Scrubber that can switch between open- and closed-loop modes depending on local discharge regulations.
Regulatory detail & full definition
Most common newbuild scrubber type, valued for operational flexibility. Open-loop in deep ocean; closed-loop when transiting open-loop-restricted areas (US territorial waters, China, Singapore, etc.). Cost ~30% higher than open-only; payback hinges on price spread between VLSFO and HSFO.