump is not a type of positive displacement pump?

<p>Centrifugal pump (C)</p> Signup and view all the answers

What kind of isolation valves may be fitted to the General Service pump?

<p>For fault finding (B)</p> Signup and view all the answers

Which pressure is typically reduced to supply various working pressures in a system?

<p>Storage pressure (D)</p> Signup and view all the answers

Which of the following pumps is not listed as a type of generic positive displacement pump?

<p>Centrifugal pump (A)</p> Signup and view all the answers

What is the primary function of a pump?

<p>To draw in fluid and increase its kinetic energy (A)</p> Signup and view all the answers

What are the two basic categories of pumps?

<p>Dynamic and Positive Displacement (A)</p> Signup and view all the answers

Which statement is true about dynamic pumps?

<p>They use centrifugal force to accelerate fluid. (D)</p> Signup and view all the answers

What mechanism is often required for dynamic pumps to function properly?

<p>A positive suction head or a priming mechanism (D)</p> Signup and view all the answers

What type of energy is primarily converted in dynamic pumps?

<p>Kinetic energy to potential energy (D)</p> Signup and view all the answers

Which component typically forms the rotor in axial flow pumps?

<p>A multi-bladed propeller (B)</p> Signup and view all the answers

What generally characterizes the flow rates and pressures of dynamic pumps?

<p>High flow rates with relatively low pressures (D)</p> Signup and view all the answers

Which of the following statements about the relationship between flow and pressure in pumps is correct?

<p>Higher pressure generally results from reduced flow rates. (D)</p> Signup and view all the answers

What is the primary characteristic of axial flow pumps?

<p>They are best suited for low pressure and high volumetric throughput. (A)</p> Signup and view all the answers

Which of the following describes a centrifugal pump with a volute type?

<p>It features a diverging nozzle that acts as a diffuser. (A)</p> Signup and view all the answers

What occurs when the impeller of a centrifugal pump rotates?

<p>Liquid is forced outwards to the discharge based on centrifugal effect. (B)</p> Signup and view all the answers

What is the effect of having the discharge valve closed when starting a centrifugal pump?

<p>It minimizes the motor starting current. (B)</p> Signup and view all the answers

In the context of centrifugal pumps, what role does the moving liquid have when it comes to suction?

<p>It helps create a lower pressure at the center of the pump. (A)</p> Signup and view all the answers

What happens if a centrifugal pump contains no liquid initially?

<p>It behaves as if an essential part is missing. (D)</p> Signup and view all the answers

How does the ratio between velocity, pressure, and volume in a centrifugal pump get determined?

<p>It depends on the size of the impeller and configuration of the volute casing. (C)</p> Signup and view all the answers

Which type of casings do centrifugal pumps commonly utilize?

<p>Volute casings and diffuser casings, either separately or in combination. (D)</p> Signup and view all the answers

What areas should be thoroughly checked for corrosion during routine inspections?

<p>High-pressure outlet pipes (B), Cooler areas subjected to blowers (C)</p> Signup and view all the answers

What does the term 'relative humidity' refer to in the context of air?

<p>The amount of water vapour present in the air (C)</p> Signup and view all the answers

What can be a consequence of allowing free moisture to remain in a compressed air system?

<p>Corrosion of components (D)</p> Signup and view all the answers

How does increasing the pressure of a specific volume of air affect its volume, according to Boyle's law?

<p>The volume decreases (A)</p> Signup and view all the answers

What should be regularly checked around the high-pressure outlet pipes?

<p>Corrosion signs (A)</p> Signup and view all the answers

What role do filters play in a compressed air system?

<p>They remove dirt and particles (A)</p> Signup and view all the answers

What happens to water vapour when high-pressure saturated air's temperature is dropped?

<p>It condenses into water (A)</p> Signup and view all the answers

What is a common solution to remove water vapor in a compressed air system?

<p>Using a refrigerated dryer system (D)</p> Signup and view all the answers

What is the purpose of a relief valve in a compressor system?

<p>To protect against overpressure due to valve seizure or blockage (C)</p> Signup and view all the answers

What alternative may be used in smaller compressors instead of relief valves?

<p>Bursting disks (D)</p> Signup and view all the answers

What device may be fitted to indicate overheating in a compressor?

