Auxiliary 1 valves & pumps Flashcards
(30 cards)
Label diaphram valve
With reference to remotely operated quick closing valves:
(a) state their purpose
(b) state where they would be fitted
(c) describe how they are tested
a) Isolate fuel or flammable liquids in the event of a fire or emergency, preventing the spread of fire.
c) On fuel oil tanks and lubricating oil tanks to control the flow of flammable liquids.
At engine rooms or other machinery spaces where fire risks are higher.
On day tanks or other storage tanks containing combustible materials
c) Quick closing valves are tested to ensure proper operation in emergencies.
The key steps include:
- Visual Inspection – Check for wear, corrosion, or obstructions.
- Manual Test – Operate the valve to ensure smooth closure.
- Remote Activation – Trigger from the control station to confirm response.
- Leakage Check – Verify no leaks after closure.
- Reset Test – Ensure the valve reopens properly.
- Maintenance Review – Check lubrication and seals.
With reference to remotely operated quick closing valves
Explain the Testing procedure
- Functional Test: Operate the valve remotely to confirm it closes fully and promptly.
- Local Operation Test: Test the manual override mechanism to ensure it works in case of remote system failure.
- Leakage Test: Check for any leaks when the valve is in the closed position.
- System Integrity Check: Inspect the control system (e.g., hydraulic, pneumatic, or mechanical) for proper functionality.
- Emergency Drill: Simulate an emergency scenario to verify the valve’s performance under real conditions.
A centrifugal bilge pump has not been operating satisfactorily, the air pump was tested and found to be operating correctly.
List FIVE faults that could have caused the problem, stating why EACH fault causes poor
operation.
Here are five potential faults that could cause poor operation of a centrifugal bilge pump, along with explanations for each:
-
Blocked Suction Line
- Debris or sediment in the suction line can restrict the flow of water into the pump, reducing its efficiency and causing cavitation.
-
Worn Impeller
- A damaged or eroded impeller loses its ability to generate sufficient pressure, leading to reduced flow and poor pump performance.
-
Air Leaks in Suction Line
- Air entering the suction line disrupts the pump’s ability to maintain prime, causing intermittent or complete loss of operation.
-
Incorrect Alignment
- Misalignment between the pump and motor can lead to excessive vibration, wear, and reduced operational efficiency.
-
Seal Failure
- A worn or damaged seal allows water to escape, reducing the pump’s capacity and potentially causing overheating or further mechanical damage.
with reference to comparing modern water lubricated stern tube bearings with those that are oil lubricated explain advantages and dis-advantages
Here’s a comparison of modern water-lubricated stern tube bearings and oil-lubricated stern tube bearings:
Advantages of Water-Lubricated Bearings:
1. Environmental Friendliness: Water-lubricated bearings eliminate the risk of oil spills, making them more eco-friendly and compliant with stricter environmental regulations.
2. Lower Maintenance: They require less maintenance since there’s no need for oil changes or filter replacements.
3. Simpler Design: These bearings often have fewer components, reducing weight and manufacturing costs.
Disadvantages of Water-Lubricated Bearings:
1. Lower Load Capacity: Water has a lower lubricating capacity compared to oil, which can limit the load these bearings can handle.
2. Stricter Tolerance Requirements: They demand tighter clearances between the shaft and bearing material to maintain proper lubrication.
3. Potential Corrosion: Exposure to seawater can lead to corrosion, though modern materials and coatings help mitigate this.
Advantages of Oil-Lubricated Bearings:
1. Higher Load Capacity: Oil provides superior lubrication, allowing these bearings to handle higher loads.
2. Better Durability: Oil-lubricated systems are generally more robust under heavy-duty operations.
3. Established Technology: These systems have been widely used and refined over decades.
Disadvantages of Oil-Lubricated Bearings:
1. Environmental Risks: Oil spills can harm marine ecosystems, and even minor leaks can lead to regulatory penalties.
2. Higher Maintenance: Regular oil changes and seal replacements are necessary to prevent leaks and maintain performance.
