How to read this note: This article mainly summarises LR Survey Procedures Manual requirements for Tailshafts / Screwshafts. Some sections add field practice supplements, such as keyless propeller fitting records, stern tube oil trend interpretation, and shaft alignment influencing factors. For practice supplements, actual survey work should still follow the latest LR Rules, approved drawings, manufacturer procedures, and class surveyor / technical department guidance.

Quick read

Understand the Note Through Four Judgement Points

A tailshaft survey is not just a single component check. It is where propulsion system risks meet: material, machining, propeller fit, bearings, sealing, corrosion protection, and class records all connect.

01 High risk, low visibility

The tailshaft is subject to torque, bending moment, axial load, and corrosion risk. Cracking, liner failure, or seawater ingress can lead to propulsion failure or propeller loosening.

02 Be conservative with keyed propellers

The keyway is a typical stress concentration area. During periodical screwshaft surveys, a keyed propeller must be removed so that MT can be carried out on the shaft taper.

03 The Chief Engineer cannot substitute for the survey

A Chief Engineer cannot carry out the tailshaft survey for classification purposes. This restriction applies in CSM and MPMS contexts. SCM is Screwshaft Condition Monitoring and does not replace the requirement to remove a keyed propeller and perform MT on the taper.

04 Reports are the baseline for future surveys

Bearing clearances, poker gauge readings, special liners, protective wrapping, repair results, and rejected shaft markings must all be traceable for the next surveyor.

Scope note: This article is a learning summary based on the provided Survey Procedures Manual. It is suitable for study, survey preparation, and field understanding. Formal decisions must still be based on the latest LR Rules, Survey Procedures, statutory requirements, and class technical review.

Document logic

Document Logic: A Closed Loop from Manufacture and Installation to In-Service Survey

This procedure is not simply a design formula. It converts rule requirements into survey work that can be performed, witnessed, recorded, and followed up by surveyors.

New construction survey at manufacturer's works

  • Material, dimensions, and machining quality
  • NDE such as UT, MT, and PT
  • Bronze / gunmetal liners and hydraulic test
  • Identification stamping and certificate endorsement

Builder / yard survey

  • Delivery condition and outstanding items
  • Shaft alignment and coupling bolts
  • Bearing clearance and poker gauge baseline
  • Sea trial and Form 2095B

Periodical survey of existing ships

  • Propeller removal, taper, and keyway NDE
  • Liner ends, welds, and flange root
  • Corrosion protection wrapping and hidden corrosion concerns
  • Repair, renewal, and class records
Survey context Description Core purpose
New Construction Survey at Manufacturer's Works New construction survey at manufacturer's works Confirm shaft manufacture, dimensions, surface quality, NDE, liners, hydraulic testing, and stamping.
New Construction Survey at Builder's / Fabricator's Yard New construction survey at builder's / fabricator's yard Confirm shaft delivery condition, installation, alignment, coupling, bearing clearances, and sea trial.
Periodical Survey of Existing Vessels / Installations Periodical survey of existing vessels / installations Check cracking, corrosion, liner looseness, propeller fit, corrosion protection coating, repairs, and record status.

Rules and prerequisites

Scope, Rule Basis, and Survey Prerequisites

Tailshaft / screwshaft procedures connect to ship rules, material rules, special service craft, offshore units, SCM, and MPMS. In the field, the first task is to confirm whether the applicable survey method permits the propeller to remain fitted, whether protective coating must be removed, and which items cannot be substituted by shipboard self-inspection.

Rule sources

The procedure itself is not the only basis

  • LR Rules for Ships: design, sea trials, periodical survey, and SCM.LR Ships
  • LR Rules for Materials: material manufacture, testing, and NDE.LR Materials Ch 5, 3.5
  • Rules for Special Service Craft: shafting and sea trial requirements for special service craft.Special Service Craft
  • Rules for Offshore Units: periodical survey requirements for offshore units.Offshore Pt 1 Ch 3, 12
  • ShipRight MPMS / SCM: machinery planned maintenance and condition monitoring schemes.ShipRight MPMS/SCM
Survey prerequisites

Confirm that the field conditions allow the required examination

  • For periodical surveys of keyed propellers, the propeller must be removed so that MT can be performed on the tailshaft taper.
  • TS Method 3 is not permitted for keyed propellers.
  • When the tailshaft is withdrawn, protective coating should be removed if its condition is suspect.
  • For flanged connections to the propeller boss, sample bolts may be removed where necessary.
  • If fiberglass or approved coating is confirmed effective at each dry docking, it should not be unnecessarily disturbed. Remove it only to the necessary extent when there is doubt.
Classification practice point: A Tailshaft / Screwshaft survey cannot be carried out by the Chief Engineer in place of a class surveyor for classification purposes. Even under Continuous Survey Machinery or MPMS notation, the required tailshaft checks must be performed or witnessed by a class surveyor.

