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Technical risk assessment

Marine and Naval Engineering Risk Assessment: Design, Machinery, Electrical and Procedure Controls

A worked example of how a marine engineering team finds, scores and controls the risks that threaten vessel stability, machinery, electrical safety, people, the marine environment and the build programme.

Updated November 2026 8 hazards assessed Review every 6 months Highest risk: Critical to Medium
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Executive summary

This assessment shows how a marine engineering team can find, rate and control the risks that matter most to vessel safety, machinery reliability and the programme that delivers the vessel. Eight risks were chosen because they are plausible in design, construction, maintenance and operation. Human error during isolation and lifting is the most serious before controls, scoring Critical, while stability, machinery and electrical risks sit at High. Each risk is scored before controls and again after existing and added controls. Most risks fall to Medium or Low once added controls are in place. The first actions are independent isolation checks, a weight report before outfit, insulation testing with an updated single line diagram and a certificate audit. The vessel is a teaching example, so every score illustrates method, not a real organization or vessel.

Focus area
Marine and naval engineering
Setting
Design, build, maintenance and operation of a small to medium sized vessel with shipyard and supplier dependencies
Method
Five by five likelihood and impact risk register

Scope

This assessment covers the design, construction, maintenance and operation of a small to medium sized vessel, from concept and stability work through to outfitting, sea trials, planned maintenance and dry docking. It looks at risks to people, structure, machinery, electrical systems, the marine environment and the programme itself. It does not cover warfare systems, classified defence design or the regulatory position of any real vessel. Vessel type, flag state, classification society requirements and yard location are assumptions made for teaching and must be confirmed by a qualified specialist.

Context

The team is a naval architecture and marine engineering group of around a dozen staff, with a chief engineer, a design lead, a structural engineer, an electrical engineer, a maintenance planner and a quality lead. Design calculations and drawings are held in engineering software and a document control system. Construction is carried out at a contracted shipyard, with equipment bought from several suppliers. Each risk is scored before controls to show its natural level, then again after existing controls and the additional controls proposed. Scores are used to order the work, not to prove that a vessel is safe.

Objectives, assets and stakeholders

The objective is to deliver a vessel that is stable, reliable and safe to operate, while protecting people, the marine environment and the programme budget. The assets in scope are the hull and structure, propulsion and auxiliary machinery, electrical distribution, fuel and chemical stores, drawings and certificates, and the reputation of the engineering team. Stakeholders include the design and build staff, the crew and master, the shipyard, suppliers, the owner, insurers, the flag and classification authorities and the wider marine community. Clear roles matter: every risk has one owner role, and the chief naval architect keeps the register current and reports to the owner each quarter.

Risk matrix: before and after controls

Each cell shows hazard numbers placed by likelihood and impact. Compare the two grids to see how controls move each hazard.

Before controls

Inherent risk

Risk before controls: rows are likelihood from almost certain to rare, columns are impact from insignificant to catastrophic. Cells list hazard numbers.
1
Insignificant		 2
Minor		 3
Moderate		 4
Major		 5
Catastrophic
5 Almost certain
4 Likely Likelihood 4, impact 3, score 12, high: H05 Likelihood 4, impact 4, score 16, high: H02 Likelihood 4, impact 5, score 20, critical: H06
3 Possible Likelihood 3, impact 3, score 9, medium: H07 Likelihood 3, impact 4, score 12, high: H04 Likelihood 3, impact 5, score 15, high: H01 H03
2 Unlikely Likelihood 2, impact 4, score 8, medium: H08
1 Rare

After controls

Residual risk

Risk after controls: rows are likelihood from almost certain to rare, columns are impact from insignificant to catastrophic. Cells list hazard numbers.
1
Insignificant		 2
Minor		 3
Moderate		 4
Major		 5
Catastrophic
5 Almost certain
4 Likely
3 Possible
2 Unlikely Likelihood 2, impact 2, score 4, low: H07 Likelihood 2, impact 3, score 6, medium: H03 H04 H05 Likelihood 2, impact 4, score 8, medium: H01 H02 H06
1 Rare Likelihood 1, impact 4, score 4, low: H08
  • Low 1 to 4
  • Medium 5 to 9
  • High 10 to 16
  • Critical 17 to 25

Hazard register

A summary first, then the detail for each hazard.

