Automatic Fire Alarm And Warning System

FIRE DETECTION AND WARNING SYSTEMS

Automatic fire alarm systems basically consist of 3 main elements. These,

- Detection

 - Evaluation

- It is alarm and intervention.

DETECTION: Automatic fire detectors are used in order to detect the fire early, depending on the characteristics of the place where it is used and the type of fire expected. In principle, the facilities to be protected by the automatic fire detection system should be protected with the full protection method, but only in some exceptional cases partial protection and selective protection should be used. In all protection, the following areas must be protected with appropriate type detectors.

 • Elevator, service and freight elevators, electrical shafts

• Cable ducts and shafts if easily accessible or not separated from adjacent areas by fire resistant partitions.

• Plumbing and heating installation shafts

• Heating ventilation equipment rooms, fresh air and return air ducts

• Storage areas

• Areas under the gallery

• Underfloor and suspended ceiling interiors

• 30cm to the ceiling or shelves inside the rooms. separated by divisions up to the distance

• Channels where used material is thrown.

It is not necessary to use detectors in wet areas such as bathrooms and toilets and shafts that do not contain electrical devices and are separated by fire-resistant partitions.

EVALUATION: The signals coming from the detection devices are evaluated according to certain parameters in the control panel, which is considered the brain of the system, according to the characteristics of the facility and the conditions of use, and transmits the measures to be taken to the necessary places. Evaluation is carried out in human-machine cooperation, giving priority to human intervention. In the absence of human intervention, pre-programmed processes are activated.

ALARM AND INTERVENTION: After the signals coming from the detectors are evaluated by the control panel, these signals are converted into control signals and audible and light alarm signals are transmitted to the required places within a certain program. At the same time, control signals are sent to the extinguishing systems to the control systems.

SYSTEM TYPES

It is possible to divide automatic fire detection systems into 2 main groups based on their working principle:

CONVENTIONAL SYSTEMS: In conventional fire detection systems, the detectors that make up the system are grouped on the basis of floor or fire compartments and connected to the system control panel. Each detector group (zone) is an alarm line and is identified by a light indicator on the control panel. If one of the detectors on the line detects, it is determined that the alarm comes from the zone in which the detecting detector is included on the control panel. In order to determine the origin of the fire, all detectors on that zone should be investigated. The light indicator on the detector, which is in the alarm position, facilitates the detection of the fire area. Application areas of conventional systems, buildings that are not high, office buildings that do not have many rooms on each floor, workshops,

ADDRESSABLE SYSTEMS: In addressable detection systems, devices such as detectors and buttons that make up the system are defined separately on the control panel. Normal, alarm and fault positions of each device can be monitored separately on the panel. Detectors and buttons can also create fire zones as software on the panel as an added convenience.

Thus, early response to the fire is guaranteed by determining both the area where the fire broke out and in which room the fire broke out at the time of the fire. In terms of alarm organization, since detectors and buttons have separate working modes, in conventional systems, detectors and buttons should be connected to the panel in separate lines, while in addressable systems, both devices can be connected to the control panel over the same line. The definition of each device is made on the panel as software. Application areas of addressable detection systems are high-rise buildings, hotels, high-risk facilities, facilities where conventional systems are not effective.

 DETECTORS

Detectors are classified according to the type of fire they will detect. Therefore, the usage patterns of the detectors are different from each other, the characteristics of the place where they will be used should be well examined and the possible fire type should be well defined.

DETECTOR TYPES

Detectors are divided into 3 main groups depending on the type of fire detected:

A. Smoke detectors

B. Constant temperature and rate of temperature rise detectors

C. Flame detectors

A. SMOKE DETECTORS: It is used to detect smoky, smoldering wood, paper, plastic, electrical fires that emit visible or invisible fire aerosols. There are three main types of smoke detectors:

a. Ionization Smoke Detector: It is a smoke detector that detects invisible fire products. It works on the principle of ionization of air. It is the most widely used detector in terms of detection principle.

b. Optical Smoke Detector: It is a type of smoke detector that detects visible smoke. It works on the principle of diffusion of light. It is the type of detector that responds early especially in plastic fires.

c. Linear Smoke Detector: It is used to detect fires that produce visible smoke. It works on the principle of tiling of light. It is used in applications where the use of other types of smoke detectors is not suitable.

B. CONSTANT TEMPERATURE AND HEAT RISE RATE DETECTORS: It is a type of heat detector that works when the temperature in a place rises above a certain temperature or when the ambient temperature rises suddenly.

It is used in humid, dusty and steamy places under normal working conditions. It is used in places where it is not appropriate to use smoke detectors because the response time is longer than smoke detectors.

C. FLAME DETECTORS: It is a detector that works according to the principle of heat radiation in the detection of fires starting from the direct flame stage. Wood, plastic, alcohol, mineral, fuel oil, phosphorus, sodium, magnesium, hydrogen etc. It is used to detect fires.

DETECTOR SELECTION: Considerations when choosing a detector:

• Detection category of the detector or detection purpose of the fire detection system

• Room height

• Environmental conditions

The location where the detector will be used is examined in terms of possible fire type and the type of detector to be selected is determined according to the degree of risk of that location. In general, the possible fire type and risk level in a space may require the selection of more than one detector type for that space. The selection and placement of detector types must be done by experts.

CONTROL PANELS

Control panels are devices that evaluate the signals coming from detectors, buttons and other devices according to a certain program and convert them into alarm and control signals according to the features of that facility and according to the given program. Control panels must include the following features:

• Being programmable according to different usage conditions

• Working according to the principle of human-machine cooperation

• Being in a modular structure and having the ability to expand

• To be able to evaluate the information coming from the sub-systems and transfer information to the upper systems.

• Protected against false alarms

• Availability of different working positions

• Availability of a backup power source to feed the system in case of power cuts

• Availability of a wide range of diagnostics reporting internal faults.

ALARM ORGANIZATION

 In automatic fire detection systems, the alarm should provide early intervention in firefighting. However, the system should not cause panic while performing this important task. 

In the event of a fire, the building personnel should be able to make some decisions, while preventing false or false alarms, information should be conveyed to the relevant places as soon as possible by the system in case of possible human errors or when people do not do what they need to do. 

The system should be able to be programmed for day and night working positions depending on the conditions of the place where it is installed. In the daytime working position, the alarm signals that come when there are personnel in the building should first be transmitted to the internal response team, if the fire is large according to the size of the fire, it should be intervened and extinguished, the system should be brought back to the normal operating position before the alarm signal is transmitted to the fire department. 

In case of a large fire, this information should be sent to the fire brigade by pressing the nearest button and switching to the 2nd alarm level. Incoming signals while in night operation mode directly switch the system to the 2nd alarm level and transfer the necessary information to the fire department. 

In the daytime operating mode, if the audible and visual warnings that bring the system to the 1st alarm level are not confirmed by the human, the system should automatically switch to the 2nd alarm level. Thus, possible human errors will be prevented. If the audible and visual warnings that bring the alarm level to the alarm level are not confirmed by the human, the system should automatically switch to the 2nd alarm level. 

Thus, possible human errors will be prevented. If the audible and visual warnings that bring the alarm level to the alarm level are not confirmed by the human, the system should automatically switch to the 2nd alarm level. Thus, possible human errors will be prevented.