New construction

New Construction Survey: What to Check at Manufacturer and Yard Stages

At the manufacturer stage, the focus is on material, machining, dimensions, and NDE. At the yard stage, the shaft is considered as part of the propulsion system, including delivery condition, alignment, coupling, bearing clearances, and sea trial baselines.

Manufacturer survey item What the surveyor should confirm
Dimensions and geometry Shaft diameter, roundness, straightness, keyway, taper, flange, and surface roughness should comply with approved drawings and strength requirements.
Surface quality Pay particular attention to stress concentration areas such as diameter changes, keyways, and the upper third of the taper. Use a profilometer or comparator blocks where necessary.
NDE MT is used for surface and near-surface cracks in ferromagnetic materials; UT is used for internal forging defects; PT is commonly used for non-magnetic materials or bronze liner welds.
Bronze / gunmetal linersBronze / gunmetal They should generally be cast in one piece and hydraulically tested before fitting. Fitting to the shaft should be witnessed by the surveyor, with close contact confirmed along the full length.
Two-piece welded liners Where CL notation is required, the joint design, PT examination, lead content not exceeding 0.5%, and shrinkage stress control requirements should be satisfied.
Identification stamping Stamp LR, SDO, control number, surveyor initials, and date. Stamping should avoid high-stress areas; if unavoidable, use low-stress or dot stamps. For straight shafting, stamping is normally on the coupling flange edge; if there is no integrally forged coupling, it should be on a visible part of the shaft not obscured by an adjustable or loose coupling. Also observe LR brand restrictions on the use of the LR mark and avoid misuse in inappropriate situations.
NDE Use
MT Surface / near-surface cracks at the tailshaft taper, keyway, flange root, etc.
UT Internal discontinuities and defects in forgings or shaft material.LR Materials Ch 5, 3.5
PT Non-magnetic materials, surface-breaking defects, and copper-alloy liner welds.
Yard installation focus Practical judgement Follow-up records
Delivery condition Confirm whether the shaft is delivered black forged, rough machined, or in final condition. If unfinished, check the shaft certificate and SDO data. Outstanding items, certificate limitations, and further survey requirements.
Shaft alignment

SPM requirement: Alignment should be carried out correctly and precisely according to the agreed procedure; the surveyor should confirm that distortion will not adversely affect alignment.

Field practice supplement: Hull / foundation deformation, support conditions, hot/cold state changes, propeller weight, and bearing load distribution are engineering judgement supplements; acceptance should still follow the approved procedure and class requirements.

 Seek local engineering TSO advice if there is doubt.
Coupling bolts Coupling bolts should be an interference fit; ISO h6/j6 may be accepted, and hydraulic bolts such as Suregrip or Pilgrim may be considered. If liquid nitrogen shrink fitting is used, future dismantling issues should be confirmed with the owner / operator.
Bearing clearance Measure shaft bearing clearances and poker gauge readings after new construction installation. Use these as the baseline for the First Entry Report and future periodical surveys.
Sea trial Multi-propeller ships should demonstrate that navigation and manoeuvring capability is retained when one or more propellers are out of operation.LR Sea trials Enter sea trial data, bearing clearances, and poker gauge readings in Form 2095B.Form 2095B

Periodical survey

Periodical Survey of Existing Ships: High-Risk Areas and Judgement Logic

The core of periodical survey is to find early signs at locations most prone to fatigue, corrosion, looseness, and fit failure. For keyed propellers, the keyway and large end of the taper must not be passed over by visual inspection only.

