Small Vessel Engineering - Compressed Air Systems Quiz

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Questions and Answers

What are THREE contaminants that may be present in an air supply for pneumatic control systems?

Water Vapour, Particulates, Emulsifications

Why are water vapour, particulates, and emulsifications undesirable in an air supply for pneumatic control systems?

They can lead to system corrosion, increased wear, and fouling of system filters.

Under what circumstances does a Fusible plug operate when fitted to an air compressor?

To protect the air side of the compressor in case of water cooling failure and overheating.

When does a Bursting Disc operate when fitted to an air compressor?

Bursting Disc operates to release pressure in the water jacket of water-cooled air compressors. Signup and view all the answers

What is the purpose of a pressure relief valve in the water jacket of a water-cooled air compressor?

To prevent overpressure and ensure safe operation. Signup and view all the answers

How can water vapour mix with oil to create a sticky emulsion in the air supply system?

Water vapour can mix with oil carried over from the compressor, forming a sticky emulsion. Signup and view all the answers

What are the potential consequences of small dirt particles being sucked into the air supply system?

Increased wear and early fouling of system filters. Signup and view all the answers

What is the purpose of a fusible plug on an air receiver in a compressed air system?

The fusible plug melts in the event of a machinery space fire, allowing the compressed air to be piped out of the space to prevent the air receiver from rupturing and fueling the fire with oxygen. Signup and view all the answers

Why should pipes in a high-pressure compressed air system not be subjected to sudden impact?

At high pressures, the pipes are under stress containing the compressed air. A sudden impact could cause the pipes to rupture and release the compressed air violently, leading to injury or fatality. Signup and view all the answers

Why should valves in a compressed air system be opened slowly?

Opening valves rapidly can cause a sudden, uncontrolled release of high volumes of compressed air, which is potentially dangerous. Signup and view all the answers

What is the maximum allowable temperature for the final stage of a compressor, as indicated by a fusible plug or alarm device?

$121^\circ\mathrm{C}$ Signup and view all the answers

What is the purpose of a bursting disc in a compressed air system?

A bursting disc protects the compressor in the event that a cooling pipe bursts, exposing the cooling water jacket to the full delivery air pressure from the compressor. Signup and view all the answers

Why is the rupture of an air receiver in a machinery space fire a serious hazard?

If an air receiver ruptures in a machinery space fire, it can provide an enormous amount of oxygen to fuel the fire. Signup and view all the answers

What hazard is associated with rapid, uncontrolled release of compressed air?

A rapid, uncontrolled release of compressed air can lead to injury or fatality due to the high energy released. Signup and view all the answers

What can happen if the pipework contains moisture?

Shock wave travelling down the pipework and resultant slamming of the water can lead to physical failure of valves and pipework joints Signup and view all the answers

Why do air receiver valves operate on a fine thread?

To take many turns to open and prevent sudden shocks to the pipework Signup and view all the answers

What is the purpose of a fusible plug in the main air receivers?

To provide safety by melting at a specific temperature and releasing pressure Signup and view all the answers

Why is a drain valve important in the main air receivers?

To allow for the removal of moisture and condensate from the system Signup and view all the answers

What is the purpose of a low-pressure alarm in the main air receivers?

To alert operators when the pressure drops below a safe level Signup and view all the answers

At what pressure should the relief valve lift in the main air receivers?

The relief valve should lift to prevent the maximum accumulation pressure from exceeding the working pressure by more than 10% Signup and view all the answers

Why is it important for the relief valve to be properly sized and set?

To prevent pressure from exceeding safe limits in case all discharge valves are shut and compressors are filling the receiver at maximum efficiency Signup and view all the answers

Explain the purpose of a fusible plug in an air receiver.

A fusible plug is specifically designed to protect the air side of a compressor should water cooling fail and the compressor begins to overheat. Signup and view all the answers

Why is it essential to have a calibrated pressure gauge on an air receiver?

A calibrated pressure gauge is essential to determine the stored pressure in the air receiver. Signup and view all the answers

Describe the primary reason for regularly draining an air receiver. What are the two potential consequences of not draining it?

Water can lead to both corrosion and also emulsification (water mixing with oil). Corrosion weakens the receiver strength and can lead to premature failure. Emulsification contaminates the air system. Signup and view all the answers

For an air receiver manhole door, explain the door sealing mechanism and how it utilizes the stored air pressure.

The manhole door seals from the inside out, using the air pressure inside the receiver to hold the manhole door in the sealed position. Signup and view all the answers

Describe the purpose and operation of a relief valve on an air receiver. Where is it vented?

A relief valve is designed to rapidly dump air in the case of overpressure, preventing a potential rupture of the air receiver. It is vented to atmosphere. Signup and view all the answers

Why should outlet valves on an air receiver be opened slowly? What potential issue are you avoiding?

Outlet valves should be opened slowly to avoid sudden pressure drops that could lead to condensation forming in the air lines. Signup and view all the answers

On the maker's nameplate, what are the three key pressure ratings listed, and what do they represent?

The three key pressures are: Test Pressure, Design Pressure, and Working Pressure. The Test Pressure is for factory testing. The Design Pressure is the maximum allowable pressure. The Working Pressure is the recommended operating pressure. Signup and view all the answers

Explain the process of how a relief valve resets after an overhaul, including the key steps and components involved.

