Marine & Maritime

Marine gas detection has a problem the rest of industry does not. The equipment has to survive salt, and it has to satisfy a regulator that may not be the one you expect.

An FPSO in Commonwealth waters, a domestic commercial vessel, a foreign flagged ship in an Australian port and a shore based bulk terminal sit under four different regulatory regimes. Getting that wrong is how a detector arrives with the wrong certificate.

What follows comes from work our engineers have done on Australian offshore facilities, port authority vessels and marine terminals.

Offshore Production, Risers And FPSOs

Subsea risers carry crude oil and LNG or LPG vertically from below the seafloor up to a floating production storage and offloading vessel or a semi-submersible platform. Around the riser moorings, the separation and processing trains, storage and the offloading pipelines, hydrocarbon gas is a constant presence rather than an occasional event.

The combustible set is methane, butane and other hydrocarbons. The toxic set is hydrogen sulphide, benzene, mercury vapour and nitrogen dioxide, alongside drilling fluids that cause skin and eye irritation, respiratory problems and carcinogenic exposure that shows up decades later.

Hydrogen sulphide deserves separate attention because it appears in both lists. It is acutely toxic in single figures of parts per million, and it is also highly ignitable, with a lower explosive limit around 4.3 percent by volume, which is 43,000 ppm. A toxic H2S sensor topping out at 100 ppm tells you nothing about flammability, and an LEL sensor calibrated for methane will respond poorly to H2S. On a sour service facility both measurements are needed, and assuming one covers the other is a common design error.

Coverage typically combines fixed point detection inside the riser moorings, processing areas, storage and offloading pipework with open path line of sight detection across the larger spans. The SafEye Quasar became the standard on offshore platforms for a specific reason: it keeps detecting through heavy beam obscuration, and offshore is where sea spray, deluge testing and salt haze make that the deciding specification.

Controllers need relay capacity for deluge release as well as alarm sirens and strobes, because on an offshore facility gas detection is usually driving fire suppression rather than only informing an operator.

Why Marine Certification Is Different

This is where marine departs from the rest of the industries we supply.

Onshore, hazardous area certification under ATEX or IECEx is generally the whole conversation. Offshore and at sea, it is the starting point. On top of it sit classification society approvals from Det Norske Veritas, the American Bureau of Shipping, Bureau Veritas and others, plus the Marine Equipment Directive for equipment on European flagged vessels.

Those are not interchangeable. A detector with IECEx certification and no DNV approval will not be accepted on a classed vessel, and the reverse applies too. When a specification names a class society, that is a hard requirement rather than a preference.

The S-Guard toxic variant carries MED, ABS, DNV, BV and KR approvals alongside ATEX and IECEx, plus a SIL 2 rating, which is the combination a classed vessel specification usually asks for. The Searchline Excel is rated to DNVGL-CG-0339 Location Class B and tested for resistance to salt mist and sulfuric atmosphere.

Australian Conditions Are Not One Set Of Conditions

Australian offshore assets sit across an extraordinary temperature spread. A facility in Bass Strait works down to minus 20 degrees Celsius. One in the Timor Sea works up to plus 60. That is an 80 degree range inside the same national fleet, and a detector specified for one may be outside its rating on the other.

Three other conditions cause more equipment failures offshore than the gas ever does.

Salt water and salt haze attack housings, glands and terminations continuously rather than occasionally, which is why 316 stainless steel and electropolished finishes are worth the cost.

Deluge foam and fire suppression retardants are corrosive and they get onto detectors during routine system testing, not only during an event.

High winds make both detection and calibration difficult. Applying calibration gas to a detector on an exposed deck in 40 knots is a different exercise from doing it in a plant room, and it is a reason to prefer instruments that hold calibration and self diagnose rather than needing frequent manual challenge.

Helipads, And Why The Wrong Flame Detector Is Dangerous

Civil Aviation Authority publication CAP 437, the standard for helicopter landing areas, requires an automatic fire suppression system covering the helipad. That system is generally triggered by flame detectors positioned around the perimeter and aimed toward the centre, with three detectors at 120 degree spacing usually considered sufficient.

Mounting is constrained from both directions. Detectors must sit as low as possible so they do not interfere with landings and takeoffs, and they still need a downward inclination toward the centre of the pad, with around 45 degrees giving the best result.

Then there is the problem that catches people out. Hot exhaust gases driven down by the rotor wash look like a fire to a conventional infrared flame detector. False activation of a deluge system during a helicopter landing would be catastrophic, so hot exhaust gas immunity is not a refinement here, it is a requirement.

That is what the CO2L variants of the F-Guard IR3 are built for, distinguishing a genuine fire from the combustion exhaust around it. The HD version adds video, which assists both with monitoring the pad and with post event investigation. AS 1670.1 Section 7 covers flame detection requirements alongside CAP 437.

