The slides, written out
AI-drawn illustration. Simplified to explain the idea, not to scale.
Slide 1 · VIBRATION IS A WARNING, NOT JUST NOISE
VIBRATION IS A WARNING, NOT JUST NOISE.
MAIN ENGINE
VIBRATION
CAUSES, CONSEQUENCES &
INVESTIGATION
Protect the engine. Protect the voyage.
UNDERSTAND IT TODAY,
PREVENT FAILURE TOMORROW.
Slide 2 · MAIN ENGINE
MAIN ENGINE
VIBRATION
WHAT COULD BE CAUSING IT?
1
TORSIONAL RESONANCE
Periodic engine excitation can coincide with a natural torsional frequency of the crankshaft and shafting system, producing excessive torsional vibration and stress. A specified barred speed range may therefore be established.
2
PROPELLER INDUCED VIBRATION
Propeller imbalance, blade damage or fouling can introduce periodic excitation into the propulsion system.
3
BEARING WEAR OR LOSS OF SUPPORT
Stern tube or intermediate bearing wear, looseness or shaft misalignment can alter shaft support and generate abnormal vibration.
4
SHAFT OR COUPLING DAMAGE
A shaft fatigue crack or coupling defect can change the dynamic behaviour of the propulsion system and produce abnormal vibration.
5
CYLINDER IMBALANCE
Unequal cylinder power, defective fuel equipment or combustion problems can create uneven engine excitation.
6
STRUCTURAL RESONANCE
Machinery excitation can coincide with a natural frequency of local ship structure, producing local vibration.
KEY TAKEAWAY: The vibration frequency, operating RPM, load and trend must be assessed together.
Slide 3 · WHY SHOULD YOU
WHY SHOULD YOU
NEVER IGNORE
ABNORMAL VIBRATION?
THE CONSEQUENCES
TORSIONAL / SHAFTING STRESS
Resonance can produce excessive alternating
stresses in crankshaft and propulsion shafting
components.
BEARING & RUNNING GEAR LOADING
Abnormal dynamic loads can increase loading
and wear of bearings and associated
running gear.
FATIGUE DAMAGE
Repeated vibration can contribute to fatigue
damage in shafts, couplings, supports and
other components.
SECONDARY EQUIPMENT DAMAGE
Persistent vibration may loosen fasteners and
damage piping, instruments, supports and
other machinery components.
STRUCTURAL VIBRATION
Local structural vibration can lead to fatigue
concerns and deterioration of affected
structures.
OPERATIONAL RISK
Severe vibration can restrict safe engine operation
and may affect the vessel's ability to maintain
the required operating condition.
REMEMBER:
Vibration is not just noise.
It is a warning of dynamic loading.
Slide 4 · SECOND ENGINEER APPROACH
SECOND ENGINEER APPROACH
OBSERVE → ISOLATE → ANALYZE
1
RECORD THE OPERATING CONDITION
Accurate data helps you understand the vibration pattern.
• Engine RPM
• Engine load
• Vibration location
• Vibration severity
• Bearing temperatures
• Exhaust temperatures
• Fuel indices / rack positions
• Scavenge air pressure
• Turbocharger RPM
• Any abnormal noise or change
2
IDENTIFY THE PATTERN
Determine how the vibration behaves with changes in operation.
RPM
Does it occur within a particular speed band?
FREQUENCY
What frequencies dominate the vibration spectrum?
LOAD
Does the condition change significantly with engine load?
TREND
Is the vibration new or progressively increasing?
3
ISOLATE THE SOURCE
Use appropriate vibration measurements at machinery / shafting bearing locations and compare the frequency spectrum with operating RPM and historical data.
✓ If propeller, bearing, alignment or shaft damage is suspected, use the appropriate inspection and diagnostic procedure rather than relying on vibration frequency alone.
CRITICAL PRINCIPLE:
A frequency signature is a diagnostic clue — not a diagnosis by itself.
| |
Slide 5 · RECTIFICATION & REPORTING
RECTIFICATION & REPORTING
WHAT SHOULD THE SECOND ENGINEER DO?
1
PROTECT THE MACHINERY
If severe vibration occurs, reduce speed as operationally safe and avoid continuous operation within an identified barred speed range.
2
CONFIRM THE SOURCE
Compare observations with:
• Maker's operating instructions
• Torsional vibration documentation
• Vibration analysis
• Maintenance history
• Bearing condition
• Alignment information
• Propeller inspection findings
3
RECTIFY ACCORDING TO CAUSE
Take appropriate corrective action based on the identified cause.
BARRED SPEED RANGE
Avoid continuous operation within the specified range and follow the approved operating procedure.
PROPELLER PROBLEM
Arrange appropriate underwater inspection, repair or drydock action as required.
BEARING / ALIGNMENT PROBLEM
Investigate bearing condition and shaft alignment and carry out corrective maintenance.
CYLINDER IMBALANCE
Check cylinder performance using appropriate pressure / power measurements and compare fuel indices and exhaust temperatures. Any adjustment must remain within the engine manufacturer's specified limits and procedure.
4
REPORT & FOLLOW UP
Record the defect, operating limitation and corrective action through the vessel's SMS as applicable, and inform the Chief Engineer / Superintendent as required.
Record
Assess Risk
Corrective Action
Inform
The ISM Code provides the framework for safe management and operation, including risk assessment and appropriate safeguards.
OBSERVE THE VIBRATION.
IDENTIFY THE FREQUENCY.
PROTECT THE MACHINERY.
FIND THE ROOT CAUSE.
Drafted by SailR from our daily lessons. AI-drawn illustration. Simplified to explain the idea, not to scale. Last updated 19 Oct 2026.
Spotted a mistake?
