Ship Main Engine
Maintenance
brought to you by: Joseph S.E. Marlissa MME-FIMarEST
Presentation Outline
Marine Machineries Failure Case
Marine Machineries Component
Fatigue
Marine Fuel Oil
Conclusion
Quiz
Marine Machineries
Failure Case
Several Case of Marine
Machineries Failure
Crank Case
Explosion
Crank Shaft
Crack
Fatigue Failure
Crack Failure
Corrosion
Piston Securing
Arrangement
Piston Crown
Crack
Crosshead
Stress
Concentration
Bed Plate
Stress
Concentration
Screw Shaft
Crack
Leak
Oil Gland
Sleeve
Engine Room
Flood
Crank Case Explosion
A main engine with 8 cylinders, 740 mm bore and the break power of 5,215
kW. The ship experienced 2 crank case explosions. The first explosion
happened in a simple form. After the engine was cooled down, all rotating
and oscillating components are being inspected, and there is no abnormal
condition related to the components. Considering the condition, the main
engine is being restarted and the ship continues to sail. Several moments
later, there’s an enormous explosion within the crankcase followed with a
serious fire . Because of the incidents, 4 crews passed away.
Figure 1
Figure 1 and 2 depicts the conditions of the integral thrust collar which after
the first explosion missed by the engineers. The figure shows that ahead thrust
pads experienced damage while its collar experienced great friction
Early Indication: There’s an abnormal vibration while ship at full speed. The
great vibration happened at flywheel area. Engineer must stop the engine
immediately and check whether the vibration caused by thrust block pads
worn or camshaft drive chain.
Figure 2
Crank Shaft Cracks
Weld Repair
• Medium speed V engine 6400 kW BHP
• Thin wall shell bearings installed on crankshaft
• This engine type commonly experienced damage due to
crank pin damage as the effect of thin wall shell bearing
damage
• The inspection finds that the bearing is misplaced in its
housing and secured with locking horns on the correct
position
Figure 3a
• This kind of error must be prevented, and the locking bolt
must be installed according to designer recommendation
torques
• The cleanliness must be maintained at all times
Figure 3b
Crack Failure
• Medium speed main engine 4500 kW BHP
• Within the inspection process, there’s a crack on the crank
pin
• There are 2 kinds of crack provided by figure below
Longitudinal
Crack
Crack
Figure 5
Branching
Crack
• Longitudinal crack is typical heat hireline crack which
caused by overheating
• Branching crack may be caused by torque
Corrosion
• This kind of damage commonly experienced by the main
engine which its piston cooling utilizes freshwater
• The corrosion caused by leakage which enable the
freshwater entering the crank case
• After laboratory examination, the freshwater contains
sulphur and already contaminated the lube oil
• The corrosion also can be caused if the lube oil infected by
microbial bacteria which can survive at the temperature of
220 C
Figure 6
Piston Securing
Arrangement
Figure 7
Figure 8
• A 6-cylinders main engine with 760 mm bore and 7612 kW
BHP
• At sea voyage, there’s a knocking sound which became
louder and louder
• Figure 8 depicts piston rod assembly, skirt and piston crown
• To prevent the rotation of 2 locking bolts, the engineer
utilizes used securing plate with thickness of approximately
3.2 mm
• The usage of securing plate is allowable for one time only
due to the bending and straightening can caused fatigue
• The knocking sound caused by repeated impact
• The repeated impact caused one of the locking bolt
experienced anti-clockwise rotation
• The rotation hits cast iron diaphragm between crank case
and scavenge space
Piston Securing Arrangement
cont’d
• The impact take place when the piston moving from the top
dead center to bottom dead center
Figure 7
• The knocking process creates spark which caused the oil
scrapper assembly fall in the crankcase
• Scavenge air and the fire enters the crank case causing
explosion
• All crank case doors kicked out from the main engine
• One of the engineer which located near the exploded
cylinder is being thrown and passed away
Figure 8
Piston Crown Crack
• Main engine with cylinder diameter of 760 mm and 6341 kW
BHP
• Oil cooled piston crown experienced crack, which enable
the lube oil entering the combustion chamber
• The checking process done by surface polishing and
etching, gave crack image at Heat Affected Zone
• The crack surely caused due to the unofficial piston crown
weld repair
Figure 9
• The welding process of steel casting material is must be
done under the recommendation of classification surveyor
• The welding process should be done with Welding
Procedure Specification equipment, welded by the certified
welder , followed by post heat treatment and NonDestructive Test (UT and PT)
