Fire-Water Spray Systems Principle

A Water Spray System for Fire Protection a different variant of the Fire Sprinkler System. Such a system is used in places where a fire is likely to spread out of control within a short duration rapidly. Examples of such places where Water Spray System for Fire Protection are required are; Transformers, Compressors, Condensate Storage Tanks, LPG bullets and Combustible fuels.

Is it compulsory to have/install, Water Spray System for Fire Protection?

It depends on the type of system, equipment or inflammable liquid in use. Suppose you are using any highly inflammable substance, combustible or catch fire and spread quickly. This system is a mandate for you.

How Water Spray System for Fire Protection, Works?

Let us take an example to be more specific and clear. In an oil-cooled transformer, the oil is likely to catch fire after a certain temperate is exceeded, and instantly the entire transformer will catch fire and burn from all sides, even though the transformer is made up of metal. To avoid this kind of fire, we use Water Spray System.

There may be multiple metal rings of detectors; a detector is nothing but a temperature sensing element. This detector ring is placed next to the most likely spots where the temperature is about to exceed or fire is about to occur. Also, the entire transformer is surrounded by multiple sprays at multiple levels. A spray is nothing, but a sprinkler without the temperature sensing, bulb.

When the fire does occur, the detector ring detects this; and gives the signal to the deluge valve or all the sprinkler surrounding the transformer to start all at once. Hence the entire transformer is flushed with water to cool it down.

There are two variants of Water Spray System for Fire Protection:

1) High-Velocity Water Spray Systems (HVWS) 2) Medium Velocity Water Spray Systems (MVWS)

High-Velocity Water Spray Systems (HVWS):

HVWS is generally used in oil-based systems, having high flashpoints. The water sprays' velocity, hitting the system under fire, is critical for successful fire extinguishing action.

Medium Velocity Water Spray Systems (MVWS):

MVWS is generally used in oil-based systems, having low flashpoints. The water sprays' velocity, hitting the system under fire, if it is high, might actually spread the fire and not extinguish it. Hence, the velocity of the water has to be in range.

Advantages of Water Spray Systems

Extinguishes fires quickly and prevents fires from spreading over a large area.

• Minimises the damage caused by fire, and reduces downtimes, protects the future of your business.

• High flexibility in design and implementation

• Reduces fumes and binds contaminants.

• Allows large open areas and thus a more flexible use of the premises.

• It uses water, a natural fire extinguishing agent available in unlimited quantities at a low price.

Medium Velocity Water Spray System (MVWS):

Fires on Hydrocarbon are more frequent due to the hydrocarbon's volatility and its property to not dissolve with water and lighter than water the fire extinguishing of hydrocarbon fire with water is not possible. In case of fire on Hydrocarbon, if the water is sprayed, due to the hydrocarbon's lightweight, it will float on the water and reignite them to fire and due to the water's speed, the fire will travel from one place to another place. However, these plant water spray system can be provided as exposure protection. That means if any plant is under fire, the plants nearby shall be kept cool with the water spray system, while the plant under fire shall be applied foam.

Hence in this case, where a plant uses hydrocarbon, the exposure should be protected with a water spray system designed as per NFPA 15.

This system is mostly used for the protection of the following.

• Expander & Sale Gas Compressors

• Off Gas Compressors etc.

Quartzoid Bulb Sprinklers (Q. B. S.) Detection is used to detect fire, which will be connected to a deluge valve for the system's auto operation. Q B Sprinklers shall be of 68 Deg or 79 Deg C or any other temperature depending upon the ambient temperature of the plant's location.

For the system's electronic automatic operation, the deluge valve shall be provided with pressure sensors, temperature sensors, and an annunciation panel.

Operation

In case of fire, the Quartzoid Bulb sprinkler shall burst due to heat that allows water in the detection pipe to drain out and allow the Deluge valve to open fully. As soon as the Deluge valve opens, the water shall flow through the piping to flow water to all water spray nozzles mounted on the plant's ceiling. The water shall be sprayed in a solid conical spray pattern to cover the entire plant floor area so that the equipment installed shall be kept cool to avoid heat radiation and further ignition of the fire.

The fire shall be control with the help of the water spray system.

The indication of the operation of the system shall be available on the control panel with Alarming Siren.

Advantages of M.V. Water Spray System

• The entire area is flooded with foam, which is very useful for fire fighting in hazardous areas, plants, storage tanks, etc., where the manual approach is difficult.

• Very quick in response.

• The fire losses are kept low as the area under fire gets foam blanket and cooling due to water content, and so chances of spreading fire are negligible.

High-Velocity Water Spray System (HVMS):

High-Velocity water spray systems are installed to extinguish fires involving liquids with 65 C or higher flashpoints. Three principles of extinguishment are employed in the system – emulsification, cooling and smothering. The result of applying these principles is to extinguish the fire within a few seconds.