Summary of hazards with scores before and after controls
No.HazardBeforeAfterOwner
H01 Stability and structural design departs from specification 15 High 8 Medium Chief naval architect
H02 Propulsion and machinery failure in service 16 High 8 Medium Chief engineer
H03 Electrical insulation failure and arc fault 15 High 6 Medium Electrical engineer
H04 Hazardous materials and chemical exposure 12 High 6 Medium Environmental and safety adviser
H05 Maintenance backlog and reliability decline 12 High 6 Medium Maintenance planner
H06 Procedural deviation and human error during isolation or lifting 20 Critical 8 Medium Operations manager
H07 Supplier and shipyard dependency 9 Medium 4 Low Procurement manager
H08 Certificate, survey and documentation gaps 8 Medium 4 Low Compliance manager
H01

Stability and structural design departs from specification

Safety Before 15 After 8

Design loads, weight estimates or stability calculations do not match the approved specification or the as built vessel, so the hull may not meet its intended margins in service.

Who or what is affected: Crew, passengers, cargo handlers and the shipyard team

Causes

Late design changes, weight estimates that are not updated and unclear ownership of the weight register.

Consequences

Reduced stability margin, excessive heel, structural overload and loss of the vessel in severe conditions.

Existing controls

  • Stability calculations are reviewed by a second engineer before issue.
  • Weight changes during build are recorded in a running weight register.

Control gaps

Weight changes raised on site are not always passed back to the design office before welding or outfit installation.

Additional controls

  • Prevent: Require an inclining test and a formal weight report before the vessel is accepted for service.
  • Detect: Compare as built weights with the design margin at each construction milestone and record any excess.
Likelihood 3 x impact 5 before; 2 x 4 after Owner: Chief naval architect Target: Within 60 days Early warning: A weight change above the agreed allowance that has not been reviewed by the design office.
H02

Propulsion and machinery failure in service

Operational Before 16 After 8

Main engines, gearboxes, shafting or auxiliary pumps fail or overheat in service, leaving the vessel without power, manoeuvring capability or cooling in a critical situation.

Who or what is affected: Crew, passengers, cargo and neighbouring vessels

Causes

Wear, fouling, poor fuel quality and missed inspections of critical machinery.

Consequences

Loss of control near hazards, collision or grounding, injury and environmental release.

Existing controls

  • Machinery is run to a planned maintenance schedule with records kept.
  • A standby pump and generator are fitted for key services.

Control gaps

Vibration and temperature trends are logged but not compared with limits set during commissioning.

Additional controls

  • Prevent: Fit condition monitoring to main bearings and shafting, with alarm limits set by the design team.
  • Respond: Maintain a written blackout and loss of propulsion procedure, and drill it twice a year.
Likelihood 4 x impact 4 before; 2 x 4 after Owner: Chief engineer Target: Within 90 days Early warning: Main bearing or cooling temperature trending above its alarm level for more than one watch.
H03

Electrical insulation failure and arc fault

Safety Before 15 After 6

Insulation breakdown, overloaded circuits or poor earthing in the distribution system cause electric shock, arc flash or fire in machinery and confined spaces.

Who or what is affected: Electricians, engineers and crew working in machinery spaces

Causes

Moisture ingress, damaged cable glands, cables run through hot areas and modifications made without updated drawings.

Consequences

Electric shock, burns, fire, loss of power and damage to machinery.

Existing controls

  • Circuit protection is sized by the electrical engineer and checked in design review.
  • Insulation resistance is tested before energising.

Control gaps

Modifications are sometimes made on board before the single line diagram is updated.

Additional controls

  • Prevent: Restrict live working to qualified staff under a written permit and provide arc rated protective equipment.
  • Detect: Run periodic insulation and earth continuity tests and trend the results.
Likelihood 3 x impact 5 before; 2 x 3 after Owner: Electrical engineer Target: Within 45 days Early warning: Insulation resistance readings falling below the trend line on any main distribution board.
H04

Hazardous materials and chemical exposure

Environmental Before 12 After 6

Fuel, lubricating oil, paints, solvents, refrigerants and cleaning chemicals are stored, used or spilled in tanks and enclosed spaces, exposing workers and the marine environment.

Who or what is affected: Shipyard workers, crew and the marine environment

Causes

Old containers, unmarked stores, poor ventilation in confined spaces and transfers done in a hurry.

Consequences

Poisoning, fire, pollution, regulator action and damage to the vessel.

Existing controls

  • Chemicals are listed on a register with safety data sheets kept on board.
  • Bunkering and transfers are supervised with drip trays in place.

Control gaps

Gas testing before entry into tanks is recorded on paper that is not reviewed later.

Additional controls

  • Prevent: Substitute low toxicity coatings where practical and limit solvent use to ventilated areas.
  • Respond: Stock spill kits at each transfer point and drill the spill response with the crew.
Likelihood 3 x impact 4 before; 2 x 3 after Owner: Environmental and safety adviser Target: Within 60 days Early warning: A confined space entered without a recent gas test record, or a spill reported to the adviser.
H05

Maintenance backlog and reliability decline

Operational Before 12 After 6

Planned maintenance is deferred or done late, spares are not available and reliability data is not used, so equipment wears faster than expected and breakdowns increase.