Figure 10
Crosshead Stress
Concentration
• A 6-cylinders main engine with 750 mm bore and 6341 kW of
BHP
• When Continuous Survey of Machinery being conducted,
number 4 and 6 cross heads bearings and cross head pin
experienced crack as shown by Figure 12
Figure 11
• Due to the findings, all of the cross head are ordered to be
inspected and the result shows all cross head experienced
same crack
Analysis: Crack initiate on stress concentration zone due to
the absence of radius on the hole peak where the thread hole
located
Bed Plate Stress
Concentration
• A 12-cylinders medium speed main engine with 410 mm
bore
• The grey cast iron bed plate of the main engine reported
experiencing a lot of crack at the bed plate
• The figure depicts that the crack initiated at “main bearing
keeps serated”
• The main cause of the crack is the stress concentration
which exceeded the limit of grey cast iron fatigue
• Some of the bed plate replaced with nodular cast iron
material and there’s no report regarding the same event
while using grey cast iron
Figure 12
Screw Shaft Crack
• Twin screw diving support ship with 1566 kW each
• Ship installed with screw shaft from forging carbon steel material and coated with liner stainless
steel (316L) start from stern tube bearings to “A” bearings
• The gap between the front and the back is being coated with glass fiber reinforced (GRP)
• Twelve (12) months after delivery, the ship torn a drift, the shaft broken off precisely at the edge
of “A” bracket liner
• Based on the inspection result, GRP coating was broken, and the seawater enters and forms
“electrolytic cell” working on stress concentration at the sleeve edge
• Figure 14 depicts that at the “A” construction, resultant from stress and corrosion fatigue
produced multi-star fracture
Figure 13
Figure 14
Leak Source
• Before ship leaves the shipyard, air pressure test
is being conducted towards assembly
propeller and tail shaft. The inspection utilized
soap water
• Figure A depicts aft seal utilized round form
rubber gasket ring and running seal with the
triangle form
• Oil gland function is to maintain the lube oil
pressure within the stern tube
• Running seal with perpendicular surface,
besides its use to maintain the pressure of the
lube oil, its function is also to prevent the
seawater enters the screw shaft cone
Figure 15
Oil Gland Sleeve
• The placement of bronze backing ring, distance piece, and
thick packing rubber is quite helpful to prevent additional
cost for machining oil gland sleeve
• This measure seems will work in a good way, but the reality
says the opposite since distance piece is too thick, resulting
the flange spigot out from the recess within the propeller
boss
• The condition explained above result in misalignment,
where the part of rubber seal ring losses its compression
Figure 16
Engine Room Flooding
• Figure 19 depicts the installation of main seawater cooling
pump onboard bulk carrier ship
• On a sea voyage, crew indicates there’s an increase of
water level underneath the engine room plate. The crew
tries to close the sea suction valves but failed
• Figure 17 depicts the water level raise to 5 m from keel
• The ship cannot be operated, and the sea suction valve
cannot be closed. This indicates the lack of maintenance
system onboard
• If the crew familiar with the onboard piping layout, as
depicts by Figure 18, there’s still a chance to prevent the
flood
Figure 18
Figure 17
Figure 19
Marine Machineries
Components Fatigue
Marine Machineries Failure because of
Fatigue
Component or
Unit Fatigue at
Operation
Component or
Unit Failure due
to Corrosion
Component or Unit
Fatigue
Component or Unit Fatigue
at Operation
Crankshaft
Generator
Straight Shafting
Screw Shaft
Crankshaft
Figure 1. Torsional Crankshaft
Fatigue Failure
• Crankshaft fatigue commonly happened because of
connection crack at crankpins or journals with crank web
• The failure caused by bending and/or torque
• Within the investigation it is essential to determine which are
the most dominant cause
• Figure 1 depicts the diagonal crack due to torsional
vibration
• It all starts from “oil hole” crank pin number 6 of 4 stroke
single acting 8-cylinders diesel engine
• The crank pin is being shrink fitted to the 2 crank webs, the
fatigue cracks continued to the crank web along 25 mm
• Main journal bearing and shaft alignment found intact
• Crankshaft has been operated for 9 years and
manufactured using tough forging material
Crankshaft
• Another crank pin failure from a scavenge pump crank
shaft start by 4-cylinders engine rotating at 92 rpm
• Figure 2 depicts the total engine running hour time 4000
hours with 83-88 rpm
• In those situation, the engine is on 2 nodes-8th order, with
critical revolution of 85 rpm