Containerised Boilers

Offshore facilities use diesel and gas fired boilers for hot water and for steam driving turbine power generation, and they are frequently containerised.

The risk is specific. Flammable gas from surrounding process operations can enter the boiler air intake, meet the burner and explode. Fixed detection inside the container is there to catch that before it reaches the intake, with alarm points typically set at 20 percent LEL for low and 50 percent LEL for high.

Certification needs IECEx as a baseline plus DNV approval, and AS/NZS 60079.0 and AS 2380.1 apply. Where the intake itself needs watching rather than the container volume, the SafEye Duct is installed across air intakes for exactly this purpose and is in service on FPSOs and offshore rigs.

Port Authority First Response

Port authorities patrol and monitor harbours, foreshores, waterways and coastal regions, and they are first response to incidents on the water. That covers commercial shipping, bulk goods storage, dockside industry and the transport of dangerous goods.

An incident might be a spillage of hazardous substances, fuel, chemicals, decomposing material or waste. Illegal dumping is a recurring problem. The threats are fire, oxygen depletion, nuisance gases, excessive emissions and water pollution, frequently with no information about what is actually in the water or the air.

First response vessels commonly act as sentry, isolation or a waterway barrier, holding position and reporting back before fire or hazmat crews arrive. Which means the crew is often the first and only source of atmospheric information, sometimes for an extended period.

Detection here is portable four gas instruments on the vessel and on the crew, covering LEL, oxygen, hydrogen sulphide and carbon monoxide, with capacity to add volatile organic compounds or a specific gas such as ammonia when the incident calls for it. Area monitors provide perimeter monitoring in sample draw or diffusion form. Everything needs intrinsic safety certification and it needs to survive weather and marine exposure, since it lives on an open boat.

Confined Spaces Afloat

Cargo holds, ballast tanks, cofferdams, double bottoms, chain lockers, pump rooms and fuel tanks are all confined spaces, and a vessel presents them in greater number and worse access than most shore facilities.

The atmospheric risks are the same as anywhere: oxygen depletion, flammable accumulation, toxic residue from previous cargo. What differs is that rescue is harder, ventilation is harder, and the space may be moving. Pre-entry testing from outside the space, using a pumped instrument and a sampling probe, matters more here than almost anywhere.

Vehicle decks on ro-ro vessels and passenger ferries are a related case, where carbon monoxide from vehicle exhaust accumulates during loading and unloading in an enclosed volume.

Who Regulates What

This is where marine differs most from other industries, and where a specification can go wrong before anyone looks at a detector.

NOPSEMA, the National Offshore Petroleum Safety and Environmental Management Authority, is Australia’s independent regulator for health and safety, well integrity and environmental management for offshore energy operations in Commonwealth waters, and in coastal waters where powers have been conferred by a state. The safety regime sits in Schedule 3 to the Offshore Petroleum and Greenhouse Gas Storage Act 2006 and the associated Safety Regulations. Certain vessels and structures are defined as facilities under that Act, which is how an FPSO comes under NOPSEMA rather than a maritime regulator. NOPSEMA is headquartered in Perth.

AMSA, the Australian Maritime Safety Authority, is the national marine safety regulator for domestic commercial vessels under the Marine Safety (Domestic Commercial Vessel) National Law Act 2012, and has delivered that system nationally since 2018, replacing seven separate state and territory models. AMSA also administers the Navigation Act 2012 covering regulated Australian vessels and foreign vessels, and performs port state control on foreign flagged ships.

Seafarer occupational health and safety on prescribed ships engaged in interstate or international trade falls under the Occupational Health and Safety (Maritime Industry) Act 1993, with AMSA as the inspectorate.

Shore based facilities, wharves, terminals and workshops fall under ordinary state work health and safety law, which means WorkSafe WA, SafeWork NSW or Workplace Health and Safety Queensland depending on location.

The practical consequence is that the same company can have gas detection sitting under NOPSEMA on a facility, AMSA on a support vessel and a state regulator on the wharf, with different certification expectations on each. That is worth establishing before equipment is ordered rather than after.

What Gastech Supplies

Fixed gas detection with marine and class society approvals for processing areas, riser moorings, storage, offloading and machinery spaces.

Open path detection for the long spans across decks, bunds and pipe racks, including detectors that keep working through sea spray and deluge testing.

Flame detection for helipads, turbine enclosures, machinery spaces and process areas, including hot exhaust immune variants where helicopter or engine exhaust would otherwise cause false alarms.

Portable gas detectors and area monitors for crews, first response vessels, confined space entry and survey work.

Controllers with the relay capacity to drive deluge, alarms and shutdown rather than only reporting.

Behind them sit project engineering, NATA calibration and service, field service, fleet management and hire for campaigns and shutdowns, from WA, NSW and QLD.

If you are specifying for a classed vessel or a facility under NOPSEMA and need to know which certificates a detector actually holds, talk to our Technical Consultants.