TS Method Judgement reminder: confirm propeller removal requirements before deciding whether a survey method is applicable.
TS Methods 1, 2, and 4 Where required by the Rules, the propeller must be removed for inspection.
Keyed propeller For all screwshaft periodical surveys, keyed propellers must be removed to allow MT of the taper.
TS Method 3 Not permitted for keyed propellers.
SCM Does not remove the requirement to remove a keyed propeller.

Differences Between Keyed, Keyless, and Flanged Connections

Type Survey focus
Keyed propeller Keyway, taper, MT, fretting, and nut locking condition.
Keyless propeller Field practice Taper contact, push-up amount, hydraulic fitting records, and mating surface condition. (Shafting / propeller assembly practice supplement; not an explicit requirement in this SPM section.)
Flanged connection to propeller boss Flange root radius, bolt tightness, and ringing. If the sound is dull or low resonance is noted, further NDE is required and sample bolts may need to be removed.
This SPM section mainly lists survey focus for keyed propellers and flanged connections to the propeller boss. Push-up amount, hydraulic fitting records, and fitting curves for keyless propellers are shafting / propeller assembly practice supplements. Actual requirements should be confirmed against approved drawings, manufacturer procedures, and applicable class rules.
Location Common defects Inspection method Main risk
Keyway Fatigue cracking, stress concentration MT, visual inspection Crack propagation, shaft fracture
Shaft cone / taper Fretting, corrosion, poor fit, cracking MT, visual inspection, contact check Propeller looseness, fatigue cracking
Large end of cone Circumferential corrosion band, suspected stress corrosion cracking MT is the main method for steel tailshaft tapers. PT is mainly used for non-magnetic materials, copper-alloy liner welds, or other applicable surface-breaking defects. Further assessment may be required. Branching circumferential stress corrosion cracks
Liner ends Corrosion, looseness, loss of sealing function Hammer sound check, visual inspection, local examination Seawater ingress to shaft material, causing hidden corrosion
Circumferential weld Weld cracking, leakage risk PT or suitable NDE Failure of corrosion protection
Flange root radius Fatigue cracking Visual inspection, NDE Flange failure, loss of torque transmission
Bolts Looseness, cracking, low resonance Ringing, NDE, removal of sample bolts Failure of propeller or coupling connection
Wrapped coating Debonding, damage, hidden corrosion underneath Visual inspection at dry docking; do not disturb if effective, remove locally or as necessary only when in doubt Hidden corrosion and loss of protective function
High-risk signal

Circumferential corrosion band at the large end of the taper

The procedure specifically notes that this may be associated with seawater ingress and branching circumferential stress corrosion cracks. Treat conservatively and arrange suitable NDE.

Field judgement

Abnormal sound when tapping the liner

The key is not only to decide whether it is loose, but to assess whether the liner has lost its core function of preventing seawater contact with the tailshaft steel.

Bolt check

Dull sound or low resonance

If ringing of flange or propeller bolts is abnormal, further NDE should be carried out and sample bolts may need to be removed.

Extended corroboration: stern tube lubricating oil contamination / metal content trends

Additional Reference Document: In the source material, IACS Rec.36 is an Additional Reference Document and may be used as supplementary data for oil-lubricated stern tube systems. It does not mean oil analysis is a fixed procedure required at every Screwshaft Survey under this SPM. Trends in metallic wear particles, water, or contamination in stern tube lubricating oil can help assess bearing, seal, seawater ingress, or abnormal wear risks; they may be included in overall judgement when field condition, history, or maintenance records need corroboration.

Response Flow After a Defect Is Found

01 | Find anomaly Cracking, corrosion, fretting, abnormal hammer sound, abnormal ringing, or coating concerns; abnormal oil trends may be used as extended corroboration (IACS Rec.36), not a mandatory procedure at every survey.
02 | Locate the area First locate whether it is at the keyway, large end of taper, liner end, circumferential weld, flange root, bolts, or wrapped area.
03 | Select NDE Select MT, PT, UT, visual inspection, hammer sound check, ringing, or further examination based on material and defect type.
04 | Assess impact Assess whether seawater exclusion, torque transmission, fatigue safety, mating surface reliability, or future operation risk is affected.
05 | Decide action Decide whether to accept the risk, repair, withdraw the shaft, refer to TSO, restrict future checks, or require renewal of the tailshaft / related parts.
06 | Update records Record conclusions, limitations, repair results, and follow-up requirements in Asset Note, Actionable Item, or Survey Report.