Who or what is affected: Maintenance staff, crew and operations managers

Causes

Pressure to keep the vessel in service, an under-resourced workshop and poor spares planning.

Consequences

Unplanned breakdowns, higher repair cost, reduced availability and safety defects left open.

Existing controls

  • A planned maintenance system schedules routine tasks for each item.
  • Defects are logged and reviewed at a weekly meeting.

Control gaps

Deferred defects are not given a fixed closing date or a risk owner.

Additional controls

  • Detect: Report overdue tasks and defect age each week to the maintenance planner.
  • Prevent: Review failure history each quarter and adjust intervals for items that fail early.
Likelihood 4 x impact 3 before; 2 x 3 after Owner: Maintenance planner Target: Within 30 days Early warning: Overdue planned tasks above an agreed count, or a defect open beyond its deadline.
H06

Procedural deviation and human error during isolation or lifting

People Before 20 After 8

Staff skip isolation steps, misread drawings or work outside the permit, so stored energy is released, a valve is opened in error or a lifting operation goes wrong while people are close to the load.

Who or what is affected: Engineers, technicians, riggers and crew

Causes

Time pressure, fatigue, shift handover gaps and unclear procedures for older equipment.

Consequences

Crushing, burns, entrapment, release of stored energy and fatal injury.

Existing controls

  • A permit to work and lockout tagout system is used for all isolation.
  • Lifting plans are prepared for heavy loads and signed by a competent person.

Control gaps

Verification is done by the person who applied the lock, so checks are not independent.

Additional controls

  • Prevent: Require two person verification of every isolation point before work starts on machinery.
  • Respond: Stop work when a permit condition changes and record the reason for each stoppage.
Likelihood 4 x impact 5 before; 2 x 4 after Owner: Operations manager Target: Within 30 days Early warning: Permits found with an isolation point not verified, or work started without a signed permit.
H07

Supplier and shipyard dependency

Supplier Before 9 After 4

Key equipment, castings or drawings arrive late, out of specification or with missing certificates, so construction stops, delivery slips or non-conforming parts are fitted.

Who or what is affected: Build team, owners and customers

Causes

Single source suppliers, long lead times and specification changes late in the build.

Consequences

Delay, cost overrun, rework and in service failure of a part that does not meet its rating.

Existing controls

  • The approved supplier list is reviewed each year.
  • Factory acceptance tests are attended for major items.

Control gaps

Certificates are filed but not compared with drawings until after installation.

Additional controls

  • Prevent: Include inspection and certificate delivery points in each supply contract, with penalties for late delivery.
  • Detect: Check incoming certificates against the drawing before installation and record any mismatch.
Likelihood 3 x impact 3 before; 2 x 2 after Owner: Procurement manager Target: Within 90 days Early warning: A critical item whose delivery date slips more than two weeks, or a certificate that does not match the drawing.
H08

Certificate, survey and documentation gaps

Legal and compliance Before 8 After 4

Surveys, certificates and safety documents are missing, out of date or not kept on board, so the vessel may be refused permission to sail and duties to the regulator are breached.

Who or what is affected: Owners, master, crew and regulators

Causes

Staff turnover, unclear ownership of certificates and paper records held in different offices.

Consequences

Detention, fines, insurance problems and loss of charter.

Existing controls

  • A certificate register lists each survey and its expiry date.
  • Document control holds the current drawings and manuals.

Control gaps

Certificates are checked only when a survey is due rather than on a monthly basis.

Additional controls

  • Detect: Audit the on board document folder against the register each quarter.
  • Recover: Set a plan to renew expired certificates before any voyage, with a named owner for each.
Likelihood 2 x impact 4 before; 1 x 4 after Owner: Compliance manager Target: Within 60 days Early warning: A certificate due to expire within 60 days with no renewal booked.

Rating method and evaluation

Each risk is rated on two five-point scales. Likelihood runs from Rare to Almost certain, and impact runs from Insignificant to Catastrophic. Multiplying the two gives a score from 1 to 25, which falls into one of four bands: Low from 1 to 4, Medium from 5 to 9, High from 10 to 16 and Critical from 17 to 25. The score orders work and does not measure safety. Inherent risk is the score before any controls. Residual risk is the score after the existing and added controls, and it must always be lower than the inherent score. Impact is judged on harm to people first, then on damage to the vessel, environmental release, delay, cost and legal standing. A risk is never rated down only because it has not yet happened. Anything still High needs senior attention and a dated plan, anything Medium needs routine controls with a named owner, and anything Low is accepted and watched. Engineers who do the work should challenge the ratings, and each rating is reviewed whenever an indicator reaches its threshold or the design changes.

