CH659711A5 - SELECTIVE GAS / SMOKE DETECTION DEVICE. - Google Patents

Description

30 The invention relates to a selective gas / smoke detection device with a plurality of suction lines connected separately at different measuring points in a room or rooms to be monitored for receiving air or gas samples at these measuring points, 35 furthermore with a gas or smoke detector connected to these lines, which reacts to the presence of a certain gas or smoke in a sample and emits a detection signal when a specified threshold value is exceeded, which in turn controls a display and / or alarm circuit, and with shut-off valves arranged in the individual suction lines, which, by a control circuit controlled, cyclically and periodically operable.

Such devices are known. For example, a fire alarm device is described in the German design specification 2,136,968, which is used to determine the presence of carbon monoxide gas that develops at the start of a fire. With this device, the various measuring points are alternately scanned in a cyclical manner by a corresponding control of the valve system, these valves being opened one after the other during a specific measuring period, so that it can be located at which measuring point a possible fire source is located.

55 Although this known fire detection device enables accurate selective detection, there are a number of important disadvantages associated with it:

Thus, the other measuring points are not connected during the scanning of a measuring point and there is therefore no detection there. With only a few suction lines, this is not a disadvantage in itself, but the more suction lines there are, the more the total cycle time increases accordingly, and the cyclical monitoring of a larger number of measuring points will therefore take a comparatively long time. If a potential source of fire occurs at one of the last measuring points of the monitoring system, the actual fire alarm can take place later than planned.

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Another disadvantage is that with continuous cyclic scanning, the valves of the various suction lines are opened and closed continuously, which results in premature wear and is quite noisy.

In addition, a continuously operating device for the permanent actuation of the valves is required, which is associated with considerable effort, particularly in larger systems.

The invention aims to create a selective gas / smoke detection device of the type mentioned at the beginning, the disadvantages mentioned not occurring and with which a reliable and rapid detection and monitoring of a large number of measuring points is possible even with longer suction lines.

For this purpose, the detection device described at the outset is characterized according to the invention in that the detector is connected to a control unit which, in the absence of a detection signal, adjusts the valves in such a way that all suction lines are openly connected to the detector at the same time, and which receive a detection signal for one scan switches, the suction lines being connected cyclically one after the other or in groups to the detector.

The invention is based on the knowledge that it is not necessary for an expedient monitoring of a plurality of measuring points to continuously scan cyclically as in the known device. Instead, measurement is carried out continuously at all measuring points at the same time, in that during normal operation all suction lines simultaneously suck gas or air from the measuring points to the detector. It is thereby achieved that the occurrence of foreign gas at one of the measuring points is detected in a time which is only a fraction of the time required for an entire sampling cycle of the individual measuring points. As soon as the detector detects foreign gas and in response gives a detection signal, this is passed on to the control circuit, which triggers an alarm and immediately switches to cyclical scanning in order to determine at which measuring point or measuring points the "stove" is located. Since the initial non-selective detection has already triggered an alarm, it does not matter whether the subsequent cyclical selective detection takes a relatively long time for a large number of measuring points, since measures can already be taken as a result of the initial alarm.

Another great advantage of the invention is that during normal operation the device works passively, i.e. with permanently open valves that do not need to move, which prevents wear and is very energy-saving. On the other hand, detection is always carried out very quickly, because the time required to perform the "total detection" corresponds to the longest measuring time for a selective measuring point, whereby measuring time must be understood to mean the total time required for each measuring point to open the related valve, rinsing lines and detector, detecting and reclosing the valve.

In a practical embodiment of the invention it is further provided that the control unit contains an alarm circuit and a sampling circuit, of which the alarm circuit generates an alarm signal upon receipt of a first detection signal from the detector, which on the one hand triggers an alarm and on the other hand the sampling circuit for cyclic actuation of the valves in the Suction lines switches on, and that display and / or registration circuits are also provided, which display or register the detection signals received during these cyclical scans. Such a control unit can also contain manual controls and settings as well as interlocks that block these manual controls when an alarm signal occurs.

