Increased suction power in an aspirating smoke detector (ASD) to shorten the transport time from a detected minimum signal level without issuing an interruption message.

Abstract

Aspirating smoke detector (ASD), which at least has, - a fire detector unit (DET) for the metrological determination of a signal level (DL) of a fire characteristic parameter, - an intake unit (L), - a power control unit (DR) for adjusting the intake power (P) of the intake unit (L), - an intake pipe (R) connected to the intake unit (L) and equipped with intake openings (OF) for drawing in room air containing smoke and / or combustion gas to be detected, - an airflow meter (SEN), in particular a flow meter, for detecting an airflow (V̇, ṁ) of the intake room air, and - an electronic control unit (MC) connected to the fire detector unit (DET), the airflow meter (SEN) and the power control unit (DR), configured to adjust the intake power (P) of the intake unit (L) to a nominal airflow value (NW) for normal operation by means of the power control unit (DR), to increase the intake power (P) from a detected minimum signal level value (MIN) by means of the power control unit (DR) to shorten the transport time (T) and to issue a fire alarm (AL) in the event of a detected fire, characterized in that - that the control unit (MC) is configured to issue an interruption message (U) intended for normal operation if the detected airflow (V̇, ṁ) exceeds a predetermined upper limit (V̇ +, ṁ +) for a minimum period of time (ZR), and - that the control unit (MC) is configured to increase the intake power (P) from the minimum signal level value (MIN) only to the extent that the airflow (V̇, ṁ) does not exceed the upper limit (V̇ +, ṁ +).

Description

[0001] The invention relates to an aspirating smoke detector. Such aspirating smoke detectors, or aspirating fire detectors, are also referred to in technical terms as ASDs (for aspirated smoke detectors).

[0002] The aspirating smoke detector considered here comprises at least one fire detector unit for the metrological determination of a signal level of a fire characteristic, an aspiration unit, a power control unit for adjusting the aspiration power of the aspiration unit, and an aspiration pipe connected to the aspiration unit and provided with aspiration openings for aspirating room air containing smoke and / or fire gas to be detected. Furthermore, the aspirating smoke detector comprises an air flow meter, in particular a flow meter, for detecting an air flow of the aspirated room air, as well as an electronic control unit connected to the fire detector unit, the air flow meter, and the power control unit.The latter is designed to adjust the intake power of the intake unit to a nominal airflow value for normal operation using the power control unit, to increase the intake power from a minimum signal level using the power control unit to shorten the transport time, and to issue a fire alarm in the event of a fire being detected. The intake unit and the fire detector unit typically form a single unit.

[0003] Such an aspirating smoke detector is known from EP 2 244 236 A1. By increasing the fan speed and thus increasing the suction power, the transport time of the sucked-in room air with smoke through the suction pipe to the fire detection unit is shortened. This enables faster fire detection.

[0004] From the applicant's EP 2 407 946 A1, an aspirating smoke detector for detecting blockages and interruptions in a pipe system is known. Air is drawn in via the pipe system from rooms and facilities to be monitored by a fan and monitored for fire characteristics. The air flow of at least a portion of the drawn-in air and the air temperature are measured. A blockage alarm is issued if the air flow falls below a predefined lower limit, and / or an interruption alarm is issued if the air flow exceeds a predefined upper limit. The fan speed increases as the air temperature increases and decreases as the air temperature decreases.

[0005] "Air flow" refers to the air volume flow V or the air mass flow m. It is therefore a time-dependent physical quantity. According to the physical relationship ṁ = ρ·V̇, air volume flow V and air mass flow m are related to each other via the density ρ.

[0006] "Normal operation" refers to normal, fire-free or smoke-free operation. This occurs, for example, after commissioning or after maintenance of an aspirating smoke detector.

[0007] The term "intake pipe" generally refers to a pipe system or hose system. The intake pipe can comprise a single pipe, preferably made of plastic, or several sub-pipes, which are split, for example, using a pipe distributor. The intake pipe typically has a circular cross-section with a diameter in the range of 1 cm to 5 cm, preferably in the range of 2 cm to 3 cm. In particular, the intake pipe has a minimum pipe length of 30 m, preferably 50 m. A plurality of intake openings are present or incorporated along the intake pipe.

