RU2626716C1 - Method for fire or overheat detection, and device for its implementation - Google Patents

Abstract

FIELD: fire safety.

SUBSTANCE: method for fire or overheating detection includes obtaining of temperature data from linear fire sensors. Fire or overheating signals are generated if linear fire sensors are operable and data of these linear fire sensors exceed the predetermined threshold values that indicate presence of fire or overheating. The set threshold values are corrected when the operating modes of the monitoring object are changed, including in the system with redundancy. After checking the linear fire sensors serviceability, the obtained temperature data for a predetermined time interval are stored, and the rate of temperature change is calculated from the stored temperature data array. The duration of a given time interval is determined based on the allowable time for fire detection. A fire or overheating detection device is used to implement the method. The device contains linear fire sensors consisting of working and mounting parts. The working part is made in the form of a long thin-walled flexible metal shell in which two sensors are placed, connected to the fire protection block, containing the main and reserve channels. Each channel includes a serially-connected analog-to-digital converter module, with input connected to linear fire sensors, a computer module with digital interfaces, one of which is used for communication with the backup channel, and the second is for communication with the monitored object, and a relay module. In each channel of the fire protection unit, an additional module is included to calculate the rate of temperature change and connected to the computer module. Sensitive elements are made of the same type and thermoresistive, each consisting of two parallel threadlike conductor strands parallel to the sheath, and connected to each other at one end of the sheath by welding and isolated from each other. A metal plug is hermetically welded to the sheath on the side of conductors connection.

EFFECT: increased accuracy of measurement of the average temperature and its increase rate in the monitored area, increased noise immunity and speed of fire or overheating detection device, its reduced weight and dimensions.

14 cl, 4 dwg

Description

The invention relates to the field of fire safety, and in particular to methods and devices for detecting fire or overheating that occur at various technical facilities where there is a risk of fire or overheating and is intended for automatic signaling of a fire or overheating, for example, in the compartments of air vehicles marine vessels, industrial installations, railway transport and other facilities.

A fire alarm device is known that contains a sensitive amplifier circuit consisting of a temperature sensor, a relay, a tuning resistor, and a control resistor, which is connected to a power source through a voltage divider resistor and a switch, and a signal element is connected to a power source through a normally open relay contact, while the additional winding is connected through a trimming resistor to a stabilized power source in the opposite polarity with respect to the temperature sensor [RF Patent No. 2024947, ublikovano 15.12.1994].

The disadvantage of such a fire alarm device should be considered low noise immunity and a limited control zone of the temperature sensor.

A six-channel fire alarm system is known, including an actuator unit and six groups of sensors connected to it — three sensors in series in a group that provide signals to actuators. The principle of operation of such a system is based on measuring temperature and its rate of change using point sensors with a thermoelectric sensitive element [Mi-171 HELICOPTER. INSTRUCTIONS FOR TECHNICAL OPERATION. BOOK III. Part 1. HELICOPTER SYSTEMS. Section 026, 1995].

However, this fire alarm system also has low noise immunity and a limited monitoring area.

A known fire alarm sensor, consisting of a pneumatic relay connected to the sensor tube and made in the form of one or more cameras, is blocked by a diaphragm and with an electrode located opposite it, while the flexible diaphragm is able to contact the electrode under the influence of pressure changes in the tube and interrupt the contact [ RF patent No. 2438184, published December 27, 2011].

The disadvantage of this fire alarm sensor is a large thermal inertia, the presence of moving parts in the sensor and low control suitability.

Also known is a pneumatic pressure sensor with a sensitive tube under gas pressure used in fire alarm systems, consisting of a pressure chamber located between a pair of deformable orifice plates and under pressure of a capillary sensor with absorbed gas. The electronic control system is located separately from the pressure sensor and is connected to it by a single wire. The circuit also contains grounding of the electronic control system and the sensor [US Patent No. 5691702, published November 25, 1997].

However, the known pneumatic fire alarm sensor also has a large thermal inertia and low controllability.

