Triple protection: Uninterruptible power supply system solution for a coastal platform

An uninterruptible power supply is mandatory on oil rigs: For safety reasons, signal lighting must be functional at all times. R. STAHL was faced with three major challenges when designing an uninterruptible power supply system for a coastal rig in the African Sea. Not only did the uninterruptible power supply system have to be protected against explosive atmospheres, it also had to adapt to the overheating conditions and the maritime climate at the rig's location.

Complete power failures or faults in the main power supply system, such as frequency fluctuations or overvoltages caused by lightning strikes, must be safely bridged on the oil rig. Above all, functional signal lights are important not only for the smooth operation of the rig, but also for the safety of all nearby ships and aircraft. Therefore, the navigation lights must not go out under any circumstances. Located off the Atlantic coast of Africa and in large caves, the platform is currently being used as a temporary storage for natural gas and is usually supplied with electrical energy by a solar power station. A battery-powered emergency power grid is installed in parallel. In addition to the power supply equipment, R. STAHL assembles further energy distribution components from its modular kit for uninterruptible power supply system solutions.

Excellent weather, harsh environment In addition to the occasional explosive atmosphere (e.g. Zone 1), tropical climate and sea air must be taken into account. Temperatures on the platform frequently exceed 35 degrees Celsius and sometimes reach peaks of 50 degrees Celsius. In such a temperature environment, the operation of the UPS battery charger generates a large amount of power losses and requires some special measures. To prevent overheating, R. STAHL installed the battery charger in the largest available bidirectional silicon steel chassis, with some special features to ensure heat dissipation: Through a patented cooling stage technology, the heat is evacuated directly from the protective housing. The heat sink is attached to the side of the chassis to facilitate the safe use of the bidirectional silicon steel equipment during maintenance.

Special performance fluctuates A stainless steel fan with motion monitoring for hazardous areas, mounted on the housing, facilitates the dissipation of heat. The fan can also be retrofitted for use in zone 1 under extreme ambient conditions. Forced cooling is controlled and monitored by an intelligent control system: the fan's operating state is adjusted depending on the current ambient temperature. Thanks to these measures, a maximum power loss of 1000 Watts can be compensated and, moreover, no heat is dissipated on the housing surface. A considerable amount of exhaust heat energy generated by battery charging is thus released to the natural environment without affecting the operation of the charger.

As with all other R. STAHL UPS solutions, the necessary explosion protection for zone 1 is ensured by a special feature that is unique on the market: an integrated Ex UPS protection monitor functions as a battery charger and battery, which can also be installed in the Ex area and which enables safe operation according to the ATEX directive and in accordance with IEC 60079 ff.

To ensure continuous lighting with a dual power supply, R. STAHL installed a switchboard with a safe parallel feed from the standard power supply and the emergency grid. The lighting switchboard is designed with two inputs for interlocking devices. In addition, each output line is independently monitored for ground faults. All functions can be activated from the outside and the condition of each output line is clearly indicated by a position handle. By installing a combination of a bidirectional silicon steel fireproof enclosure (Ex d) and an enclosure with added connection room safety (Ex e), R. STAHL was able to achieve a very compact, weight-optimized system that could be installed in the extreme spaces on coastal platforms. All external metal parts of the seawater-resistant bidirectional silicon steel enclosure are made of SS316 stainless steel. This material is used in offshore environments without further surface treatment.

100% process safety in hazardous areas: Modular UPS solutions in detail The range of UPS solution components includes battery chargers, various explosion-proof rechargeable batteries (lead gel, NiCd, NiMH), charge monitoring technology including alarm annunciators, DC power distributors and inverters up to 3000 VA for various performance classes. In addition, R. STAHL offers a wide range of explosion-proof enclosures, for example the GUBox series features an Ex e connection room. R. STAHL also offers modules for user-specific explosion protection requirements.

Figure 1: The explosion-proof uninterruptible power supply system provided by R. STAHL uses a battery device on a coastal platform to ensure safe power supply in the event of a failure.

Figure 2: Due to very high ambient temperatures, the explosion-proof enclosure is equipped with a heat sink and a fan

Figure 3: Ex UPS protection ensures charger and battery monitoring, which is definitely necessary in Ex zone 1

Figure 4: The dealer solution with safe parallel feed ensures continuous power supply for lighting, also suitable for hazardous areas