AME 1 End of Unit

Answer:

C. 93% aluminum, 4% copper, 3% magnesium; used for superstructure components

Explanation:

Duralumin is primarily an aluminum alloy containing approximately 93% aluminum, 4% copper, and 3% magnesium. Its key properties are high strength-to-weight ratio and good corrosion resistance, making it suitable for superstructure components on marine vessels like decks, bulkheads, and frames.

Why the other options are incorrect:

• A. 90% copper, 10% aluminum; used for propeller blades: This composition describes aluminium bronze, not duralumin. While both are used in marine applications, their specific properties and applications differ.
• B. 70% copper, 29% zinc, 1% tin; used for heat exchanger tubes: This composition describes admiralty brass, not duralumin. Brass alloys are primarily copper-zinc based, while duralumin is an aluminum alloy.  
  1. Resources: Standards & Properties - Copper & Copper Alloy Microstructures: Brasses

  

  www.copper.org

• D. 80% copper, 20% lead; used for plumbing pipes: This composition describes lead brass, which is not commonly used due to health concerns related to lead exposure. Additionally, lead brass is not suitable for marine environments due to its susceptibility to corrosion. Duralumin is an aluminum alloy, not a copper-based alloy.

Answer:

B. Kitchen cutlery

Explanation:

Austenitic stainless steel is commonly used for kitchen cutlery due to its excellent corrosion resistance, durability, and ease of cleaning. It's also non-reactive, meaning it won't alter the taste of food.

Answer:

A. 90% copper, 10% aluminum; used for propeller blades

Explanation:

Aluminium bronze typically consists of around 90% copper and 10% aluminum. It's widely used for marine applications, especially propeller blades, due to its excellent combination of strength, corrosion resistance, and resistance to cavitation.

Why the other options are incorrect:

• B. 70% copper, 30% zinc; used for electrical wiring: This composition describes brass, not aluminium bronze. While brass is used for some electrical applications, it's not the primary choice for marine environments due to its lower corrosion resistance compared to aluminium bronze.
• C. 60% copper, 40% tin; used for engine bearings: This composition describes bronze, not aluminium bronze. Bronze is used for bearings due to its good anti-friction properties, but aluminium bronze offers superior strength and corrosion resistance for marine applications.
• D. 80% copper, 20% lead; used for plumbing pipes: This composition describes lead brass, which is not commonly used in modern applications due to health concerns related to lead exposure. Aluminium bronze offers better corrosion resistance and mechanical properties for marine environments.

B. Bronze, stainless steel, and ductile iron: Due to their combination of strength, corrosion resistance, and durability.

This is the correct answer as it accurately lists the three materials commonly used for ship's side valves and provides a concise explanation of their suitability.

Why the other options are incorrect:

• A. Cast iron: While cast iron can be used in some marine applications, it's generally not suitable for ship's side valves due to its brittleness and susceptibility to corrosion in the harsh marine environment.
• C. Aluminum and copper: While both aluminum and copper have their applications in marine engineering, they are not typically used for ship's side valves. Aluminum may lack the necessary strength and corrosion resistance, while copper is often alloyed with other metals (like tin to form bronze) to improve its properties for marine use.
• D. Plastic and rubber: These materials are not suitable for ship's side valves due to their lack of strength and durability to withstand the pressures and harsh conditions of the marine environment. They are also susceptible to degradation from exposure to saltwater and UV radiation.

Answer:

C. 63% tin, 37% lead; used for electrical connections

Explanation:

Solder is primarily an alloy of tin and lead, with the most common composition being 63% tin and 37% lead. This composition is known as eutectic solder and has a low melting point, making it ideal for joining metals. A common application on board a marine vessel would be for electrical connections.

Why the other answers are incorrect:

• A. 60% copper, 40% zinc; used for pipe joints: This composition describes brass, which is used for pipe joints, but it's not solder. Solder is a metal alloy used for joining metals together, typically with a lower melting point than the metals being joined.

   

  1. Solder - Wikipedia

  

  en.wikipedia.org

• B. 90% lead, 10% tin; used for electrical connections: While this is a type of solder, it contains a high percentage of lead, which is harmful and has been phased out in many applications due to environmental concerns. Modern solders primarily use tin and lead, or lead-free alternatives.
• D. 80% copper, 20% aluminum; used for propeller blades: This composition describes an aluminum bronze alloy, which is not solder. Solder is a low-melting point alloy specifically designed for joining metals.

Answer:

C. 316 has added molybdenum, enhancing corrosion resistance.   

The primary difference between stainless steel grades 304 and 316 lies in the addition of molybdenum to 316. This element significantly improves the steel's resistance to corrosion, particularly in environments with high chloride content, such as marine applications.   

Why D is the correct answer:

D. Grey cast iron is brittle and susceptible to fracture under marine conditions.

This is the correct answer because it directly addresses the primary reason why grey cast iron is unsuitable for ship's side valves: its brittleness. The marine environment is harsh, with potential for impacts, pressure fluctuations, and corrosion, which can easily lead to fractures in grey cast iron.

