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Propeller damage can be obvious or hidden. A strike on the quay leaves a bent blade that anyone can see. A slow loss of efficiency from erosion leaves nothing visible from the deck. Propeller damage in Nagoya can be assessed by a Diver without dry-docking, and an early assessment saves money.
The first signs are often vibration, a change in noise from the stern, a loss of speed at the same engine load, higher fuel consumption or unusual torque readings. A ship that has touched the bottom, a fender or a floating object should be checked even if nothing appears wrong. Crew often notice a new vibration before any other symptom.
The main causes of propeller damage are contact with the quay or the seabed, rope and net entanglement, floating debris, cavitation erosion and corrosion. Heavy fouling can also hide damage and cause performance loss. Ships operating in shallow, silty or busy waters are more likely to suffer from contact and debris.
The Diver first films the propeller as found. He then cleans it if needed and inspects each blade, noting bends, cracks, missing material, nicks and erosion. He checks the cone and cap, the boss and the surrounding stern frame. The photographs and the video go to the surveyor and the engineers.
Where it is possible, the Diver measures how far a blade tip is bent, the length of a crack or the size of a missing piece. Propeller makers and class societies have limits for repair and for continued use, and the measurement allows the surveyor to compare. Pitch and shape checks usually need a workshop and special equipment.
If damage is suspected, reduce power if the ship is at sea and avoid running the propeller at critical revolutions. At the berth, avoid turning the propeller unless necessary. Tell the owner and the class society, and call us for an inspection. Take note of the time, position and what happened.
After the assessment, the options include continued operation with monitoring, a repair afloat, or dry-docking for a repair or replacement. We report the facts and the surveyor decides.
A rope guard, careful berthing and avoiding debris-filled water all help. Regular inspections catch small problems early.
A common case involves a ship that has touched a fender or a mooring structure during berthing. There is a slight vibration afterwards, and nobody can say where it comes from. A Diver inspects and finds a bent blade tip, a few millimetres out of line. Dressing and a closer look at the shaft seal may be enough. Without the dive, the ship might have sailed with the damage and developed a bigger problem.
Call or write with the ship's name, the berth, what happened and the symptoms. We will arrange an inspection dive as soon as the berth and the weather allow.
Q1. What are the early signs of propeller damage?
Vibration, a change in noise from the stern, loss of speed at the same engine load, higher fuel use and unusual torque readings.
Q2. What are the main causes of propeller damage?
Contact with the quay or seabed, rope and net entanglement, floating debris, cavitation erosion and corrosion.
Q3. Can a Diver measure how bent a blade is?
Yes, where access allows. Pitch and exact shape checks, however, need workshop equipment.
Q4. What should be done first if damage is suspected?
Avoid unnecessary use of the propeller, note the time and position, inform the owner and class, and arrange a Diver inspection.
