Fire Protection And Extinguishing Systems Engineering Essay

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The function of Sprinkler system is able to check the fire taking place and control the fire spread out, by the way it could make serious problems. The conduction of current flow is causing by water put out the fire. There are damage with the valuable equipment and some sensitive computer in the work place. Even if switching off the water, power supply, emissions, there are also caused the unwanted damage. Maintain the drying equipment is often important all the time.

Water mist and NOVEC 1230 fire protection system that is quick, efficient, and relatively safe for occupants and the environment. Pre-action system prevents unwanted water damage.

Other specialized extinguishing agents, for example foam and dry powders are able to extinguish most fire that would be a long lasting effect on the electrical equipment. Fortunately, there have some other fire extinguishing system. It is able to protect these highly valuable and sensitive equipments.

When the requirement of choosing the systems, the first point considers the special risk area and where is the most useful for extinguishing media with its characteristics.

Different types of fire extinguishing system

i) NOVEC 1230 System

Novec 1230 need less energy for a less heat of has a low heat of evaporation, water greater than twelve-five times to change to gaseous status. The liquid of Novec 1230 is a evaporate pressure which is about twelve times that of water, indicatory the fast to that it could convert the mode by a fluid to a gas. From 25oC, the air could stay 40% by volume of the agent without it re-condensing to fluid mode. A boiling point of Novec 1230 is 49oC.

NOVEC 1230 fire extinguish system has zero ozone exhausting possible. It has no color, liquefied gas with condensed and in suppression with most of flammable liquids and gases. It is reserved by a liquid and compressed which is a colorless, a mist of non-conductive electrically. It has not any remainder on sensitive equipment after discharge. It could use on toxicity for extinguishing in work place area at design concentration. The NOAEL include about cardiac sensitization 9%. It is able to concentrate of 9% volume in work place area without available evacuation time. A lot of fire suppression systems have considered on supply concentration of 6.25-9%. NOVEC 1230 could not take the place of oxygen. So, it can use safety in work place area.

Advantages of NOVEC 1230 are as follows:

- The less concentration of NOVEC 1230 need because low risk in egress and little visual obscurity.

- The low amount of agent discharge required that is able to less over-pressurization of the safe coverage place.

- It has relative safety for occupants because low toxicity at liquefied gases.

- Put an end to fire quickly and effectively while automatic detection system detects the fire.

- It could avoid re-ignition concentration levels kept for a period time.

- Clean gaseous agent leaving no residue on valuable equipment after discharge.

- Zero ozone depleting potential and low global warming potential

No significant reduction in oxygen levels.

Electrically nonconductive.

Can be stored and discharge from typical halon gas hardware

Disadvantages of NOVEC 1230 are as follows:

- System composition and operation are more complicated

- Installation, repair, maintenance and refill are more costly

- After discharge, take more time to restore

- Fire extinguishing effect affected by external factors.

- Extinguishing agents carry health hazard

- Usually one-shot protection

- Short duration of protection

- Limited time for egress dependence on concentration

Direct contact with vaporizing liquid being discharged will strong chilling effect and can cause frostbite burns by cold temperature

- Cardiac sensitization of the heart to epinephrine

- Noise produced by system discharge once it start

- Turbulence effect emerge when high-velocity discharge from nozzles could dislodge substantial objects and move unsecured objects

- Evacuation deterred by reduced visibility due to condensation of water vapor during vaporizing liquid being discharged.

