A floating production storage and offloading unit(FPSO) is a vessel used in offshore production for producing, storing, cleaning, and loading extracted oil or natural gas. Systems like this have become the main method in many offshore productions regions around the world. As with other applications in flammable environments, the electrical control of certain processes requires explosion-protected solutions to minimize the risks to people, the environment, and the machine.
A well-known American control system manufacturer wanted to equip an FPSO vessel belonging to one of their end customers with a complete electrical solution. To achieve this, the control system manufacturer required different ATEX- and IECEx-certified enclosures for Zone 1 and temperature class T4 so that the solution could be equipped with remote I/O systems. The enclosure dimensions ranged from 1000 × 1500 × 450mm to 800 × 2100 × 1000mm(W/H/D). All enclosures should comply with the Ex pyb type of protection. In addition, the control system manufacturer required an external override function to enable the remote I/O systems to continue operating safely even when the purge and pressurization control unit is shut down.
To meet these requirements, the Pepperl+Fuchs engineers opted to use the 6500 Series purge and pressurization system. This system consists of a control unit, an enclosure protection vent, and a manifold valve, forming the basis for the required explosion-protected enclosure solution. The enclosures themselves are made entirely of SS316L stainless steel, making them suitable for the harsh offshore conditions aboard the FPSO vessel. Special vibration dampers installed between the base and the enclosure protect the enclosures and electrical components from any potential mechanical damage caused by engine vibrations and sea conditions.
To ensure that the solution included the required external override for the purge and pressurization system, a combination of relays and contactors certified for use in Zone 1 had to be installed in the circuit. In the event of problems on the FPSO, the remote I/O system is now able to override the purge and pressurization system control unit via an output and continue to operate safely, since air continues to flow through the needle valve and pressure is maintained.

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