Improvement of preventive fire protection at a tank farm

Tank farms are used for the storage of highly flammable and explosive substances; Consequently, preventive fire protection is of major importance. When rehabilitation of such a tank farm is planned, contractors often recommend extensive – and thus costly – measures. A fire-protection solution developed by TÜV SÜD demonstrates that an equivalent level of safety can also be reached with a far more cost-effective solution. A central role in damage limitation is played by early fire detection using thermographic cameras.

Numerous tank farms throughout Germany store petrol, diesel, kerosene or liquefied petroleum gas (LPG). In contact with air, these highly flammable substances can form explosive mixtures. Given this, tank farms require special measures in the field of preventive fire protection. If rehabilitation of fire-protection systems becomes necessary at an older tank farm, far-reaching measures should be taken, not only by way of precaution but also to exclude possible liability risks. And yet not every measure that is technologically feasible is also necessary in case of a rehabilitation, as can be seen from the example of a tank farm in Bavaria, Germany.

The tank farm is located at a basin of a river port in Bavaria. The part of the tank farm in need of rehabilitation covers 24 tanks with a storage volume of between 600 and 2,000 cubic metres. The tank farm is used for intermediate storage of highly flammable fluids with flame points of < 21 degrees Celsius, as outlined in the German hazardous substances legislation. In fire inspections and on-site inspections after incidents, the inspectors had identified major non-conformities in the fire-extinguishing system. To replace the outdated and non-conforming system, an engineering firm submitted an extensive list of measures. These measures fully satisfied all regulatory requirements but represented a very cost-intensive solution, requiring a full rehabilitation using traditional extinguishing systems. For the tank-farm operating company, the costs of implementing these measures would have added up to 1.7 million euros.

In fire protection, the challenge lies in connecting well-founded technological knowledge and legal know-how. In practice this means harmonising reasonable engineering services and legal applications to obtain a cohesive, economically feasible and easily implemented fire-protection concept.

Alternative solution developed by TÜV SÜD

At the operating company’s request, TÜV SÜD’s third-party experts validated the individual measures and the cost-effectiveness of the rehabilitation plan submitted by the engineering firm. Owing to the large number of deficiencies identified in the tank farm, the experts first prepared a list of priorities with the measures necessary to fulfil the safety requirements and achieve the protection objectives. They arrived at the conclusion that not all of the proposed measures actually needed to be implemented. Starting from this finding, they then drew up an alternative fire-protection concept that would ultimately reduce the projected costs by one third.

TÜV SÜD’s rehabilitation plan included the fire-protection infrastructure already in place at the tank farm, such as a non-automatic foam extinguishing system with a total foaming-agent supply of 10,500 litres distributed across two tanks, two submerged pumps in the port basin with a pump capacity of 180 m3 per hour to ensure water supply for fire fighting and sprinkling the shells and the roofs of the tanks, manual triggering of the shut-off valves and a transformer station powered by the regional energy supplier. The feed-in of emergency power was effected by the local professional fire department.

The engineering firm, by contrast, had planned to replace the entire fire-extinguishing system. They wanted to install three mobile extinguishing-agent distribution systems in container form for remote controlled sprinkling and foaming of the tanks. This solution would have required the installation of new electrical, operational and control systems as well as new pipe routes connecting the extinguishing-agent distribution systems with the fire-fighting systems in the tank fields. The costs for the three extinguishing-agent distribution systems in container form alone would have added up to around 1.2 million euros.

Implementation of three packages of measures

The alternative rehabilitation concept developed by TÜV SÜD, which also met the requirements of the Bavarian Building Code (BayBo [1]), provided for three essential packages of measures to achieve the protection and safety objectives.

First, installation of a fully automatic infrared measuring system made by DIAS Infrared to ensure early fire detection. The system’s seven thermographic cameras are installed on pan-tilt units. They detect changes in temperature at the surfaces of the tanks made of different materials and located in the area monitored by the cameras, before these changes in temperature can cause a fire. As the cameras can move, the areas to be monitored can be divided into sectors. The cameras then approach these sectors cyclically in sequence. To protect the cameras against external influences, they are housed in ventilated and heated weatherproof enclosures (Fig. 1). Monitoring focuses primarily on the safety devices of the tanks, pumps and motors and on the filling systems on the tank-farm premises. The control room at the tank farm and the local professional fire department are notified immediately as soon as the temperature exceeds a certain limit. The measure package also includes remote triggering of the extinguishing-agent supply from the control centre and automation of the safety devices.

In addition, it covers rehabilitation of the sprinkler and foam-extinguisher system. In this context, TÜV SÜD’s solution provided for replacement of the leaking and corroded pipe sections with new pipes and for installation of three fixed foam-extinguishing systems in the form of foam monitors to fight incipient fires directly. In addition, a mobile foam monitor was planned as a backup.

A third focus area concerns safeguarding the power supply required for early fire detection and fire fighting. According to the regional energy supplier, power outages may have a duration of at least 30 minutes. Given this, the tank-farm needed an independent power supply system that was able to ensure power supply for at least 2 hours. The experts relied on battery buffering and a diesel operated emergency power unit to solve this problem.

Protection objectives and equivalent safety level reached

The fire-protection solution presented by TÜV SÜD was agreed with both the tank farm’s operating company, the municipal authority and the professional fire department. The three measure packages also complied with the required protection objectives and the safety levels. And ultimately, they proved far more cost-effective than the solution initially proposed. Since rehabilitation of the tank farm, early fire detection in conjunction with improved fire-protection infrastructure has become a central part of damage limitation. Since the rehabilitation concept was implemented, the tank-farm’s operating company – working with the professional fire department – has been able to effectively counteract all possible scenarios of incipient fire effectively and at an early stage, even in cases of power loss or when access to the tank farm is blocked (see Figures 2 and 3).

Classification under the Bavarian Building Code (Bayerische Bauordnung, BayBo)

Tank farms are installations of a special type and use (special structures). Their operation involves the handling and storing of highly explosive or flammable substances. Protection measures and safety precautions thus not only fall within the operating company’s responsibility but are also a matter of public interest. Given this, the BayBO stipulates requirements including material requirements which, as “General clauses of fire protection”, help to support the protection objectives defined in Article 12. However, according to article 3 (1) deviations from the technical building regulations are possible if an alternative solution is found that is equivalent in terms of fulfilling the general requirements in paragraph 1. In other words, the requirements laid down in the Building Code are deemed complied with if the generally recognised rules of architecture and technology are fulfilled.

For more information, go to www.tuev-sued.de/is or www.dias-infrared.de

Reference

1 “Bavarian Building Code” as amended by publication of 24 July 2015.