TST Engineering Services | Module 32 Vessel Dry Docking Infographic

Professional visual recap

This visual overview now uses the upgraded TST training plates for the highest-value dry-docking inspection themes: document preparation, hull and dock-bottom checks, underwater fittings / thrusters, rudder drop measurement and stern tube / propeller-shaft inspection.

Dry dock preparation and document package chart — **Preparation package:** brings together PMS review, survey status, Class white list, shell expansion, GA, fore peak / fore plan, damage control plan, docking plan, fire control plan, repair specification, spares, contractors, isolations, critical path and shore services.

Hull dock-bottom and thickness gauging inspection chart — **Hull / dock-bottom route:** a first walk-round should cover the keel and block lands, flat bottom, bilge turn, shell plating, bulbous bow, propeller, rudder, anodes, boot-top line and all areas selected for close-up or thickness gauging.

Thrusters stabilisers and underwater fittings inspection chart — **Underwater equipment:** bow thrusters, stabilisers, sea chests, overboards, transducers and anodes must be checked against the docking plan, clearances, coating condition, wear, seal integrity and freedom of movement.

Rudder drop measurement using a trammel gauge — **Rudder drop measurement:** the trammel gauge is used internally at the tiller / steering flat between fixed reference points to monitor vertical movement of the rudder system and to identify wear in the carrier / pintle support arrangement.

1. Why dry dock?

Dry docking is the controlled grounding of a ship onto a planned block arrangement so normally submerged parts can be accessed safely. The aim is to inspect, repair, survey, test, coat and return the vessel to service in a verified condition.

Chief Engineer focus: integrity, safety, reliability, efficiency, Class acceptance and evidence.

Underwater areas exposed

Shell plating, coatings, bilge keels and anodes.
Sea chests, ship-side valves and overboards.
Bow/stern thrusters, stabilisers and sensors.
Rudder, propeller, shaft seals and stern tube.

2. Class, statutory rules and governance

IACS / Class

Uniform rule implementation, survey scope, surveyor attendance, approved repairs, NDT, pressure testing and repair records. Dry-dock work is governed by the vessel’s actual Class rules, approved drawings, survey status report and any outstanding Conditions of Class or recommendations.

Lloyd’s Register / DNV / other Class

Always work to the ship’s assigned Class society rules and maker limits. Dry-dock acceptance criteria for rudder clearances, stern tube wear-down, steel renewals, welding procedures and pressure tests must come from Class-approved data, not guesswork.

Statutory / SMS

SOLAS, MARPOL, Load Line, ISM/SMS, Flag, Port State and company procedures control safety, pollution prevention and certificate validity. The SMS should define permits, isolations, contractors, toolbox talks, risk assessments, handovers and close-out records.

Class notation — what it means

Class notation is the coded description recorded by the Classification Society showing what standard the ship, hull, machinery and any special features have been built and maintained to. It is necessary because it defines the survey basis, the technical standard to be maintained, insurance/commercial confidence, and whether the ship remains fit to trade. In oral answers, explain that notation drives what surveys, inspections and repair standards must be applied during dry dock.

Oral exam rule: exact acceptance limits must come from vessel drawings, maker manuals, Class rules, Flag requirements and the company SMS. Do not invent limits in an oral answer.

3. Planning timeline and preparation

Time before dock	Management focus	Chief Engineer delivery point
5–10 years	Fleet plan, statutory cycle, likely yard region and major project horizon.	Do not allow dry dock to become a last-minute repair stop.
24–18 months	Business case, Class/Flag window, budget range and mandatory survey scope.	Separate mandatory work from optional improvement work.
12 months	Tender specification, drawings, coating strategy and vendor list.	Yard cannot price accurately without drawings and acceptance criteria.
9–6 months	Pre-docking inspections, long-lead spares, OEM attendance, Class agenda and risk register.	Use previous defects and condition monitoring to order spares early.
3–1 months	PTW/LOTO, hot work, tank entry, shore services, manpower, daily meeting structure and emergency plan.	Freeze scope where possible and control changes formally.

TST dry dock preparation and document package infographic — This TST plate should sit alongside the planning sections. It visually summarises the minimum dry-dock document pack: PMS review, survey status report / Class due list / white list, shell expansion, GA plan, fore plan, damage control plan, docking / block plan, fire control plan, previous thickness reports, repair specification, spares, contractors, LOTO / PTW matrix, budget / critical path and shore services / manpower plan.

