4 Stroke Engines

Question 1

Preparing 4 stroke engine from cold

Answer 1

• Inform Bridge and/or chief engineer
• Check LO sump level, governor LO
• Check expansion tank then pre-heat ME to 60 degrees with CW system and check coolers, monitor pressure and temps.
• Start LO pre-lube pump, check pressure, temps, leaks, cooler
• Start LO purifier
• Start economiser circ pumps to pre-heat economiser
• Check FO Service tank level is sufficient and drain any water

• Open indicator cocks and engage turning gear, use turning gear to slow turn for 2 revs, monitoring amps and indicator cocks.
• Disengage turning gear.
• Check pressure of Air Receivers, top up if needed and drain moisture

• Open start air valve
• Turn on air, observing indicator cocks
• Close indicator cocks
• Ensure fuel system is lined up & parameters are normal
• Startup engine, check fuel racks and do a round of the engine, monitor parameters
• Inform bridge ready for standby
• Inform CE

Question 2

4 stroke LO distribution inside engine

Answer 2

Travels through the main oil gallery drillings to the main bearing where it travels through drilled holes in the crankshaft to the big end bearings. It then travels up through the conrod and into the piston where it cools the crown and drains from the skirt. There are also 3 bar spring-loaded jet nozzles spraying the piston skirt continuously.

Question 3

4 stroke crankcase inspection

Answer 3

Inform bridge and ensure that there are enough engines available for the load
PPE
Isolate engine
Confined space entry procedure

Question 4

How to do tappet clearance on 4 stroke

Answer 4

PPE
Isolate engine
Open indicator cocks and engage turning gear
Open cylinder head covers
Turn flywheel to firing TDC markings on flywheel (push rods will not be tight)
Slide feeler gauge under (1mm inlet, 1.5mm exhaust)
Tighten v/v bolt then loosen while waiting for push rod to start moving freely (sweet spot)
Then tighten the locking bolt and remove the feeler gauge
Do for all cylinders and test

Question 5

Cylinder head mountings on 4 stroke

Answer 5

Spring loaded safety valve
Rocker arms
Inlet valves
Exhaust valves
Start air valve
Indicator cock
Cooling water inlet/outlet
Exhaust temp sensor

Question 6

4 stroke engine parameters

Answer 6

LO = 4.5 bar 65 degrees
FO = 6.5-7 bar 115 degrees (HFO viscosity = 12-14cSt)
HT = 4-4.5 bar 80 degrees into engine 87 out, through CAC1 then 94 degrees out

LT = 3 bar 40 degrees through CAC2 then 45 out CAC2
T/C LO = 3 bar
Charge Air = 2.5 bar 50 degrees
Main Bearings temp = 80-87 degrees
Exhaust gases = 380-420 degrees
TC in = 420 degrees
TC out = 290 degrees
Economiser in = 290 degrees
Economiser out = 200 degrees

Question 7

Why is the correct tappet clearance essential?

Answer 7

• Tappet clearance is the clearance between the cam and the roller on the pushrod, taken between the rocker arm and the valve stem tip.
• This clearance has to be perfect to ensure that the timing of the valves and fuel injection is optimal and to allow for thermal expansion of the v/v spindles to prevent leakages.
• If the clearance is too high, the valve would be open for a shorter timeframe as it would open late & close early, leading to hammering.
• If clearance is too low, the valve would be open too long, leading to high unit temps and the valve could even be open slightly for the full cam rotation.

Question 8

What pressure is fuel oil injected at?

Answer 8

~450 bar

Question 9

4 stroke alarms and trips (Wartsila 12V46)

Answer 9

• Trips
LO temp 80 (60-65)
HT temp after 110 (85-95)
Exhaust gas after cylinder 550
LO pressure 2 bar (4 bar)
OMD
Main bearing temps
Cylinder liner temps
Crankcase pressure
Mechanical & Electrical overspeed
Rated speed not reached

• Alarms only
Charge air temp 75 (40-60)
TC LO pressure
HT pressure 2 bar (3-4.5)
LT CAC 2 bar (3-4.5)
FO 4 bar (8 bar)
SA pressure 18 bar (30 bar)