Early fire detection in a tank farm
Numerous defects were found in the fire extinguishing system of a tank farm in Bavaria, Germany. TÜV SÜD Industrie Service was commissioned to develop a fire protection concept for the refurbishment. In deviation from the usual regulations, an alternative concept was proposed, coordinated and implemented with the operator, the responsible authority and the professional fire brigade. Early fire detection with a fully automatic infrared measuring system is now a central damage limitation component.
Appropriate technical and organisational measures shall be taken against fires in tank farms and their immediate vicinity to prevent fires and explosions and reduce their effects. This is because the hazard potential of substances stored in tank farms lies essentially in their flammability and in their ability to form explosive mixtures with air. Large damage events occur very rarely in tank farms. When they do occur, however, emergency responders are called upon to rule out far-reaching consequences. Preventive fire protection therefore plays a central role in countering potential hazards effectively and at an early stage.
Keeping an Eye on Technical and Legal Objectives
Fire protection must meet defined protection goals. This also applies to existing systems in which, for example, preventive fire protection is to be improved during renovation works. But not everything that is technically feasible in terms of fire protection makes sense in practice. It is not unusual that very extensive measures are planned and implemented – in some cases in order to exclude any liability risks right from the beginning.
The central challenge is to coordinate and optimise reasonable engineering services and the application of the law. This is because fire protection requires a high degree of technical knowledge and legal know-how. This is of great importance because demanding situations need to be evaluated according to specific protection goals and comprehensible risk considerations have to be made. At the end of the complete process, a conclusive and economically justifiable fire protection concept should be the result, which is granted the approval of the authorities and the professional fire brigade and is easy to implement in practice.
Classification According to Building Law
Tank farms are facilities of a special kind and use. The operation is connected with the handling and storage of materials with explosive properties or increased fire hazard. For this reason, protective measures and safety precautions – as with other special constructions – are not only the responsibility of the operator but are also of public interest. For this reason, the Bavarian Building Code (BayBO) contains, among others, material requirements, which serve as a ‘general stipulation of fire protection’ for the protection goals defined in Article 12.
Accordingly, structural installations shall be arranged, erected, modified and maintained in such way that the occurrence of a fire and the spread of fire and smoke are prevented and the rescue of people and animals and effective extinguishing work in the event of a fire are enabled. According to Article 3, paragraph 1, however, the technical building regulations may be deviated from if an alternative solution fulfils the general requirements of paragraph 1 to the same extent. This means that if the generally recognised rules of architecture and technology are observed, the requirements and regulations laid down in law shall be deemed to have been complied with.
Refurbishment of the Tank Farm in Bavaria
During fire and accident inspections on the site of a tank farm in Bavaria, various test experts found considerable defects in the fire extinguishing system. For the planning of the refurbishment, an engineering office submitted a catalogue with extensive renovation measures, for which 1.7 million euros were budgeted. Independent TÜV SÜD engineers validated the plans. In the part of the tank farm that needs refurbishment, there are 24 tanks in which easily flammable liquids with a flashpoint (FP) of < 21 degrees Celsius are stored temporarily in accordance with hazardous substances legislation. The capacity of the tanks varies between 600 and 2,000 m3.
The following fire protection infrastructure existed at the time of the assessment: a non-automatic foam extinguishing system with a total foam agent supply of 10,500 litres distributed over two tanks, two submersible pumps in the nearby harbour basin with a capacity of 180 m3/h each for the shell and roof sprinkling of the tanks as well as the extinguishing water supply, a manual triggering of the shut-off valves and a separate transformer station, which was fed by the regional energy supplier. Emergency power was planned to be provided by the local professional fire brigade.
Extinguishing Agent Control Centres Planned with New Infrastructure
During the assessment of the proposed renovation concept, TÜV SÜD engineers noticed that the engineering office’s catalogue of measures actually aimed at a complete renewal of the fire extinguishing system. Among other things, the installation of three extinguishing agent control centres in container form was proposed. The DIN-compliant solution was to ensure remote irrigation and foaming of the tanks. Also included were the necessary electrical, operating and control systems for the remote-controlled operation of the extinguishing agent control centres as well as the installation of new pipeline routes from the fire extinguishing control centres to the fire extinguishing equipment in the tank fields. The estimated costs only for the three planned extinguishing agent centres, including the new and complex infrastructure, amounted to approx. 1.2 million euros.
Alternative Refurbishment Concept
The TÜV SÜD engineers drew up a list of priorities with essential measures required for the refurbishment. This was necessary due to the large number of defects identified. In order to achieve the protection objectives, the following measures were proposed in detail in the form of three steps to be implemented:
Installation and commissioning of an early fire detection system, consisting of a fully automatic infrared measuring system from DIAS Infrared, which detects a possible fire event via temperature changes in the monitored area before a fire can occur. The following areas are monitored: safety devices and valves of the tanks, pumps, motors and other electrical systems in the explosion zone, refuelling stations (filling islands for tank trucks) as well as the transfer zones for ship unloading and train refuelling.
The system consists of seven thermal imaging cameras on pan-tilt heads. This allows the monitored areas to be subdivided into sectors which are approached cyclically one after the other. Exceedance of a certain temperature value is immediately reported to the control room of the tank farm as well as the local professional fire brigade. The cameras are housed in a weather-proof housing with ventilation and heating (Fig. 1). Thus they are well protected against external influences. Further measures are the remote triggering of the extinguishing agent supply from the control room and the automation of the safety equipment.
Renovation of the piping system of the foam extinguishing and sprinkler system by replacement of leaky and corrosion-affected pipe sections. In addition, three permanently installed foam extinguishing systems in the form of foam monitors are to be integrated for incipient fire and firefighting. In addition, a mobile and thus flexible foam monitor must be provided.
Ensuring power supply for early fire detection and firefighting: according to the regional energy supplier, the maximum duration of a power failure is at least 30 minutes. As redundancy, independent emergency power must be provided for a period of two hours by battery buffering and additionally by means of a diesel-powered emergency power generator.
Effective Improvement of Preventive Fire Protection
The alternative fire protection concept was coordinated and implemented with the operator of the tank farm, the responsible municipal authority and the professional fire brigade. Early fire detection in conjunction with additional measures to optimise the fire protection infrastructure is now an essential part of damage limitation. This enables the tank farm operator, in cooperation with the professional fire brigade, to counter possible scenarios of fire emergence early and effectively – even in the event of a power failure and blocked access by a freight train, as shown in the example scenarios in Fig. 2 and Fig. 3. Compared to the previous concept, the TÜV SÜD fire protection concept with early fire detection from DIAS Infrared saved the tank farm operator around one third of the originally estimated refurbishment costs – with the same safety level as well as compliance and achievement of the required protection objectives.
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