Wireless Low Power Flame Detector

Abstract

The wireless flame detector (100) includes at least one optical sensor (122) having an electrical characteristic that varies with incident radiation. A measurement circuit (120) is coupled to the at least one optical sensor (122) and configured to provide an indication regarding the electrical characteristic of the at least one optical sensor (122). A controller (116) is coupled to the measurement circuit (120) to receive the indication and is configured to operate in a low-power mode during which a key flame indicator is monitored, and a second mode that provides a complete flame detection process. The controller (116) is configured to enter the second mode upon detecting an event while operating in the first mode. A method (200) for operating the wireless low-power flame detector (100) is also provided.

Description

[Technical Field]

[0001] background The process control and monitoring industry supports a wide range of process industries. Some process industries use or process materials that are highly flammable or even explosive. Examples of such industries include petroleum extraction and refining, as well as chemical processing facilities. In such environments, fire and explosion are significant hazards. Indeed, the operation of electrical equipment in such environments is often subject to regulations regarding power levels as well as the housing of such electrical equipment.

[0002] In some cases, power levels comply with one or more intrinsically safe specifications so that, even during an electrical fault, the device cannot ignite a potentially explosive atmosphere. One example of an intrinsically safe specification is the standard entitled "APPROVAL STANDARD INTRINSICALLY SAFE APPARATUS AND ASSOCIATED APPARATUS FOR USE IN CLASS I, II, AND III, DIVISION 1 HAZARDOUS (CLASSIFIED) LOCATIONS, CLASS NUMBER 3610," published by Factory Mutual Research in October 1998. Intrinsic safety requirements generally specify low energy levels that are simply not possible to comply with in circuits involving high voltages, high currents, and / or high wattage, such as AC circuits.

[0003] Housings for electrical equipment are sometimes required to be explosion-proof, meaning that even if a fire occurs within the electrical equipment, the flame or explosion cannot reach the exterior of the explosion-proof housing. Examples of explosion-proof ratings include ATEX certification to Ex-d standards EN60079-0 and EN60079-1 for potentially explosive atmospheres. Explosion-proof housings are typically relatively bulky so that they have sufficient mechanical robustness to contain an internal explosion without bursting. These enclosures are typically very robust metal enclosures designed to withstand the pressures of an explosion. However, for optical equipment, the enclosure must have some sort of window to allow light to pass through to the surrounding environment.

[0004] In these highly volatile environments, it is useful, and sometimes necessary, to use one or more flame detectors so that any flames within the process environment can be quickly detected and extinguished. Flame detectors, unlike residential smoke detectors, are optical instruments that are sensitive to flame radiant emissions, and often use UV and / or IR sensors for such purposes.

[0005] Industry regulations such as EN54 Part 25 pose further challenges with regard to alarm transmission times and battery life. Given the nature of detection using radiated emissions and the required operational specifications, current designs are limited.

[0006] Providing a wireless, battery-powered flame detector with improved power consumption / management would benefit the art, allowing such devices to be used in more locations, thereby improving process safety in such sensitive locations. Summary of the Invention

[0007] The wireless flame detector includes at least one optical sensor having an electrical characteristic that varies with incident radiation. A measurement circuit is coupled to the at least one optical sensor and configured to provide an indication regarding the electrical characteristic of the at least one optical sensor. A controller is coupled to the measurement circuit to receive the indication and is configured to operate in a low-power mode during which a key flame indicator is monitored, and a second mode that provides a complete flame detection process. The controller is configured to enter the second mode upon detecting an event while operating in the first mode. A method of operating a wireless low-power flame detector is also provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a flow diagram of a method for operating an industrial optical flame detector. [Figure 2] 1 is a schematic diagram of an industrial optical flame detector according to one embodiment of the present invention; [Figure 3] 1 is a block diagram of a circuit for an industrial optical flame detector according to an embodiment of the present invention; [Figure 4] FIG. 1 is a flow diagram of a method for operating an industrial optical flame detector in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS FIG. 1 is a flow diagram of a method for operating an industrial optical flame detector. Modern industrial flame detection systems, such as system 10, are based on a process of active, continuous monitoring of the environment. As shown in FIG. 1, system 10 continuously monitors signals from flame sensors 14 using a central processing unit 12 to detect signs of flame 16. The flame detection sequence is based on relatively complex processing techniques designed to eliminate false alarms. However, complex processing requires significant energy, which leads to high infrastructure costs and complexity. The power requirements for running complex processing have typically required hardwiring the flame detector to the process. However, hardwiring the flame detector adds wiring expense and time, which increases the cost of initial installation as well as the cost of any subsequent relocation of the flame detector. As described herein, a wireless, low-power flame detector is a device that is not connected to any wires. Therefore, any communication with the flame detector is wireless, and the flame detector is not powered by any wires connected to it.

[0010] The embodiments described herein generally provide a wireless, low-power flame detector that includes a low-power sleep mode during which a key fire indicator is constantly monitored, but without complex false alarm prevention processing. The system monitors the key fire indicator using very low power and is configured to be sensitive only to a very narrow spectrum of optical wavelengths corresponding to the wavelength of fire radiation. Once the very low power operation identifies an event based on monitoring the key fire indicator, the system is triggered to wake up and perform complex false alarm prevention processing to verify the presence of a fire.

[0011] 2 is a schematic diagram of an industrial optical flame detector according to one embodiment of the present invention. The flame detector 100 includes a metal housing 102 having an optical window 104 through which the flame detector 100 detects a flame. The flame detector 100 communicates wirelessly with a control room / panel 106. In some embodiments, the housing 102 may be explosion-proof and / or the circuitry within the housing 102 may comply with intrinsic safety specifications. When the flame detector 100 detects a flame in its environment, the flame detector 100 wirelessly communicates the flame detection to the control room / panel 106.

[0012] 3 is a block diagram of a circuit for an industrial optical flame detector according to one embodiment of the present invention. The circuit 110 of the flame detector 100 includes a battery 112, indicated at 114, configured to provide sufficient operating energy for all components of the flame detector 100. In some embodiments, the battery 112 can be a rechargeable battery, such as a rechargeable lithium-ion battery. Preferably, the battery is configured to be field replaceable.

[0013] The circuit 110 also includes a controller 116 configured to execute a set of instructions for providing flame detection, stored in an internal memory or an external memory coupled to the controller 116. The controller 116 can be any suitable combination of hardware or software for performing the processing necessary for flame detection. The controller 116 can be or include a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a microprocessor, or a microcontroller. The controller 116 preferably includes a low-power sleep mode, and the controller 116 can have an adjustable clock to operate at a lower frequency when in the low-power mode. As used herein, a low-power sleep mode includes any mode that operates at a lower power level than normal controller operation. Various techniques can be used to reduce the power of the controller in sleep mode. In one example, the controller may stop or reduce computational performance but retain any current data. In another example, some or all peripheral functions may be reduced or disabled. In one embodiment, the controller 116 is a microprocessor. The controller 116 enters a low-power sleep mode and continuously checks for the detection of one or more key flame indicators while in low-power sleep mode. During low-power sleep mode, complex power-consuming processes are not used in the background. If a key flame indicator is then detected, the controller 116 exits low-power sleep mode and performs complex flame detection processes, including complex false alarm prevention processes. The controller 116 preferably remains in active mode until a flame is no longer detected, at which point it again enters low-power sleep mode.

[0014] The controller 116 is coupled to wireless communication circuitry 118. Wireless communication circuitry 118 preferably provides two-way communication to the controller 116. However, embodiments in which the wireless communication circuitry 118 is configured solely to transmit information to one or more remote devices may also be practiced. The wireless communication circuitry may transmit the flame detection information to the control room / panel 106 (shown in FIG. 2) using any suitable wireless communication protocol or frequency, now known or later developed. Examples of suitable wireless communication protocols / frequencies include GSM networks, including those operating at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz; Code Division Multiple Access (CDMA); IEEE 802.11b, IEEE 802.11g, IEEE 802.11n, IEEE 802.11a; Bluetooth®; WiMax (IEEE 802.16 standard); IEEE 802.15.4; and WirelessHART (IEC 62591).

[0015] 3, circuitry 110 also includes measurement circuitry 120 coupled to or included within controller 116. Measurement circuitry 120 provides digital indications of measurements obtained from one or more optical sensors 122. Measurement circuitry 120 may include one or more analog-to-digital converters and / or appropriate multiplexing circuitry for interfacing the one or more analog-to-digital converters to sensors 122. Additionally, measurement circuitry 120 may include appropriate amplification circuitry and / or linearization circuitry as may be appropriate for the various types of optical sensors used.

[0016] The optical sensor 122 includes any suitable device having electrical properties that change in response to incident electromagnetic radiation. The electromagnetic radiation can be in the visible spectrum or in the non-visible spectrum, such as IR and / or UV. The optical sensor 122 is positioned proximate to the window 104 so that radiant energy passing through the window 104 is detected by the optical sensor 122. Suitable examples of optical sensors include, but are not limited to, photodiodes, phototransistors, charge-coupled devices (CCDs), and complementary metal-oxide semiconductor (CMOS) devices. In addition, the optical sensor 122 can include a combination of devices, whether of the same type (i.e., an IR photodiode operating in conjunction with a UV photodiode) or different types (i.e., an IR photodiode operating in conjunction with a CMOS sensor).

[0017] FIG. 4 is a flow diagram of a method for operating an industrial optical flame detector according to one embodiment of the present invention. Method 200 begins at block 202, where a wireless, low-power flame detector enters a low-power mode and continuously checks for the detection of one or more key flame indicators during the low-power mode. In embodiments using a controller with a low-power mode, the controller is placed in the low-power mode during execution of block 202. Additionally or alternatively, only optical sensors 122 that provide low-power operation, such as low-power phototransistors, are used during block 202. Notably, no complex power-consuming processes are used in the background during execution of block 202. In one example, a key fire indicator monitored during block 202 is radiant energy in the ultraviolet spectrum, e.g., having a wavelength in the range of 10 to 400 nanometers. One or more additional optical sensors 122 can also be used during the low-power mode. For example, an IR optical sensor (having a relatively narrow optical spectral sensitivity of approximately 4 to 4.5 μm) can be used to rapidly detect the presence of a flame and further improve discrimination between flame sources and non-flame background radiation. If the system detects a signal from one or more optical sensors, method 200 transitions to block 204, where the system is triggered to exit its low-power mode and implement complex flame detection processing, including complex false alarm prevention processing, as shown in block 206. During this state, the complex flame detection processing can be the same as that used in conventional techniques or can include a combination of conventional techniques and data / signals acquired during low-power operation. If, in block 206, controller 116 (shown in FIG. 3) determines that the detection is not a false alarm, the flame detection is communicated to one or more remote devices using wireless communication circuitry 118 (shown in FIG. 3). Preferably, the system remains in full-power mode until a flame is no longer detected, at which point it returns to low-power operation, as shown at 208.

[0018] As can be appreciated, the embodiments described herein generally provide a wireless, low-power flame detector that is very low power and sensitive to a very narrow optical wavelength spectrum corresponding to the wavelength of fire radiation, and that can monitor one or more key fire indicators. Once the system is triggered by an event, it terminates its low-power operation and provides full flame detection processing. In one example, this essentially adds an additional layer of ultraviolet sensors that trigger the system to activate. By using the embodiments described herein, the flame detector remains in low-power mode most of the time, thereby facilitating extended battery operation.

Claims

1. A wireless flame detector comprising: at least one optical sensor having an electrical characteristic that varies with incident radiation; a measurement circuit coupled to the at least one optical sensor and configured to provide an indication of the electrical characteristic of the at least one optical sensor; and a control device coupled to the measurement circuit to receive the instruction, the control device configured to operate in a low power mode during which a key flame indicator is monitored, and a second mode providing a complete flame detection process, the control device configured to enter the second mode upon detecting an event while operating in the first mode; wireless flame detectors, including

2. 10. The wireless flame detector of claim 1, further comprising a wireless communication circuit operably coupled to the controller and configured to communicate wirelessly with at least one remote device.

3. 3. The wireless flame detector of claim 2, further comprising a battery operably coupled to the measurement circuit, the controller, and the wireless communication circuit.

4. The wireless flame detector of claim 1 , wherein the at least one optical sensor includes a photodiode.

5. The wireless flame detector of claim 1 , wherein the at least one optical sensor includes a phototransistor.

6. 10. The wireless flame detector of claim 1, wherein the at least one optical sensor is configured to be sensitive to radiation in the 4-4.5 um optical band.

7. 10. The wireless flame detector of claim 1, wherein the at least one optical sensor is configured to be sensitive to radiation in the ultraviolet spectrum.

8. 10. The wireless flame detector of claim 1, wherein the at least one optical sensor comprises a plurality of optical sensors, the plurality of optical sensors comprising a first optical sensor sensitive to ultraviolet radiant energy and a second optical sensor sensitive to infrared radiant energy.

9. 10. The wireless flame detector of claim 1, wherein the complete flame detection process includes a false alarm prevention process.

10. 10. The wireless flame detector of claim 1, further comprising a metal housing that houses the at least one optical sensor, the measurement circuitry, and the controller.

11. The wireless flame detector of claim 10 , wherein the metal housing includes an optical window.

12. The wireless flame detector of claim 11 , wherein the at least one optical sensor is positioned proximate to the optical window.

13. 13. The wireless flame detector of claim 12, wherein the metal housing is explosion-proof.

14. 1. A method of activating a wireless flame detector, comprising: providing a control device having a plurality of processing modes, the plurality of processing modes including a first mode and a second mode, wherein power consumption of the control device during the first mode is lower than power consumption during the second mode; monitoring at least one key flame indicator using an optical sensor while the controller is in the first mode; selectively transitioning to the second mode when a flame event is detected during the first mode; performing a flame detection process in the second mode; and selectively providing a flame detection output based on said flame detection process; A method comprising:

15. 15. The method of claim 14, further comprising returning to the first mode after providing the flame detection output.

16. 15. The method of claim 14, wherein providing the flame detection output is performed using wireless communication.

17. 15. The method of claim 14, wherein monitoring at least one key flame indicator while the controller is in the first mode comprises monitoring ultraviolet radiation in an environment of the wireless flame detector.

18. 20. The method of claim 17, wherein performing flame detection processing includes processing one or more optical sensor signals to provide false alarm prevention.

19. The method of claim 14 , wherein an additional optical sensor signal is used during the second mode.

20. 20. The method of claim 19, wherein the flame detection process is based on signals from a plurality of optical sensors.

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