Oil Storage Tanks Fire Suppression

Description

Oil Storage Tanks Fire Suppression System

Fire Detection and Extinguishing:When discussing Fuel Storage, the threat of fire is obvious and so is the need for a reliable, fast reacting fire detection and suppression system

For tackling oil or organic fuel fires (petrol, diesel, kerosene), extinguishing foam is the only effective solution. The fire protection concept is determined by the tank design and the liquids stored in it.

If, for example, it is an oil tank with a floating roof, the fire detection or extinguishing system will be concentrated on those areas in which the flammable liquids come into contact with the air (oxygen). In this instance, the correct solution would be a rim seal extinguishing system combined with a linear heat detector cable.

If the tank has a fixed roof, the fire must be tackled by spraying the extinguishing foam inside the tank. As the extinguishing foam is less dense than oil, it will float on top of the liquid. This will therefore create a shield against oxygen and the fire will be extinguished. In addition to tank protection, the corresponding extinguishing devices must also be used for oil silos.

Cooling:                                                                                                                                                                    Foam Fire Protection System is fire suppression system. Its success is mainly depends on proper mixing of foam concentrate along with air and water, to form a uniform foam blanket to extinguish flame.

In addition to a tank extinguishing system, the tanks must be cooled from the outside. For this purpose, close circular pipelines with nozzles are installed on the outer surface. Should a neighboring tank catch fire, the water cooling system will prevent the contents of the tank from overheating. This therefore stops a fire spreading from one tank to the next.

Back Ground of Foam Fire Protection System

Water is known for suppressing fires, but unfortunately not best in all the cases. Water is not effective on an oil fire, and can be of no use during emergency. To suppress oil fire foam is reliable to use, since it prevent the direct contact of fire with oxygen, resulting in suppression of the combustion.

Application of Foam Fire Protection System

Foam Fire Protection System is designed for countering the oil (light diesel oil/Heavy furnace oil) fuel fires. Often foam protection is used for protecting oil tank and extinguishing fire in oil tanks. Foam system serves two purposes, first to extinguish fire in oil tank and the second function is to cool the tank from outside by installing close circular pipelines around the tank and maintaining the temperature under control in case of neighboring tank fire. This is very helpful in preventing the fire spread from one tank to another.

Foam Fire Protection System Design Principles

Divas below are the design basics which need to be given due importance before installing Foam system:

• The fixed foam system operates automatically with the assistance provided by a fire detection system around the tank. Senses the rapid rate of temperature rise or pre-set maximum temperature or both to ensure that any fire on rim seal is detected within 10 seconds of occurrence. Peripheral nozzles discharge the extinguishing foam agent to protect the rim seal area of storage tanks.
• The complete system should be designed as per NFPA-11 regulations.
• Concentration of foam is a very important factor and it should be 100 % AFFF type, and stored in a tank of double of its capacity and it is discharged through a foam pump of capacity of 200 %.
• The minimum effective capacity of each foam concentrate tank and foam pumps should be designed for the protection of one largest fuel oil tank at its design capacity for a minimum duration of 60 minutes.
• Automatic foam protection system covers an area of oil storage tank and its surroundings. As fire detection system sense any smoke in the surroundings, automatic foam protection system starts working automatically.
• Foam concentrate will be sucked by the 2 foam inductors of 100% capacity, one of motor driven and another of diesel engine driven pump.
• Special attention shall be given for foam pumps material and the complete system should be designed as per the TAC norms.
• The minimum effective capacity of foam concentrate tank should keep in consideration while designing and there should be an extra margin of 10 % over the calculated capacity.The material used for making tanks shall be of carbon steel of Grade ‘B’ and there should be inner lining of 2 mm of FRP.
• • LDO tanks should be well equipped with foam proportioner.
  • Water required for foam system is supplied by hydrant system mains.
  • Supply line of oil tanks should be equipped with automatic solenoid at the upstream of foam proportioner.
  • In foam protection system, the network of pipelines has been done over the ground on RCC foundation.
  • Foam carrying pipelines should be of stainless steel.
  • For fixed roof type tanks, foam application rate should be 3% and foam solution shall be 6 lpm/sq.m.
  • Special components like non-return valves, strainers and isolation valves of pumps etc. should be used to avoid mixing of water with foam concentration.

  Strainers should be used at the water inlet point so that raw impurities could be captured there and non-return valve in the pipelines avoids mixing of water with foam.

• Schematic Diagram
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