4. Planning and preparation checklist

Previous thickness-gauging reports, steel-renewal history and coating reports ready.
PMS review completed: all recurring defects, due maintenance, spares and outstanding jobs extracted into the dry-dock package.
Survey status report, Class due list / “white list”, memoranda, Conditions of Class and statutory survey items reviewed.
Shell expansion, GA plan, fore peak / fore plan, docking plan, damage control plan and fire control plan available.
Tank plan, capacity plan, hydrostatic / stability data and docking stability calculations checked.
Sea chest, overboard, echo sounder, log, transducer, stabiliser, thruster and sonar clearances confirmed against docking blocks.
Survey plan and surveyor attendance request issued; completed CSM items prepared for surveyor credit where applicable.
Repair plan split between yard work, riding squad / contractors and ship staff work.
Long-lead spares, approved materials, class-approved welding consumables and vendor attendances confirmed.
ROB for fuel, lubes, paint, chemicals and sludge recorded for docking stability and yard controls.
Tools, calibration certificates, measuring gear and consumables available.
Safety instructions, fire protection plan, emergency response plan, enclosed-space plan and contractor induction pack issued.
LOTO / isolation register, PTW matrix, electrical isolation plan and ship–yard interface responsibilities agreed.
Engine-room manpower plan, watchkeeping arrangement, budget, vendors, contractors and critical path controlled.

5. Dock entry and critical period

Critical period effect: Block reaction acts upward at the keel, so the ship’s effective KG rises and GM reduces. This is why docking stability, free-surface effect and tank management are critical from stern touch until the vessel is fully landed.

Before pump-down

Docking plan and block plan checked.
Trim/drafts, tank soundings and stability confirmed.
Clearances for sea chests, transducers and hull fittings verified.
Dock master, bridge, engine room and mooring communication agreed.

Critical period

From stern touch until full landing on blocks. Continuously watch stability, list, trim and block landing. Avoid uncontrolled transfers, slack tanks and any action that could further reduce GM.

6. Yard services and dry-dock safety interfaces

Services

Shore power, fire main, potable/technical water, sewage, steam/condensate, compressed air, cooling water and waste disposal.

Access and lifting

Gangways, lighting, staging, scaffold tags, cranes, certified lifting gear, emergency access and rescue routes.

Safety controls

PTW, LOTO, fire watch, hot work, enclosed spaces, gas testing, emergency drill, CO2 isolation and toolbox talks.

7. International shore connection – SOLAS Ch II-2 / FSS Code

The international shore connection connects an external fire-fighting water supply to the ship's fire main. It is not a shore power, sewage or potable-water connection.

8. First dock-bottom walk

The first walk is a photographic condition survey with ship staff, yard, Class where required, coating representative and relevant OEM/vendors.

Record side, frame, vertical reference, tag and defect size.
Assign repair action, priority and Class/OEM hold point.
Photograph before/after repair and attach close-out evidence.

Route

Bulbous bow, forefoot, bow flare, shell plating, coatings, bilge keels, sea chests, valves, sensors, anodes/ICCP/MGPS, stabilisers, thrusters, rudder, propeller, stern seal and stern tube.

9. Hull scrub, coating, thickness measurement and NDT

Hull dock-bottom and thickness gauging inspection guide — This TST inspection plate is used to explain the **first dock-bottom walk, hull scrub, coating assessment, ultrasonic thickness measurement, NDT selection and defect recognition**. It is intended to support oral answers on where you inspect first, how you grid and record gauging points, and what findings trigger repair or Class involvement.

Coating and hull scrub

High-pressure wash removes fouling and salts so the true coating condition can be assessed. Then examine the boot-top, flat bottom, bilge turn, shell plating and bulbous bow for blistering, flaking, pitting, grooving, cracking, impact damage and marine growth. Mark suspect areas for close-up survey or steel gauging.

Thickness gauging

Prepare steel to bright metal, mark the gauging grid, apply couplant, take repeated readings and compare them against original thickness, previous readings and the approved minimum / renewal thickness. Record locations carefully because trend evidence is as important as the isolated number.

NDT methods

VT – general visible condition, deformation and coating defects.
PT – non-porous surface-breaking cracks.
MT / MPI – ferromagnetic surface cracks around welds / attachments.
UT – thickness measurement and internal flaw indication.
RT – internal weld / structure examination where specified.

What triggers escalation?

Measured thickness at or below approved minimum, extensive pitting or grooving, deformation, cracked welds, wasted edges, coating failure in critical areas or any indication that strength is compromised. At that point, involve Class, repair planning and any additional close-up survey or NDT required.

Thickness measurements are not just numbers — they are a maintenance trend, a Class evidence trail and the basis for steel renewal decisions.

10. Sea chests, valves, overboards, anodes and sensors

Sea chests

Clean growth, inspect gratings, brackets, internal coating, corrosion, MGPS/ICCP and renew gaskets as required.

Sea valves

Open/remove as required, inspect body, seat, disc, spindle, fasteners, overhaul, operate and pressure/leak test.

Before flooding

Every opening, plug, valve, manhole and temporary blank must be accounted for, sighted, secured and signed off.

