Two types of propellers are commonly found in vessels: Fixed Pitch Propeller (FPP) and Controllable Pitch Propeller (CPP).
The mechanism of fixed pitch propeller is self-explanatory by its name; the blades in such propeller are joined with the propeller boss hence its pitch remains unchanged. On the other side, in controllable or variable pitch propeller, the propeller blades are affixed to the boss while allowing the pitch to modify through hydraulic system. However, both propeller systems have some advantages and disadvantages.
The CPP allows the main engine to start with blade pitch set to 0. This effect in less fuel consumption while diminishing the workload on various engine bearings and its shafting during the starting procedure.
Engineers, who are employed on vessels with CPP drive, should take into account the following safety measures before operating it:
- Operation from remote position: The CPP from remote control position is operable for ahead, astern and stop position and monitor the pitch position indicator located close by the stern shaft.
- Operation from emergency position: Run the CPP from Emergency control position, it is placed near the stern shaft for ahead, astern and stop position and checks the pitch position indicator.
- Check for leakages: Keep checking for oil leakage from the system. Make sure there is no outflow otherwise the system will fail at later stage of operation.
- Maintain the oil level: Observe vigilantly and make sure that the oil level in the hydraulic tank of the system maintains up to the required quantity consistently. Alongside this pay attention to the working condition of all the alarms present inside the tanks.
- Check the pressure: Do not compromise on loss of pressure once the desired angle of pitch is obtained.
- Start the engine at zero pitch angle: The compelling reason to start the engine at zero pitch angle is to gain zero propeller resistance especially at the start which will lead to less amount of load on the shaft bearings.
- Check all the parameters: Being a significant precaution to be taken before operating CPP, it is important for the mariners to calculate if all the parameters of the main engine are working within limits. Under such domain the checking of the temperature of all bearings including shaft bearings is noteworthy.
- Carry out hydraulic oil analysis: Analysis of hydraulic oil used in the CPP weighs considerably and should be carried out on board to examine the condition and water intrusion.
- Run engine at constant speed: Engineers should put into account that the engine runs at constant speed, even at reduced load, as the shaft generator is fixed with power Take off/Gear constant ratio for power production.
- Perform frequent overboard checks: Frequent overboard checks are highly crucial to scrutinize the working during starting of CPP and to observe any oil leakage from the sealing ring.
- CPP is rather an expensive and complex installation than a Fixed Pitch Propeller. Moreover, it serves multi-purposely; it eases the use of other fuel efficient machinery such as shaft generator and relieves the burden on the ship’s engine. While appointing an engineer officer onboard it must be considered that the person is capable enough to know the system inside-out as it is a core component of the main engine in a vessel.
Maritime Survey Australia can assist you to take into account safety measures before operating your vessel. We can help inspect your Safety Equipment, Machinery and Engineering and Systems and Navigational Equipment.