[0008] They can be located at equal intervals along the intake pipe, such as every 4 m to 8 m.

[0009] The signal level of a fire parameter to be determined metrologically is typically a concentration level or a concentration value of detected smoke or of a detected fire gas as a possible fire parameter. Smoke contains smoke particles of different particle sizes, which are also referred to as smoke aerosols. A typical fire gas is, for example, carbon monoxide or ammonia. The fire detector unit can have an optical detector unit, e.g. one based on the scattered light principle or the transmitted light principle, or a gas sensor sensitive to fire gases, such as a CO gas sensor. The minimum signal level value is dimensioned in particular so that there is a sufficiently high probability of a possible fire event, i.e. is significant for a possible fire event.The determination of the minimum signal level value can be based on empirical values ​​from a similar fire monitoring environment or can be carried out using measurement technology through an on-site fire test.

[0010] The signal level of a fire parameter to be determined by measurement is typically a concentration level or a concentration value of detected smoke or of a detected fire gas as a possible fire parameter. The minimum signal level value is particularly dimensioned such that there is a sufficiently high probability of a possible fire event, i.e. is significant for a possible fire event. The intake unit - typically a fan - and the fire detector unit are usually, but not necessarily, housed in a common housing as a structural unit. Viewed in the direction of flow, the intake unit can be located upstream or downstream of the fire detector unit. The fire detector unit can have an optical detector unit based on the scattered light or transmitted light principle and / or a gas sensor unit for fire gases.

[0011] Aspirating smoke detectors usually have a fan (aspirator). This extracts air samples from rooms via an intake pipe and feeds them to a fire detection unit. The intake pipes can extend over several hundred meters. Therefore, sucked-in smoke must be detected along their entire length to the fire detection unit. The time required for this is also referred to as dead time or transport time. For long intake pipes, the transport time can be in the range of minutes. For example, the maximum transport time for a pipe length of 200 m, an average flow velocity of 1 m / s, and smoke intake at a pipe end remote from the fire detection unit is 200 seconds.

[0012] Typically, an ASD planner calculates the key parameters to ensure that an aspirating smoke detector complies with the relevant standards, such as the European standard EN 54-20, in this case in the version valid at the time of this patent application from February 2009, or the North American standard UL268, preferably from the 6th or 7th edition. Various parameters play a role here, such as the pipe length, the room size, the number of aspirating openings, the aspirating pressure and the sensitivity of the fire detector unit. Various software-supported planning tools are available for the technical design of an aspirating smoke detector, such as the ASYST planning tool from Siemens. Once the parameters have been determined, a technician assembles the aspirating pipe, drills aspirating openings in the form of holes in the aspirating pipe and configures the fire detector unit according to the specifications.

[0013] Typically, the fan's intake power is also adjusted via the set speed in order to set an airflow with a nominal airflow value through the intake pipe. This speed then remains constant in smoke- or fire-free normal operation over the lifetime of the detector. In this normal operation, an aspirating smoke detector is therefore parameterized with a low fan speed in order to extend its service life and to minimize the noise level during intake. The reason for the static setting is to detect interruptions with a corresponding increase in airflow, or to detect blockages of the intake openings due to dirt with a corresponding decrease in airflow over the course of the operating time of the aspirating smoke detector. As soon as the airflow deviates by ± 20% from the nominal airflow value, e.g. according to the aforementioned EN 54-20, the aspirating smoke detector must issue a fault within a time period of 300 seconds specified in the standard.The UL268 standard, preferably from the 6th or 7th edition, specifies 90 seconds instead of the aforementioned 300 seconds. The nominal airflow value, measured in liters per second or liters per minute, is typically set during commissioning of an aspirating smoke detector.

[0014] Based on the aforementioned EP 2 407 946 A1, it is an object of the present invention to provide an improved aspirating smoke detector. Finally, it is an object of the invention to provide an aspirating smoke detector that operates more reliably.

[0015] The object of the invention is achieved by the subject matter of claim 1. Advantageous embodiments of the present invention are specified in the dependent claims.

