BWTS Troubleshooting: 10-Point Checklist Before Class Survey
A ten-step BWTS pre-survey checklist used by working ETOs to clear UV, electrochlorination and filter-stage faults before the class surveyor steps onboard.
Why most BWTS class findings happen before the system even runs
Nine out of ten BWTS deficiencies we attend during the run-up to an intermediate or special class survey are not caused by a hardware failure. They are caused by a calibration certificate that has lapsed, a sample-line valve that someone closed during dry-dock paint touch-up, or a UV intensity sensor that drifted because nobody ran the cleaning cycle for three months. By the time the surveyor opens the BWMP and asks for the last commissioning test report, the vessel either has the paper trail or it does not — and there is no shortcut to producing it once they are aboard.
This checklist is built from the recurring root causes we have logged over multiple Convention compliance dates. It is not a substitute for the maker's manual or the vessel-specific BWMP. It is a pre-survey walk-through that takes roughly four to six hours per ballast pump line, and that consistently clears the most common D-2 findings before they get written up. If you run it the week before the surveyor boards, you do the surveyor's job for them — and they reward that with shorter visits.
1. Confirm the system type is correctly recorded in the BWMP and IOPP supplement
Start in the office, not the engine room. Pull the Ballast Water Management Plan and the IOPP Form B supplement. Match the maker, model and serial number printed inside the BWTS local panel against the documented records. We have seen vessels with an Alfa Laval PureBallast 3.1 listed in the BWMP and a 3.2 retrofitted on board after a yard period — same brand, different software baseline, different UV reactor footprint, different commissioning requirement. A mismatch here is an automatic finding and a costly amendment cycle.
Also confirm the system is type-approved by the flag administration the vessel currently flies. USCG type approval is not the same as IMO BWMS Code certification; a vessel calling US ports needs both. The certificate package onboard must include the AMS letter (if applicable) or the USCG type approval certificate, plus the IMO BWMS Code certificate, plus the operation, maintenance and safety manual, plus the latest commissioning test (CT) report. Missing any one of those four is a Convention-level non-conformity.
2. Walk every sample point and prove it can deliver a representative sample
The biological sample-point arrangement is the single most overlooked item on board. After the surveyor sees the certificates, the first physical thing they ask to see is the sample line: where it taps, whether the tap is isolated from the pump suction, and whether the operator can actually fill a clean sample bottle from it in under thirty seconds without venting the ballast main.
Open every sample valve, watch the flow, look for biofouling on the strainer, and confirm the line is not cross-connected to the ballast main vent. If the tap is downstream of the treatment unit, also verify there is no residual chlorine bleed-through that would corrupt a D-2 indicative analysis. Replace any sample bottle that is older than two years — UV-degraded plastic gives false TRO readings on indicative kits.
3. Verify UV lamp intensity at full power against the maker's minimum threshold
On UV-based systems (Alfa Laval, OptiMarin, BIO-UV, Trojan), the single most common in-service failure is UV intensity dropping below the maker-defined minimum because the quartz sleeve has clouded or because the wiper mechanism has jammed in a corner position. Run a treatment cycle in test mode, watch the UV intensity trend on the HMI, and confirm each reactor maintains the threshold for the duration of a worst-case ballasting cycle (typically three hours at full flow).
If a single lamp is reading low, swap it with a known-good spare and re-run the cycle. If the entire reactor is reading low, schedule a quartz sleeve clean before the survey — not during. Doing it in front of the surveyor turns a routine inspection into a witnessed maintenance event, and that gets recorded in the survey letter.
4. On electrochlorination systems, check the TRO sensor calibration certificate
Electrochlorination systems (Erma First, Techcross, Hyde GUARDIAN-EC) rely on a Total Residual Oxidant sensor to confirm that the disinfectant concentration at the inlet meets the certified treatment dose. That sensor has a calibration interval — usually six months for the analytical electrode and twelve months for the sample-conditioning module. If either certificate has lapsed, the surveyor will flag the system as not in a known-good state regardless of whether it functions.
Calibration kits are inexpensive and can be carried aboard. The procedure is documented in the maker's manual and takes roughly an hour per sensor. We carry calibration solutions on every BWTS dispatch — do not wait until the night before the survey to discover yours have evaporated below the fill line.
5. Verify the neutralisation / dechlorination loop on de-ballast
Electrochlorination treatment requires neutralisation (sodium bisulphite injection or equivalent) before the ballast water is discharged. The neutralisation pump, the dosing tank level switch, the flow meter and the post-neutralisation TRO sensor all need to be proven on a de-ballast cycle. We have seen vessels pass on a ballasting test but fail on de-ballast because the bisulphite metering pump's check valve was stuck open and the line was siphoning silently.
Run a controlled de-ballast cycle in test mode. Confirm the bisulphite consumption matches the calculated dose for the volume discharged. Confirm the post-neutralisation TRO reading drops below the discharge limit (typically 0.1 mg/L for USCG, varies by flag). Photograph the HMI trend and store the screenshot in the BWMP folder.