A known system for detecting fire on aircraft, containing two (primary and backup) units for detecting fire and a set of pneumatic fire detectors connected in parallel with the detection units. Sensors can be in one of three states: normal, faulty, and in a state where a fire is detected. Introduction to the system of additional connections allows you to identify a specific sensor that has detected a fire. [US Patent No. 8094030, published January 10, 2012].

The disadvantage of such a fire detection system is also a large thermal inertia, the presence of moving parts in a pneumatic sensor and low controllability.

Closest to the proposed invention is a fire or overheating detection system adopted for the prototype, including a sensor, with two sensitive elements (thermistor and thermistor), the first of which is made of a material with a positive temperature coefficient of resistance, and the second is a material with a negative temperature coefficient resistance and the device connected to the sensor. The method implemented in this system, adopted as a prototype, makes it possible to detect such sensor malfunctions as an open, short circuit, and also to determine the average temperature in the controlled zone and the size of the sensor zone subjected to increased temperature locally by the resistances of two sensitive elements and evaluate the dynamic changes in the measured parameters [US Patent No. 7098797, published August 29, 2006].

The disadvantage of this method and system of fire detection is the use of a sensor that has significant thermal inertia and requires the installation of a separate sensor for each channel in the redundant system. In addition, the accuracy of the average temperature in such a system is affected by the spread of characteristics and instability of the thermistor sensitive element, as well as the increased level of interference associated with the need to measure the resistances of the sensitive elements using the outer shell of the sensor.

The problem to which the invention is directed is to increase the accuracy of measuring the average temperature and its rise rate in the controlled area, increase the noise immunity and speed of the device for detecting fire or overheating, as well as reducing its weight and dimensions.

The problem is solved by a method of detecting fire or overheating, which consists in the fact that they obtain temperature data from linear fire sensors, monitor the health of linear fire sensors, generate signals about a fire or overheat in case of serviceability of linear fire sensors and if the temperature data exceeds these linear fire sensors previously predetermined threshold values that indicate the presence of a fire or overheating and adjust the predetermined threshold values when changing the operating modes of the object and control, including in a redundant system, while after monitoring the health of linear fire sensors, save the obtained temperature data for a given time interval and calculate the rate of temperature change from the stored temperature data array, and the duration of the specified time interval is determined based on the permissible time for fire detection.

New in the claimed invention is that after monitoring the health of linear fire sensors, they save the obtained temperature data for a given time interval and calculate the rate of temperature change from the stored temperature data array, while calculating the rate of temperature change, in contrast to the known technical solutions, instead of measurements on two temperature values, an array of temperature data is used, stored for a time interval, the duration of which is determined based on the permissible time for fire detection. This prevents the possibility of formation of false signals about a fire and increases the accuracy of calculating the rate of temperature change in the controlled area.

The problem is solved by a device for detecting fire or overheating, containing linear fire detectors consisting of a working and mounting parts, while the working part is made in the form of a long thin-walled flexible metal shell, in which two sensitive elements are placed connected to the fire protection unit containing the main and backup channels, each channel including a series-connected module of analog-to-digital converters, to the input of which linear fire detectors are connected , a calculator module with digital interfaces, one of which is used to communicate with the backup channel, and the second - to communicate with the monitoring object and a relay module, while an additional module is included in each of the channels of the fire protection unit, designed to calculate the rate of change of temperature and connected with a calculator module, sensitive elements are made of the same type of thermoresistive, each of which is two identical threadlike conductive parallel to the shell f conductors made of metal with a positive temperature coefficient of resistance and with a close to linear dependence of resistance on temperature, connected together at one end of the shell by welding and isolated from each other, from the shell and from the second sensitive thermoresistive element with a thermally conductive insulating material, to the shell with the connection side of the conductive conductors, a metal plug is hermetically welded, and on the other hand, where the free ends of the conductive conductors protrude beyond the shell To connect the fire protection unit to the external electrical circuit, the enclosure is sealed with high-temperature adhesive or sealant.