<p>An alarm device at 121°C (A)</p> Signup and view all the answers

Where should relief valves be fitted in a compressor system?

<p>After each stage of the compressor (B)</p> Signup and view all the answers

What happens if the fusible plug melts in a compressor?

<p>It releases pressure to prevent overheating (D)</p> Signup and view all the answers

What is the key function of clearance volume in a compressor?

<p>To indicate the amount of air left after compression (C)</p> Signup and view all the answers

How should relief valves be tested?

<p>By an authorized service agent with calibrated equipment (A)</p> Signup and view all the answers

What is the primary purpose of the pressure relief valve in the water jacket of water cooled air compressors?

<p>To protect against high delivery air pressure in case of a cooling pipe burst (A)</p> Signup and view all the answers

What is the main function of a variable delivery pump in a hydraulic system?

<p>To control direction, speed, and load of cylinders (D)</p> Signup and view all the answers

What prevents fluid from flowing back into the header tank during high-pressure conditions?

<p>Non-return valves (D)</p> Signup and view all the answers

In pneumatic systems, how is waste air typically handled?

<p>Vent to the atmosphere (B)</p> Signup and view all the answers

What is the role of the 5/2 valve in a pneumatic cylinder operation?

<p>To maintain pressure on the cylinder when 3/2 valves are released (C)</p> Signup and view all the answers

What is a primary disadvantage of direct pneumatic/hydraulic logic control over long distances?

<p>It can lead to inefficiencies (B)</p> Signup and view all the answers

What is the initial requirement to achieve electrical control in pneumatic/hydraulic systems?

<p>Sense the condition of the process (C)</p> Signup and view all the answers

What does an air flow control valve enable in a pneumatic cylinder?

<p>Controls the speed of the cylinder (B)</p> Signup and view all the answers

What is one benefit of using electrical control in pneumatic/hydraulic systems?

<p>Reduction in required components (B)</p> Signup and view all the answers

Flashcards

What is a pump?

A machine drawing in fluid and increasing its kinetic energy, creating pressure for flow.

What is a dynamic pump?

A pump type utilizing centrifugal force to accelerate fluid radially or axially, converting kinetic energy to pressure.

What is a positive displacement pump?

A pump type where a moving component directly displaces the fluid, creating pressure.

What is pump head?

The difference in pressure between the suction and discharge sides of a pump.

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What is an axial flow pump?

A pump type that utilizes a multi-bladed propeller to accelerate fluid axially.

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What is cavitation in a pump?

When a pump is unable to draw fluid from its suction side due to insufficient pressure.

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What is a single-stage pump?

A pump operating with a single impeller stage, usually for lower pressure applications.

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What is a multistage pump?

A pump with multiple impeller stages connected in series, achieving higher pressure output.

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Centrifugal Pump

A pump specifically designed to handle large volumes of liquid, commonly chosen for bilge pumps due to their efficient handling of water.

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Piston Pump

A type of positive displacement pump where a reciprocating piston or plunger moves within a cylinder to displace the fluid.

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Screw Pump

A pump that uses a rotating screw to transport fluid, known for its high flow rates and ability to handle viscous materials.

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Diaphragm Pump

A pump that uses a flexible diaphragm to move fluid, often used for delicate liquids or in applications where pulsation is undesirable.

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Reciprocating Compressor

A type of air compressor utilizing a reciprocating piston to compress air, known for its versatility and relative simplicity.

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Rotary Compressor

A type of air compressor using rotating elements to compress air, known for its smooth operation and high efficiency.

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Working Pressure

The pressure at which a compressed air system operates, typically lower than the storage pressure in the receiver.

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Storage Pressure

The pressure at which compressed air is stored in the receiver, usually higher than the working pressure to ensure enough air for various operations.

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Volute Type Centrifugal Pump

A pump type that utilizes a volute casing, which is a diverging nozzle that surrounds the impeller. This creates a pressure gradient that helps convert the fluid's kinetic energy to pressure.

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Axial Flow Pump

A centrifugal pump type characterized by a large impeller that moves fluid axially, commonly used for high volume, low pressure applications.

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Diffuser Vane

A device used in centrifugal pumps to further increase the pressure of the fluid by slowing it down and converting its kinetic energy to pressure.

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Velocity, Pressure, and Volume Relationship in Centrifugal Pumps

The ratio of velocity, pressure, and volume in a centrifugal pump is determined by the size and shape of the impeller and the surrounding volute casing.

