08 Oct Alternative remedy
When a tank farm manager in Germany commissioned TÜV SÜD Industrie Service to develop a fire protection concept the technical experts, thinking out of the box, proposed a solution which relies on early fire detection using a fully automated infrared measurement system as a key element of damage limitation. Michael Daub (TÜV SÜD Industrie Service GmbH) and Torsten Welz (DIAS Infrared GmbH) explain.
Fire protection must ensure certain safety objectives and is thus not an end in itself. However, not everything that is technically feasible in fire protection is also sensible. Many stakeholders plan and recommend over-the-top measures to exclude all possible liability risks. The key challenge in fire protection lies in workable coordination and optimisation of engineering services and applicable law thus functional fire protection requires both in-depth engineering expertise and legal know-how. This is extremely important as the process involves evaluation of complex situations according to specific safety objectives and traceable risk assessments. The outcome should be a cohesive, financially viable fire protection solution that is approved by the competent authorities and the fire department and is easy to implement in practice.
Fundamentals of building law
Building law designates tank farms as installations of a special type and use as their operation involves the handling and storing of highly explosive or flammable substances. As for all other special structures, preventative fire protection plays a key role for the technical safety of buildings and structures. Given this, protection measures and safety precautions not only fall within the operating company’s responsibility but are also a matter of public interest.
In this instance, the Bavarian Building Code (BayBO) thus also includes a “General fire protection clause”, which includes material and other requirements and helps to support the safety objectives defined in Section 12.
According to this clause, building structures must be laid out, constructed, modified and maintained in a manner that prevents fires and smoke from developing and spreading and permits rescue of people and animals as well as effective firefighting measures in the event of fire. However, according to article 3 (1), deviations from the technical building regulations are possible if an alternative solution is found that is equivalent with respect to 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.
Various technical inspectors had identified numerous non-conformities in fire-extinguishing equipment during fire inspections and on-site inspections after incidents at the tank farm in Bavaria and an engineering firm presented a long list of extensive rehabilitation measures with a total volume of 1.7 million euros. As a result, the tank farm managers commissioned TÜV SÜD to carry out third-party validation of the plans.
The relevant part of the tank farm, located at a harbour basin, comprises 24 tanks with volumes between 600 and 2,000 cubic metres. The tanks are used for intermediate storage of highly flammable fluids with flame points of < 21 degrees Celsius, as outlined in the German hazardous substances legislation.
At the time of the inspection, the fire protection infrastructure consisted of: a non-automatic foam-extinguisher system with a total foaming agent supply of 10,500 litres distributed across two tanks, two-submerged pumps in the nearby harbour basin with a pump capacity of 180 m3 per hour for sprinkling tank shells and roofs and providing water supply for firefighting, a manual trigger system of the shut-off valves and a transformer station powered by the regional energy supplier with emergency power was supplied by the local professional fire department.
An initial rehabilitation concept
While reviewing the proposed rehabilitation concept, the TÜV SÜD engineers noticed that the list of actions proposed by the engineering firm provided for complete replacement of the fire-extinguishing system suggesting the installation of three mobile extinguishing-agent distribution systems in container form. The solution, which was in conformity with the German industrial standards, was designed to enable remote-controlled tank sprinkling and foaming. It also included the electrical, operational and control systems needed for remote-controlled operation of the extinguishing-agent distribution systems and the installation of new pipe routes connecting the extinguishing-agent distribution systems with the firefighting systems in the tank fields. The estimated costs added up to 1.2 million euros for the three extinguishing-agent distribution systems and their complex infrastructure alone.
Keeping the safety objectives in mind, the TÜV SÜD engineers drew up a list of priorities including essential measures to be implemented due to the large number of defects identified. Paramount for achieving the safety objectives by means of the alternative solutions were three packages of measures which included :
Establishment and commissioning of an early fire-detection system
The system, from DIAS Infrared, includes a fully automatic infrared measurement system that detects changes in temperature in the monitored area, thus possible fire risks, before a fire can start. Monitoring focuses on the safety devices of the tanks, motors and pumps and the filling stations on the tank farm premises. The infrared measurement system comprises seven thermographic cameras on pan-tilt units, which divide the areas to be monitored into sectors that they cover in sequence. If the pre-set temperature is exceeded, an alarm is immediately triggered in the tank farm control centre and the local fire department. The cameras are located in weatherproof ventilated and heated enclosures (Fig. 1) to protect them from external influences. The package of measures also includes remote triggering of the extinguishing-agent supply from the control centre and automation of the safety devices.
Rehabilitation of the existing piping system
Replacing leaking and corroded pipe sections of the foam extinguishing and sprinkler systems. In addition, three fixed foam extinguishing systems in the form of foam monitors must be integrated into the system to fight incipient fires and the spreading of fires. On top of this, a mobile foam monitor for maximum flexibility must be provided.
Reliable provision of the power supply
Essential for early fire detection and firefighting and because, according to information submitted by the regional energy supplier, power outages may last up to a minimum of 30 minutes. To ensure a fully redundant system, an independent emergency power supply must be provided which uses battery buffering and a diesel-powered emergency generating set to provide power supply for up to two hours in case of a power outage.
The alternative fire protection concept developed by TÜV SÜD was discussed and agreed with the tank farm operating company, the responsible local authority and the fire brigade, and was implemented. Early fire detection, in conjunction with additional measures to improve fire protection infrastructure, is now a key element of damage limitation. The tank farm operating company, in collaboration with the fire department, can now respond early and effectively to possible fire scenarios – even in the case of a power outage or if access to the tank farm is blocked by a cargo train, as shown in the model scenarios in figures 1 and 2.
Costs reduced by one-third
By applying the measures described here, the experts were able to compensate for the existing weaknesses in the fire protection infrastructure. Compared to the previous concept, the fire protection solution presented by TÜV SÜD, which builds on an early fire-detection system developed by DIAS Infrared, saved around one-third of the originally estimated costs of rehabilitation for the company operating the tank farm. The solution also achieved the safety objectives and safety level required.