Write short notes on: a) Water spray systems b) BLEVE c) UVCE d) SCBA.

Q 6 : Write short notes on: a) Water spray systems b) BLEVE c) UVCE d) SCBA.

Water spray system

Water Based Systems are designed to direct the water at the required density, from nozzles having predetermined patterns to completely impinge water into the hazard surface being protected. They are designed to use effectively in a variety of special hazards applications including flammable and combustible liquid hazards as well as transformers and turbines.

water based systems which can be used as/with the following systems/equipments, applicable as per the specific requirements :

• Hydrants
• Sprinklers
• High Velocity Water Spray Systems (H. V. W. S. Systems)
• Medium Velocity Water Spray Systems (M. V. W. S. Systems)

A Fire Sprinkler is the part of a Sprinkler Systems. They are generally located at ceiling level, connected with the system of water pumps and tanks. With the effect of fire at the site, due to the rise in heat the predetermined temperature reaches causing a glass component in sprinkler head to fail resulting in discharge of water spray from sprinkler head.

Sprinkler Systems help to reduce the growth of a fire. Sprinkler Systems can also involve into more effective and advanced systems like water mist systems which give finer water droplets.

This system proves very effective in protecting high rise buildings, warehouses, malls, auditoriums and other similar public houses.

High Velocity Water Spray Nozzles
This system works uniquely effective against fire hazards involving heavy or medium oil.
This systems operates using the specifically designed nozzles depending on the fire area , requirement of shape of spray cone and the water flow.
This system has capacity to reach to the surface of burning oil penetrating the flame zone .This results into most important phenomenon called ‘Emulsification’ i.e. formation of the non-combustible emulsion layer of oil-water on the surface of the burning oil. This emulsification along with the cooing smothering effects extinguishes the fire.
High Velocity Water Spray Systems also can be used to protect Circuit Breakers & Transformers.

Medium velocity water spray sprayers provide a continuous water spray with medium velocity consisting of finely divided water droplets. These systems are ideal in fighting against the fire involving light oils. As emulsification is not possible in this case, the high velocity water spray systems cannot work in this type of fire.

These systems sprayers are mostly used in combination with the other effective fire fighting systems. The specifically designed nozzles produce a cooling spray which has very high capacity to absorb the heat

This water jet is sprayed on the adjacent plants and structures which ultimately minimizes the damage and the risk of explosion.


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WHAT IS A BLEVE?

A BLEVE is a boiling liquid expanding vapor explosion, which occurs when pressurized liquid inside of a vessel, such as a propane tank, reaches temperatures higher than that liquid’s boiling point. If the vessel can no longer contain the pressure inside of the sealed tank due to the high temperatures, it will mechanically fail, causing the explosion.

Whether or not a fire occurs is contingent on if the liquid inside of the tank is flammable. If it is, a fire will often occur. If the vessel contains non-flammable liquid (such as a steam boiler), a BLEVE will occur, but the vapors will not ignite.

Heat does not have to be present for a BLEVE to occur. Mechanical damage or overfilling can also cause the vessel to explode.

A second-stage BLEVE can occur if a vessel releases combustible vapor into an area where it then mixes with air in the presence of a source of an ignition. Then, the explosion can stress the heated vessel and cause it to rupture, resulting in an explosion of the vapor.

Precautions to avoid BLEVE

• Maintenance of the cargo tank  at regular interval
• Relief valve to be functional at all time
• The size of the relief valve to be fitted should be as per the International Gas code
• Emergency preparedness of all ship staff
• During the gas cargo transfer, avoid general cargo, stores, compressed gas operation within the vicinity of the gas cargo operation
• No oil or fuel bunkering operation should be carried out during or before the cargo operation
• Keep checking the mooring lines to ensure the ship is well fastened to the pier/ dock
• An LP-Gas detector shall be readily available for use at the berth
• any cargo transfer during the night or dark hours should be done in the presence of ample lights, both in port and on the ship
• The Connection area, stop valves etc. should be clearly marked and visible without any hindrance on their way while the cargo transfer is going on
• Fire fighting equipment should always be present and accessible during the operation
• Enough warning signs should be placed to ensure all the personnel (shore and ship staff) know about the cargo transfer operation and precautions to be taken
• Always think of safety first

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