Likelihood, impact and rating bands

Likelihood

  • 5 Almost certain: Expected to happen in most circumstances.
  • 4 Likely: Will probably happen in many circumstances.
  • 3 Possible: Could happen at some time.
  • 2 Unlikely: Not expected, but it could happen.
  • 1 Rare: Only in exceptional circumstances.

Impact

  • 1 Insignificant: No lasting effect. Handled within routine work.
  • 2 Minor: Small effect that is quickly corrected.
  • 3 Moderate: Noticeable effect that needs managed effort to correct.
  • 4 Major: Serious effect on people, delivery or reputation.
  • 5 Catastrophic: Severe or lasting effect that threatens the whole activity.

Bands (likelihood x impact)

  • Low (1 to 4): Accept and monitor.
  • Medium (5 to 9): Manage with routine controls.
  • High (10 to 16): Senior attention and a treatment plan.
  • Critical (17 to 25): Act first. Do not proceed until reduced.

Monitoring, escalation and review

Review this assessment every 6 months, and sooner when an indicator below reaches its threshold.

Early-warning indicators and escalation thresholds
Indicator to watchEscalate when
Weight growth recorded against the design margin at each build milestone.Escalate to the chief naval architect when growth uses more than the agreed allowance, and stop outfit work on that area until it is reviewed.
Main machinery temperature and vibration alarms in service.Escalate to the chief engineer at once for any alarm, and to the operations manager if the same alarm repeats within one week.
Isolations recorded on permits without a second person verification.Escalate to the operations manager on the first missed verification, and stop the task until an independent check is made.
Certificates due to expire within 60 days without a booked renewal.Escalate to the compliance manager at 60 days, and to the owner representative if no renewal is booked within 30 days.
Critical supplier deliveries slipping more than two weeks.Escalate to the procurement manager when a slip is first reported, and to the build director if the slip moves the delivery date.

Contingency arrangements

If a serious event occurs, such as a loss of propulsion near hazards, an electric shock, a fire or a serious lifting injury, the master or chief engineer stops the activity, makes the area safe and calls emergency services where needed. The operations manager isolates the affected system using the emergency procedure and records what happened. The compliance manager informs the owner, insurer and the relevant flag and classification contacts as the applicable rules require, and the environmental adviser contains any release. Work moves to standby equipment, and the build team is told what changed and when work can restart.

Prioritized action plan

  1. Hold a weight report review and plan an inclining test before outfit, owner chief naval architect, within 60 days.
  2. Verify every isolation point with a second person on all machinery work, owner operations manager, within 30 days.
  3. Update the single line diagram and test insulation on all main boards, owner electrical engineer, within 45 days.
  4. Audit the on board certificate folder against the register, owner compliance manager, within 60 days.
  5. Add inspection and certificate delivery points to all critical supply contracts, owner procurement manager, within 90 days.

Conclusion

Safe marine and naval engineering depends on a few steady habits: checking weights against margins, independent verification of isolations, tested electrical systems, reliable maintenance, controlled suppliers and complete certificates. The highest scores sit with human error during isolation and with machinery and structural risks, and each has actions that bring the residual score down. Treat the register as a living record, review it on the stated cycle, and seek qualified marine engineering and classification advice for any real vessel or design decision.

Assumptions and limitations

Assumptions

  • The vessel is a single hull, non-classified commercial or support vessel with a conventional diesel propulsion plant.
  • Flag state and classification society rules apply, but their exact content is not specified and must be confirmed by a specialist.
  • The shipyard holds its own quality system and works to approved drawings issued by the design team.
  • Staff are trained engineers and crew who follow a permit to work and lockout procedure for all isolation work.

Limitations

  • The scores are teaching examples and do not describe any real vessel, yard or design.
  • Marine and naval rules, stability criteria and electrical codes differ by country and change, so specialist review is needed.
  • This is educational content and does not replace a formal site-specific risk assessment or advice from a licensed engineer.

Related frameworks to study

  • Hierarchy of controls
  • Failure mode and effects analysis
  • Bow tie analysis of hazards and barriers

Technical Risk Assessment

China, India, United States, Indonesia, Pakistan, Nigeria, Brazil, Bangladesh, Russia, Japan, Mexico, Philippines, Vietnam, Egypt, Turkey, Germany, United Kingdom, France, Italy, Canada, South Korea, Australia, Spain.

For Learning Reference Only: This assessment demonstrates how risk assessment principles are applied in a practical setting, providing a useful reference for learning and understanding. Actual assessments may be adapted to suit specific site conditions and circumstances.

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