Safety
Prevent hazardous gases, hazardous liquids, chemicals, and reactive substances from endangering crew, ship, and environment.
LR Rules · BWTS Review Guide · Reay's Note
BWTS Safety Survey Guide
The focus of LR Rules Pt.5 Ch.25 is not simply to confirm whether a BWTS meets the D-2 biological discharge standard. It treats the BWTS as an onboard machinery, piping, electrical, control, hazardous gas and chemical system, and checks whether it can be safely designed, installed, reviewed, and verified on board. Surveyors need to connect the technology category, risk assessment, PFD (Process Flow Diagram), P&ID (Piping and Instrumentation Diagram), BWMP (Ballast Water Management Plan), TAC (Type Approval Certificate), OMM (Operation, Maintenance and Safety Manual), and functional tests, so that ventilation, detection, isolation, bypass, alarms, and shutdown logic all correspond with each other.
Quick Read
10-second takeaway: confirm safe installation first, then discuss D-2 compliance.
The whole chapter can be reduced to four decision frames that reveal the real purpose of LR's BWTS review.
No impact on essential functions
A BWTS failure must not prevent ballasting or deballasting, and must not affect essential services such as propulsion, power generation, steering, and fire safety.
Onboard integration safety
Piping, ballast tanks, ventilation, electrical systems, controls, hazardous areas, and material compatibility must be reviewed together.
Plan review and onboard verification
PFD, P&ID, BWMP, TAC, OMM, risk assessment, and onboard functional tests must be mutually consistent.
01 | Technology Categories
BWTS Technology Categories and First Risks
If the technology category is misidentified, the downstream review of ventilation, detection, hazardous areas, fire safety, and isolation may all go in the wrong direction.
| Category | Technology type | First risks for surveyors |
|---|---|---|
| Category 1 | UV / UV + AOT / UV + TiO₂ / UV + plasma | UV radiation, electrical safety, pressure equipment, filter blockage |
| Category 2 | In-line flocculation | Chemicals, sediment, chemical storage and handling |
| Category 3a | Membrane separation + N₂ deoxygenation | Nitrogen asphyxiation, oxygen-enriched exhaust, pressure/vacuum protection |
| Category 3b | Inert gas deoxygenation | CO₂, CO, oxygen depletion, inert gas system safety |
| Category 3c | In-tank inert gas deoxygenation | Ballast tank pressure, P/V devices, gas accumulation in tanks |
| Category 4 | Full-flow electrolysis | Hydrogen, chlorine, explosion, TRO neutralisation |
| Category 5 | Side-stream electrolysis | Concentrated treated liquid, hydrogen, chlorine, higher ventilation demand |
| Category 6 | Stored chemical injection | Chemical storage, leakage, corrosion, fire-fighting compatibility |
| Category 7a / 7b | Ozone injection | Ozone toxicity, oxygen enrichment, gas-liquid separation, ozone destructor |
| Category 8 | In-tank heat treatment + N₂ deoxygenation | High temperature, nitrogen asphyxiation, ballast tank pressure control |
02 | Rule Sections
Key Points by Rule Section
Each section is presented in two layers: what to review, and what surveyors should watch for. This helps build a practical plan-review and field-inspection context.
Section 1General requirements
This section defines the scope of the LR chapter: the focus is the design, construction, and onboard installation safety of the BWTS, not replacing IMO, flag Administration, or competent authority requirements for D-2 discharge performance.
- It explains that the purpose of BWTS is to prevent the transfer of harmful aquatic organisms and pathogens through ballast water and sediments.
- It defines hazardous gas, hazardous liquid, hazardous substance, BWTR (Ballast Water Treatment Room), and air lock.
- It confirms that hazardous exhaust must be led to a safe location.
- The class notations include BWTS and BWTS*; the latter indicates that the system has also been approved under LR's type approval procedure.
First confirm the BWTS technology category and the hazardous gases/liquids it may generate. If the category is wrong, the ventilation, detection, hazardous area, and fire-safety requirements may also be wrong.
Section 2Functional requirements
Although short, this section sets the safety baseline for the whole chapter: BWTS failure, shutdown, or maintenance must not remove the ship's basic ballasting capability or affect essential services such as propulsion, power generation, steering, or fire safety.
- A BWTS failure must not prevent ballasting or deballasting.
- It must not affect essential onboard services.
- It must not create hazards under normal or foreseeable failure conditions.
- The review must include the post-failure operating path, not only whether the equipment runs in normal mode.
Bypass, isolation, and fail-safe behaviour are core checks. The real question is whether safe ballasting/deballasting remains possible after failure.
