Section 11 Screwshafts, tube shafts, propellers and water jet units

11.1.1 The requirements of this Section are only applicable to the first screwshaft survey on or after 1 January 2016 for yachts delivered before 1 January 2016. For subsequent screwshaft surveys, see Pt 1, Ch 4, 10 Screwshafts, tube shafts, propellers and water jet units.

11.1.2 For screwshaft survey requirements on yachts delivered on or after 1 January 2016, see Pt 1, Ch 4, 10 Screwshafts, tube shafts, propellers and water jet units.

11.2.1 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.

11.2.2 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.

11.2.3 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.

11.2.4 All other shafts not covered by Pt 1, Ch 4, 11.2 Frequency of surveys 11.2.1 are to be surveyed at intervals of 2¹/₂ years.

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

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

11.2.7 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.

11.2.8 Athwartship thrust propellers and shaftings are to be surveyed at intervals not exceeding five years, see Pt 1, Ch 4, 6.2 Complete Surveys 6.2.2.

11.3.1 All screwshafts are to be withdrawn for examination by LR's Surveyors at the intervals prescribed in Pt 1, Ch 4, 11.2 Frequency of surveys 11.2.1. 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 controlgear.

11.3.2 Directional propeller units are to be generally examined so far as possible, including the propellers, shafts, gearing, controlgear and primary electrical components, inclusive of control and protection devices.

11.3.3 Water jet units are to be generally examined so far as possible, including the impeller, casing, shaft, shaft seal, shaft bearing, inlet and outlets channels, steering nozzle, reversing arrangements, and controlgear. On completion an operational test is to be carried out.

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

11.4.1 Where oil lubricated shafts with approved oil glands are fitted or where approved water lubricated sternbush bearings are fitted, and the Owner has complied with the requirements of Pt 1, Ch 4, 11.4 Screwshaft Condition Monitoring (SCM) 11.4.2 or Pt 1, Ch 4, 11.4 Screwshaft Condition Monitoring (SCM) 11.4.3, the ShipRight descriptive note SCM (Screwshaft Condition Monitoring) may be entered in column 6 of the Register Book.

11.4.2 Oil lubricated bearings:

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

   • water content,
   • chloride content,
   • bearing material and metal particles content,
   • oil ageing (resistance to oxidation).

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

3. Oil consumption is to be recorded.

4. Bearing temperatures are to be recorded (two temperature sensors or other approved arrangements are to be provided).

5. Facilities are to be provided for measurement of bearing weardown.

6. Oil glands are to be capable of being replaced without withdrawal of the screwshaft.

11.4.3 Water lubricated bearings:

1. A means of monitoring and recording variations in the flow rate of lubricating water using two independent sensors is to be provided.

2. A means of monitoring and recording variation in the shaft power transmission is to be provided.

3. A maximum permitted weardown of the sternbush is to be submitted and approved wear monitoring equipment is to be fitted. The weardown allowance is to include both the absolute maximum allowable wear down and the weardown at which it is recommended to carry out an inspection and maintenance. An alignment analysis considering both the newly installed clearance and the proposed absolute maximum allowable weardown, demonstrating that the system will operate satisfactorily within these two limits, is to be submitted and approved.

4. For open loop systems the manufacturer is to submit information regarding the required standard of lubricating water filtration and lubricating water filters or separators are to be fitted which are able to achieve this requirement:

   • The lubricating water supply is to be fitted with continuous water sediment measuring or turbidity monitoring equipment with the results being recorded and retained on board and made available to LR on request; alternatively
   • There is to be a LR approved extractive sampling and testing procedure with the records held on board and made available to LR on request.

   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. Where a closed cycle water system is used, the pumping and water filtration systems are to be considered part of the continuous survey cycle and are to be subject to a Periodical Survey. Water analysis is to be carried out regularly at intervals not exceeding six months. Samples are to be taken under service conditions and are to be representative of the water circulating within the sterntube. Analysis results are to be retained on board and made available to LR on request.

   The analysis is to include the following parameters:

   1. Chloride content;

   2. Bearing material and metal particles content.

6. The shaft is either to be constructed of corrosion resistant material or protected with an approved corrosion resistant protective liner or coating. Where a protective liner or coating is used, this shall meet the requirements of Pt 11, Ch 2, 4.14 Corrosion resistant liners on shafts, and a means of assessing the condition of this liner is to be submitted and approved.

7. Glands are to be capable of being replaced without withdrawal of the screwshaft.

8. There is to be a shaft starting/clutch engagement block to inhibit starting the shaft until lubricating water flow has been established. This is to only act as a starting block; low lubricating water flow after shaft start is to be alarm only with no shutdown.

9. Alternative arrangements are subject to special consideration.

The means of monitoring and recording lubricating water flow and shaft power variation are to be submitted for approval.

11.4.4 For maintenance of the descriptive note SCM the records of all data collected in Pt 1, Ch 4, 11.4 Screwshaft Condition Monitoring (SCM) 11.4.2 and Pt 1, Ch 4, 11.4 Screwshaft Condition Monitoring (SCM) 11.4.3 are to be retained on board and audited by LR annually.

11.4.5 Where the requirements for the descriptive note SCM have been complied with, the screwshaft need not be withdrawn at surveys as required by Pt 1, Ch 4, 11.3 Normal surveys 11.3.1 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 (Pt 1, Ch 4, 11.4 Screwshaft Condition Monitoring (SCM) 11.4.3.(f)). The remaining requirements of Pt 1, Ch 4, 11.3 Normal surveys 11.3.1 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 4, 11.3 Normal surveys 11.3.1. For water lubricated bearings, the screwshaft is to be withdrawn for examination, as Pt 1, Ch 4, 11.3 Normal surveys 11.3.1, when the ship reaches 18 years from the date of build or the third Special Survey, whichever comes first.

11.5.1 A Modified Survey may be accepted at alternate five-yearly surveys for shafts described in Pt 1, Ch 4, 11.2 Frequency of surveys 11.2.1 provided they are fitted with oil lubricated bearings and approved oil glands, and also for those in Pt 1, Ch 4, 11.2 Frequency of surveys 11.2.2 and Pt 1, Ch 4, 11.2 Frequency of surveys 11.2.3.

11.5.2 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.

11.5.3 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.

11.5.4 Where the descriptive note SCM has been assigned as described in Pt 1, Ch 4, 11.4 Screwshaft Condition Monitoring (SCM) 11.4.1 and all data is found to be within permissible limits, partial withdrawal of the shaft may not be required. Where doubt exists regarding any of the above findings the shaft is to be withdrawn to permit an entire examination.

11.6.1 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.

11.6.2 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 removal of the key will be required. Oil gland and seals are to be examined and dealt with as necessary. Weardown is to be measured and found satisfactory. Propeller and fastenings are to be examined.

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