3. Complexity: These systems often involve more components, increasing initial costs and potential points of failure.
Draw and label the following butterfly valve
state 3 reasons that may cause a relief valve to fail to lift should excessive pressure occur (3)
Here are three reasons a relief valve may fail to lift under excessive pressure:
- Valve Blockage – Debris or contamination in the valve can obstruct its operation, preventing it from opening.
- Incorrect Calibration – If the valve’s set pressure is improperly adjusted, it may not activate at the intended pressure level.
- Spring Failure – A weakened or broken spring can prevent the valve from responding to pressure changes effectively.
explain how the correct operation of a relief valve is ensured (4)
Ensuring the correct operation of a relief valve involves several key practices:
- Regular Maintenance: Periodically inspect and clean the valve to prevent blockages or corrosion that could hinder its function.
- Calibration: Adjust the valve to the correct set pressure using manufacturer guidelines to ensure it activates at the intended pressure level.
- Functional Testing: Perform tests to verify the valve opens and reseats properly under simulated pressure conditions.
- Component Checks: Inspect critical parts like springs, seals, and seats for wear or damage, replacing them as needed.
- Environmental Considerations: Protect the valve from extreme temperatures or corrosive environments that could affect its performance.
With reference to centrifugal pumps for bilge/ballast purposes. Explain the specific problems which may arise using the pumps for these purposes
Certainly! Here’s a more concise version:
Common problems with centrifugal pumps in bilge/ballast systems:
1. Debris & Solids – Can clog the impeller, reducing efficiency.
2. Marine Growth – Causes blockages in seawater ballast systems.
3. Corrosion & Wear – Continuous exposure to seawater damages components.
4. Cavitation – Low suction pressure leads to vibrations and impeller damage.
5. Air Leaks – Prevent proper priming, reducing flow.
6. Low Fluid Levels – Air pockets form, lowering efficiency.
7. Seal & Bearing Failures – Worn components lead to leaks and mechanical issues.
Label this gate valve
Label this certifugal pump
With reference to ships side valves state why grey cast iron is not suitable material
Ship’s Side Valves – Why Grey Cast Iron is NOT Suitable
Key Reasons:
- Brittle Material – Prone to fracture under impact or sudden pressure changes.
- Corrosion Issues – Lacks resistance to seawater, leading to rapid deterioration.
- Pressure & Shock Limits – Cannot withstand dynamic forces, water hammer effects, or mechanical stresses.
- Regulatory Restrictions – Prohibited for seawater intake/discharge valves by maritime regulations.
With regards to overboard sea valves state with reason 2 suitable materials
Two suitable materials for ship’s side valves are:
- Bronze – Bronze is highly resistant to seawater corrosion, making it an excellent choice for maritime applications. It also has good mechanical strength and ductility, reducing the risk of brittle failure under pressure.
- Stainless Steel – Stainless steel offers superior corrosion resistance, especially in marine environments. It is strong, durable, and can withstand high-pressure conditions, making it ideal for ship-side valves handling seawater intake and discharge.
State with reasons the regular maintenance required to ship side valves.
Ship-Side Valve Maintenance
- Inspect for corrosion, leaks, and wear.
- Lubricate moving parts to prevent seizing.
- Test operation by opening/closing periodically.
- Replace seals/gaskets to maintain integrity.
- Apply corrosion protection coatings.
- Dry dock checks for internal wear & replacement.
Explain why centrifugal pumps are not self priming
Centrifugal pumps are not self-priming because they cannot handle air effectively. They rely on liquid in the volute casing to generate suction, and without it, the impeller spins without drawing fluid.
With reference to thermostatic three way valve state three examples of their use in the systems of a diesel engine
thermostatic three-way valve in a diesel engine system regulates fluid temperature by directing flow between cooling and bypass circuits. Three examples:
- Engine Cooling – Maintains optimal temperature by routing coolant through a heat exchanger or bypass.
- Lubricating Oil Control – Ensures proper viscosity by directing oil to a cooler or bypass.