New in the claimed invention is that each of the channels of the fire protection unit includes an additional module designed to calculate the rate of change of temperature and connected to a computer module that implements noise-proof computational algorithms. Also new in the claimed invention is that the sensitive elements are made of the same type of thermoresistive, each of which is two identical filamentous conductive wires parallel to the shell, made of metal with a positive temperature coefficient of resistance and with a close to linear dependence of resistance on temperature, connected between at one end of the shell by welding and isolated from each other, from the shell and from the second sensitive thermoresistive a thermally conductive insulating material, a metal plug is hermetically welded to the shell, on the side of the connection of the conductive conductors, and on the other hand, where the free ends of the conductive wires protrude beyond the shell to connect to the external electrical circuit of the fire protection unit, the shell is sealed with high-temperature adhesive or sealant , which allows you to create a more compact and noise-resistant design of a linear fire sensor and increase its accuracy and speed.

In FIG. 1 is a diagram of a fire or overheating detection device. In FIG. 2 is a sectional view of a fragment of a linear fire sensor. In FIG. 3 is a section AA of FIG. 2. In FIG. 4 is a graph explaining an algorithm for calculating a rate of change of temperature.

A method for detecting fire or overheating is as follows.

Temperature data is obtained from linear fire detectors, the health of linear fire detectors is monitored, and fire or overheating signals are generated if the linear fire detectors are operational and the temperature data exceeds these linear fire detectors of predetermined threshold values that indicate a fire or overheating and correct threshold values when changing the operating modes of the monitoring object, including in a redundant system, while after monitoring the health of linear sensors Cove fire stored temperature data obtained over a predetermined time interval and calculating the rate of temperature change. When calculating the rate of temperature change, an array of temperature data is used, stored for a time interval, the duration of which is determined by the permissible time for fire detection. Also important is the ability to correct threshold values for the average temperature and its rise rate according to additional information from sensors characterizing the operating modes of the monitoring object. Such correction will allow, by lowering the thresholds for the average temperature at lower operating conditions of the control object, to increase the rate of fire detection and reduce the likelihood of false positives by increasing the thresholds for the rate of temperature rise in transition modes of operation of the control object. If a malfunction is detected in one of the channels of the redundant system, in the serviceable channel, in order to reduce the likelihood of false alarms, threshold levels for the average temperature and the rate of temperature rise are increased. With a sharp increase in temperature caused by a change in the operating mode of the monitoring object, when there is no additional information about these modes, the threshold value is increased only for the rate of temperature rise during the transition process, accompanied by a change in temperature. As a sign characterizing the beginning and end of the transition process, an indirect parameter is used - the simultaneous change in temperature data of all linear fire sensors installed in the controlled area.

A device for implementing a method for detecting fire or overheating contains linear fire sensors 1 (their number can be from 1 to N), consisting of a working 2 and mounting 3 parts, while the working part is made in the form of a long thin-walled flexible metal shell 4 made of high-temperature alloy, for example, from KhN78T alloy with a thickness of 0.2 mm, in which two sensitive thermoresistive elements 5 are placed, made, for example, from H50K10 or nickel alloy, connected to the fire protection unit 6 containing the main channel 7, e elements of which have an additional index "A" and a backup channel 8, the elements of which have an additional index "B". One of the sensitive thermoresistive elements of each linear fire sensor is connected to the main channel 7, and the second sensitive thermoresistive element isolated from it is connected to the backup channel 8. The shell of each linear fire sensor is isolated from the sensitive thermoresistive elements and connected to the housing of the fire protection unit 6 and the housing object of control. The following modules are installed inside the main channel 7: a module of analog-to-digital converters 9, to the input of which linear fire detectors are connected, a calculator module 10 with digital interfaces, which is connected to the calculator module of the backup channel 8 and to the systems of the monitoring object, relay module 11 and additional module 12 .

To implement the module of the calculator 10 microcontrollers are used, with a capacity of sixteen or thirty-two, having a sufficient amount of internal memory and having high speed, which allows you to implement at the software level all the algorithms for the operation of the device. An additional module 12 for calculating the rate of temperature change can be implemented on a separate microcontroller, in this case, temperature data is supplied to it from the calculator module 10, or can be implemented on a software level, as part of the calculator module 10.

