Section 12 Screwshafts, tube shafts and propellers

12.1.1 Shafts with keyed propeller attachments and fitted with continuous liners or approved oil glands, or made of approved corrosion resistant materials, are to be surveyed at intervals of five years when the keyway complies fully with the present Rules.

12.1.2 Shafts having keyless type propeller attachments are to be surveyed at intervals of five years, provided they are fitted with approved oil glands or are made of approved corrosion resistant materials.

12.1.3 Shafts having solid coupling flanges at the after end are to be surveyed at intervals of five years, provided they are fitted with approved oil glands or are made of approved corrosion resistant materials.

12.1.4 All other shafts not covered by 12.1.1 to 12.1.3 are to be surveyed at intervals of 21/2 years.

12.1.5 Controllable pitch propellers for main propulsion purposes are to be surveyed at the same intervals as the screwshaft.

12.1.6 Directional propeller and podded propulsion units for main propulsion purposes are to be surveyed at intervals not exceeding five years.

12.1.7 Water jet units for main propulsion purposes are to be surveyed at intervals not exceeding five years, provided the impeller shafts are made of approved corrosion resistant material or have approved equivalent arrangements.

12.1.8 Dynamic positioning and/or thruster-assisted mooring and athwartship thrust propellers and shaftings are to be surveyed at intervals not exceeding five years.

12.2.1 For self-propelled disconnectable units, screwshaft surveys held afloat at five-yearly intervals are to comply with the following:

1. Measurement of bearing weardown.
2. Verification of tightness of oil glands.
3. Examination of propeller and fastenings.
4. Verification on board of documentation of stern tube lubricating oil analysis carried out at regular intervals not exceeding six months. Each analysis, to be carried out on oil samples taken under service conditions and representative of oil within the stern tube, is to include the following minimum parameters:
   1. Water content.
   2. Chloride content.
   3. Bearing material and metal particle content.
   4. Oil ageing (resistance to oxidation).
5. Verification of records of oil consumption and bearing temperatures.

12.2.2 Directional propeller and podded propulsion units are to be dismantled for examination of the propellers, shafts, gearing and control gear.

12.2.3 Dynamic positioning and/or thruster-assisted mooring and athwartship thrust propellers are to be generally examined so far as is possible and tested under working conditions afloat for satisfactory operation.

12.2.4 Podded propulsion unit screwshaft roller bearings are to be renewed when the calculated life at the maximum continuous rating no longer exceeds the survey interval. See Pt 5, Ch 9, 6.3 Propulsion shafting 6.3.8 of the Rules for Ships.

12.3.1 If a self-propelled unit enters dry dock any time after five years from the previous dry-docking, date of build or date of commissioning, as applicable, a complete screwshaft survey is to be held.

12.3.2 All screwshafts are to be withdrawn for examination by LR's Surveyors. The after end of the cylindrical part of the shaft and forward one third of the shaft cone, or fillet of the flange, is to be examined by a magnetic particle crack detection method. In the case of a keyed propeller attachment, at least the forward one third of the shaft cone is to be examined with the key removed. Weardown is to be measured and the sterntube bearings, oil glands, propellers and fastenings are to be examined. Controllable pitch propellers, where fitted, are to be opened up and the working parts examined, together with the control gear.

12.3.3 Directional propeller and azimuth thruster units are to be dismantled for examination of the propellers, shafts, gearing and control gear.

12.3.4 Water jet units are to be dismantled for examination of the impeller, casing, shaft, shaft seal, shaft bearing, inlet and outlets channels, steering nozzle, reversing arrangements, and control gear.

12.3.5 Dynamic positioning and/or thruster-assisted mooring and athwartship thrust propellers are to be generally examined so far as is possible and tested under working conditions afloat for satisfactory operation.

12.3.6 Podded propulsion unit screwshaft roller bearings are to be renewed when the calculated life at the maximum continuous rating no longer exceeds the survey interval. See Pt 5, Ch 9, 6.3 Propulsion shafting 6.3.8 of the Rules for Ships.

12.4.1 Monitoring records are to be reviewed at annual survey for all units assigned the ShipRight descriptive note SCM (Screwshaft Condition Monitoring). The records that are to be maintained for oil and water lubricated bearings are detailed in the following sections.

12.4.2 Oil lubricated bearing records are to be available on board that include the following:

1. Lubricating oil analysis is to be carried out regularly at intervals not exceeding six months. Each analysis is to include the following minimum parameters:
   1. Water content;
   2. Chloride content;
   3. Bearing material and metal particles content;
   4. Oil ageing (resistance to oxidation).

   Note: Oil samples are to be taken under service conditions and are to be representative of the oil within the sterntube.

2. Oil consumption
3. Bearing temperatures

12.4.4 For maintenance of the descriptive note SCM, the records of all data collected inPt 1, Ch 3, 12.4 Screwshaft Condition Monitoring (SCM) and Pt 1, Ch 3, 12.4 Screwshaft Condition Monitoring (SCM) are to be retained on board and audited by LR annually.

12.4.5 Where the requirements for the descriptive note SCM have been complied with, the screwshaft need not be withdrawn at surveys as required by 12.3.2, provided all condition monitoring data is found to be within permissible limits and all exposed areas of the shaft are examined by a magnetic particle crack detection method or an alternative approved means for shafts with a protective liner or coating (see Pt 5, Ch 6, 4.1 Screwshaft Condition Monitoring (SCM) 4.1.3 of the Rules and Regulations for the Classification of Ships). The remaining requirements of Pt 1, Ch 3, 12.3 Complete surveys are to be complied with. Where the Attending Surveyor considers that the data presented is not sufficient to determine the condition of the shaft, the shaft may be required to be withdrawn in accordance with Pt 1, Ch 3, 12.3 Complete surveys. For water lubricated bearings, the screwshaft is to be withdrawn for examination, as Pt 1, Ch 3, 12.3 Complete surveys, when the unit reaches 18 years from the date of build or the third Special Survey, whichever comes first.

12.5.1 A Modified Survey may be accepted at alternate five-yearly surveys for shafts described in Pt 1, Ch 3, 12.1 Frequency of surveys, provided that they are fitted with oil lubricated bearings and approved oil glands, and also for those in 12.1.2 and 12.1.3.

12.5.2 The Modified Survey is to consist of the partial withdrawal of the shaft, sufficient to ascertain the condition of the stern bearing and shaft in way. For keyless propellers or shafts with a solid flange connection to the propeller, a visual examination to confirm the good condition of the sealing arrangements is to be made. The oil glands are to be capable of being replaced without removal of the propeller. The forward bearing and all accessible parts, including the propeller connection to the shaft, are to be examined as far as possible. Weardown is to be measured and found satisfactory. Where a controllable pitch propeller is fitted, at least one of the blades is to be dismantled complete for examination of the working parts and the control gear.

12.5.3 For keyed propellers, the after end of the cylindrical part of the shaft and forward one third of the shaft cone is to be examined by a magnetic particle crack detection method, for which dismantling of the propeller and removal of the key will be required.

12.6.1 The Classification Committee will be prepared to give consideration to the circumstances of any special case upon application by the Owner.