[0016] The fire alarm control panel or control center can also be implemented as a cloud application in a cloud infrastructure. In this sense, the aspirating smoke detector can receive the warning message "via the cloud" from a higher-level cloud fire alarm control panel or control center. The warning message is issued if, for example, at least one other aspirating smoke detector in the vicinity of this aspirating smoke detector has already reported a fire alarm or an impending fire, e.g., in the form of a pre-alarm, to the fire alarm control panel or control center. The local correlation increases the probability of an actual fire in the vicinity of the installed aspirating smoke detector. In this case, an "anticipatory" increase in the aspirating power is advantageous for the earliest possible fire detection.

[0017] According to the invention, the object of the invention is achieved by an aspirating smoke detector in which the electronic control unit is also configured or programmed to issue an interruption message intended for normal operation if the detected airflow exceeds a predetermined upper limit for a minimum period of time. Furthermore, the control unit is configured or programmed to increase the intake power (using the power control unit) from the minimum signal level only to the extent that the airflow does not exceed the upper limit.

[0018] The targeted, limited increase in the aspiration power, achieved by the control unit via the power control unit, advantageously prevents the issuance of a false interruption signal, in addition to enabling faster fire detection by the fire detector unit. This avoids unnecessary inspection of the aspirating smoke detector by a service technician.

[0019] If the intake power is increased only to such an extent that the airflow does not exceed, or just barely exceeds, the nominal airflow value, this increase is, in principle, not time-limited. In practice, however, regardless of whether a fire is detected or not, the intake power is reduced again, preferably at the latest after a specified waiting period, such as 10, 20, or 30 minutes, until the airflow reaches the nominal airflow value again.

[0020] With the return to normal operation, the noise development caused by the increased suction power and the mechanical overload of the aspirating smoke detector, which shortens its service life, caused by the increase, decreases again.

[0021] According to one embodiment of the aspirating smoke detector, the aspirating smoke detector has a communication interface connected to the control unit. The control unit is configured to increase the suction power of the suction unit to shorten the transport time upon receipt of a warning message from the communication interface, in particular a warning or attention signal.

[0022] In other words, in this case, the control unit is configured or programmed to increase the intake power of the intake unit using the power control unit such that the airflow does not exceed the upper limit. The communication interface can, for example, be a wired communication interface for connecting a detector or bus line that connects the higher-level fire control panel or control center to the aspirating smoke detector. Alternatively, the communication interface can be a wireless communication interface, such as a WLAN, Bluetooth, or a mobile 3G, 4G, or 5G data interface. The aforementioned communication interface can, for example, be based on an internet protocol.

[0023] According to a further embodiment, the control unit of the aspirating smoke detector is configured or programmed to analyze and evaluate the signal level of the fire characteristic to determine whether or not a fire event has occurred. It is also configured or programmed to reduce the suction power of the suction unit after the analysis and evaluation have been completed, and regardless of the minimum period, such that the airflow falls below the upper limit again, in particular so that the airflow returns to the nominal airflow value. If no fire event is detected, the aspirating smoke detector returns to normal operation.

[0024] According to a further embodiment, the electronic control unit is configured or programmed to issue a blockage message if the detected air flow falls below a predetermined lower limit for a predetermined minimum period of time.

[0025] As described above, the term “air flow” refers to the air volume flow V or the air mass flow m. The latter are linked to each other via the density ρ according to the physical relationship ṁ = ρ·V̇. The density ρ is determined according to the physical relationship ρ=pRf⋅T with the air pressure p, with the gas constant R f for the air and is linked to the air temperature T. The density ρ is thus proportional to the air pressure p and inversely proportional to the air temperature T.

[0026] For the aspirating smoke detector according to the invention, it can be assumed in principle that the density ρ is essentially constant during normal operation of the aspirating smoke detector, i.e., it changes by less than 3%, in particular by less than 2%. Such density changes therefore have no practical impact on the airflow monitoring for the aspirating smoke detector. The air flow rate can be measured, for example, using a vane anemometer as a flowmeter. The air flow rate can be determined from the measured average flow velocity multiplied by the known internal pipe cross-section.