Repairs and alterations

Repair, Renewal, and Corrosion Protection: Repairable Does Not Mean Uncontrolled

Tailshaft repair involves material, heat effects, fit condition, and future class records. Even apparently local liner wear requires confirmation of lead content, cooling, post-weld NDE, and tight contact condition.

Bronze liner repair

Bronze liner weld repair conditions

  • Lead content of liner material and filler metal must not exceed 0.5%.
  • Machine worn areas smooth first.
  • Cool both ends of the repair area to avoid disturbing the shrink fit.
  • Peen after each weld pass.
  • After machining to final size, carry out PT or suitable crack detection.
  • Confirm the repaired liner area remains tightly fitted to the shaft.

If a bronze liner is repaired by welding and the attending surveyor is fully satisfied with the result, a Condition of Class for re-examination should normally not be raised. An appropriate record should still be kept in the Asset Note for future survey reference.

Shaft renewal

Tailshaft renewal requirements

  • Identification stamps on a rejected tailshaft must be cancelled by cross-cutting.
  • The replacement shaft must come from an approved works.
  • Confirm material strength, chemical composition, and thermo-mechanical process information.
  • Confirm dimensional tolerances, straightness, roundness, and approved drawings.
  • Complete suitable NDE and new identification stamping.
  • Record the rejected shaft and replacement shaft markings in the report.
Coating design

Conditions for a 5-year survey cycle

  • The coating must be of an LR approved type.
  • Fiberglass should be applied in multiple layers and wound in opposite directions.
  • Resin should be applied between layers, with the shaft rotated during application.
  • A suitable step or taper should be provided at the connection with the bronze liner.
  • Follow the manufacturer's requirements for surface preparation, temperature, mixing, application, and curing.
  • A 5-year survey cycle may be assigned only after the next Screwshaft Survey confirms all conditions are met or restored to satisfactory condition.

The applicable scenario for a 5-year survey cycle is narrow: mainly where short bronze liners are fitted at the bearings, the shaft sections between liners are protected by fiberglass or other approved coating, and that wrapped area is enclosed within the sterntube; not every tailshaft with wrapping or coating automatically qualifies.

Corrosion Protection / Wrapping

On multi-shaft ships, if protective coating on an exposed shaft section between the stern tube and A-bracket is damaged and indications suggest poor coating application rather than simple mechanical damage, the surveyor may require withdrawal of the tailshaft / screwshaft to check whether the wrapped shaft section inside the stern tube is similarly affected.
TSO escalation: If a non-welded bronze liner repair is proposed, or if unapproved coating, special joint design, alignment concerns, or unusual cracking risk is encountered, refer to the relevant TSO or Global TSO - Materials & NDE for technical confirmation.

Certification and reporting

Certification, Reporting, and Class Records: Making the Next Survey Traceable

Tailshaft survey records are highly valuable because many risks appear only after long-term accumulation. A good report does more than close the current survey; it preserves special designs, repairs, numerical baselines, and concerns that future surveyors need to follow.

01 | Shaft certificate After final machining, the surveyor should endorse both the original and duplicate shaft certificates.
02 | Liner notation When two-piece or multi-piece liners are joined by an approved method, the certificate should note the circumferential weld information.
03 | First Entry Enter sea trial data, bearing clearances, and poker gauge readings in Form 2095B.Form 2095B
04 | Asset Note Special conditions such as two-piece welded liners or bronze liner weld repairs should be made available for future surveyors.
05 | Actionable Item Items requiring follow-up, such as fiberglass or approved coating wrapping, should be tracked.
Situation Record requirement Practical purpose
Liner welded from two pieces Note it in the Shaft Certificate and Asset Note. Remind future surveys to check the circumferential weld for cracking or leakage risk.
Tailshaft wrapped with fiberglass or approved coating Create an Actionable Item and follow it up at dry docking or the relevant survey. Prevent corrosion under the wrapping from being hidden by an apparently intact surface.
Bronze liner weld repair completed satisfactorily If a bronze liner is repaired by welding and the attending surveyor is fully satisfied with the result, a Condition of Class for re-examination should normally not be raised; an appropriate record should still be kept in the Asset Note for future survey reference. Preserve the repair method, area, and points for future survey reference.
Wrapped area examined satisfactorily Mark CMM as continues satisfactory. Maintain condition monitoring and the future survey baseline.
Tailshaft rejected and renewed Record the rejected and replacement shaft identification marks in the report. Prevent the rejected shaft from being reused for classification purposes and preserve traceability.