ii) Pre-action sprinkler system

The pre-action sprinkler systems have dry, wet and deluge systems. The purpose of protection area is determined by different system. There have two types of systems that are single interlock, and double interlock. The two system operation is similar. The different of these systems are which operate before or after of fire detection. The typically the activation of a heat or smoke detector, takes place prior to the "action" of water introduction into the system's piping by opening the pre-action valve, which is a mechanically latched valve (i.e., similar to a deluge valve). In this way, the system is essentially converted from a dry system into a wet system. Its purpose is to reduce the undesirable time delay of water delivery to sprinklers that is inherent in dry systems. Prior to fire detection, if the sprinkler operates, or the piping system develops a leak, loss of air pressure in the piping will activate a trouble alarm. In this case, the pre-action valve will not open due to loss of supervisory pressure, and water will not enter the piping. The operation of double interlock systems is similar to deluge systems except that automatic sprinklers are used. That requires both a "preceding" fire detection event, typically the activation of a heat or smoke detector, and an automatic sprinkler operation take place prior to the "action" of water introduction into the system's piping. Activation of either the fire detectors alone, or sprinklers alone, it will not allow water to enter the piping without the concurrent operation of the other. Because water does not enter the piping until a sprinkler operates, double interlock systems are considered as dry systems in terms of water delivery times, and similarly require a larger design area.

Advantages of pre-action sprinkler system are as follows:

Numerous system designs can be used dependent on design goals.

Better outer appearance and be harmonious with decoration needs

Sharply reduce heat release rate and pre-wet combustibles

Disadvantages of pre-action sprinkler system are as follows:

Large costs of installation system and after maintenance. Pre-action system is very complicated including a lot of additional components, especially a heat of fire detection system that let the higher cost of construction building.

Alteration difficulties

When using the dry-pipe systems, pre-action sprinkler systems need particular size that would affect the future alteration system. The system alteration had to design again the location of the fire detection to make sure operation normally.

May be decreased dependability.

The high level of complication by pre-action systems that might let the system not operation in case of fire. Therefore, keeping good maintenance is required.

iii) Water mist system

Water mist system is a fire protection system by using very small water sprays for the efficient control, suppression, or extinguishment of fires using limited volumes of water. It put fire by heat extraction, oxygen displacement and blocking of radiant heat. It control or extinguish fires by a combination of flame cooling by droplet vaporization, oxygen concentration reduction by steam production, and cooling at the burning surface similar to conventional sprinklers.

The potential for less water damage is particularly beneficial in occupancies such as data processing centers and telephone central offices. Conversely, water mist systems cannot be used for direct application on materials that react with water to produce violent reactions or hazardous by products.

Advantages of water mist system are as follows:

Reduction in thermal exposure, threat to occupants or fire.

Fire suppression - a sharp reduction in heat and prevention of re-ignition.

Fire extinguishment - complete suppression.

Temperature control, in which the room temperatures are reduced to acceptable level for safe egress and reduced damage

Exposure protection in which combustibles adjacent to the fire are wetted.

Stability problem found in the large piping system

Good replacement of halons extinguishment system that is ozone-depleting substance.

Water mist system is relatively low in cost compared with gaseous agents.

Water is non-toxic and harmless to the environment.

Water flow rate required by water mist is significantly less than that required by a sprinkler system so as to reducing water damage.

Water mist systems can be activated by a variety of using

Disadvantages of water mist system are as follows:

Difficulty in extinguishing deep-seated Class A fires.

Dependence upon electrical power to operate the water pumping system

Lightness of the mist tends to dissipate the droplets, diluting their ability to reach obstructed areas.

Water is delivered under high pressure, significantly smaller droplets than a sprinkler system.

Suitability of the extinguishing system

The operating theatre in a hospital

Special risk - operating theatre in a hospital have lot of expensive electricity equipments. The safety of patient inside the operating theatre is the most important thing to consider.

Water damage - the equipments inside the operating theatre is very expensive, so that the water damage of fire extinguishing system is need to be considered. By this reason, Pre-action sprinkler system is not recommended because the equipments are electrically conductive. NOVEC 1230 and water mist system are non- conductive. They have not residue left. Clean agent systems can react quickly to extinguish a fire in early stage. Using early detection and rapid extinguishment, it is effective within a few seconds of initial discharge. Both systems can eliminate the fire and reduce the damage to the equipments. The shorter the response time, the less consequential damage will be.

NOVEC 1230 system is more suitable in the slow-spreading electronic fires because the extinguishing gas can filled up the inside part of the computer and block the burning chain reaction quickly.

