The detection requirements of the industrial plants operating in the fields such as textile, chemistry and food differ depending on the ambient conditions. While designing fire detection in an industrial plant, the appropriate method of detection and the detection devices suitable for this method must be selected according to the plant-specific process-induced ambient conditions and the starting manner of a potential fire as originating from smoke, temperature or flame. Improper product selection in the design of fire detection may lead to losses of life and property due to the spread of the fire throughout the plant as result of the incapability to detect it in time.
Another potential result of the improper product selection may be the generation of false alarms by the fire detection system and consequently the loss of reliability of the system. In this article, the detection solutions recommended to be used in compliance with different ambient characteristics for the industrial plants.
One of the most common examples for the challenging ambient conditions is the presence of air-borne dust in the environment. For instance, there may be air-borne flour powder in the food processing plants; dust originating from cotton, fiber etc. in the textile plants; wood powder and dust originating from wood chips in the furniture production plants; cement powder in the cement production plants; and metal powder in the metal processing plants and foundries.
The use of point type smoke detectors in dusty environments is not suitable because they will lead to false alarms. In the dry dust-containing drought environments, the clogging of the sampling holes and pipes can be prevented by using active air suction smoke detectors and applying reverse air blow at regular intervals.
This solution will not be suitable because dust will be sticky if the dusty environment also contains moisture. In this case, the use of cable type temperature detectors or special type beam detectors capable of distinguishing dust and smoke should be considered.
In the metal powder-containing environments, the detection solution can be ensured by using active air suction smoke detectors with their special metal filters.
Another challenging ambient condition is the presence of process-induced vapor or smoke in the environment. The environment may contain vapor in the production areas such as animal husbandry plants where hot water is used for washing. In the workshops where welding processes are carried out, welding smoke may rise to the ceiling if there is no hood system installed. This solution is not suitable because the smoke detection system will lead to false alarms if the environment contains process-induced vapor or smoke.
In such environments, detection with cable type temperature detectors will be the proper solution. While selecting product for cable type temperature detector, attention should be paid that the activation temperature is suitable for the maximum ambient temperature.
In the petrochemical plants, fire may start upon direct inflammation of combustible/flammable materials within the environment. For instance, the use of flame detectors in a manner that they can view combustible/flammable materials is the most appropriate solution for early detection because solvent-induced fires will start upon direct inflammation in the dye plants. Flame detectors have sensors of different types such as UV, IR, UV/IR, IR3 as per the wave length at which they detect flame and the proper product must be selected depending on the materials within the environment as well as the characteristics of the environment.
For instance, the flame detectors fitted with UV sensors only must not be used in a manner that they will be directly exposed to sunlight, lightning radiation, welding beam, electric arc and halogen lamps in order them not to generate false alarms because they will be excessively sensitive to such factors.
The IR3 sensor-fitted flame detectors are suitable for use in the places where there is the risk of hydrocarbon / concurrent hydrogen-hydrocarbon induced fire. The UV/IR sensor-fitted flame detectors are suitable for use in the places where there is the risk of fire induced by hydrocarbon based fuel and gas / hydroxyl / hydrogen / metal / inorganic etc.
Sparks to arise in the process lines such as dust collection systems, planing machines, palletizing plants, crushers, elevators, conveyor lines and sizing units may lead to fire and explosion in the plants. As a precaution for this risk, such process lines must be protected by special detection and extinguishing systems against sparks and hot particles.
Fiberoptic cable type temperature detection solution can be used along long-distance conveyor lines, along long cable galleries/tunnels, on roof-mounted solar panels, in dusty and contaminated large-scale production areas, ex-proof environments, areas such as furnaces and boilers where temperature is high, at power plants and in widespread tank farm areas.
By fiberoptic cable type temperature detection usable within the ranges much longer than normal cable type temperature detection, the starting point of a fire can be detected at high precision and many fire zones can be defined on a single cable.
For cold storage room applications below 0°C, special cable type temperature detectors resistant to these degrees can be used. For cold storage rooms, the detection solution with active air suction smoke detectors featuring special heating solution against freezing at suction points can also be considered.
For the high-ceiling storages, the use of point type smoke detectors for smoke detection is not suitable due to the delay in detection and the difficulty in accessing the detectors during the maintenance processes. For such areas, the active air suction smoke detector solution or the beam type smoke detector solution is suitable.
In the use of beam type smoke detectors, it must be made sure that there is no obstacle such as mobile crane that may impede the beam and no bird enters the environment for the prevention of the contamination of the detector. In the storages, the rack detection is also required to be used in accordance with the relevant standards by passing the pipes of the active air suction smoke detectors through the rack in the places where the height of the rack exceeds 10 m in addition to the general space detection.
As a precaution for combustible/flammable gas leakage that may occur at the connection points on the natural gas line in the plant, natural gas (methane) detectors must be placed at these points. In the battery charging areas, hydrogen gas detector must be used at the point where hydrogen gas which is lighter than air will rise and accumulate in order to detect combustible hydrogen gas occurring during the charging process. If the battery charging area is an outdoor area and there is no such ceiling where gas can accumulate, a construction may need to be made for the application convenient for detection by the gas detector.
The detection devices to be used in the environments classified as hazardous area which contain explosive substances or where the possibility of explosion is high must be selected in a manner that they will be suitable for the information about the environment such as zone, equipment group, category, type of explosive material and explosion surface temperature and must be certified by the certification bodies such as ATEX. Ex-proof devices must be installed in compliance with their protection type.
Damages that will occur in the plant and the length of the period during which no production will be made in the plant may lead to material damages up to millions as well as fire that will break out in an industrial plant may cause losses of life. The protection of the plant against fire in accordance with the standards and in the most proper manner will prevent losses of life and property.