[0027] Alternatively, the air volume flow can be measured using a thermal air flow sensor, such as a hot wire anemometer, the output signal of which, however, is a measure of the air mass flow m. If no significant changes in the ambient temperature, air pressure or humidity in the sucked-in room air are to be expected, an uncompensated thermal air flow sensor can be used as a flow meter. In more demanding application environments for the aspirating smoke detector, such as those with large fluctuations in the ambient temperature and / or air humidity, such a thermal air flow meter can comprise a compensation device as described in the aforementioned EP 2 407 946 A1. To take into account a detected air temperature, a detected air pressure and / or a detected air humidity, the compensation device can have a temperature sensor and, if necessary, a pressure sensor or humidity sensor.Such a compensated thermal airflow sensor can therefore function as a flow meter. A corresponding temperature, air pressure, or humidity sensor can be integrated into the intake unit or the thermal hot-wire anemometer itself.

[0028] According to one embodiment, the electronic control unit has a non-volatile memory for data access to the upper and lower limit values, as well as to the nominal airflow value and the minimum period. The upper limit value is 1.2 times the stored nominal airflow value, and the lower limit value is 0.8 times the stored nominal airflow value. The minimum period is set, in particular, to a value in the range of 60 seconds to 600 seconds, preferably to a value of 90 seconds or 300 seconds, or to a value of 90 seconds ± 3 seconds or 300 seconds ± 3 seconds. The non-volatile memory is, for example, an EPROM.

[0029] Alternatively, the upper and lower limits and the minimum period may be specified in a national, regional or international standard, such as EN 54-20, preferably as of February 2009.

[0030] Finally, the suction unit of the aspirating smoke detector according to the invention can be a fan or ventilator whose suction power increases with increasing speed n of the fan.

[0031] The electronic control unit is preferably a microcontroller, which is usually present or required for the entire control of the aspirating smoke detector. Furthermore, the microcontroller can have one or more integrated A / D converters for the metrological recording of the previously described input variables such as air volume flow, air mass flow, signal level, and, if applicable, air temperature, air pressure, and humidity. It can also have analog and / or digital input and output units (I / O) as well as communication interfaces for issuing a fire alarm, an interruption message, or a blockage message. The upper and lower limit values ​​for the air flow, the nominal air flow value, the minimum period, and the minimum signal level value can be stored in a non-volatile memory (EPROM) of the microcontroller.In addition, the power control unit and / or electronic components for signal conditioning or signal processing of the aforementioned input variables can already be integrated in the microcontroller.

[0032] The invention and advantageous embodiments of the present invention are explained using the following figures as examples. They show: Fig. 1 an example of the structure of an aspirating smoke detector in smoke-free normal operation, Fig. 2 the example according to Fig. 1 in case of a detected fire, and Fig. 3 an example of an aspirating smoke detector according to the invention.

[0033] Fig. Figure 1 shows an example of the design of an aspirating smoke detector ASD in smoke-free normal operation. On the left, an aspirating / detector unit ADE is shown as a structural unit, to which an aspirating pipe R with a plurality of distributed aspirating openings OF is connected. The latter are usually holes drilled into the aspirating pipe R. The aspirating openings OF typically have a non-uniform cross-section in order to achieve essentially the same "hole sensitivity" for all aspirating openings OF. This means that in normal operation, each of the aspirating openings OF draws in approximately the same volume per unit of time. K denotes a calibration hole located at the right end of the pipe. The holes shown in the left part of the Fig. The suction / detector unit ADE shown in Figure 1 comprises a suction unit L in the form of a fan, such as a radial fan, and a fire detector unit DET arranged upstream in the flow direction. With v Mis the mean flow velocity. The air flow or air volume flow sucked in by the intake unit L corresponds to the volume per time of the product of the mean flow velocity v M and from the internal cross-section of the intake pipe R.

[0034] Fig. 2 shows the example according to Fig. 1 in the event of a detected fire. Room air containing smoke to be detected is sucked in at an intake opening OF, symbolized by a flame symbol, and transported through the intake pipe R to the fire detection unit DET. The lightning symbol on the fire detection unit DET symbolizes a detected fire event. This is the case when a detection signal DL emitted by the fire detection unit DET exceeds a specified minimum detection level MIN. In the example of the Fig. Figure 2 shows how the sucked-in room air fills a transport or pipe section ST with smoke. T denotes the corresponding transport time. The transport time T is the product of the average flow velocity v M and from the indicated transport route ST. As described above, the transport time T can be up to several minutes.