Section 3Performance requirements
The performance requirements here do not repeat the D-2 biological performance review. They confirm that, once installed on board, the BWTS can maintain ballast system capacity, pressure conditions, and safety boundaries under normal worldwide operating conditions.
- Review onboard usability and safety performance, not D-2 biological performance.
- BWTS capacity must match ballast capacity and account for normal worldwide operating conditions.
- Pressure loss, fire, overheating, explosion, asphyxiation, and material effects all need assessment.
- Hazardous substances must not accumulate in ballast piping or tanks, and treatment by-products must not cause long-term damage to ballast tank coatings.
Check BWTS TRC (Treatment Rated Capacity) against ballast pump capacity; when pump flow is too high, the BWMP must restrict operation.
Section 4Documents for review
This is one of the most frequently used sections during plan review. LR is not looking at a single maker catalogue, but whether BWTS equipment documents and onboard installation documents align with each other and support a complete safety review.
- The BWTS package should include the treatment technology description, PFD (Process Flow Diagram), material specifications, pressure and temperature ratings, and chemical flammability/toxicity/reactivity information.
- Control, alarm and safety system diagrams, risk assessment, hazardous-area equipment and electrical data, and type approval certificates should all be included in the review.
- Onboard installation documents should include P&ID (Piping and Instrumentation Diagram), general arrangement (GA), hazardous area plan, ventilation plan, and fire safety plan, plus electrical data and watertightness test reports.
- For retrofit projects, the existing ballast system P&ID and the modifications must be submitted.
Do not review only maker drawings. Connect the TAC (Type Approval Certificate), OMM (Operation, Maintenance and Safety Manual), BWMP, onboard P&ID, GA, hazardous area plan, ventilation plan, electrical drawings, fire safety plan, and risk assessment.
Section 5Materials
Material review is not only about strength or pressure rating. It asks whether materials can maintain function and isolation when exposed to actual chemicals, oxidants, treated water, and by-products.
- Materials must comply with LR manufacturing, testing, and certification requirements.
- The suitability of hazardous or reactive materials must be included in the risk assessment.
- Chemical storage tanks and related piping must withstand the actual chemicals used.
- If non-metallic materials do not meet fire-resistance requirements, they must be isolatable from other ship systems by steel or approved fire-resistant isolation valves, with fail-safe characteristics.
Material review must consider chemical compatibility, not only pressure rating.
Section 6Risk-based study
Risk assessment is not a formality. It demonstrates that the BWTS package, ballast system integration, abnormal conditions, and alternative designs have been systematically examined, especially how hazardous substances are generated, leak, accumulate, and are mitigated.
- Assess the safety of the BWTS package, onboard integration, and alternative designs.
- Cover normal, abnormal, leakage, hazardous-substance accumulation, and system-amplification risks.
- Treatment technology, by-products, neutralisation method, ballast tank coatings, existing fittings, hull strength, isolation valves, and hazardous areas should all be included.
- Flammable/toxic gases and chemical storage and handling arrangements must be reviewed together with actual arrangement, ventilation, detection, and shutdown logic.
The risk assessment should answer where leakage may occur, where gas may accumulate, how the system will shut down safely after failure, and whether essential services may be affected.
Section 7Piping systems
Piping review should treat the BWTS as a system that may interact with ballast water, chemicals, freshwater, compressed air, inert gas, and sampling lines. Any cross-connection may become a hazardous-substance migration path.
- Piping and fittings must comply with ship piping, machinery-space piping, and tanker piping requirements.
- Chemical piping should follow the concepts applied to liquid chemical carriers.
- If seawater or freshwater piping may be contaminated by hazardous substances, it should also be considered under hazardous chemical piping concepts.
- Piping for active/reactive substances must be separated from other ship piping, and plastic piping must comply with LR requirements for plastic pipes.
Pay particular attention to cross-connections to prevent hazardous substances from entering non-hazardous areas.
Section 8Machinery equipment
This section brings BWTS-related machinery, pressure components, filters, degassing equipment, gas bottles, and treatment units into the class safety logic. During field inspection, do not only compare drawings; also check actual support, discharge, and maintenance conditions.
- Air pipes, sounding pipes, and overflow pipes must comply with ballast system requirements.
- Chemical injection pipes, concentrated treated-liquid injection pipes, inert gas injection pipes, and sampling points must be rigid and properly supported.
- Degassing equipment must prevent leakage, and exhaust must be led to a safe location on the open deck.
- Hydrogen must be below 4% LEL before discharge, and failure must trigger BWTS shutdown.
