Курсовая работа по модулю/дисциплине «Инжиниринг кип» на тему: «Fire and Gas Detection Philosophy»

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CONCEPT OF FIRE AND GAS DETECTION
1.2 Types of fire alarm sensors

INTRODUCTION

Detector sensors are fire technical means that transmit a notification of a fire to a receiving and control device. Usually, round white boxes that are mounted on the ceiling are equipped with several sensors. Detectors are installed on various objects and are used taking into account the environment in which they will be located. Modern fire alarm detectors are installed in houses, apartments, public places, offices and enterprises.
The fire protection system can notify the fire service about a minor fire in time. If the alarm system is additionally connected to the fire extinguishing system, that the fire source will be extinguished in a matter of seconds after the sensor detects a potential threat.
The purpose of this course work is to explain philosophy of fire and gas detection, list types of alarm sensors and technological scheme of fire and gas detectors.
According to the goal, the following tasks should be done:

To consider philosophy of fire and gas detection
To list types of alarm sensors
To present scheme of fire and gas detectors

This topic is relevant because early fire detection is crucial and plays a very important role in protecting and saving lives and properties. Having a fire detection system can significantly reduce damages and maximize fire control efforts. It is also one of the most fundamental steps you can take for fire safety measures. Even if you are sleeping or busy working, early fire detection will warn you and help you respond quickly so you'll be out of danger. Here are some good reasons why you need fire detection systems at home or your business.

CONCEPT OF FIRE AND GAS DETECTION

1.1 Concept of fire and gas detection

Grief is a set of, as a rule, self–sustaining complex physicochemical processes, the basis of which are fast-flowing oxidation reactions accompanied by the release of a large amount of heat and light.