[0035] Fig.Figure 3 shows an example of an aspirating smoke detector ASD according to the invention. The functional structure of the aspirating / detector unit ADE is shown in detail. In the right-hand part of the aspirating / detector unit ADE, which is implemented as a modular unit, a pipe connection AN can be seen, to which the aspirating pipe R is connected. The aspirating / detector unit ADE itself comprises the fire detector unit DET for the metrological determination of the signal level DL of a fire parameter. In the present example, the latter is a smoke concentration level. The aspirating smoke detector ASD or the aspirating / detector unit ADE further comprises a power control unit DR, which is configured to adjust an aspirating power P of the aspirating unit L. In the present case, the aspirating unit L is a fan, whose aspirating power P is controlled by changing the fan speed n. Lcan be adjusted. In addition, the aspirating smoke detector ASD or the aspirating / detector unit ADE has an air flow meter SEN for measuring the air flow V, ṁ of the drawn-in room air. The air flow is an air volume flow V or an air mass flow ṁ. The air flow meter SEN outputs a corresponding air flow measurement signal, which represents the air volume flow V̇ or the air mass flow ṁ.

[0036] Furthermore, the aspirating smoke detector ASD or the aspirating / detector unit ADE has an electronic control unit MC connected to the fire detector unit DET, the airflow meter SEN, and the power control unit DR. The latter is typically a microcontroller and is configured or programmed to adjust the aspirating power P of the aspirating unit L to a nominal airflow value NW for (smoke-free) normal operation using the power control unit DR. The aspirating power P can be adjusted in the form of an open or closed control loop, based on a currently measured air volume flow V or air mass flow ṁ in comparison with the nominal airflow value NW stored in an electronic memory MEM of the control unit MC.The MC control unit is further configured to issue a fire alarm AL in the event of a detected fire, and to issue an interruption message U during normal operation if the detected air flow V̇, ṁ exceeds a specified upper limit value V̇ +, ṁ + for a minimum period ZR. The fire alarm AL and, if applicable, the interruption message U and a blockage message V can be output via the MC electronic control unit, e.g., at a bus interface of the ADE intake / detector unit.

[0037] The control unit MC is also designed or programmed to increase the intake power P by means of the power control unit DR from a minimum signal level value MIN of the signal level DL, i.e. when the minimum signal level value SIG is exceeded, in order to shorten the transport time T of sucked-in room air with smoke and / or fire gas through the intake pipe R to the fire detector unit DET.

[0038] In particular, the control unit MC according to the invention is configured or programmed to increase the intake power P by means of the power control unit DR from the detected minimum signal level value MIN only in such a way that the set air flow V, ṁ does not exceed the upper limit value V̇ +, ṁ + . Both the minimum signal level value MIN and the upper limit value V +, ṁ + for the air volume flow V̇ or for the air mass flow ṁ can be stored in the electronic memory MEM for a computational comparison by the control unit MC.

[0039] Furthermore, the electronic control unit MC can be configured to issue a blockage signal V if the detected air flow V̇, ṁ falls below a predefined lower limit value V̇ -, ṁ - for a predefined minimum period ZR. This lower limit value V̇ -, ṁ - can also be stored in the electronic memory MEM for computational comparison by the control unit MC. List of reference symbols ADE suction / detector unit AL fire alarm, alarm AN pipe connection, nozzle ASD aspirating smoke detector DET fire detector unit DL signal level DR power control unit, driver K Calibration hole L Intake unit, fan, pump MC electronic control unit, microcontroller MEM memory, electronic memory, EPROM MIN Minimum signal level n L Fan speed NW nominal air flow value OF intake opening, bore P intake power PAR operating parameters R intake pipe, pipe system SEN air volume meter, flow meter, air mass meter ST transport route T Transport time U Interruption message V Blockage message v M average air flow velocity ZR period m air mass flow V̇ air volume flow ṁ + upper limit ṁ - lower limit QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 2 244 236 A1