- Filters, pressure components, heat exchangers, gas bottles, ozone generators, electrolytic units, and UV units must comply with acceptable standards and testing requirements.
On board, check support, exhaust direction, leakage collection, maintenance space, nameplates, and certificates.
Section 9Electrical and control
Electrical and control systems determine whether BWTS safety functions actually work. LR focuses on whether alarms, detection, shutdown, valve position, bypass recording, and hazardous-area electrical equipment can maintain a safe state after failure.
- Control, alarm, and safety systems must comply with LR control engineering requirements.
- Spaces where hazardous gases may exist must have audible and visual gas detection alarms; detectors must be suitable for the actual gas type.
- Flammable gas alarms must not be set above 30% LFL; shutdown must not be set above 60% LFL.
- Bypass and isolation valves must have position indication, and activation must alarm and be automatically recorded.
- Power or control failure must not make the BWTS hazardous; the safety shutdown system should be independent of the BWTS control system as far as practicable.
During commissioning, test alarms, shutdown, valve position indication, bypass recording, gas detector response, and ventilation interlocks.
Section 10BWTR location and boundaries
The location, boundary bulkheads, fire integrity, gastight doors, air locks, ventilation, and exhaust locations of the BWTR (Ballast Water Treatment Room) directly affect whether hazardous gases or chemicals may spread to accommodation, machinery spaces, or other non-hazardous spaces.
- BWTR boundaries, fire integrity, penetrations, and chemical storage tank structures must meet the requirements.
- BWTRs using chemicals and chemical storage rooms must not be located in accommodation spaces; ventilation exhausts and openings must be away from accommodation entrances, air intakes, and openings.
- Ozone systems must be installed in dedicated compartments, separated from other spaces by gastight boundaries, often with air locks.
- Spaces with explosive or toxic gases generally require at least 30 air changes per hour.
- BWTR ventilation for electrolysis, ozone, deoxygenation, or chemical injection systems must be independent, with exhaust locations arranged according to gas density.
For ventilation, check independence, intake/exhaust locations, failure alarms, interlocked shutdown, hazardous gas density, and safe distance from exhaust outlets.
Section 11System arrangements
This is the core section of the chapter and the easiest to review incorrectly. It connects category applicability, bypass/isolation, electrical load, TAC/BWMP operating limits, pressure protection, hazardous areas, and special tanker arrangements.
- Use the applicability table according to the BWTS category.
- Bypass, isolation, or override arrangements must be provided, and bypass/isolation arrangements must meet electrical and control safety requirements.
- Generator capacity must be proven by electrical load analysis; the BWTS must be operated according to the TAC and BWMP, and TRC must not exceed TAC limits.
- Where ballast piping or tanks may experience overpressure or vacuum, P/V valves, P/V breakers, relief valves, or high/low pressure alarms must be provided.
- Exhaust from inert gas or nitrogen deoxygenation systems must be led to a safe location on the open deck; electrical equipment in hazardous areas must be suitably certified.
For tankers, prevent hazardous substances from cargo areas entering non-hazardous areas through BWTS piping, sampling lines, or auxiliary lines.
Section 12Fire safety
A BWTS may introduce new fire, explosion, toxicity, corrosion, and chemical reaction hazards. Fire safety review must check whether these new hazards weaken the existing fire safety design; original space assumptions cannot simply be reused.
- BWTS may introduce fire, explosion, toxicity, corrosion, and chemical reaction hazards.
- Fire safety systems must consider material and chemical compatibility.
- BWTRs, chemical storage rooms, and hazardous gas spaces must have suitable detection, fire-fighting, and suppression arrangements.
- If chemicals or reactive substances are incompatible with existing extinguishing media, the original fire safety design cannot simply be reused.
Do not only ask whether extinguishers are present. Confirm whether extinguishing media may react with chemicals, generate toxic gas, or affect existing fixed fire-extinguishing system performance.
Section 13Installation arrangements
This section applies the previous requirements to actual ship arrangements, especially where tankers may use a single in-line BWTS to serve ballast tanks in both cargo and non-cargo areas. It requires isolation and arrangement controls to prevent hazard transfer.
- Tankers may use a single BWTS to serve ballast tanks in both cargo and non-cargo areas.
- The key purpose is to prevent hazardous gases, liquids, or contaminated ballast water from cargo areas communicating with non-hazardous areas.
- Installation arrangements must align with Section 11 requirements for isolation, hazardous areas, sampling, bypass, piping, and controls.
- Review together with arrangement drawings, piping drawings, equipment category tables, and actual onboard valve locations.