• The condition will give vibrational tension of 53780 kN/m2
with the crank shaft service hours of 12000 days
• Crack initiated from the lower part of the crank pin to the oil
hole, and continued to the upper part of the crank pin
Figure 2. Scavenge Pump Crack
• From the micrograph result, there’s a big structure and the
crankpin predicted weak towards shock and could not
receive heat treatment in a from of soft annealing
Figure 3. Scavenge Pump Macrostructure
Source: Lloyd’s Register Circulation Papers
Crankshaft
Figure 4. Crankshaft Failure (plus
fillet)
Figure 5. Crankshaft Failure
(recessed fillet)
• Figure 4 and 5 depicts the failure which initiated at the fillet
radii in a form of recessed or plus
• Some of the crack case related to inclusion or pitting
corrosion which give local stress concentration, those area
will experience high stress
Crankshaft
• It is complicated to interpret crankshaft failure during
operation
• Figure 6 depicts the stress load which form propagation
channel from cracks on crankshaft, moreover at recessed
type fillet radii
• The figure also shows that the stress distribution is
complicated enough, but on the other side from the
direction and crack extension, we can determine “stress
pattern” which leads to the cause of failure
Figure 6. Crankshaft Failure
(Recessed Failure)
Generator Straight
Shafting
• Figure 7 depicts several fatigue failure which experienced
by straight shafting
• The failure caused by bending fatigue where welded
reinforcement fin cause stress expansion effect
• Crack initiated at the edge of reinforcement fin
• Eventhough the bending stress fluctuation only around
31027 kN/m2, it can be considered as the wear increase
towards generator’s back bearing
Figure 7. Generator shaft failure
Generator Straight
Shafting
• Figure 8 depicts the failure of a coupling due to torsional
vibration
• Eventough the stress is not too high, there’s too many metal
cut at fillet radii which allows the installation of coupling
bolts and sharp notches without dressing
• The installation increased stress concentration
• The coupling should have bigger diameter compared to
free surface from fillet to flange
Figure 8. Shaft torsional failure
Screw Shaft Failure
• 3.5 % of surveyed screw shaft yearly amount must be rejected
• The screw shaft failure mainly caused by grounding, submerged foreign object collision or
because of fatigue
• The defect caused by fatigue mainly classified into 2 categories
Fatigue
Failure
Torsional
vibration
Bending
stress
• Torsional vibration related with corrosion and stress concentration in the end of the liner
• Bending stress reacted towards key-way, or the end part of biggest cone which
experienced heavy notch effect
Screw Shaft Failure
• Figure 12 depicts the unusual tear down of tailshaft
• The failure takes place at the cone
• The propeller of the affected ship is experienced bad
weather and entangled with a rope which stopped the
main engine
• Figure 13 depicts the crack initiated at the same channel
within key-way and continued in a spiral way caused by
torsional load
Figure 12. Tailshaft Failure
• The key-way crack is acceptable, and the failure gave the
example to design the key-ways along with its stress reliver
Figure 13. Keyway Fracture
Screw Shaft Failure
• Figure 14 depicts the failure caused by water enters the liner
which experienced hire line crack
• Even though the liner looks strong and tight , there’s a
perspiration indication which explains the seawater entering
within the tailshaft
• After the machining process, the crack with the depth of 89
mm has found
Figure 14. Water Penetrating
Through Liner
Component or Unit
Fatigue
Component or Unit
Fatigue due to Corrosion
Crankshaft
Tailshaft
Main Engine
Crankshaft
• Corrosion is one of the cause of fatigue
• Corrosion decrease the material strength and accelerates
fatigue
• Corrosion usually invisible in a form of pitting
• Corrosion pits at early stage, gives sharp notches which
resulted in high stress concentration
• Sharp fillet, recess fillet, holes are the most possible area
where the corrosion appears
• Figure 8 depicts the corrosion pitting at the crank pin and
fillet radii
Figure 8. Torsional Crankshaft
Fatigue Failure
Tailshaft
• Tailshaft commonly very susceptive experiencing corrosion
because of seawater penetration
• The seawater flows into the liner due to the damage of the
rubber ring
• Figure 15 depicts the tailshaft with the diameter of 38 mm
• The crack is the result of sweater penetration within the liner
• After the machining process, the tailshaft shows the failure in
a form of star cracks
Figure 15. Tailshaft Failure
Main Engine Corrosion
• Corrosion can be caused by the use of the damaged lube oil
• The lube oil damage can be caused by several factors such as
