Rim Seal floating roof tank fires represent one of the most dangerous threats for chemical and petrochemical storage farms. Industry data base shows that the oil industry has experienced several rim seal fires worldwide and some of them have developed into very large disasters. The causes of such disasters start with a rim seal fire that breaks out and grows undetected to a point that it spreads over the whole seal area and therefore the floating roof tank becomes surrounded by fire. In the worst case scenario, the intense heat radiated is absorbed partially by the tank shell and the pontoon until the point that the metal sheets lose their mechanical stability. In such conditions the roof is no longer capable to float normally and can incline causing the roof to sink under the fuel with a consequential full surface fire. The most efficient way to avoid such fires to develop uncontrolled is that of installing a fire detection and suppression system. Such systems specified by NFPA 11 provides well proven methods of firefighting on floating roof tanks. However, such systems have a reaction time from fire detection to suppression that still leaves many oil companies concerned about the fire suppression performance.
|It is in fact paramount that a fire on a floating roof tank is to be suppressed as soon as possible. In this respect an additional system is supplied and integrated with the tank floating roof in order to provide early fire detection and instantaneous fire suppression within the rim seal zone. Such packages are capable of detecting instantaneously the fire outbreak in the rim seal zone and discharge in seconds a charge of fire extinguishing agent directly on the zone where the incipient fire has developed. This strategy has been proven successful when the rim seal packages are interconnected with the main foam system that is automatically activated seconds after the rim seal unit has discharged. For such reasons the units are instrumented with low and high pressure switches that monitors the status of the unit as well as its activation. Those instruments are connected to the main control system or F&G that manage the system logics and triggers the traditional foam system.
Rim seal unit on a floating roof tank Fire Protection is a part of rim seal fire detection and suppression solutions for the protection of floating roof tanks. The solutions available are several and each one is designed to cope with a specific tank seal design, fuel content and environmental condition.
The Rim Seal Fire Suppression Systems are available based on the following extinguishing agents: