Section 18 Screwshafts, tube shafts and propellers

18.1.1 The requirements of this Section are only applicable to the first screwshaft survey scheduled on or after 1 January 2016 for ships delivered before 1 January 2016. For subsequent screwshaft surveys, see Pt 1, Ch 3, 17 Screwshafts, tube shafts and propellers.

18.1.2 For screwshaft survey requirements on ships delivered on or after 1 January 2016, see Pt 1, Ch 3, 17 Screwshafts, tube shafts and propellers.

18.2.1 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.

18.2.2 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.

18.2.3 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.

18.2.4 All other shafts not covered by Pt 1, Ch 3, 18.2 Frequency of surveys 18.2.1 to Pt 1, Ch 3, 18.2 Frequency of surveys 18.2.3 are to be surveyed at intervals of 2¹/₂ years.

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

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

18.2.7 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.

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

18.3.1 All screwshafts are to be withdrawn for examination by LR's Surveyors at the intervals prescribed in Pt 1, Ch 3, 18.2 Frequency of surveys 18.2.1 to Pt 1, Ch 3, 18.2 Frequency of surveys 18.2.4. The after end of the cylindrical part of the shaft and the forward one-third of the shaft cone, or fillet of the flange, are 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 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 controlgear.

18.3.2 Directional propeller and podded propulsion units, inclusive of the propellers, shafts, gearing, controlgear and the primary electrical components including any control and protection devices, are to be dismantled if considered necessary and generally examined as far as practicable.

18.3.3 Water jet units, including the impeller, casing, shaft, shaft seal, shaft bearing, inlet and outlet channels, steering nozzle, reversing arrangements, and controlgear are to be generally examined so far as practicable.

18.3.4 Dynamic positioning and/or thruster-assisted mooring and athwartship thrust propellers are to be generally examined so far as possible in dry dock and tested under working conditions afloat for satisfactory operation. All accessible parts, including sealing, locking and bearing faces, and any other moving parts are to be examined. Non-destructive examination is to be carried out as considered necessary by the Surveyor on blade/fin roots. Consideration may be given to condition monitoring schemes for determining the condition of the unit.

18.3.5 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, 5.3 Propulsion shafting 5.3.7.

18.3.6 Stationary supporting structure and any erosion protection inserts or doublers are to be examined in way of any propulsion devices.

18.4.1  Monitoring records are to be reviewed at annual survey for all vessels 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.

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

1. Lubricating oil analysis to be carried out regularly at intervals not exceeding six months. Each analysis is to include the following minimum parameters:

   • water content,
   • chloride content,
   • bearing material and metal particles content,
   • oil ageing (resistance to oxidation) , minimum testing to include Viscosity and Total Acid Number (TAN).

   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.

18.4.3 Further information is provided in the LR document ShipRight Procedure Machinery Planned Maintenance and Condition Monitoring.

18.4.4 Water lubricated bearing records are to be available on board that include the following:

1. A record of variations in the flow rate of lubricating water.

2. A record of variations in the shaft power transmission.

3. Wear monitoring records for the sternbush.

4. For open loop systems the records from equipment for continuous monitoring of water sediment or alternatively records from a LR approved extractive sampling and testing procedure are to be available on board.

   Records of cleaning and replacement of lubrication filters/separators are to be maintained on board. The pumping and water filtration system is to be considered part of the continuous survey cycle and is to be subject to a Periodical Survey.

5. For closed cycle water systems the records from water analysis results carried out regularly at intervals not exceeding six months are to be retained on board. The analysis is to include the following parameters:

   1. Chloride content

   2. Bearing material and metal particles content.

   Note Samples are to be taken under service conditions and are to be representative of the water circulating within the sterntube.

   Note Records of cleaning and replacement of lubrication filters/separators are to be maintained on board. The pumping and water filtration system is to be considered part of the continuous survey cycle and is to be subject to a Periodical Survey.

18.4.5 For maintenance of the descriptive note SCM, the records of all data collected in Pt 1, Ch 3, 18.4 Screwshaft Condition Monitoring (SCM) 18.4.2 and Pt 1, Ch 3, 18.4 Screwshaft Condition Monitoring (SCM) 18.4.4 are to be retained on board and audited by LR annually.

18.4.6 Where the requirements for the descriptive note SCM have been complied with, the screwshaft need not be withdrawn at surveys as required by Pt 1, Ch 3, 18.3 Normal surveys 18.3.1, provided all condition monitoring data are 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 Pt 5, Ch 6, 4.1 Screwshaft Condition Monitoring (SCM) 4.1.3.(f). The remaining requirements of Pt 1, Ch 3, 18.3 Normal surveys 18.3.1 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, 18.3 Normal surveys 18.3.1. For water lubricated bearings, the screwshaft is to be withdrawn for examination, as Pt 1, Ch 3, 18.3 Normal surveys 18.3.1, when the ship reaches 18 years from the date of build or the third Special Survey, whichever comes first.

18.5.1 A Modified Survey may be accepted at alternate five-yearly surveys for shafts described in Pt 1, Ch 3, 18.2 Frequency of surveys 18.2.1, provided they are fitted with oil lubricated bearings and approved oil glands, and also for those in Pt 1, Ch 3, 18.2 Frequency of surveys 18.2.2 and Pt 1, Ch 3, 18.2 Frequency of surveys 18.2.3.

18.5.2 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. Wear down 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 controlgear.

18.5.3 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.

18.5.4 Where the requirements for the descriptive note SCM have been complied with, as described in Pt 1, Ch 3, 18.4 Screwshaft Condition Monitoring (SCM) 18.4.1 and all data are found to be within permissible limits, partial withdrawal of the shaft will not be required. Where doubt exists regarding any of the above findings, the shaft is to be withdrawn to permit an entire examination.

18.6.1 For shafts where the Modified Survey is applicable, upon application by the Owner, the Committee will be prepared to give consideration to postponement of the survey for a maximum period of half the specified cycle provided a Partial Survey is held.

18.6.2 The Partial Survey is to consist of the propeller being backed off in any keyed shaft and the top half of the cone examined by an efficient crack detection method for which the removal of the key will be required. On ships less than 15 years old, propellers with keyless connections to the screwshaft are not required to be backed off. Exposed areas of screwshaft, oil gland and seals are to be examined and dealt with as necessary. Weardown is to be measured, recorded and reviewed at each screwshaft survey and found satisfactory. Propeller and fastenings are to be examined.

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