The sensitive elements are made of the same type of thermoresistive, each of which is two identical filamentous conductive wires parallel to the shell, the diameter of which can be, for example, 0.2 mm, made of metal with a positive temperature coefficient of resistance and with a linear dependence of the resistance on temperature , interconnected at one end of the shell by welding and isolated from each other, from the shell and from the second sensitive thermoresistive ementa thermally conductive insulating material 13, for example, magnesium oxide layer of 0.2 mm when the outer diameter of the working part of the line sensor fire of 1.2 mm. A metal plug 14 is hermetically welded to the shell, on the side of the connection of the conductive wires, and on the other hand, where the free ends of the conductive wires protrude outside the shell 4 to connect to the external electrical circuit of the fire protection unit 6, the shell 4 is sealed with a high-temperature adhesive, for example, K -300 or sealant. The use of thermoresistive sensitive elements in a linear fire sensor in the form of two filamentous conductive conductors interconnected will significantly reduce the external diameter of the linear fire sensor and, thereby, reduce its thermal inertia. In addition, the complete isolation of sensitive thermoresistive elements will significantly increase the measurement accuracy and noise immunity of the linear fire sensor and the device for detecting fire or overheating in general. At the same time, the linear fire sensor, in addition to the working part, contains an installation part, which will allow to avoid unnecessary connections during its installation in the fire hazard zone and, due to this, make the device for detecting fire or overheating more compact.

A device for detecting fire or overheating works as follows.

The analog-to-digital converter module 9 provides power to the linear fire sensors 1 and converts the output signals of these linear fire sensors into a digital code, which is transmitted via an internal interface to the calculator module 10 for further processing. For continuous monitoring and troubleshooting of linear fire sensors (open circuit, short circuit, etc.), the readings of two sensitive thermoresistive elements of the same linear fire sensor are compared, tolerance control (the resistance of each sensitive thermoresistive element must be within the limits corresponding to the range of measured temperatures ), as well as monitoring the physical compliance of the parameters (for example, the average temperature in the area of the compressor of a gas turbine engine n must exceed the average temperature in the region of the turbine). To ensure high accuracy of temperature measurement in the module of the calculator 10, the output signals of all linear fire sensors are filtered and their static characteristics are linearized. In the module of the calculator 10, threshold values are also generated for the average temperature and its rise rate for each linear fire sensor. These threshold values can increase by 20% to 50% for the linear fire detector in which a malfunction of a specific sensitive thermistor element was detected. The set thresholds can be adjusted in various ways. If the calculator module 10 receives information on the operating modes of this control object from the systems of the control object via an external interface (for example, information on the position of the engine control lever, temperature and pressure at the engine inlet, fuel consumption, speed and flight altitude), such continuous correction of the threshold for average temperature is carried out, which increases the level of overheating and fire for higher modes of operation of the control object and lowers it for lower modes.

For the rate of temperature rise, the set threshold values are corrected not by the parameters characterizing the mode of operation of the monitoring object, but by the rate of change, and only for the duration of the transition process. In the event that the relevant information is not received from the systems of the monitoring object, then only threshold values for the temperature rise rate are increased and only during the transition process, when a certain minimum level of the temperature rise rate is simultaneously exceeded for all linear fire detectors installed in the monitored zone.

The formation of signals about a fire or overheating is carried out in the module of the calculator 10 in the event that the corresponding threshold values are exceeded. The overheat signal is generated by the average temperature, and the fire signal is formed by the average temperature or by its rate of rise. In the event that any of these signals appears simultaneously in the main channel 7 and in the backup channel 8, information about a fire or overheating enters through the information exchange channel into the corresponding systems of the monitoring object, causing light and / or sound alarms to be triggered. At the same time, by a signal from the calculator module 10, the relay contacts are closed in the relay module 11. This duplicates information about a fire or overheating, transmitted in the form of a digital code, and the automatic fire extinguishing system can also be activated. An additional module 12 implements calculations of the rate of change of temperature (the most noise-free options are presented below). Moreover, in the additional module 12 for a given time interval, the duration of which is determined based on the time required to detect a fire (usually it is limited to a range of 3s to 5 s), based on temperature data coming from the calculator module 10 with a resolution of, for example, 125 ms, form an array of information for a time from 10 s to 15 s save it.