Patient safety - The water of both pre-action sprinkler system and water mist system may be harmful to the patient in surgical operation. Only NOVEC 1230 in suitable concentration is harmless. But the discharges NOVEC 1230 cause thermal shock (may cause tissue to freeze)

The NOVEC 1230 fire extinguishers system is a good choice for operating theatre in a hospital because it is good for slow-spreading electronic fires. NOVEC 1230 extinguishers leave no residue. However, the concentration of NOVEC 1230 system need to be consider carefully to allow the staffs state safety inside the operation theatre for a period of time to take care of the patient inside before evacuation.

The control room of a railway station

Special risk - control room of a railway station control a lot trains and affecting a large amount of passages. It also filled with expensive electricity equipments.

Water damage - the equipments inside the control room is very expensive, so that the water damage of fire extinguishing system is need to be considered. By this reason Pre-action sprinkler system is not recommended because the equipments are electrically conductive.

Reduce damage - Unlike sprinkler system, NOVEC 1230 and water mist system are non- conductive. They have not residue left. Clean agent systems can react quickly to extinguish a fire in early stage. Using early detection and rapid extinguishment, it is effective within a few seconds of initial discharge. Both systems can eliminate the fire and reduce the damage to the equipments. The shorter the response time, the less consequential damage will be.

NOVEC 1230 system is more suitable in the slow-spreading electronic fires because the extinguishing gas can filled up the inside part of the equipment of control room and block the burning chain reaction quickly.

Resume operation time - NOVEC 1230 is chosen to protect occupied area such as control rooms. Operation of the control centre can brought back in very short time.

The NOVEC 1230 fire extinguishers system is a good choice for control room because it is good for slow-spreading electronic fires. NOVEC 1230 extinguishers leave no residue. However, the concentration of NOVEC 1230 system need to be consider to allow the staffs state safety inside the control room for a period of time before evacuation. The system should make sure the safety of all passengers.

The escalator machine room of an underground railway station

Special risk - the escalator machine room of an underground railway station is using electricity power. The fire may possible cause by overheat of machine, the temperature of the fire may quite high. Also, if escalator suddenly stops, the large amount of passengers on the escalator may have danger.

Electricity conductivity - the equipments inside the escalator machine room is using electricity power. So, pre-action sprinkler system is not recommended because it is electrically conductive. If a fire occurs, the sprinkler active, the escalator will suddenly stop, the large amount of passengers on the escalator may have danger.

Extinguishment performance - NOVEC 1230 agent systems can react quickly to extinguish a fire in early stage. But the heat of the machine may not drop rapidly. The machine may still operate and keep generate heat. It has the risk of re-ignited and cause more danger. A rapidly fire may occur after the concentration of extinguishing agent (NOVEC 1230) drop to an ignitable level.

Water mist system is more suitable in the rapidly-spreading electronic fires because the droplets absorbing a significant amount of heat from the fire. This can also cooling the machines and reduce damage and re-ignited of fire.

The generator room of a hotel

Special risk - the generator room of a hotel is using electricity power. The fire may possible cause by overheat of machines. The temperature of the fire may quite high and the fire grows rapidly.

Electricity conductivity - the equipments inside the generator room is using electricity power. So, pre-action sprinkler system is not recommended because it is electrically conductive. The water damage is high.

Extinguishment performance - NOVEC 1230 agent systems can react quickly to extinguish a fire in early stage. But the heat of the machine may not drop rapidly. The machine may still operate and keep generate heat. It has the risk of re-ignited and cause more danger. A rapidly fire may occur after the concentration of extinguishing agent (NOVEC 1230) drop to an ignitable level.

Water mist system is quickly and reliable in the rapidly-spreading electronic fires because the droplets absorbing a significant amount of heat from the fire. This can also cooling the machines and reduce damage and re-ignited of fire.

Pre-action sprinkler can also be use if do not consider the water damage of the generator room. It also reliable and the extinguish performance is good in rapidly fires.

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