Surveyor checklist

Surveyor Checklist: Turning the Procedure into Practical Steps

The following checklist can be used as a prompt before attendance and during manufacturer, yard installation, and periodical surveys. Formal surveys should still be adjusted according to applicable rules, actual ship arrangements, and class system requirements.

Step 1 | Confirm the survey type first
Type Survey focus
New construction survey at manufacturer's works Material, machining, dimensions, NDE, liners, hydraulic test, stamping.
Builder / yard survey Delivery condition, certificates, alignment, coupling, bearing clearances, sea trial.
Periodical screwshaft survey Propeller removal, MT, corrosion, liners, keyway, taper, bolts.
Repair / renewal survey Repair method approval, NDE, certificates, stamping, reports.
Protective coating survey Coating approval, adhesion condition, dry docking effectiveness; remove only to the necessary extent when in doubt and check for corrosion underneath.
Step 2 | Document review before attendance

Drawings and certificates

  • Approved drawings
  • Shaft certificate
  • Material certificate

NDE and machining

  • NDE reports
  • Dimensional and surface quality records
  • Liner hydraulic test and fitting records

Installation baseline

  • Shaft alignment procedure
  • Bearing clearance records
  • Poker gauge readings

Historical records

  • Previous survey reports
  • SCM / MPMS status
  • Asset Note / Actionable Item
Step 3 | Manufacturer and yard survey checklist
Manufacturer

Manufacturer survey

  • Whether the shaft material comes from an approved manufacturer.
  • Material strength, chemical composition, heat treatment / thermo-mechanical process.
  • Shaft diameter, length, flange, taper, keyway.
  • Surface quality, especially stress concentration areas and the upper third of the taper.
  • Whether UT and MT have been completed in accordance with the Rules.
  • Whether bronze / gunmetal liners are cast in one piece, hydraulically tested, and fitted under surveyor witness.
  • Whether stamping locations avoid high-stress areas; use low-stress or dot stamps where necessary and observe LR brand restrictions.
Builder / yard

Builder / yard survey

  • Confirm delivery condition and outstanding items.
  • Carry out shaft alignment in accordance with the agreed procedure (SPM requirement).
  • May also note hull / foundation deformation, support conditions, hot/cold state, and propeller weight effects on shaft line (field practice supplement).
  • Whether coupling bolts are interference fitted.
  • Whether future dismantling issues have been confirmed if liquid nitrogen shrink fitting is used.
  • Bearing clearances and poker gauge readings have been established as baseline.
  • Complete Form 2095B data after sea trial.Form 2095B
Step 4 | Periodical survey checklist
Inspection item Judgement point
Whether the propeller must be removed Remove when required under TS Methods 1, 2, and 4; keyed propellers must be removed for taper MT.
TS Method 3 Not permitted for keyed propellers.
Protective coating If the coating is confirmed effective at each dry docking, it should not be unnecessarily disturbed. If condition is suspect, remove locally or to the necessary extent to confirm the shaft material underneath.
Flange bolts Remove sample bolts as necessary; carry out further NDE if ringing is abnormal.
Large end of taper and keyway Check for fretting, corrosion, circumferential corrosion band, and signs of cracking.
Liners and welds Use hammer sound checks for looseness; for two-piece liners, pay attention to cracks in circumferential welds.

Field learning

Common Field Pitfalls

These mistakes usually do not come from not knowing what to check, but from mistaking a scheme, survey method, or visible condition for sufficient evidence.

Pitfall Correct understanding
Assuming SCM removes keyed propeller removal Incorrect. A keyed propeller still needs to be removed during periodical survey for taper MT.
Assuming the Chief Engineer can substitute for tailshaft survey Incorrect. The tailshaft survey for classification purposes cannot be carried out by the Chief Engineer.
Checking the shaft body but not the keyway The keyway is a high-risk fatigue crack origin, especially for keyed propellers.
Abnormal liner tapping sound not followed up Assess whether seawater exclusion has been compromised; do not merely record that there was a sound.
Ignoring fiberglass wrapping because it appears intact If cracking, debonding, blistering, or water ingress is suspected, local removal may still be required to verify the condition underneath.
Stamping in a high-stress area or misuse of LR brand Stamping may create stress concentration; avoid high-stress locations or use low-stress / dot stamps; the LR brand mark must not be misused in inappropriate situations.
Bronze liner weld repair without lead control or post-weld PT Lead content in base and filler materials must not exceed 0.5%, and crack detection is required after completion.
Two-piece welded liner not recorded in certificate / report Follow-up information should be left for future surveys, especially circumferential weld checks.

