Recently, safety inspectors identified a potential hydrogen sulfide emission problem on board an offshore drilling vessel. When they threatened to halt operations, our customer faced an urgent regulatory and safety crisis. Hydrogen sulfide (H2S) is acutely hazardous at relatively low concentrations and unacceptable emissions from tank vents left the vessel at risk of shutdown — with big safety, operational, and commercial consequences. Eldridge was brought in to design a reliable, maintainable capture-and-exhaust solution that would restore compliance and allow safe continuous operation.
Situation and Constraints
The vessel’s emissions originated from five separate tank exhaust vents located around the exterior of the vessel. Any solution had to include these elements:
- Capture 100% of H2S continuously at all five pickup points;
- Be removable to allow regular inspections and maintenance of the tank vent assemblies; and
- Ductwork routed within the vessel’s constraints without interfering with other equipment or operations.
The remote offshore location and the vessel’s regulatory exposure added urgency and a premium on reliable performance.
Primary Design Challenge — Capture Performance
The primary technical problem was determining the correct pickup velocity and total air volume. At each capture point, Eldridge had to guarantee complete capture 24/7. We performed a focused assessment of vent geometries, expected plume characteristics, and worst-case emission scenarios. We used that data to determine the size and shape of each capture hood. Then we calculated air flow rates so that each hood provided sufficient velocity at all operating conditions. The result was a specification that ensured containment of even intermittent releases. It also prevented fugitive H2S escape under varying wind and vessel-motion conditions.
Secondary Design Challenge — Duct Routing and Integration
With capture sizing defined, the secondary challenge was routing ductwork from the hoods to exhaust discharge points. The routing had to minimize pressure losses, avoid obstructions, and allow easy access for inspection and maintenance. Eldridge developed a duct layout that balanced short, direct runs where possible with gradual bends and appropriate supports to preserve flow performance and structural integrity. Where space was constrained, compact transitions and custom bends were used to maintain capture effectiveness without compromising vessel operations.
Inspection and Maintenance Access
One important design requirement for the capture hoods was removability. The capture hoods were engineered so technicians could quickly remove or open units to inspect and service the underlying tank vents without extensive disassembly. Quick-release fastenings, gasketed flanges, and inspection ports were incorporated so the customer’s maintenance crews could comply with routine and regulator-driven inspections with minimal downtime.
Implementation and Outcome
Eldridge delivered detailed designs, shop-fabricated components, and installation support tailored to the vessel’s layout. The completed system provided verified capture of tank vent emissions at all five points, was straightforward to maintain, and met the inspectors’ expectations. As a result, the vessel avoided operational shutdown, resolved the regulatory concern, and restored a safe working environment for crew and contractors.
Conclusion
This project highlights how targeted design — combining careful capture-velocity analysis, practical duct-routing solutions, and maintainable hardware design — can rapidly resolve hazardous emissions on complex offshore assets. For operators facing fugitive gas challenges, such as a hydrogen sulfide emission problem, a solutions-first approach that emphasizes verified capture performance and maintainability is essential to staying safe, compliant, and operational.