[0003] EP 2 407 946 A1 [0004, 0014, 0027]

Claims

[1] Aspirating smoke detector (ASD), which has at least - a fire detector unit (DET) for the metrological determination of a signal level (DL) of a fire parameter, - a suction unit (L), - a power control unit (DR) for adjusting a suction power (P) of the suction unit (L), - an intake pipe (R) connected to the intake unit (L) and provided with intake openings (OF) for sucking in room air containing smoke and / or fire gas to be detected, - an air flow meter (SEN), in particular a flow meter, for detecting an air flow (V̇, ṁ) of the sucked-in room air, and - an electronic control unit (MC) connected to the fire detection unit (DET), the air flow meter (SEN) and the power control unit (DR), configured to set the intake power (P) of the intake unit (L) to a nominal air flow value (NW) for normal operation by means of the power control unit (DR), to increase the intake power (P) from a detected minimum signal level value (MIN) by means of the power control unit (DR) to shorten the transport time (T) and to issue a fire alarm (AL) in the event of a detected fire, characterized by , - that the control unit (MC) is designed to issue an interruption message (U) intended for normal operation if the detected air flow (V̇, ṁ) exceeds a predetermined upper limit value (V̇ +, ṁ +) for a minimum period (ZR), and - that the control unit (MC) is designed to increase the intake power (P) from the minimum signal level value (MIN) only to the extent that the air flow (V̇, ṁ) does not exceed the upper limit value (V̇ +, ṁ +). [2] Aspirating smoke detector (ASD) according to claim 1, wherein the aspirating smoke detector (ASD) has a communication interface connected to the control unit (MC), and wherein the control unit (MC) is configured to increase the suction power (P) of the suction unit (L) in order to shorten the transport time (T) in the event of receiving a warning message from the communication interface, in particular a warning or attention signal. [3] Aspirating smoke detector (ASD) according to claim 1 or 2, wherein the control unit (MC) is designed to reduce the suction power (P), in particular shortly before reaching the end of the minimum period (ZR), by means of the power control unit (DR) in such a way that the air flow (V, ṁ) falls below the upper limit value (V̇ +, ṁ +) again. [4] Aspirating smoke detector (ASD) according to one of claims 1 to 3, wherein the electronic control unit (MC) is set up to analyse and evaluate the signal level (DL) of the fire parameter to determine whether a fire event is present or not, and is set up to reduce the suction power (P) of the suction unit (L) after completion of the analysis and evaluation and independently of the minimum period (ZR) in such a way that the air flow (V, ṁ) falls below the upper limit value (V̇ +, ṁ +) again, in particular that the air flow (V, ṁ) returns to the nominal air flow value (NW). [5] Aspirating smoke detector (ASD) according to one of the preceding claims 1 to 4, wherein the electronic control unit (MC) is configured to output a blockage message (V) if the detected air flow (V̇, ṁ) falls below a predetermined lower limit value (V̇ -, ṁ -) for a predetermined minimum period (ZR). [6] Aspirating smoke detector (ASD) according to claim 5, wherein the electronic control unit (MC) has a non-volatile memory (MEM) for data access to the upper and lower limit values ​​(V̇ +, ṁ +; V̇ -, ṁ -) as well as to the nominal air flow value (NW) and to the minimum period (ZR), wherein the upper limit value (V̇ +, ṁ +) is 1.2 times and the lower limit value (V̇ -, ṁ -) is 0.8 times the stored nominal air flow value (NW) and wherein the minimum period (ZR) has a duration value of 90 seconds or 300 seconds. [7] Aspirating smoke detector (ASD) according to claim 6, wherein the electronic control unit (MC) has a non-volatile memory for data access to the upper and lower limit values ​​(V̇ +, ṁ +; V̇ -, ṁ -) with respect to the nominal air flow value (NW) and to the minimum period (ZR), wherein the upper and lower limit values ​​(V̇ +, ṁ +; V̇ -, ṁ -) and the minimum period (ZR) are defined in a national, regional or international standard, in particular by the European standard EN 54-20, preferably with the edition of February 2009, or by the standard UL268, preferably from the 6th or 7th edition.

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