a. Oxidation
b. Water penetration into lube oil system
c. The leak of combustion product from cylinder
• If one of the factors above occurred, it can lead to corrosion pitting formation and
resulted in fatigue
Main Engine Corrosion
There’s a lot of proposal made to prevent or prolong the
corrosion or abrasion detailed below
• Material surface contact
a. Smooth surface material (Ra 0.5 micron)
b. Hardening one of the component
c. Nitriding one of the component
d. Surface plating
e. Phosphate coating
Figure 18. Preferential Failure by
Fretting Corrosion
f. Gasket for the material movement
Main Engine Corrosion
• Fitting and surface smoothness
a. Exceeding the limit during compress
b. Utilizing rough surface material without machining
c. Peened one of the surface
• Surface lubrication
a. Prevent the relative movement
b. Making oil groove and system sealing
c. The usage of special lubricant such as
Figure 18. Preferential Failure by
Fretting Corrosion
Marine Fuel Oil and
Consumption
Introduction to Marine Fuel Oil
• The commonly used fuel oil worldwide is the residual fuel oil
• Residual fuel oil is a leftover product from the process to get the lighter fraction
• The mixture of the residue is very complex, depends on the source of crude oil and refinery
complexity
• At the beginning marine fuel oil produced from residue, atmospheric or vacuum distillation
process
• The process produced unsatisfying result and to overcome it the distillation is continued to
the second stage which influenced marine fuel oil character detailed below
a. The reduction of residue within the fuel
b. Increase of density
c. Increase of micro carbon value
d. The increase of compatibility and stability
e. Possibility of small particles contamination from catalisator
Introduction to Marine Fuel Oil
Figure 1. Process of Residual Fuel Oil Production
Marine Fuel Oil Terminology
• Marine fuel oil grade sold under different names including Bunker Gas Oil
• Bunker gas oil is the type of distillate fuel which color is clear and clean and does not
contain residual components
• Diesel fuel (HSD and MDF) still contains small part of residual component
• Various names used by the supplier for residual fuel including the terminology of Bunker-C,
Heavy fuel oil, bunker fuel oil, and marine fuel oil. This type of fuel have higher viscosity
compared to the others. That is why HFO is cheaper relative to the others
• Fuel oil with maximum viscosity at temperature of 50 C, commonly used label “IF”
• For example, IF 180 is the fuel with maximum viscosity of 180 cSt at 50 C
Marine Fuel Oil Terminology
Table 1. Fuel Names Currently Used by some Major Oil Companies
Density
• Density is an absolute ratio between mass and volume at specific temperature which denotes
in SI unit kg/m3. As standard reference, 15 C is the temperature used for density calculation
• Density is needed for the quantity calculation to determine the optimum size of the gravity disc
of the centrifuge/purifier
• Specific gravity of a substance is the ratio between mass and volume at the same temperature
• Relative density of a substance is a ratio between mass of a volume at temperature t1 towards
the mass of water volume at temperature t2
• API Gravity is an arbitration scale embraced by The American Petroleum Institute to express
relative density of oil
• In general, density measured at various temperature, but to simplify the measurement, the
density measured at temperature where the fuel oil is stored
Viscosity
• Dynamic viscosity can also be called as absolute viscosity
• Marine fuel oil viscosity usually expressed in the term of kinematic viscosity which measured
in stokes
• Kinematic viscosity is the ratio between absolute viscosity and density measured at the
same temperature
• 1 centistokes = 1 mm2/s
• Sometimes viscosity quoted in “Engler”, “Saybolt”, or “Redwood”
Viscosity
Table 2. Viscosity Conversion Tables
Table 3. Viscosity Conversion Tables
Viscosity
•
•
•
•
The temperature control determined based on viscosity if the pour point of fuel oil is low
Maximum fuel viscosity to be transferred is 800-1000 cSt
While fuel injection to the diesel engine and boiler also viscosity dependent
Most of the motorship already equipped with fuel viscosity controller, therefore injection
temperature estimation normally not needed
Viscosity
Table 2. Viscosity-Temperature Chart
Table 4. Injection Temperatures for a Range of Viscosities
Propeller Law
• Fuel Oil Coefficient
Where;
D
= Ship Displacement
V
= Speed in knots
F
= Fuel burned per 24 hours (in tons)
Empirical Coefficient
• Cargo
= 60000-70000
• Tanker
= 70000-75000
• Container = 70000-80000
Propeller Law
• Admiralty Constant
“C” constant depends on the hull form (block coefficient) and line factor. Typical value used