Confirm the actual arrangement matches the approved drawings, including isolation points, valve types, hazardous areas, and exhaust locations.
03 | Surveyor Focus
Review Focus for Surveyors
Use this section as a quick risk index before plan review and onboard inspection.
Questions to Keep Asking During Review
- Is this BWTS UV, electrolysis, ozone, deoxygenation, chemical injection, or a hybrid system?
- Are bypass/isolation/override arrangements available, indicated, and recorded?
- Do gas detectors match the actual gases, and are alarm/shutdown setpoints correct?
- Does ventilation have adequate capacity, correct locations, failure alarms, and interlocked shutdown?
- For tankers, are hazardous substances from cargo areas prevented from contaminating non-hazardous areas?
- Does TRC match ballast pump flow? If not, does the BWMP limit maximum operating flow?
- Can pipe materials, valve materials, gaskets, seals, and ballast tank coatings withstand BWTS products?
04 | Field Checklist
Suggested Onboard Inspection Checklist
Separating document check, physical verification, and functional testing makes it easier to find mismatches between drawings and the ship.
ADocument check
- Type Approval Certificate (TAC)
- Operation, Maintenance and Safety Manual (OMM)
- Ballast Water Management Plan (BWMP)
- PFD, P&ID, general arrangement
- Material certificates, chemical MSDS, risk assessment report
- Electrical load analysis, hazardous area plan, ventilation plan, fire safety plan
- Control, alarm, and safety system diagrams
- Pressure vessel/filter certificates, pressure test and functional test records
BOnboard verification
- BWTS model, nameplate, and capacity match the TAC
- Actual piping matches the approved P&ID
- Bypass, isolation, non-return valves, blanks, and spool pieces are correctly located
- Exhaust outlet locations meet safe-distance requirements
- BWTR doors are gastight/self-closing and air locks function correctly
- Ventilation direction, flow rate, and interlocks are correct
- Gas detector locations are reasonable and testable
- Chemical storage, leakage collection, and labelling are correct
CFunctional test
- BWTS normal start/stop
- Bypass activation alarm and recording
- Remote indication of isolation valves
- Ventilation failure alarm and shutdown
- Gas detection alarm and shutdown
- Ballast tank high/low pressure alarm and shutdown
- Over-flow limitation, filter backwash, neutralisation system
- Emergency stop and fail-safe state after power loss
05 | Common Confusion
Most Common Confusions
These misunderstandings most easily push the review away from class safety and installation integration.
| Common confusion | Correct understanding |
|---|---|
| BWTS meets D-2 = LR installation accepted? | Not necessarily. D-2 is environmental performance; this LR chapter focuses on class safety and installation. |
| With TAC, no onboard installation review is needed? | Wrong. TAC is type approval; onboard installation still requires LR review. |
| Is bypass always non-compliant? | Not necessarily. Bypass may be a safety or failure measure, but it must comply with BWMP, TAC, alarm, and recording requirements. |
| Is ventilation only about flow rate? | No. Independence, exhaust location, gas density, interlocks, and shutdown must also be checked. |
| Because UV systems do not generate hazardous gas, can they be treated as low priority? | No. Electrical, UV radiation, overheating, pressure, and filter risks still exist. |
| For tankers, is explosion-proof equipment enough? | Not enough. Check whether hazardous areas expand and whether cargo and non-hazardous areas are isolated. |
| Are small-bore chemical lines unimportant? | No. Small-bore lines can still cause hazardous-substance migration, corrosion, or toxic exposure. |
06 | Review Logic
Summary Review Points
Close with ten points that are easy to share externally or use in internal training.
- This chapter reviews BWTS installation safety, not simply D-2 discharge performance.
- The first step is always to confirm the BWTS technology category and hazard sources.
- BWTS failure must not affect ballasting/deballasting or essential services.
- Bypass, isolation, fail-safe behaviour, alarms, and recording are core review points.
- For hazardous gases, review detection, ventilation, exhaust location, hazardous areas, and shutdown logic.
- Tankers must prevent hazardous substances from cargo areas entering non-hazardous areas through the BWTS system.
- Chemical, ozone, electrolysis, and deoxygenation systems all require risk assessment.
- Onboard survey cannot stop at document checking; alarms, shutdown, ventilation interlocks, and bypass recording must be tested.
- TAC, BWMP, OMM, P&ID, hazardous area plan, ventilation plan, and fire safety plan must be consistent.
- In practice, always refer to the latest LR Rules, flag Administration requirements, IMO conventions, and approved drawings.