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Initial Fluid Requirement in Centrifugal Pumps

The suction stroke action of a centrifugal pump relies on maintaining fluid within the pump. If the pump is initially empty, it's as if a vital part is missing.

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Starting Centrifugal Pumps

To minimize the motor starting current, it is common to start centrifugal pumps with the discharge valve closed or partly open.

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Load on Centrifugal Pumps

The load on a centrifugal pump is directly proportional to the mass flow rate. This means that a higher flow rate results in a higher load on the pump.

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Relief valve in an air compressor

A safety device fitted to air compressors after each stage to prevent overpressure due to valve malfunctions. They are designed to vent air in case of excessive pressure buildup.

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Bursting disk

A thin metal disc designed to rupture at a predetermined pressure, acting as a safety device on smaller air compressors.

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Fusible plug

A safety device fitted in the air delivery casings of air compressors to prevent overheating. They melt and release pressure if the compressor loses its cooling medium.

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Overheating protection on the final stage

A safety device required on the final stage of air compressors to alert operators of excessive temperatures. It can be either a fusible plug or an alarm.

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Pressure relief valve in the water jacket

A mandatory safety device on water-cooled air compressors installed in the water jacket. It protects the compressor if a cooling pipe bursts, preventing water from entering the air system.

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Volumetric efficiency

The ratio of air drawn in per stroke to the total volume displaced by the piston.

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Clearance volume

The volume of air remaining in the cylinder after the compression stroke is completed.

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Valve loss

The reduction in pumping efficiency caused by delays in the opening and closing of suction and delivery valves.

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Why is moisture removal crucial in compressed air systems?

Moisture in compressed air can cause corrosion, oil emulsions, and gumming of components.

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What are filters in compressed air systems for?

Filters remove particles from compressed air, protecting equipment from damage.

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What is relative humidity in relation to compressed air?

Relative humidity is the amount of water vapor in the air compared to the maximum it can hold at that temperature.

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How does Boyle's law affect compressed air?

Boyle's law states that the volume of a gas is inversely proportional to its pressure at a constant temperature.

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How does temperature affect water vapor in compressed air?

As compressed air cools, the volume decreases further, causing water vapor to condense into liquid water.

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What is a refrigerated dryer in a compressed air system?

A refrigerated dryer removes water vapor from compressed air by cooling it below the dew point.

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Where are drains typically found in compressed air systems?

Compressed air systems often have drains at the compressor, storage bottle, and filters to remove accumulated water and oil.

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Why is regular maintenance important for compressed air systems?

Regular inspection and maintenance of air compressors and related equipment is crucial for optimal system performance.

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Variable Delivery Pump

A pump that adjusts the flow of hydraulic fluid to control the direction, speed and load of cylinders. It is protected against overpressure by relief valves and prevents backflow with non-return valves.

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Relief Valve

A type of valve used in hydraulic systems that releases excess pressure if it exceeds a preset limit, preventing damage to the system.

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Non-Return Valve

A valve designed to prevent the backflow of fluids in a hydraulic system, ensuring that fluid only moves in one direction.

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Logic Control Pneumatic System

A type of pneumatic system that uses logic control to create complex systems with multiple choices, often found in diesel engine management.

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Air Flow Control Valve

Used in pneumatic systems to control the speed of a cylinder by regulating the flow of air to the actuator.

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Electro-pneumatic Control

A pneumatic system that uses electrical sensors and actuators to control pneumatic valves, offering greater precision and control over long distances.

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Electro-hydraulic Control

A system that directly controls hydraulic valves using electrical signals and actuators, providing remote and precise control over hydraulic functions.

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Process Sensing

The process of detecting and measuring the state of a system or process, often using sensors, to provide information for control decisions.

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Study Notes

Auxiliary Equipment - 1

  • This course is a revision course designed for the Second Engineer Small Vessel Certificate of Competency.
  • The course covers a wide range of topics, including auxiliary equipment.
  • The course duration is one week, and additional preparation is recommended (at least 6 weeks before the course).
  • Past SQA exam questions are included as a study aid.