In the simplest version, to calculate the rate of temperature change in the stored array, for example, for a fire detection time of 3 s, two equal parts are selected from the last values, 24 values each and the average temperature value in each part is found. In this case, the rate of temperature change is determined by the formula:

- скорость изменения температуры;

- rate of change of temperature;

- среднее значение температуры за более поздний интервал времени, равный t₀;

- the average temperature for a later time interval equal to t ₀ ;

- среднее значение температуры за более ранний интервал времени, равный t₀;

- the average temperature for an earlier time interval equal to t ₀ ;

t ₀ - set fire detection time.

.In this embodiment, the calculation of the rate of change of temperature is carried out with a delay equal to

.

An option that avoids this effect is that with a linear increase in temperature (Fig. 4) for equal time intervals t ₂ -t ₁ = t ₃ -t ₂ = t ₀ find two sums S ₁ and S ₂ consisting of 24 temperature measurements each. In this case, the rate of temperature rise is found by the formula:

- скорость изменения температуры;

- rate of change of temperature;

S ₂ is the sum of the later temperature measurements;

S ₁ is the sum of earlier temperature measurements;

t ₀ - set fire detection time.

The calculation of the sums of S ₁ and S _{2 is} carried out in a continuous (sliding) mode, when with the advent of a new measured value, it shifts the previous value to the left along the time axis, and the “oldest” of all values is discarded.

To detect flames with different combustion temperatures at earlier stages and at points farthest from linear fire detectors, it is necessary to increase the time t ₀ for detecting a fire and, accordingly, reduce the threshold value for generating a fire signal by the rate of temperature rise. In this case, in the additional module 12, the temperature rise rate is simultaneously calculated for several values of t ₀ , for example, for 3s, 5s and 10s, and in the module of the calculator 10, the corresponding operation thresholds are set, for example, 2 ° C / s, 1 ° C / s and 0.5 ° C / s.

Tests of an experimental sample of a fire or overheating detection device with a linear fire sensor with two similar thermoresistive sensitive elements showed the following results.

1. The time for detecting a fire or overheating at an average temperature of the proposed linear fire sensor is approximately 3 times less than that of the known analogues, and the accuracy of operation at an average temperature is more than 4 times higher and can be 5 ° C with linearization of the static characteristic.

2. The time of fire detection by local exposure to a flame with a temperature of 1100 ° C for a 150 mm long section of a linear fire sensor is comparable to analogues, does not exceed 3 s and remains at this level when the temperature drops to 600 ° C.

3. The mass and dimensions of linear fire detectors in a redundant fire detection system are reduced by approximately 2.5 times compared with the known fire or overheating detection devices.

4. The resistance of the heat-conducting insulating material of the linear fire sensor remains high even at a temperature of 600 ° C and is at least 500 kOhm.

5. Despite the compact design, the linear fire sensor withstands vibration with levels up to 30g in the frequency range from 10 to 2000 Hz and single impacts with shock acceleration levels up to 45g and a duration of 11 ms.

Thus, the proposed method for detecting fire or overheating and a device that implements this method can improve the accuracy of measuring the average temperature and its rise rate in the controlled area, increase the noise immunity and speed of the device for detecting fire or overheating with a more compact design, in comparison with the known analogues.

Claims (14)

