1. Power Card: This card shows the pressure-volume relationship throughout the power stroke of the engine. The area enclosed represents the work done per cycle. The indicator drum rotates in phase with the piston movement

Procedure:

• Fix a diagram paper on the indicator drum.
• Draw an atmospheric pressure line.
• Connect the cable to the indicator cam and open the indicator cock.
• Press the stylus on the paper to obtain the power card.

From the above sketch,

• 1-2 piston is moving upwards, scavenging the cylinder
• 2-3 Scavenging ports are shut, exhaust closing
• 3-4 Compression
• 4-5 Fuel injection and combustion cause rapid rise in pressure
• 5-6 Expansion: Piston forced down by expanding gases
• 6-7 Exhaust opens, cylinder blowdown, rapid pressure drop
• 7-1 Scavenge ports open, scavenging commences

2. Draw Card: Also known as an “Out of phase card”, this card provides a detailed representation of the entire combustion process, including compression, injection, ignition, maximum pressure (Pmax), and expansion. The indicator drum rotates 90° out of phase with the piston stroke.

Procedure:

• Fix a diagram paper on the indicator drum.
• Open the indicator cock and press the stylus on the paper while manually pulling the wire to rotate the drum and obtain the draw card.

3. Compression Card: Taken with fuel supply cut off, this card illustrates the compression pressure within the cylinder. It helps detect problems like worn cylinder liners, faulty piston rings, or leaking exhaust valves.

Procedure:

• Shut off the fuel supply to the cylinder.
• Replace the paper and follow the same steps as for the draw card to record the compression card.

4. Light Spring Diagram: This card uses a weaker spring to record the pressure variations during the exhaust and scavenging phases. It aids in detecting issues with these processes.

Procedure:

The procedure is similar to a power card, but with a light spring and a different phase movement during compression.

Fuel consumption and power output:

• Daily monitoring of fuel oil consumption alongside brake horsepower (BHP) provides a direct measure of fuel efficiency. Compare with results with Sea trial record.
• A rise in SFOC without a corresponding increase in BHP may indicate inefficiencies, such as poor combustion or mechanical losses.

Exhaust gas analysis:

• The exhaust gas temperature of each cylinder can indicate combustion quality and identify any imbalances or faults, such as incomplete combustion or poor fuel injection.
• Observing the color and composition of exhaust gases (e.g., black smoke indicating incomplete combustion or blue smoke suggesting oil burning) provides additional clues about engine performance.

Scavenge air pressure and temperature:

• These values, especially in relation to engine load, are required for assessing the performance of the turbocharger and air cooler system. Lower-than-expected scavenge air pressure can indicate turbocharger or air cooler malfunction.

Engine Speed (RPM) vs. Load:

• This relationship helps in determining if the engine is overloaded. A high power output at low RPM suggests an overload condition.
• Direct measurement of shaft power via a torsionmeter system, which measures torque and RPM, provides a measure of power delivered to the propeller.

Fuel System Performance:

• Ensure proper working of fuel pumps, injectors, and fuel delivery pressure. Faulty fuel systems may result in poor combustion and reduced power output.

Vibration Monitoring:

• Detecting unusual vibrations can identify problems with bearings, shafts or other mechanical components.

Lubricating Oil Analysis:

• Regular analysis can reveal signs of wear or contamination, indicating potential mechanical issues.