Valves

  • Types of valves (simple plug cock, ball valve, screw-lift valve, screw-down non-return valve, butterfly valve, gate valve, diaphragm valve, quick closing valves, 3-way valves, valve chests)
  • Construction and application of different types of valves.
  • Materials used in valve construction (cast iron, steel, bronze, brass, stainless steel, etc.)
  • Compatibility of materials with fluids, including corrosion and erosion aspects.

Pumps

  • Types of pumps (positive displacement, centrifugal)
  • Basic classification of pumps, positive displacement and centrifugal
  • Typical pump applications in systems
  • Basic pump symbols
  • Types of positive displacement pumps (electric motor driven reciprocating pump, lobe pump, gear pump, rotating piston pump, screw pump, vane pump)
  • Positive displacement pump relief valves and system flow pulsation damping
  • Centrifugal pumps, construction, theory of operation, volute casing and diffuser issues, priming methods.

Compressed Air Systems

  • Knowledge that the compressed air system commonly has two pressure levels (30-40 bar for starting air, and 7-10 bar for control air).
  • Basic system layout and components (air compressors, air receivers)
  • Compressed air system safety and safety devices (isolation and draining of system, safety valves, fusible plugs, compressor bursting discs, compressor lifting heads, pressure cutouts)
  • Hydraulic and pneumatic control principles explained

Steering Gears

  • Basic functions of a steering gear
  • Types of steering gear construction (2-ram and rotary vane)
  • Knowledge of signal transmission from remote steering positions.
  • Feedback control within steering system
  • Hydraulic system for a steering gear system (constant and variable pressure)
  • Steering gear protection and redundancy (split hydraulics, dual pumping arrangements, isolating valves, by-pass valves, movement limiters, and shock valves)

Propulsion

  • Basic theory of propellers (number of blades, skewed etc.)
  • Methods of securing the propeller to the propeller shaft
  • Configurations of propeller systems (including water jet, Azipod and Voith Schneider propulsions)
  • Controllable Pitch Propellers (CPP)
  • Configurations and construction of transverse thrusters (fixed drive, fluid drive, water jet)
  • Safety devices and manual control (fail safe / fail set)

Transmission and Shaft Arrangement

  • Shaft support bearing types and construction (plain bearing, roller bearing)
  • Thrust bearings (tapered roller bearings and thrust collars)
  • Bearing lubrication
  • Stern tube bearings (lining, oil and water lubricated)
  • Stern seals (lip seals, mechanical seals)
  • Rigid and flexible shaft connections (fitted coupling bolts, flange, hydraulic muff, steel diaphragm)
  • Basic shaft alignment and Shaft coupling alignment (lateral and angular)

Electrical Plant

  • Basic construction and operational principles of AC alternators
  • Production of voltage and current
  • Pole/speed relationship
  • Exciters
  • Speed control
  • Automatic voltage regulators (AVR)
  • Response to change in load
  • Synchronizing and paralleling alternators manually and automatically
  • Synchronization lamps, load sharing, speed droop and voltage droop
  • Switchboard layout (including main alternators, main switchboard, emergency alternator, emergency switchboard)
  • Switchboard safety devices
  • Main breakers, earth leakage detection, preferential tripping, sequential starting, and discrimination protection.
  • Fuse types and applications
  • Shore power connection and safe operation of electrical plant
  • Neutral point insulated distribution
  • Essential and non-essential consumers
  • Earth fault tracing.
  • Basic construction and operational principles of 3-phase/single-phase motors
  • Direct on-line starting, alternative starting arrangements
  • Torque and current characteristics, safety protection, fault finding, single phasing
  • Basic construction and operational principles of batteries
  • Lead-acid, alkaline, Ni-ion, charging circuits, inspection, maintenance, safety, testing, recovery from blackout.
  • Electrical safety (legislation - COSWP, safe isolation, safe testing procedures)
  • Maintenance and troubleshooting of electrical lighting circuits, including navigation lights
  • Introduction to transformers, transformers classifications, construction
  • Essential electrical components, wiring techniques, circuit diagrams, testing
  • Transformers
  • Safety aspects of electrical systems
  • Principles and safety practice
  • Operation and maintenance
  • Practical use
  • Fault

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Description

Test your knowledge on the characteristics and functions of various types of pumps and compressors. This quiz covers centrifugal pumps, positive displacement pumps, and the operational aspects of engine starting pressures. Understand key concepts to solidify your grasp on fluid mechanics.

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