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?

It reduces the size of the air receivers needed. Signup and view all the answers

Which pump is not a type of positive displacement pump?

Centrifugal pump Signup and view all the answers

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

For fault finding Signup and view all the answers

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

Storage pressure Signup and view all the answers

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

Centrifugal pump Signup and view all the answers

What is the primary function of a pump?

To draw in fluid and increase its kinetic energy Signup and view all the answers

What are the two basic categories of pumps?

Dynamic and Positive Displacement Signup and view all the answers

Which statement is true about dynamic pumps?

They use centrifugal force to accelerate fluid. Signup and view all the answers

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

A positive suction head or a priming mechanism Signup and view all the answers

What type of energy is primarily converted in dynamic pumps?

Kinetic energy to potential energy Signup and view all the answers

Which component typically forms the rotor in axial flow pumps?

A multi-bladed propeller Signup and view all the answers

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

High flow rates with relatively low pressures Signup and view all the answers

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

Higher pressure generally results from reduced flow rates. Signup and view all the answers

What is the primary characteristic of axial flow pumps?

They are best suited for low pressure and high volumetric throughput. Signup and view all the answers

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

It features a diverging nozzle that acts as a diffuser. Signup and view all the answers

What occurs when the impeller of a centrifugal pump rotates?

Liquid is forced outwards to the discharge based on centrifugal effect. Signup and view all the answers

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

It minimizes the motor starting current. Signup and view all the answers

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

It helps create a lower pressure at the center of the pump. Signup and view all the answers

What happens if a centrifugal pump contains no liquid initially?

It behaves as if an essential part is missing. Signup and view all the answers

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

It depends on the size of the impeller and configuration of the volute casing. Signup and view all the answers

Which type of casings do centrifugal pumps commonly utilize?

Volute casings and diffuser casings, either separately or in combination. Signup and view all the answers

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

High-pressure outlet pipes Signup and view all the answers

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

The amount of water vapour present in the air Signup and view all the answers

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

Corrosion of components 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?

The volume decreases Signup and view all the answers

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

Corrosion signs Signup and view all the answers

What role do filters play in a compressed air system?

They remove dirt and particles Signup and view all the answers

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

It condenses into water Signup and view all the answers

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

Using a refrigerated dryer system Signup and view all the answers

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

To protect against overpressure due to valve seizure or blockage Signup and view all the answers

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

Bursting disks Signup and view all the answers

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

An alarm device at 121°C Signup and view all the answers

Where should relief valves be fitted in a compressor system?

After each stage of the compressor Signup and view all the answers

What happens if the fusible plug melts in a compressor?

It releases pressure to prevent overheating Signup and view all the answers

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

To indicate the amount of air left after compression Signup and view all the answers

How should relief valves be tested?

By an authorized service agent with calibrated equipment 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?

To protect against high delivery air pressure in case of a cooling pipe burst Signup and view all the answers

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

To control direction, speed, and load of cylinders Signup and view all the answers

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

Non-return valves Signup and view all the answers

In pneumatic systems, how is waste air typically handled?

Vent to the atmosphere Signup and view all the answers

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

To maintain pressure on the cylinder when 3/2 valves are released Signup and view all the answers

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

It can lead to inefficiencies Signup and view all the answers

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

Sense the condition of the process Signup and view all the answers

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

Controls the speed of the cylinder Signup and view all the answers

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

Reduction in required components Signup and view all the answers

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.