Glossary

Key Terms and Definitions

The glossary keeps the original terms and concise definitions for quick reference when reading class documents or communicating in the field.

Term / abbreviation Meaning Description
Tailshaft Tailshaft The shaft section near the stern that connects to the propeller.
Screwshaft Screwshaft Often used in documents in a similar sense to tailshaft.
Stern tube Stern tube The stern shafting structure containing stern tube bearings and seals.
Liner Liner Protects the tailshaft from seawater corrosion, commonly bronze or gunmetal.
Keyway Keyway The groove that transmits torque for a keyed propeller; also a stress concentration location.
Shaft cone / taper Shaft cone / taper The fitted area between propeller and tailshaft, where fretting, corrosion, and cracking require attention.
Fretting Fretting Wear and oxidation caused by small relative movement at mating surfaces.
NDE / MT / UT / PT NDE Respectively: non-destructive examination, magnetic particle testing, ultrasonic testing, and penetrant testing.
SCM Screwshaft condition monitoring Screwshaft Condition Monitoring, a class condition monitoring scheme.
MPMS Machinery Planned Maintenance Scheme Machinery Planned Maintenance Scheme, a class-approved maintenance scheme.
TSO / SDO Technical support / service delivery office TSO handles technical issues; SDO relates to certification, service delivery, and survey data.
Asset Note / Actionable Item Asset note / actionable item Used by future surveyors to check special designs, repairs, or items requiring continued follow-up.

Review points

Summary: Fourteen Review Points for Tailshaft Survey

Technical and Survey Points

  • The tailshaft is a high-risk propulsion component; survey attention focuses on cracking, corrosion, mating surfaces, liners, and alignment.
  • During periodical survey of a keyed propeller, the propeller must be removed and MT carried out on the tailshaft taper; TS Method 3 is not permitted for keyed propellers.
  • The tailshaft survey for classification purposes cannot be delegated to the Chief Engineer. This restriction applies to CSM and MPMS contexts. SCM is Screwshaft Condition Monitoring and does not replace the keyed propeller removal and taper MT requirement.
  • At the manufacturing stage, pay attention to dimensions, keyway geometry, surface roughness, the upper third of the taper, and NDE.
  • Bronze / gunmetal liners should generally be cast in one piece and hydraulically tested; two-piece welded liners must meet the requirements and be PT examined.
  • Tailshaft liners must not be secured to the tailshaft by pins.
  • During periodical survey, the keyway, large end of taper, liner ends, circumferential welds, flange root, and bolts are all high-risk areas.

Records and Follow-Up

  • A circumferential corrosion band at the large end of the taper should be treated with high suspicion, as it may relate to seawater ingress and stress corrosion cracking.
  • Fiberglass or approved coating may provide corrosion protection. If it is found effective at dry docking, it should not be unnecessarily disturbed; when in doubt, the surveyor may require removal to the necessary extent to inspect the shaft material underneath.
  • Bearing clearances and poker gauge readings at new construction must be recorded as baselines for later in-service surveys.
  • Liquid nitrogen shrink fitting of coupling bolts may create future dismantling difficulty and should be confirmed with the owner / operator.
  • Bronze liner weld repair requires control of lead content, cooling, post-weld PT, and confirmation of tight contact; if satisfactory, a Condition of Class should normally not be raised, but an Asset Note should be kept.
  • A 5-year survey cycle applies only to a specific stern-tube internal wrapping arrangement, not automatically because wrapping or approved coating is fitted.
  • Identification stamps on rejected tailshafts must be cancelled. Replacement shafts must come from approved works and undergo material, dimensional, and NDE confirmation.
  • Special designs, welded liners, protective coatings, and repair results should be properly reflected in certificates, Asset Notes, Actionable Items, or Survey Reports.