11. Bow/stern thrusters, stabilisers and sensors

Thrusters stabilisers and underwater fittings inspection guide — This TST inspection plate shows the main dry-dock checks for **bow thruster tunnels and lip seals, stabiliser fins and trunks, sea chests, overboards, transducers, salinometer intakes and sacrificial anodes**. Use it to explain both the inspection points and the reason these items must be confirmed against the docking plan before entry.

Thruster inspection

Confirm tunnel / blade clearances against the docking plan before docking.
Apply LOTO before tunnel entry or blade work.
Inspect tunnel coating, gratings, welds, sacrificial anodes and rope guards.
Check blade condition, cavitation, nicks, erosion, hub condition, shaft wear and lip-seal integrity.
Record radial / axial clearances, leakage and any evidence of impact or rope damage.

Stabilisers and sensors

Inspect fin surface, trunk interface, seals, hydraulic linkages, pintles / bearings and fairings.
Check freedom of movement and secure stowage / locking where fitted.
Protect speed logs, echo sounders, EM sensors, multibeam arrays and reference cells from blasting and coating damage.
Inspect sea chests, overboards and salinometer intakes for blockage, corrosion, wastage and correct security.

Chief Engineer oral point: always mention the docking plan. These appendages can be seriously damaged if their projection below the baseline or local block clearance is not checked in advance.

12. Rudder inspection, pintle bushing and trammel gauge

Rudder drop measurement using a trammel gauge at the tiller steering flat — **Redefined trammel-gauge use:** this gauge is used **internally** at the **tiller / steering flat** between fixed reference points to measure the vertical movement (drop) of the rudder system. The baseline setting is recorded and future readings are compared against it; any increase indicates wear somewhere in the rudder support arrangement, such as the carrier, pintle / bush or related bearing surfaces.

How it is used

Select two fixed reference points at the tiller / carrier area.
Insert and lightly seat the trammel gauge internally between the reference faces.
Lock the setting, withdraw carefully and measure / record the baseline.
Repeat at later inspections and compare with previous records and permitted limits.

Why it matters

Detects rudder drop / wear trend.
Helps identify wear at pintles, bushes, sleeves or carrier support surfaces.
Supports Class decisions on renewal, repair or further dismantling.
Links directly with jumping clearance, side clearance and freedom-of-movement checks.

What else to inspect

Rudder plating, horns, welds, drain plugs and signs of water ingress.
Rudder stock / coupling condition and carrier-bearing area.
Pintle, bush and sleeve condition at top and bottom locations.
Evidence of distortion, cracking, coating breakdown or impact damage.

Oral-answer line

“I would measure rudder drop internally at the tiller / steering flat with a trammel gauge, compare the reading with the baseline and previous dry-dock records, then assess whether the wear trend points to carrier or pintle / bush deterioration.”

13. Propeller, CPP, stern tube and poker gauge

Stern tube and propeller shaft inspection guide — This TST plate is intended to explain the **propeller / CPP checks, stern-tube seal inspection and poker-gauge wear-down measurement**. Use it to support oral discussion of leakage, cavitation, rope damage, seal condition, shaft / bearing wear and the importance of comparing readings with maker and Class-approved limits.

Propeller and CPP

Inspect blades for cracks, bends, impact damage, cavitation erosion, pitting and edge wastage.
Check hub, cone, locking arrangement and any signs of movement.
For CPP, inspect for hub leakage, oil condition issues and any sign of seal or mechanism problems.

Stern-tube sealing

Inspect aft and forward seals for leakage, scoring, overheating evidence and seal-face damage.
Look for rope / line damage around the aft seal and rope guard areas.
Review bearing temperatures, oil condition, drain records and alarm history.

Poker gauge / wear-down reading

The poker gauge is used at the maker’s specified access point to determine the clearance between the shaft and stern-tube bearing. The reading is compared with previous dry-dock results and the permitted maker / Class limit to establish the wear trend and decide whether further action is needed.

Key oral point

Never invent stern-tube wear limits. State that the acceptable clearance / wear-down limit must come from the vessel’s maker manual, approved drawings and Class requirements.

14. Before flooding and return to service

Hull openings shut and signed off.
Sea valves reassembled, operated and tested.
Temporary blanks removed or confirmed as required.
Tools, staging and debris removed.
Thrusters, stabilisers and rudder/propeller areas clear.
CO2 and safety systems restored and tested.
Permits closed and isolations removed.
Dock cleaned and waste documentation complete.
Flooding plan agreed with dock master.
Bilges, seals and hull openings monitored during flooding.
Machinery/function tests and sea trials planned.
Class/statutory/PMS records updated.

15. Chief Engineer oral exam triggers

Docking method

Why slight stern trim? What is the critical period? What happens to GM?

Inspections

How do you conduct the first dock-bottom walk? How do you measure rudder drop and shaft wear-down?

Close-out

What is the international shore connection? What must be verified before flooding and return to service?