6. Test the BWTS-to-IAS interface and verify the operator can override only what is permitted
BWTS systems are increasingly integrated with the integrated automation system (IAS) so the deck officer can initiate a treated ballasting cycle without leaving the cargo control room. That convenience creates an audit boundary. The surveyor will check that the override permissions match the BWMP — typically the operator can start and stop the cycle from the IAS but cannot bypass any safety interlock or alarm acknowledgement from there.
Walk through the override matrix in the BWTS operator manual. Try each override from the IAS HMI. Confirm the audit log on the BWTS panel records who initiated which action and when. If the audit log has gaps, the surveyor will request the cause; if you cannot explain the gap, expect a finding.
7. Exercise every alarm — and acknowledge them from the correct station
The BWMP defines which alarms are routed to the engine control room, which to the bridge and which to the cargo control room. We have repeatedly seen vessels where the BWTS critical alarm (UV reactor failure, low TRO, filter differential pressure trip) is routed to a panel that nobody is staffed to watch during a de-ballasting cycle. The surveyor's standard test is to force one of those alarms and check the response time.
Force each alarm in turn (most BWTS HMIs have an alarm test mode that does not require breaking real signal lines). Confirm the alarm appears at the correct station within the maker's defined response time, and that the alarm acknowledgement is recorded in the audit log with the operator's tag or user ID. If the user ID logs blank, the surveyor will assume the system is not being operated under named accountability.
8. Review the maintenance log and align it with the spare parts inventory
The surveyor will spot-check the maintenance log against the spare parts inventory. If the log says you replaced two UV lamps in the last quarter but the spare parts inventory shows no consumption of UV lamps, that is a finding. The fix is procedural, not technical: align the log entries with the storeroom record before the survey, and have the receipts ready for any spare consumed in the period since the last audit.
If the system has been operated for the entire reporting period without any maintenance entries logged, the surveyor will assume the system has not been maintained. That is worse than a normal-wear finding. Add at least the routine quarterly inspection entries — backed by real evidence — into the log before the surveyor boards.
9. Confirm the commissioning test (CT) and challenge-test (CT-DG-2) records are aboard and current
Since IMO BWM.2/Circ.70/Rev.1 entered into force, the commissioning test (BWMS Code section 5) is mandatory for new installations and certain post-overhaul events. The challenge-test results, including the indicative analysis at sample points before, during and after treatment, must be available aboard. Vessels that have undergone a yard period since their last CT often miss this.
If the CT is missing or older than the latest required revision, organise an indicative analysis with a qualified service supplier ahead of the survey. The supplier needs roughly a week to schedule, sample and report — start that conversation as soon as the survey window is confirmed, not after.
10. Stage the operator demonstration — same operator, same scenario, every time
The surveyor will ask the duty operator to demonstrate a full treated ballasting cycle, from line-up to system stop. The operator should be the same person who is named in the BWMP as the responsible officer for that cycle. We have seen vessels where the demonstration was given by a junior engineer who had never executed the actual line-up — the result was a documentation finding because the surveyor concluded the named operator was not trained.
Rehearse the demonstration with the duty operator the day before. Stage the line-up. Practice the alarm responses. Have the operator narrate the cycle so the surveyor can confirm awareness of treatment parameters and discharge limits. This is the part of the survey that costs nothing to prepare for and that consistently makes the difference between a clean survey and a multi-page deficiency list.
Closing — when to call an ETO before the surveyor calls one
If any of the ten items above cannot be cleared with the ship's electrical and engineering crew during a single watch, the cost-benefit math is straightforward: call a marine ETO with BWTS commissioning experience before the surveyor arrives. A pre-survey attendance, with the calibration kit and the spare lamps and the loop-test gear, takes a day and produces a clean report. A finding written by a class surveyor takes weeks of correspondence to clear, and may include a follow-up attendance at a port where you would rather be sailing.
We attend BWTS pre-survey work at all major US ports under the standard wizard flow. Use the related links below to request a system-specific dispatch, or to source a calibration spare or a UV lamp replacement before the survey window opens.
FAQ
- How long does a full BWTS pre-survey attendance take?
- Approximately four to six hours per ballast pump line, on a quiet vessel with co-operative crew. Plan a full day for a Panamax bulker with two ballast pumps and a parallel treatment skid.
- Can a ship's electrician do this without a class-experienced ETO?
- Items 1, 2, 7 and 10 are within most ship's electrician scopes. Items 3, 4, 5 and 9 typically need either a maker's service agent or an experienced marine ETO with the right calibration kit and a current understanding of the BWMS Code revisions.
- Which class societies are we set up to write the report for?
- DNV, BV, ABS, Lloyd's Register, Türk Loydu, RINA, ClassNK and IRS. Each report is formatted to the requesting society's template.
Request BWTS pre-survey attendance
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Source BWTS sensors and spares
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