End test crib sheet Flashcards
1
Q
Advantages & Disadvantages of Grease
A
- +Lubricates and also seals against contaminants entering a bearing.
- +Under normal conditions it does not require a retention system to remain in the desired location.
- +solid additives such as graphite are held in suspension
- the fluid level does not have to be controlled accurately
- -Poor cooling effect, heat is not dissipated such as with circulating oil
- -High viscosity gives resistance to motion so does not suit many applications where low torque/ high speed
- -difficult to handle with regard to change output, metering and draining
- Temperature sensitive. Low viscosity index
2
Q
Water Contamination Sources
A
- Leakage from Oil Coolers
- Charge air coolers
- steam heating coils
- condensation
- blow-by gases from diesel engine combustion spaces
- leakage at tank vents (exposed to weather)
- Coolant from Jacket water leaks through cracks & seals
- Contamination from top-up oil
3
Q
TBN Definition
A
- Total Base Number is a measurement of the capacity of engine oil for neutralising strong acids from combustion of fuel oil
- It is NOT a measure of how alkaline an oil is but instead measures the oil’s ability to neutralise acids
4
Q
Indicators of Microbial Contamination
A
- Increased acidity of the oil
- Unusual smells (rotten eggs)
- Sliminess of the oil
- Honey coloured films on the journals
- Corrosion pitting of the journals
- Black graphitic pitting in cast iron
- Black stains on white metal and black deposits
- Sludge accumulation in crankcase and sump
5
Q
Centrifugal Drawing
A
draw it
6
Q
Duplex Filter design requirements
A
- As Per SOLAS must be located so that any leak or spray cannot come into contact with a hot surface
- Filter bowls should be of metal construction
- There should be adequate save-all located underneath
- The change over cock handle should be fitted so it covers the live filter to prevent accidental opening of a live pressurized filter
- There must be a drain on the bowl
- There must be an air vent on top
- Needs a differential pressure alarm or high vacuum alarm to indicate that the filter needs changing
7
Q
Purifier & Clarifier definitions & differences
A
- Purifiers are used for the separation of two liquids of different densities (fuel and water)
- Clarifiers are used for separating solid impurities
- The main constructional difference between the two is that a purifier has a gravity disc to control the water side of the purification whereas the clarifier doesn’t use any water so doesn’t require one.
8
Q
Advantages of a central cooling system
A
- +Cheaper materials for pipes and valves can be used due to the use of treated fresh water which results a far reduced risk of corrosion
- +With a constant level of temperature being maintained, irrespective of sea water temperature, this gives stability and economy of operation of the machinery.
- +By using treated fresh water, we see a substantial reduction in maintenance when compared to older sea water systems. Fewer saltwater pipes with corrosion and fouling problems
- +Modern plate coolers bring in an enhanced level of heat transfer, again with less maintenance and down time for cleaning
- +The higher water speeds possible in the freshwater system, resulting in reduced pipe dimensions and installation costs
9
Q
Conditions to be met for corrosion to occur
A
here must be an anode
* There must be a cathode
* An electrolyte must be present
* An electron pathway should exist
10
Q
Advantages of plate heat exchangers
A
- Total stripping allows inspection and complete mechanical cleaning
- Ease of maintenance, easy to open up and clean or remove plates
- Damaged plates can be renewed relatively easily
- High efficiency-due to corrugated plate profile and flow distribution
- Low weight and size in comparison to shell & tube heaters
- Good corrosion/erosion resistance
- Size can be altered by adding and removing plates
- Single frame can be used for cooling several different fluids
- Smaller than tubular
11
Q
Jacket Water Testing
A
- we test for chromate in the water which normally sits around 100 ppm but should never go below 550 ppm, exact levels of concentration will be detailed by the engine manufacturer.
- We also test for alkalinity of the water which should not exceed 9.8 Ph, this is controlled via a chrome inhibitor which is designed to establish an alkalinity below a pH of 9.8.
- The third test is for chloride content. Saltwater leaking from the heat exchangers is the most common source of chloride.
- The cooling water system of each engine should be tested weekly to determine the chrome inhibitor level and the chloride and alkalinity levels.
12
Q
Turbocharger terminology:
Inducer
Diffuser
Volute casing
Nozzle Ring
firtree blade root
damping wire
A
- Inducer
The inducer is the part of the turbocharger that first draws in air. It increases the air’s speed before it goes to the main compressor blades, helping start the compression process efficiently. - Diffuser
The diffuser slows down the high-speed air from the compressor wheel, converting its speed into higher pressure. This helps increase the air pressure, which is crucial for better engine combustion and performance. - Volute Casing
The volute casing is the spiral-shaped housing that surrounds the compressor and turbine wheels. It collects compressed air from the compressor and directs exhaust gases to the turbine. It ensures smooth airflow and maintains pressure, enhancing turbocharger efficiency. - Nozzle Ring
The nozzle ring contains fixed vanes that direct exhaust gases onto the turbine wheel at the right angle and speed. This helps the turbine work more efficiently by optimizing gas flow, improving the turbocharger’s performance. - Firtree Blade Root
The firtree blade root is a special design for attaching turbine blades securely to the turbine wheel. It allows for safe attachment even with thermal expansion and mechanical stress, preventing the blades from coming loose during high-speed operation. - Damping Wire
The damping wire is inserted into turbine blades to reduce vibrations. It absorbs and dissipates vibrational energy, reducing the risk of blade fatigue and failure, thus extending the blades’ lifespan and maintaining turbocharger reliability.
13
Q
Air start Regulations
A
- The minimum capacity of the air compressors should be matched to the starting air requirements of the engine
- All high pressure lines in the system to be of solid drawn pipe
- There must be at least 2 starting air receivers
- The total capacity of the air receivers must contain sufficient air to provide 12 starts for a reversing engine or 6 starts for a non-reversing engine with CPP
- Two or more air compressors are to be fitted having a total capacity capable of charging the air receivers within 1 hour from atmospheric pressure to the pressure sufficient for the number of starts required
14
Q
Air bottle drawing
A
draw it
15
Q
Air start valve drawing
A
draw it