After an overhaul, a relief valve is reset using a calibrated test rig. The adjusting screw alters the compressive force of the spring to set the point where air pressure overcomes the spring to relieve pressure. The lock screw and seal cap ensure this setting is fixed, and the valve is completed with a dated test pressure tag. Signup and view all the answers

Why is it imperative that a relief valve is set accurately, especially as a surveyable item and part of safety protection?

It is imperative to set a relief valve accurately because it is a surveyable item, meaning it is subject to inspection and regulation, and it forms a key part of the safety protection system, ensuring that excessive pressure is relieved to prevent hazardous conditions. Signup and view all the answers

Explain the potential consequences of water droplets being carried over with the air through the system, leading to further corrosion problems.

If water droplets are carried over with the air through the system, it can lead to further corrosion problems. The water can cause oxidation and degradation of metal components, potentially leading to system failures, leaks, and reduced operational life. Signup and view all the answers

Describe the process of emulsification and how it can lead to operational failures in compressed air systems.

Emulsification is the process where water vapor mixes with oil, creating a sticky emulsion. This emulsion can gum up system components, leading to operational failures further downstream in the compressed air system. Signup and view all the answers

Explain the purpose of a pressure relief valve in the water jacket of a water-cooled air compressor.

The purpose of a pressure relief valve in the water jacket of a water-cooled air compressor is to relieve excessive pressure in the water jacket, which could potentially cause damage or failure of the compressor if not properly regulated. Signup and view all the answers

Describe the operating principle and purpose of a fusible plug fitted to an air compressor.

A fusible plug is a safety device fitted to an air compressor that melts or fuses at a specific high temperature, allowing the release of pressure and preventing catastrophic failure of the compressor due to overheating. Signup and view all the answers

Explain the function and operating principle of a bursting disc fitted to an air compressor.

A bursting disc is a safety device fitted to an air compressor that is designed to rupture or burst at a predetermined high pressure, allowing the release of compressed air and preventing catastrophic failure of the compressor due to excessive pressure buildup. Signup and view all the answers

Describe three potential consequences of particulate matter being introduced into an air supply system for pneumatic control systems.

Three potential consequences of particulate matter being introduced into an air supply system for pneumatic control systems are: 1) Abrasive wear and damage to components, 2) Clogging or blockages in valves and actuators, and 3) Reduced system efficiency and performance. Signup and view all the answers

Explain the significance of accurately setting a pressure relief valve in terms of compliance with regulations and safety standards.

Accurately setting a pressure relief valve is significant in terms of compliance with regulations and safety standards because relief valves are often surveyable items subject to inspection and must be set correctly to ensure they operate within specified safety limits and prevent hazardous overpressure conditions. Signup and view all the answers

Describe the potential impact of water vapor, particulates, and emulsifications on the performance and reliability of pneumatic control systems.

Water vapor, particulates, and emulsifications can have a significant negative impact on the performance and reliability of pneumatic control systems. Water vapor can cause corrosion, particulates can lead to abrasive wear and clogging, and emulsifications can gum up components, all of which can result in reduced efficiency, operational failures, and decreased system lifespan. Signup and view all the answers

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Study Notes

Air Supply Contaminants and Safety

Three contaminants that may be present in an air supply for pneumatic control systems are water vapour, particulates, and emulsifications.
These contaminants are undesirable as they can cause corrosion, operational failures, and reduce system performance.

Air Compressor Safety Devices

A Fusible plug operates when fitted to an air compressor under high-temperature conditions (above 69°C/155°F), releasing compressed air to prevent explosion.
A Bursting Disc operates when fitted to an air compressor under extreme pressure conditions, releasing compressed air to prevent explosion.

Pressure Relief Valves

The purpose of a pressure relief valve in the water jacket of a water-cooled air compressor is to prevent over-pressurization and potential explosion.
A pressure relief valve is set to lift at a specific pressure to release excess air and prevent damage to the system.

Air Supply System Hazards

Water vapour can mix with oil to create a sticky emulsion in the air supply system, causing operational failures.
Small dirt particles in the air supply system can clog valves and pipes, causing system failure.
Rapid, uncontrolled release of compressed air can cause injury or damage.

Air Receiver Safety

A fusible plug on an air receiver prevents the receiver from overheating (above 69°C/155°F) and releasing compressed air.
A bursting disc on an air receiver releases compressed air under extreme pressure conditions.
A low-pressure alarm in the main air receivers alerts operators of low air pressure.
A relief valve in the main air receivers lifts at a set pressure to release excess air and prevent damage to the system.
A drain valve in the main air receivers is important to remove moisture and contaminants.
Air receiver valves operate on a fine thread to control air flow and prevent sudden release of compressed air.

Air Receiver Maintenance

Regularly draining an air receiver prevents corrosion and operational failures.
Not draining an air receiver can lead to corrosion and operational failures.
A calibrated pressure gauge on an air receiver ensures accurate pressure measurement.

Relief Valve Operation

A relief valve resets after an overhaul by re-seating the valve and adjusting the set pressure.
Accurate setting of a relief valve is imperative to prevent system damage and ensure compliance with regulations and safety standards.

Compressor and Air Supply System Operation

Water droplets carried over with the air can cause corrosion and operational failures.
Emulsification occurs when water vapour mixes with oil, leading to operational failures in compressed air systems.
Particulate matter in an air supply system can cause corrosion, operational failures, and reduce system performance.

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