The burn zone is a part of the space in which the processes of thermal decomposition or evaporation of combustible substances and materials (solid, liquid, gases, vapors) take place in the volume of the diffusion flame torch.
Burn can be flaming (homogeneous) and flameless (heterogeneous). In flaming burn, the burn zone boundaries are the surface of the burning material and a thin glowing layer of flame (the oxidation reaction zone), in flameless – the incandescent surface of the burning substance.
Burn is an example of flameless combustion can be the burning of coke, charcoal, or smoldering, for example, felt, peat, cotton, etc.
Subsonic burn (deflagration) – unlike explosion and detonation proceeds with low speeds and is not connected with formation of a shock wave. Subsonic burn includes normal laminar and turbulent flame propagation, supersonic – detonation.
Detonation differs from burn in those chemical reactions and the process of energy release go with the formation of a shock wave in the reacting substance, and the involvement of new portions of explosive in the chemical reaction it occurs at the shock wave front, and not by thermal conductivity and diffusion, as in burn. As a rule, the detonation rate is higher than the burn rate, however, this is not an absolute rule. The difference in the mechanisms of energy and substance transfer affect the speed of the processes and the results of their action on the environment, however, in practice, a variety of combinations of these processes and transitions of detonation into burn and vice versa are observed. In this regard, chemical explosions usually include various fast-flowing processes without specifying their nature.
Burn is divided into thermal and chain. The basis of thermal burn is a chemical reaction capable of proceeding with progressive self-acceleration due to the accumulation of the released heat.
Chain burn occurs in cases of some gas-phase reactions at low pressures. Thermal self-acceleration conditions can be provided for all reactions with sufficiently large thermal effects and activation energies. Burn can start spontaneously as a result of spontaneous ignition or be initiated by ignition. Under fixed external conditions, continuous burn can proceed in a stationary mode, when the main characteristics of the process – reaction rate, heat output, temperature and composition of products do not change over time, or in a periodic mode, when these characteristics fluctuate around their average values. Due to the strong nonlinear dependence of the reaction rate on temperature, Burn is highly sensitive to external
conditions. The same property of burn determines the existence of several stationary modes under the same conditions see Provisions 1 and 2. The process of burn is divided into several types: flash, ignition, ignition, spontaneous combustion, spontaneous ignition, explosion and detonation.
In addition, there are special types of burn: smoldering and cold-flame burning. Flash is the process of instantaneous combustion of vapors of flammable and combustible liquids caused by direct exposure to an ignition source.
Ignition is the phenomenon of the occurrence of burn under the action of the ignition source. Ignition – ignition, accompanied by the appearance of a flame.
At the same time, the rest of the mass of the combustible substance remains relatively cold.
Self–ignition is a phenomenon of a sharp increase in the rate of exothermic reactions in a substance, leading to the occurrence of burn in the absence of an ignition source. Self–ignition is self-ignition, accompanied by the appearance of a flame.
In production conditions, sawdust and oiled rags can self-ignite. Gasoline, kerosene can self-ignite.
Explosion is a rapid chemical transformation of a substance (explosive burn), accompanied by the release of energy and the formation of compressed gases capable of mechanical work.
For a fire to occur, a combustible environment is necessary, as well as certain external conditions that contribute to the appearance and development of burn
Fire detector is an electrical product, which is installed directly on the protected object for transmitting an alarm notification about a fire to a fire control device and/or notifying and displaying information about the detection of fires. Most often, detectors transmit information about their condition to the loop of a fire receiving and monitoring device. The detector detects a fire by monitoring changes in the physical parameters of the environment caused by the fire and/or generates a fire alarm item. Fire detectors are not a means of measurement, they use non-metric scales of names or order. Detectors are the most important elements of fire alarm systems and automation. They mainly determine the capabilities and characteristics of the system as a whole. Separate types of detectors (linear, multipoint) can be produced not as a single product, but as separate sensitive elements and processing units, processing units and pipes selected by the consumer (aspiration).
Detector sensors are fire technical means that transmit a notification of a fire to a receiving and control device. Usually, round white boxes that are mounted on the ceiling are equipped with several sensors. Detectors are installed on various objects and are used taking into account the environment in which they will be located. Modern fire alarm detectors are installed in houses, apartments, public places, offices and enterprises.
The fire protection system can notify the fire service about a minor fire in time. If the alarm system is additionally connected to the fire extinguishing system, that the fire source will be extinguished in a matter of seconds after the sensor detects a potential threat.
Fire detectors are arranged in such a way as to perform a number of functions:
Fire detection at its first manifestations and the inclusion of an audible alert. Rapid detection is achieved due to a change in temperature, a change in the density of the medium, open fire, uncharacteristic substances in the air (soot, gas, aerosol).
The polluted environment should not obstruct or block the operation of the detectors. Dust, impurities, and high humidity do not interfere with the proper operation of the sensors.
Mechanical influences should not interfere with the operation of the detectors.
The devices have different technical features, but must be consistent with uniform installation standards. When designing, it is necessary to rely on the controlled object and the fire load.
The detectors of fire systems work according to the same formula. When there is smoke in the room, gas or flame appears, the sensors react by sending a signal to the receiver. When the signal is processed and a threat is detected, a command to start a sound siren comes to the detector, and information about a fire in a certain sector comes via the network to the dispatcher's control panel.
Substandard detectors are considered units that identify only fire. High-quality devices include devices equipped with several blocks that react to various precursors of ignition (smoke, gas, heat). The sensor reads the quality of air flows, increasing safety in case of fire.
An autonomous device works a little differently. Due to the small radius of action, such devices are designed to ensure security in apartments, small warehouses, garages, etc.
Modern fire-fighting units have an attractive design, color coloring. Therefore, the detectors will become an addition to the interior for the house.
Installation of detectors does not cause problems. To fix the box with sensors on the ceiling, it is enough to install a hook in this place. Periodically, the detector must be cleaned of dust, as well as batteries must be changed.
There are several types of detectors that can detect the presence of heat, smoke or flame. Each type has its own pros and cons.
Smoke ionization devices are most often criticized. This happens because these devices show good performance only with smoke consisting of fine suspensions. The emission of charged substances causes radioactive radiation, therefore the installation of such detectors is prohibited in places of permanent human habitation.
Optical smoke detectors will not detect the ignition of gas, will not react to the action of solvent, organic liquids, because these substances do not form smoke.
Flame sensors will be able to detect a threat in the ultraviolet or infrared range. In fact, the flame sensor works perfectly only when there is an active fire. If the fire starts with smoldering, the effectiveness of such a sensor is nullified.
Since there are no sensors with ideal characteristics, it is recommended to use complex devices. Motley detectors in fire systems will be able to respond to stimuli, increasing safety by quickly and correctly responding to a fire.
Components of the fire alarm system and their functions:
The control panel is a device that analyzes the state of all fire loops and sensors and provides a command to start fire automation.
A monitor /display panel or an automated workplace is a device that records the state of the fire alarm system.
Uninterruptible power supply — the element is necessary to ensure the continuous operation of the alarm system.
Fire detectors are special sensors that effectively detect ignition and able to flame products (carbon monoxide, smoke, etc.). Detectors are usually classified depending on the object of detection into thermal, smoke, flame and CO sensors; in addition, there are also multi-sensor sensors that respond simultaneously to several signs of ignition. The system is also equipped with a special manual fire detector – a "red button" installed in an accessible place.
Actuators are elements of automatic fire extinguishing or other important systems.
Warning devices – repeaters, loudspeakers and sirens that give an alarm.
An alarm notification is a signal that occurs, for example, as a result of the impact of a small part of the heat generated by a fire on a sensitive element. Information carriers can be the processes of thermal conductivity, diffusion, fluid and gas flow. The smell of smoke, warning of the danger of fire, is transmitted by diffusion or air current.
To convert the controlled physical factor of the fire into a signal suitable for further processing, the design of the fire detector includes sensitive elements. The most common conversion of a controlled fire factor is made into an electrical signal.
Depending on the mode of operation of the sensitive elements, the detector device can be divided into the following options:

sequential conversion of the sensor element signal;
comparison and processing of signals from multiple sensing elements;
comparison and signal processing of the sensing element and the reference element

According to the dependence between the controlled parameter and the output signal, the detectors are divided into:

analog — with continuous dependence;
threshold — with relay dependence. The detector becomes threshold if there is at least one elementary converter with a relay characteristic

Automatic fire detectors, depending on the possibility of their re -activation after operation, are divided into the following types:

returnable detectors with the possibility of re—activation are detectors that can return to the control state from the fire alarm state without replacing any nodes, as soon as the factors that led to their operation have disappeared. They are divided into types:
detectors with automatic re—activation - detectors that, after being triggered, independently switch to the control state;
detectors with remote re—activation - detectors that can be switched to the control state by means of a remote command;
detectors with manual activation — detectors that can be switched to the control state by means of manual switching on the detector itself;
detectors with replaceable elements — detectors that, after being triggered, can be transferred to the control state only by replacing some elements;
detectors without the possibility of re—activation (without replaceable elements) - detectors that, after being triggered, can no longer be transferred to the control state.

Automatic fire detectors by type of signal transmission are divided into:

dual-mode detectors with one output for transmitting a signal about both the absence and the presence of signs of fire;
multi-mode detectors with one output for transmitting a limited number (more than two) types of signals about the state of rest, fire alarm or other possible states;
analog detectors that are designed to transmit a signal about the magnitude of the value of the fire sign controlled by them, or an analog/digital signal, and which is not a direct fire alarm signal

There are several types of fire alarms that differ in the principle of operation.
Threshold fire alarm system is a system of alarm detectors with a fixed threshold of sensitivity. It includes a set of equipment, but when one of the sensors is triggered, a general alarm signal is generated and transmitted (the number of the triggered sensor and the room in which it is installed are not specified). Such systems are cheaper, easy to install and maintain, and are suitable for relatively small buildings.
An address fire alarm system also consists of a whole set of devices, but when a specific detector sends an alarm signal, an exchange protocol is triggered in the alarm loop, which allows you to determine which sensor has triggered and provide more accurate information about the territory and type of danger that has arisen.
Address-analog fire alarm system — works on the principle of collecting information from "intelligent" detectors. Sensors in such a system make constant measurements of temperature, smoke, etc. and transmit information to the fire alarm station, which analyzes the nature of changes in these parameters and, if necessary, generates an address alarm. This monitoring method is used for early detection of an alarming situation, obtaining data on the need for maintenance of devices due to contamination or other factors. Its distinctive feature is the ability to set and change the sensitivity threshold of detectors, individually configure and reconfigure devices to adapt to the conditions at the facility.
In addition to fire alarms, aspiration systems for early fire detection have come into use. Aspiration smoke detection systems make it possible to detect a fire in the shortest possible time and take all necessary measures to localize the source of ignition. This significantly reduces the threat level for employees, as well as minimizes material damage from fire.

1.2 Types of fire alarm sensors

Let's consider all the sensors that are used in detecting a fire.