This system is mostly used for the protection of the following.

• Transformers, oil-filled types of equipment of power stations

• Turbo-alternators and other

• Oil fired boiler rooms, oil quenching tanks.

Transformer protection shall contemplate on essentially complete impingement on all exterior surfaces except the underside, which may be protected by horizontal projection.

Transformers present particular design problems for Water spray protection, primarily due to their irregular shape and necessary clearances for the high voltage equipment. Generally speaking, there is much more interference with the water flow on the transformer's sides than at their top. Due to this reason, the protection usually involves a large number of small capacity projectors than a few bigger ones. Often it will be necessary to put more water on the transformer than required to achieve complete impingement and total envelopment.

All system components shall be so located as to maintain minimum clearances from live parts. “Clearance” is the air distance between Water Spray Equipment, including piping nozzles and detectors and un-insulated live electrical components at other than ground potential. The minimum clearance is 900 mm under normal conditions. During the operation of the Water Spray system, they are intended for use as safe.

The nozzles shall be installed in rows around the transformer and above the oil condenser. Quartzoid Bulb Sprinklers (Q. B. S.) Detection is used to detect fire, which will be connected to the deluge valve for the system's auto operation. Q B Sprinklers shall be of 68 Deg or 79 Deg C or other temperatures depending upon the ambient temperature of the plant's location.

A Deluge system (automatic High-Velocity Water Spray System) is a fixed fire protection system, which totally floods an area with pressurized water through piping with open nozzles & sprinklers. The system piping is empty until a hydraulic or other release system activates the controlling valve. The deluge valve has an inlet, outlet & priming chamber. The inlet & outlet are separated from the priming chamber by the valve chamber & diaphragm. In the” SET “position, the pressure is applied to the priming chamber through a restricted prime line. The pressure is trapped in the priming chamber & holds the clapper on the seat due to the differential area. When the pressure is released from priming chamber faster than it is supplied through the restricted priming chamber line, the clapper move & allow the inlet water supply to flow through the outlet into the system and associated alarm device.

A water spray system is installed to control fire & to provide cooling &/or exposure protection to such risks where an extinguisher is always not possible or even desirable, e.g. fire involving flammable fluids having flashpoints below 650 C (1500 F).

In case of fire, the Quartzoid Bulb sprinkler shall burst at rated temperature due to heat that allows water in the detection pipe to drain out and allow the Deluge valve to open fully. As soon as the Deluge valve opens, the water shall flow through the piping to flow water to all water spray nozzles mounted on the piping around the transformer. The water shall be sprayed in a Hollow conical spray pattern to cover the transformer's entire area so that the fire on the transformer shall cool due to emulsification and fire getting extinguish due to cutting off oxygen due to the coverage pattern of the nozzle.

The fire shall be control and extinguished with the help of the H. V. water spray system. The indication of the operation of the system shall be available on the control panel with Alarming Siren.

Advantages of HM.V. Water Spray System

• The entire Transformer is flooded with water, which extinguishes fire at the earliest and avoids further destruction.

• Very quick in response.

• The fire losses are kept low as the fire area gets cooling due to water, and so chances of spreading fire are negligible.

WATER CURTAIN SYSTEM

WATER SPRAY NOZZLES

These are similar nozzles as sprinkler, but there is no bulb used, and they have an open orifice that could not hold the water pressure.

These nozzles have a threaded inlet and deflector at the outlet and fitted on the pipe array-like sprinkler. This system spray water from all nozzles as the control valve gets open, and therefore the area under fire receive water. The adjacent area also gets water and reduces the chances of spreading the fire.

WATER SPRAY SYSTEM

The water spray system is basically most useful for various tanks storing hazardous liquids or chemicals.

The system consists of a water reservoir, a pump of suitable capacity and pressure, delivery main and distribution pipe array, main control valve(known as deluge valve), water spray nozzle, and heat-sensing element.

In a fire, the heat-sensing element, mainly bulb type sprinklers, burst when the rated temperature arrives and causes an open deluge valve due to pressure difference. The valve floods complete main and distributed pipes and starts spraying from all the water spray nozzles at a time.

The spray remains under operation till the deluge valve is rest manually. This is the most reliable and suitable system for tank protection as well as exposure protection.

Advantages of Water Spray System

• The entire area is flooded with water, hence very useful for fire fighting in a hazardous area, basement, storage tanks, etc.

• Very quick in response.

• The fire losses are kept low as the area adjacent to the fire also gets water protection, so the chances of spreading fire are negligible.

Disadvantages of Water Spray System

• As the entire system gets flooded with water, the water damage is more.

• This system needs maintenance and periodic checking of automatic operation for reliability during a fire.