Why the other options are incorrect:

• A. Grey cast iron is highly resistant to corrosion in marine environments. This is incorrect. While cast iron can exhibit some corrosion resistance in certain conditions, the marine atmosphere, with its high salt content and humidity, is particularly aggressive, leading to rapid deterioration of grey cast iron.
• B. Grey cast iron possesses exceptional strength and ductility for withstanding marine conditions. This is incorrect. Grey cast iron is actually known for its low tensile strength and poor ductility, making it unsuitable for applications that require resistance to stress and strain, such as ship's side valves.
• C. Grey cast iron is lightweight, making it ideal for shipboard applications. While weight is a consideration in ship design, it's not the primary factor in choosing valve materials. Other materials like bronze or stainless steel offer better performance in marine environments while also being relatively lightweight.

B. Copper-nickel alloy: Due to its excellent corrosion resistance and heat transfer properties.  

1. Copper-Nickel Alloys

www.copper.org

Explanation:

Copper-nickel alloys, specifically those containing copper and nickel, are the preferred choice for seawater-cooled heat exchangers in marine vessels. These alloys offer exceptional corrosion resistance, which is crucial for components in direct contact with seawater. Additionally, copper-nickel alloys have excellent heat transfer properties, ensuring efficient heat exchange.  

1. Corrosion resistance of copper-nickel alloys

nickelinstitute.org

2. Copper Nickel Heat Exchangers: Benefits & Suitable Applications - YouTube

www.youtube.com

While other materials like stainless steel and aluminum alloys have some advantages, copper-nickel alloys provide the optimal combination of properties for this specific application.

Why the other answers are incorrect:

• A. Cast iron: While cast iron is strong and cost-effective, it is highly susceptible to corrosion in the marine environment. This would quickly degrade the heat exchanger's performance.
• C. Stainless steel: Stainless steel offers good corrosion resistance, but it is generally less efficient at heat transfer compared to copper-nickel alloys. This can impact the overall efficiency of the heat exchanger.
• D. Aluminum alloy: Although aluminum alloys have good heat transfer properties and are lightweight, they are susceptible to corrosion in seawater, especially in the presence of salts and other impurities. This would significantly reduce the heat exchanger's lifespan.

Copper-nickel alloys provide the optimal combination of corrosion resistance and heat transfer efficiency for seawater-cooled heat exchangers in marine applications.

B. Copper-nickel alloy: Due to its excellent corrosion resistance and heat transfer properties.  

1. Copper-Nickel Alloys

www.copper.org

Explanation:

Copper-nickel alloys are the preferred choice for seawater cooling pipes due to their exceptional resistance to corrosion in marine environments. This is crucial for ensuring the longevity and reliability of the piping system. Additionally, copper-nickel alloys exhibit good heat transfer properties, which can enhance the efficiency of the cooling system.  

1. Cu-Ni Alloy Resistance to Corrosion and Biofouling - Copper Development Association

www.copper.org

While other materials like stainless steel offer corrosion resistance, copper-nickel alloys generally excel in this area, especially in seawater conditions. Cast iron and ductile iron are susceptible to corrosion, and while they might be cost-effective initially, the long-term costs associated with maintenance and replacement can outweigh the initial savings.

Why the other answers are incorrect:

• A. Cast iron: While cast iron is strong and cost-effective, it is highly susceptible to corrosion in the marine environment. This would quickly degrade the pipe and lead to leaks and other issues.
• C. Stainless steel: While stainless steel offers good corrosion resistance, it can be more expensive than copper-nickel alloys for large-diameter pipes. Additionally, the thermal conductivity of stainless steel is lower than copper-nickel, which can affect heat transfer efficiency in cooling systems.
• D. Ductile iron: Ductile iron is stronger than cast iron, but it is still susceptible to corrosion in seawater. It may not offer the same level of durability and longevity as copper-nickel alloys in this specific application.

Copper-nickel alloys provide the optimal combination of corrosion resistance, heat transfer properties, and durability for seawater cooling pipes in marine vessels.

B. Bronze: Due to its corrosion resistance and good bearing properties.

Explanation:

Bronze, specifically nickel-aluminum bronze, is the most common material for large marine vessel propellers. This choice is primarily due to its excellent corrosion resistance, which is crucial for components submerged in seawater. Additionally, bronze offers good bearing properties, which help to reduce wear and tear.  

1. Why nickel aluminium bronze is used for VEEM Propellers

veemmarine.com

2. A Guide to Different Types of Bronze Alloys - MetalTek International

www.metaltek.com

3. Industrial - Selecting Bronze Bearing Materials - Copper Development Association

www.copper.org

While other materials like stainless steel and aluminum alloys have their advantages, bronze remains the preferred choice for large marine propellers due to its overall performance and cost-effectiveness.

Why the other answers are incorrect:

• A. Cast iron: While cast iron is strong and inexpensive, it is not suitable for marine propellers due to its susceptibility to corrosion in saltwater environments. Corrosion can weaken the propeller over time, reducing its efficiency and safety.
• C. Stainless steel: Stainless steel is highly resistant to corrosion, but it is generally too heavy for large marine propellers. The weight of the propeller directly impacts the vessel's fuel consumption and performance.
• D. Aluminum alloy: Although aluminum alloys are lightweight and offer good corrosion resistance, they may not have the necessary strength and durability for large marine propellers, especially in demanding conditions.