Safety on deck.
And below.

The tanks on an LNG tanker are designed with effective thermal insulation in order to keep the natural gas, which has been cooled to between -161 C and -164 °C, in liquid form. However, LNG boils even at these low temperatures, which results in the continuous presence of gaseous methane as "boil-off gas". This is either used as fuel for the turbines propelling the ship or re-liquefied and returned to the tank.

Specific boil-off gas (BOG) compressors are used for BOG management. These compress the gas for use in the LNG carrier's drive motors or, alternatively, are part of the recondensers – the system used to re-liquefy the gas. In order to meet the strict safety requirements, explosion-protected remote I/O control stations are used to control the compressors. They transmit signals from sensors and actuators intrinsically safely via fieldbus systems to a control system; additionally, they enable comprehensive diagnostics in order to prevent failures. Space is scarce on ships. So, the stations, which include I/O modules, display elements and signalling equipment, must be as compact as possible.

The intrinsically safe IS1+ remote I/O station from R. STAHL is perfectly sized. Featuring 8- or 16-channel Ex i modules, it saves space and weight. It is also particularly robust and resistant to vibrations. It has been granted the required international Ex approvals, as well as all essential ship certifications, including DNV GL, ABS and ClassNK. A robust Ex e stainless steel enclosure with single, double or triple doors, combined with seawater-resistant seals, provides protection against the saline environment which also increases the IS1+ system's lifetime.

The insulated cargo tanks on LNG transport vessels must guarantee that extremely low temperatures are maintained over long periods of time. Continuous temperature monitoring is therefore a must-have. The pressure in the tanks, which can increase as the LNG evaporates, must also be continuously monitored and, if necessary, regulated. In addition, limit level detection sensors guarantee safety while ensuring that the tank capacity is utilised to its fullest. These are accompanied by sensors for leak detection and pressure monitoring in areas filled with safety inert gas, control solutions for unloading pumps and BOG compressors, alarm systems, safety valve monitoring, and much more.

Suitable explosion-protected HMIs, combined with remote I/O systems and communication systems, provide a continuous overview, which guarantees maximum safety. These must also be designed in a way that they are resistant to seawater and vibrations and suitable for use in a wide temperature range. The panel PCs and KVM operating stations within R. STAHL's SHARK device platform meet these requirements perfectly. They present all measuring and diagnostics data in a clear format. Of course, they are available for Zone 1 and Zone 2, as well as in rugged designs for operation on ships.

At the destination, pumps on-board the LNG tankers are used together with movable insulated loading arms in order to unload the cargo. The extremely flammable, cryogenically cooled LNG demands that these are also explosion-protected. Explosion-protected, seawater-resistant (where possible) control terminals combined with a flameproof panel and a terminal box with increased safety is an absolute must. Operation via explosion-protected portable control devices is possible using wired handheld transmitters or pluggable suspended devices. Wireless control systems provide even more convenience and are not subject to wear and tear. In this case, the receiver is installed in a flameproof CUBEx enclosure on the hydraulic unit. The position monitoring for the loading arms can be integrated into the central HMI as part of the overall process monitoring. This means that each arm must be equipped with an Ex-protected remote I/O system that transmits the corresponding position of the arm.

Even when all safety-related regulations for the IGC type 2G LNG tanker have been implemented, signalling devices are extremely important on board. The only way to ensure that the crew, ship, machines and environment are all protected and can be rescued in the event of an accident is by ensuring evident, clear warnings are triggered if hazards are present. The signalling devices themselves must not become a source of a hazard. They must therefore always be designed so that they are explosion-protected. The ideal combination of audible and visual signalling devices must be determined according to the type and design of the ship. R. STAHL offers a wide range of signalling devices for hazardous areas, which are also suitable for offshore use. The Ex d type of protection, for instance, guarantees safety for flashing beacons in the FX15, FL6S and FL60 series. Multi-signal devices in the MS series feature an Ex e connection chamber. The flashing beacon and continuous beacons in the 6161 series combine the Ex d and Ex e types of protection.

A similarly extensive range of loudspeakers, alarms and horns are available for issuing audible warnings in hazardous areas on ships. Two series, comprising 85 products in Ex d versions, even go as far as combining a flashing beacon and horn in one, which reduces the effort required for installation. Particularly advantageous in this respect is the YODALEX/2 series, which is certified according to IECEx and ATEX, and features combined signalling devices with an especially wide range of functions.