1. A method for detecting fire or overheating, which consists in obtaining temperature data from linear fire detectors, monitoring the health of linear fire detectors, generating fire or overheating signals if the linear fire detectors are working, and if these linear fire detectors exceed a predetermined threshold values that indicate the presence of a fire or overheating and adjust the specified threshold values when changing the operating modes of the control object, including in a system with redundant characterized in that, after monitoring the health of linear fire sensors, they save the obtained temperature data for a given time interval and calculate the rate of temperature change from the stored temperature data array, and the duration of the specified time interval is determined based on the permissible time for fire detection. 2. The method according to p. 1, characterized in that additional data is obtained from sensors characterizing the operation mode of the monitoring object, the threshold values for the average temperature are continuously adjusted according to the data obtained, and the threshold value for the temperature rise rate is increased only for the duration of the transient processes, which are accompanied by an increase in temperature. 3. The method according to p. 1, characterized in that in the case of a sharp increase in temperature caused by a change in the operating mode of the monitoring object, when the temperature data of all linear fire sensors change at the same time, the threshold value for the temperature rise rate during the transition process, accompanied by temperature change. 4. The method according to p. 1, characterized in that to calculate the rate of temperature change, divide the stored temperature data into two parts, calculate the average temperature in each of these two parts, find the difference between these two average temperatures and divide the found difference for a given time of fire detection. 5. The method according to p. 1, characterized in that for calculating the rate of temperature change, divide the stored temperature data array into two parts equal in the number of measurements, summarize the stored temperature data in each part, and subtract the amount with the previously obtained temperature data from sums with temperature data obtained later, and by dividing this doubled difference by the square of the specified fire detection time, the rate of temperature change is found, assuming that the temperature rises according to a linear law. 6. The method according to p. 5, characterized in that to calculate the rate of temperature change at the same time use not one, but two or three specified time intervals for fire detection and for each of them set their threshold value for generating a fire signal. 7. The method according to p. 1, characterized in that if a malfunction is detected in one of the channels of the system with redundancy in the serviceable channel, threshold levels for the average temperature and for the temperature rise rate are increased. 8. A device for detecting fire or overheating, containing linear fire detectors, consisting of a working and mounting parts, while the working part is made in the form of a long thin-walled flexible metal shell, in which there are two sensitive elements connected to the fire protection unit, containing the main and backup channels, each channel includes a series-connected module of analog-to-digital converters, to the input of which linear fire detectors are connected, a computer module with digital interfaces, one of which is used to communicate with the backup channel, and the second - to communicate with the monitoring object and a relay module, characterized in that an additional module is included in each of the channels of the fire protection unit, designed to calculate the rate of change of temperature and connected to the module of the calculator, the sensitive elements are made of the same type of thermoresistive, each of which is two identical filamentous conductive wires located parallel to the shell, made They are made of metal with a positive temperature coefficient of resistance and with a close to linear dependence of the resistance on temperature, interconnected at one end of the shell by welding and isolated from each other, from the shell and from the second sensitive thermoresistive element with a thermally conductive insulating material, to the shell from the connection side of conductive veins, a metal plug is hermetically welded, and on the other hand, where the free ends of the conductive wires protrude beyond the shell to connect to external electrical circuit of the fire protection unit, the shell is sealed with high-temperature adhesive or sealant. 9. The device according to p. 8, characterized in that the shell of the working part of the linear fire sensor with an increase in diameter passes into the shell of the mounting part, while the conductive wires of the working part of the linear fire sensor with an increase in diameter go into the conductive wires of the mounting part, protruding shell limits. 10. The device according to p. 8, characterized in that the calculator module continuously monitors the health of linear fire detectors, which uses tolerance monitoring of breaks and short circuits of all thermoresistive sensitive elements that are connected to it through an analog-to-digital converter module, and comparing the data on the measured temperature with the temperature data obtained from the backup channel. 11. The device according to p. 10, characterized in that in the event of a malfunction of linear fire sensors in one of the channels in the backup channel, thresholds for fire and overheating are increased, information about which is stored in the calculator module, for that linear fire sensor, which failed one of the two sensitive thermoresistive elements. 12. The device according to p. 8, characterized in that in the case of a sharp increase in temperature caused by a change in the operating mode of the test object, when the rate of temperature increase calculated in the additional module according to the readings of all linear fire sensors exceeded the minimum specified threshold, the calculator module increasing the threshold value for the rate of temperature rise during the transition process, which is accompanied by an increase in temperature. 13. The device according to claim 8, characterized in that the threshold values for the average temperature are continuously adjusted in the calculator module according to the data received via the digital interface on the operating modes of the monitoring object, and threshold values for the temperature rise rate increase only for the duration of the transient processes , which are accompanied by an increase in temperature. 14. The device according to p. 8, characterized in that in the additional module the calculation of the rate of change of temperature is carried out in accordance with the methods described in clause 4, clause 5 and clause 6 according to the temperature data obtained from the calculator module.

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