by shipyard during sea trial test detailed as follows
• Cargo
= 435
• Tanker
= 420
• Container = 385
Propeller Law
• Apparent Propeller Slip
Where;
P
= Propeller Pitch (ft)
R
= Rpm
V
= Ship speed (knot)
Beaufort Scale
• Francis Beaufort is the inventor sea wind speed unit
• Francis Beaufort came from Britain Royal Navy
• Beaufort scale the wind speed as detailed below
Table 5. Beaufort Scale
Calculation Example
Tanker ship with below specification
• Ship power 16500 kW
• Speed 110 RPM (100% MCR)
• Propeller Pitch 4.2 m/rotation
At East 48 degree D.D. noon condition
• Cruising speed 12.8 knot, speed 04 rpm due northeast, ship displacement 28000 ton (2.2 m
by stern)
• Wind direction due southwest (30 degree) – 5 knot (Beaufort Scale 2)
• Sea current due South (0 degree) – 0.32 m/second
Calculation Example
Calculates
• Apparent Propeller Slip
• Wind Resistance
• Current Resistance
• Real Ship Speed
• Fuel Oil Consumption Coefficient
• Admiralty Constant
Calculation Example
• Apparent Propeller Slip
Calculation Example
• Wind Resistance
Calculation Example
• Current Resistance
Calculation Example
• Current Resistance
Calculation Example
• Actual Ship Speed
Calculation Example
• Fuel Oil Coefficient
Calculation Example
• Admiralty Constant
Conclusion
Failure and Fatigue of Marine
Machineries
The main cause of marine machineries fatigue and failure are
• Pressure differential between maximum combustion pressure and the cylinder exceeds 5%
• Mechanical vibration acceleration more than 5G which caused by excessive clearance
between piston and cylinder liner
• Neglect the intermediate or predictive maintenance between the 2 schedules of main engine
general overhaul
• Not conducting actual or simulation towards engine fuel oil cut off/tripping devices
• Not conducting routine laboratory analysis towards lube oil
• Misalignment of shafting
• Human errors and shore’s management support
a. Not reading engine maker maintenance or operation manual
b. Lack of competency
c. Crew’s language barriers
d. The usage of ingenuine spare parts
e. The delay of maintenance or spare part supply
f. The lack of shore based management support
Failure due to the Use of MFO
HSD and MDF
• It is adequate enough only to maintain the purification and filtering system
• The checking of fuel oil pump timing
• Injection must be test according to engine maker recommendation
HFO
• The preheater can only increase the fuel oil temperature until it reaches 110 C
Bio Diesel
• Mixing is not the same with blending
• Blending process must be done equally passing through the ventury tube with catalyst
titration and fuel additives
Quiz
1. Crank case explosion can be caused be several deficiency such as
Lack of circulation lubrication within the main
engine
Yes
No
Blowby exhaust gas at two strokes with under
piston scavenging within the crankcase, while
fuel oil tripping device for oil mist detector fail
to stop the main engine
Yes
No
Excessive vibration in axial direction where
torsional vibration damper fails to perform its
function
Yes
No
Yes
No
The change of shafting alignment due to centre
line run out
2. Several engine makers requires big end bearing and connecting rod bolts to be replaced
at 20000 running hours, with the reason of “normal fatigue lifetime”. The material fatigue can
be caused by
Lubricating oil pressure fails to lubricate the
rotating and oscillating engine components
Yes
No
There’s frequent overspeeding, even though the
tripping device still functioning
Yes
No
Yes
No
Yes
No
Influenced by cyclically stress, in form of sheer
and beding forces which leads to excessive
tensile stress, which caused bolts material
elongation which will be exceeding the limit of
plastic region
Caused by combination of vibration with center
line out and/or crank web’s deflection
3. A main engine utilizes IF 380 cSt at 40 C density 0.96 gram/cm3. While engine maker
requires the injector’s injection viscosity at 17 cSt. At which temperature the fuel oil must be
reached at main engine injectors
134 C
Yes
No
109 C
Yes
No
124 C
Yes
No
Because of steam supply, pressure and
temperature not adequeate enough where
the boiler pressure only 6 bar, steam
temperature reach fuel oil preheater at 110 C,
and at the injector the temperature only 90-92
C. Due to the statements, the chief engineer
blends IF 380 cSt at 90 C with HSD/MDF with
the ratio of 70% IF 380 cST with the HSD/MDF
30% at the mixing tank
Yes
No
4. Based on propeller-law, slip propeller influenced by
Utilization of inappropriate fuel
Yes
No
The change of propeller pitch as the effect of
propeller blade deformation which collide
with the underwater semi-submersible foreign
object
Yes
No
High Beaufort scale and sea current
Yes
No
Yes
No
Navigational error