Gas detectors are mandatory on tankers and can be life savers if used correctly. The market is expanding as new technology emerges to meet growing demand
Gas detection is covered by Regulation XI-1/7 – which the International Convention for the Safety of Life at Sea (SOLAS) brought into force in July 2016. It made it mandatory for all applicable vessels to carry portable gas detectors onboard and test them regularly. “Every ship to which it applies shall carry an appropriate portable atmosphere testing instrument or instruments. As a minimum, these shall be capable of measuring concentrations of oxygen, flammable gases or vapours, hydrogen sulphide and carbon monoxide prior to entry into enclosed spaces,” it states. Under SIRE inspection criteria, there is a need for gas detection instruments to undergo regular calibration. Unfortunately, despite these regulations, the same mistakes continue to be made at sea.
Those mistakes can cost lives, as the January 2021 incident onboard BW Offshore’s FPSO Espoir Ivoirien off the Ivory Coast tragically highlighted. The company confirmed that two fatalities were caused by a leakage of hydrocarbons into a tank where work was being performed. The subsequent investigation will reveal if the people in the tank were equipped with gas detectors and if the devices were working.
The market for marine gas detectors is large. Since 1999, one provider, Martek Marine, has supplied over 30,000 shipsets across the globe with more than US$100M of sales to date. One of its latest devices, the MGC Simple+, is a clip-on portable gas sensor that uses infra-red technology, giving it immunity to sensor poisoning. It emits and detects infrared light through a series of chambers containing concentrations of different gasses in the local atmosphere. As the photons pass through these chambers, they excite symmetric and asymmetric vibrations in the gas molecules. The detector then calculates and converts the infrared radiation absorbed by gas particles present and displays the level to the user.
There is no contact with gas particles, meaning that the detectors do not need oxygen to work. The unit has a three-year battery life and in normal use it does not need calibration. It is IP68 rated and works in 1.5 m of water and in inflammable and oxygen-free environments and collects data for incident analysis. Similar devices from Martek Marine, such as Marine 4 and Marine 5, incorporate multiple gas detection and crew-safe detection and incident data logging.
“Investigation revealed a crack in the inert gas deck seal drain line passing though the ballast tank”
Martek Marine also supplies fixed gas detection systems such as the MM2000, which is an intelligent addressable gas detection system designed to provide flammable, toxic and asphyxiant gas detection. The addressable fixed gas detection system is suitable for many applications and is guaranteed to be SOLAS and ISGOTT compliant. The MM2000 fixed gas detection system covers the requirements of charterers such as ExxonMobil – a key competitive advantage. The system is set to detect hydrogen sulphide at ExxonMobil Minimum Environmental and Safety Criteria levels, ensuring protection from the highest threat to crew members on crude oil vessels. A single four-core cable enables the system to monitor from one to 32 sensors at any time, while the simple system loop sensor cable ensures low-cost installation.
Another fixed gas detection system with multiple sensors is available from Consilium, which has a modular system, based on the Consilium Common Platform. The CGD50/500 Gas detection system can be expanded to up to 64 sensor locations. CGS50/500 is based on a cabinet with the same outer dimensions and mounting dimensions as the well-known Salwico SW2020 gas sampling system. The pipe connections for gas sampling are just slightly changed. “Backward compatibility is important to our customers,” says Consilium product manager Fredrik Jonasson. “We had good reason to switch to the Consilium Common Platform for the new CGS50/500, but keeping the cabinet size was an important decision to make the physical replacement easier,” he said.
Instances of gas detection actually saving lives often go unreported. One instance that received coverage from the Nautical Institute was a case of gas vapours detected in a ballast tank. A tanker was alongside and crew were preparing to discharge the cargo of gasoline when the fixed gas detection system alarm sounded. Hydrocarbon vapours had been detected in water ballast tank 4S. To rule out a potential malfunction of the gas detection system, ship staff performed the required checks with portable gas meters. These checks confirmed the presence of hydrocarbons in the tank.
The vessel was taken to anchor as a safety precaution. A contingency plan to inert the ballast tank atmosphere was prepared and approved by class and coast state authorities before it was carried out. The vessel was subsequently brought back to berth and the cargo was discharged. After discharge the vessel was re-anchored and a detailed investigation was carried out to determine why cargo vapours had entered the ballast tank.
The investigation revealed a crack in the inert gas (IG) deck seal drain line passing though ballast tank 4S. Additionally, the non-return valve was not operating correctly. At the time of loading and during topping up, the main IG isolation valve was left open after the IG system was stopped. The gases from the tank leaked back though the inoperative non-return valve, allowing cargo vapours to reach the deck seal. The ‘wet’ type deck seal performed its function by not allowing cargo vapours to pass, and the vapours were subsequently flushed out through the drain line that passed through ballast tank 4S. However, the hole in the drain line released water and cargo vapours into the ballast tank.
As the tanker industry looks towards meeting IMO’s GHG targets, there will be an increase in large-scale electrical systems onboard, and these will incorporate lithium-ion (li-ion) batteries. Nexceris was engaged by the US Navy to produce a gas detection sensor to improve the safety of such battery installations on board ships. The wonderfully named Li-ion Tamer sensor system uses unique information about the condition of the li-ion battery through monitoring of off-gas events from the cells. This can provide the early warning necessary to act and prevent a battery fire.