- Fuel Preheating – Keeps fuel at the right temperature for efficient combustion in cold conditions.
With reference to thermostatic three-way valves describe how they operate
A three-way valve controls fluid flow between three ports, allowing for mixing, diverting, or isolating flow. Here’s how it works:
- Flow Control – The valve has an internal mechanism (such as a ball, plug, or diaphragm) that directs fluid between different pathways.
- Mixing or Diverting – Depending on its design, it can mix two fluid streams into one or divert flow between two outlets.
- Actuation – It can be manually operated or automated using an actuator to adjust flow based on system requirements
Explain how cavitation damage occurs within a pump
Cavitation damage occurs when vapor bubbles form and collapse due to low pressure in the pump. Their violent implosion creates shockwaves that erode the impeller and casing, reducing efficiency and potentially leading to pump failure.
State with reasons two operational cause of increased cavitation with in a pump
Two operational causes of increased cavitation in pumps are:
- Low Net Positive Suction Head (NPSH) – If the available NPSH is insufficient, the pressure at the pump inlet drops below the liquid’s vapor pressure, leading to bubble formation and cavitation damage.
- High Pump Speed – Excessive rotational speed increases velocity and reduces pressure at the suction side, accelerating cavitation and causing erosion.
Describe three types of wastage that may occur on the internal surfaces of a ships side valve that is made of nodular cast iron
Three types of wastage that can occur on the internal surfaces of a ship’s side valve made of nodular cast iron include:
- Corrosion – Exposure to seawater and oxygen leads to electrochemical reactions, causing material degradation over time. prolonged exposure can result in pitting and surface weakening.
- Erosion – High-velocity fluid flow, can wear down the valve’s internal surfaces. This is exacerbated by suspended particles in seawater, leading to thinning of the material.
- Cavitation Damage – Rapid pressure changes within the valve can cause vapor bubbles to form and collapse violently, creating localized shockwaves that erode the metal surface.
Describe 2 reasons other than imbalance for propellers induced vibration
Two causes of propeller-induced vibration, aside from imbalance, are:
- Cavitation – When pressure drops around the propeller blades, vapor bubbles form and collapse violently, creating shockwaves that lead to vibration and structural damage.
- Wake Flow Disturbance – Uneven water flow from the hull or nearby structures disrupts the propeller’s movement, causing irregular forces that result in vibration.
State why centrifugal pumps aren’t self-priming.
Centrifugal pumps aren’t self-priming because they rely on liquid at the impeller to generate suction. If the pump casing is empty, air prevents proper fluid movement, making external priming necessary. Unlike positive displacement pumps, they cannot create enough vacuum to draw liquid into the system on their own.
State the purpose of the hunting gear in a hydraulic-hydraulic steering system
The hunting gear in a hydraulic-hydraulic steering system acts as a feedback mechanism that ensures precise rudder positioning. Here’s how it works:
- Rudder Position Feedback – It transmits the rudder’s actual position to the pump control lever, preventing overcorrection.
- Automatic Correction – When the rudder reaches the desired angle, the hunting gear adjusts the pump stroke to stop further movement.
- Smooth Steering – It prevents oscillations and ensures stable rudder control, improving maneuverability.
State with reasons a type of pump suitable for the each of these services.
- main fresh water cooling
- oily water seperator supply
- emergency fire pump
- steering gear
- fuel transfer
Main Fresh Water Cooling – Centrifugal Pump
- Provides continuous flow and high efficiency for cooling systems.
- Handles large volumes of water with minimal maintenance.
Oily Water Separator Supply – Mono pump (pig tail)
- Ensures consistent flow for effective separation giving good laminate flow.
- Can handle viscous fluids and oil-water mixtures.
Emergency fire pump - Vane pump
- Self priming and provides a good head pressure for fire fighting.
Steering Gear – Variable Displacement Pump
- Adjusts flow rate based on rudder movement demand.
- Ensures smooth and responsive steering.
Fuel Transfer – Rotary Gear Pump
- Delivers precise fuel flow with minimal pulsation.
- Suitable for handling various fuel types. **
