Common BWTS Installation Mistakes and How to Avoid Them
Updated
The most common BWTS installation mistakes are undersizing the system for the ballast flow, a poor or skipped 3D survey leading to on-site clashes, choosing a technology that cannot handle the trade's salinity or UV transmittance, late equipment procurement, weak electrical sizing, and rushing commissioning. Each has a straightforward preventive: size to real flow, scan thoroughly, match technology to trade, order long-lead items early, run a load study, and complete the dry checks before sampling.
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Key takeaways
- Undersizing the system to save space permanently derates ballasting; always size to the ship's real rated flow in m³/h.
- A proper 3D laser scan prevents costly on-site clashes and is one of the cheapest ways to de-risk a congested retrofit.
- Match the technology and its type-approved envelope to the trade's real salinity and UV transmittance, and confirm USCG approval where needed.
- Order long-lead equipment early and run procurement in parallel with class approval; procurement is usually the critical path.
- A load study for the ballasting condition prevents generator overload discovered at commissioning.
- Work the commissioning checklist in order and complete the dry checks before biological sampling.
Mistake 1: Undersizing the System
The most damaging mistake is choosing a system rated below the ship's ballast pump flow to fit a tight space or trim the budget. It looks fine at commissioning but permanently derates ballasting, lengthening every port call and straining the pumps.
The fix is to size the system to the ship's real rated ballast flow in m³/h, confirmed from the pump data during survey, and to accept the space and cost that flow demands. Space problems are solved by engineering, not by derating the treatment.
Where space is genuinely impossible, the answer is a more compact technology or a different reactor arrangement, not a smaller flow rating.
Mistake 2: Skipping or Rushing the 3D Survey
A poor survey — relying on outdated as-built drawings or a quick visual check instead of a 3D scan — leads to clashes discovered during fitting, when redesign and rework are far more expensive than getting it right on paper.
The fix is a proper 3D laser scan producing a millimetre-accurate point cloud, so equipment, foundations, and pipe routing are modelled and clashes resolved before steel is cut.
On a congested engine room the scan pays for itself many times over in avoided rework. It is one of the cheapest ways to de-risk the whole project.
Mistake 3: Wrong Technology for the Trade
Choosing electrochlorination for a ship that regularly ballasts in fresh or brackish water, or UV for a ship trading in turbid low-UVT water, produces a system that is compliant on paper but cannot reach dose in service. The result is failed treatment and non-compliant discharge.
The fix is to map the ship's real trade — the salinity and water clarity of the ports it actually calls — and match the technology and the type-approved operating envelope to that map before committing.
Confirm USCG type approval as well as IMO where the trade includes United States waters, so the system is legal in every trading area.
Mistake 4: Late Procurement and Weak Scheduling
Ordering the main equipment only after class approval, rather than in parallel, adds the full procurement lead time to the schedule and can delay the installation by months. Procurement, not fitting, is usually the critical path.
The fix is to run engineering, class approval, and procurement in parallel, ordering long-lead items — reactor, electrolyser, power supply, control cabinet — as soon as the system is selected.
Prefabricating spools and foundations ashore from the 3D model while the ship trades further compresses the out-of-service window.
Mistake 5: Under-Engineered Electrical Integration
Fitting a system without a load study, then discovering at commissioning that the generators overload during ballasting, is a recurring and avoidable failure. Undersized DC cabling and poor earthing cause nuisance trips that plague the system in service.
The fix is a proper load study for the ballasting condition as part of the class-approved electrical documentation, correct cable sizing for current and run length, and sound earthing and bonding.
The control integration must correctly read the ballast flowmeter so dose control tracks actual flow; a wrong flow signal quietly causes under- or over-treatment.
Mistake 6: Rushing Commissioning
Jumping to biological sampling before completing the mechanical and functional checks is how a commissioning test fails on something mechanical — a backflush valve, a silted dP sensor, an unprimed dosing pump — that a dry check would have caught.
The fix is to work the commissioning checklist in order: mechanical, functional and dose, alarms and interlocks, calibration, then sampling. Trend the readings rather than taking single snapshots.
Sea Clean AS supports installation and commissioning, coordinates sampling with independent ISO 17025 laboratories (Sea Clean is not itself an accredited lab), and attends 0–24h in Norway and the North Sea region and by arrangement elsewhere. Contact post@seaclean.no to scope the work early.
Frequently asked questions
What is the most common BWTS installation mistake?
Undersizing the system for the ship's ballast flow to save space or cost. It permanently derates ballasting and lengthens every port call. Sizing to the real rated flow, and solving space problems through engineering rather than derating, avoids it.
Why do BWTS retrofits run over schedule?
Most often because long-lead equipment is ordered late, after class approval, adding the full procurement lead time to the schedule. Running engineering, class approval, and procurement in parallel and prefabricating ashore keeps projects on time.
How do I avoid a failed commissioning test?
Complete the mechanical and functional checks — filter backflush, valve line-up, dose or TRO target, neutralisation, alarms, interlocks, and sensor calibration — before biological sampling, and trend readings rather than taking single snapshots.
Can the wrong technology be installed by mistake?
Yes. Fitting electrochlorination on a ship that ballasts in fresh water, or UV on a ship in turbid low-UVT water, gives a system that cannot reach dose in service. Matching technology and its approved envelope to the real trade prevents this.
Sources
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