Voluntary class notation for Tailshaft Monitoring.
Purpose
To offer operators the opportunity to avoid withdrawing the tailshaft if indications show that the tailshaft and stern tube bearing and its systems are working satisfactorily.
Benefits
DNV will not require any specific time interval between
complete tailshaft surveys, and the owner:
Avoids time-consuming operations during dry docking
Avoids the risk of damaging to the system during withdrawal
Reduces costs
Achieves an opportunity to monitor that the condition of the stern tube bearing and tailshaft are in good condition due to the system being followed up. When the system is properly implemented, the crew will be able to foresee possible damage and take preventive action
Features
This class notation is applicable to conventional propulsion systems. Tailshaft monitoring implies monitoring of the sterntube bearing, water content of the lub oil and litre lub oil refilled:
The stern tube bearings are oil lubricated.
A high-temperature alarm is fitted on the aft stern tube bearing.
Where one interchangeable sensor is fitted, one spare sensor is to be stored on board.
The setting of the stern tube high-temperature alarm should not exceed 65°C.
The sealing rings in the stern tube sealing box must be replaceable without having to withdraw the shaft or remove the propeller.
A system for measuring bearing wear must be fitted.
Electrical grounding of the shafting is mandatory.
The system must allow representative oil samples to be taken for an analysis of the oil quality under running conditions.
A written procedure for how to take oil samples is to be evaluated.
TMON gives the owner the opportunity to leave the tailshaft in position without pulling it out of the stern tube provided:
The technical requirements are met.
The TMON Record File is kept updated.
Oil samples are regularly analysed and found to be satisfactory by a recognised laboratory.
All stern tube bearing temperature values are within the manufacturer's recommended or limit values.