A fixed pitch propellor (FPP) is typically a single component cast from Bronze. The blades are not removable so if they incur damage, repair is the preferred option. The alternative of propellor replacement is both costly and not short on lead time.
ATZ can support you with inspections and repairs afloat, in dock or even with a dive team. Either way, ATZ can support all your class approved FPP propellor requirements.

Fixed pitch propellors

Fixed pitch propellors are to be found on almost every vessel type, but most usually installed on ocean going vessels, for example:

  • Container vessels
  • Tankers
  • Bulk carriers
  • Dry cargo vessels
  • Passenger liners

That means a large variety of sizes and designs, but normally three, four or five blades and either standard or high skew in design.  High skew blades are applied to suppress cavitation-induced pressure impulses. By skewing the blade, it is possible to reduce the vibration level to less than 30% of an unskewed design. 

Fixed Pitch Repair

Due to the wide range of applications, the type of attention that a fixed pitch propellor could require is extremely varied and could be:

  • Propellor blade straightening due to grounding 
  • Cavitation repair 
  • Cracking due to impact damage or secondary effects of corrosion or cavitation
  • New blade tip installation by welding if tip damage is excessive

When damage is incurred, repair is the best way forward. Cropping damaged parts is an option but, at best, only a temporary solution. In time damaged blades will damage the delicate and well-balanced propulsion system. Besides, a damaged or fouled blade causes efficiency loss and will increase fuel costs. Either way, repair is always the efficient choice.

FPP Servicing

Even without the type of damage described above, a fixed pitch propellor will always require a minimum of servicing at dry dock and may also require attention in service: These activities include:

  • Polishing due to build-up of marine growth
  • Blade modification for increased efficiency
  • Balancing to reduce vibration
  • Inspection and non-destructive testing to meet class survey requirements

Inspection and polishing activities can be carried out in line with class requirements or in line with the owners needs for propellor efficiency.

Propellor Servicing or Repair needs. 

ATZ with our partner Aegir Marine are in position meet your propellor servicing or repair needs. 

FPP repairs will mostly take place afloat or at the shipyard but we can offer all options:

  • Vessel afloat, we work with qualified and experienced diving companies.
  • At the shipyard (basically anywhere), our propeller expert will carry out or supervise any required works to your propellor.
  • In-house, in our fully equipped workshop an excellent propeller repair team will carry out the repair. Our repairs are comprehensively supported by our in-house hydrodynamic engineer to ensure we return you and efficient and well-balanced propellor.

All our repair procedures are set up in close partnership with the classification society and are followed by detailed reports.


FAQ’s

Whats the difference between a fixed pitch propellor (FPP) and controllable pitch propellor (CPP)?

A fixed pitch propeller is typically cast in a single piece and has its pitch set at the factory. The propellor is tailor made for the vessel and is optimised for efficiency and minimised noise and vibration.
A controllable pitch propellor has separate blades that can rotate relative to the hub of the propellor. This means that the direction and speed of travel of the vessel can be changed without changing shaft rpm, or even changing the direction of shaft rotation. CPP propellors are typically required where a far greater range of manoeuvrability is required, or the vessels operational profile is more varied.

How are FPP propellors fitted?

The propellors are typically fitting on to a coned tail shaft. The equally coned propellor hub is hydraulically opened and pushed on to the propellor cone. When the hydraulic pressure is released the propellor shrinks on the tail shaft and grips it. The friction between the two components causes the propellor to rotate in line with tail shaft rotation. A propellor nut is also employed to axially locate the propellor and prevent loss of friction.
Propellor removal is the reverse.

Do I have to remove my propellor to repair it?

In most cases no. Repairs that can be carried out in situ are polishing cracks and cavitation damage, tip repair and straightening. More extensive repairs involving addition of material may need a controlled environment that requires transport of the propellor to a suitable facility.

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