Although in principle it is possible for the device according to the invention to work with a simple set of suction pipes which jointly open into a detector, a more differentiated system is preferable for practical reasons. According to a preferred embodiment of the device according to the invention, it is designed in such a way that each suction line opens into a first collecting piece and, via a branch, into a second collecting piece, which collecting pieces are connected to the detector via separate feed lines, with the first feed line of the first collecting piece controlled main valve is located, which is open during normal operation and closes when switching to cyclical scanning, and that controlled valves are arranged in the suction lines, which close the branches during normal operation and open them one after the other or in groups when switching to cyclical scanning. The valves in the closure lines can expediently be three-way valves.

In this embodiment, it is also advantageous if a vacuum pump is connected to the suction side on the outlet side for suction, so that suction is maintained by the detector.

Such an embodiment works quickly and appropriately. In normal operation, there are open connections between the various measuring points and the first collecting piece while the main valve is open, so that detection can be carried out continuously. When the detector detects foreign gas and sends a detection signal to the control unit, the main valve is closed and it is switched over to selective sampling of the suction line valves, the branches being brought openly one after the other into connection with the second collector piece, the one in direct Connection to the detector is established. A great advantage of this device is that immediately after the main valve is closed, the gas present in the detector and in the first supply line is quickly sucked out by the pump, so that the selective scanning and detection can follow almost immediately.

The connection of the vacuum pump to the output side of the detector also offers the possibility of easily evacuating the detector for control purposes.

For the fastest possible suction with cyclical scanning of the suction lines, it is also advantageous

if the suction lines continuously have sufficient suction power. This can expediently be achieved in that a circulation line, provided with an adjustable valve, connects the first collecting piece directly to the pump. In this embodiment, the connections between the measuring points and the first collecting piece remain open and after the main valve is closed, the circulation line has the effect that the entire length of the suction lines is still suctioned outside the detector. When the cyclic scanning is switched on, the branches are then opened one after the other to the second collecting piece, the necessary suction power already being present in the corresponding suction line, so that no time is lost for generating the negative pressure for the intended suction power.

For reliable monitoring, especially in a system with extensive suction lines, it is advisable to periodically check the suction lines for their suction capacity, as a result of Ver5

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dirt blockages could arise. For this purpose, a gas flow meter can expediently be arranged in the second feed line between the second collecting piece and the detector. For an automatic periodic control, a timer circuit can also be provided for the control unit, which periodically actuates the sampling circuit for periodic control of the suction lines, approximately once every 24 hours. A locking circuit should also be provided, which, controlled by the alarm circuit, prevents this circuit when the alarm circuit has received a detection signal. Such an interlock is expedient, since otherwise in the event of an alarm state the cyclic scanning activated by the alarm and the periodic cyclical scanning could interfere with one another.

The invention is particularly suitable for selective gas detection, in which the detection of a specific gas in a gas or air sample is carried out by means of a reagent gas which reacts with this gas. For this purpose, a reagent gas metering container can be connected directly to the second collecting piece and via a controlled reagent valve to the first collecting piece. The control circuit actuates this reagent valve in such a way that it is open during normal monitoring and closes cyclically when gas is detected and switched, so that no more reagent gas can enter the first collecting piece.

It is also possible that the reagent dosing container is connected to the first collecting piece via a reagent line provided with a controlled reagent valve and that branches between the reagent valve and the dosing container connect this reagent line to the suction lines in the vicinity of their measuring points. The chosen arrangement depends on the given conditions. If the reagent gas reacts quickly with the gas to be detected, the first embodiment is preferable, but if the reagent reacts sluggishly or small amounts of gas are to be detected, the second embodiment is preferred, in which the reagent gas is already introduced at the measuring points.

The detection device according to the invention according to one of these two designs is particularly suitable as a fire safety device, the measuring points being arranged in rooms which contain polyvinyl chloride, e.g. Insulating cable included, which releases HCl when heated. The reagent gas can then be made from ammonia, which develops with this HCl NH4 Cl mist, which can be reliably detected by a suitable ionization detector.

The detection of HCl by means of ammonia in an ionization detector is known per se from the Belgian patent specification 760.528, while the detection of ammonia with the aid of HCl is described in the Dutch patent application 68 18301.

The invention is explained using exemplary embodiments with reference to the drawings. Show of this:

FIG. 1 shows a schematic illustration of a first embodiment of the detection device according to the invention,

FIG. 2 shows the same schematic representation of a second embodiment, which is a variant of that of FIG. 1, and

FIG. 3 shows a block diagram of a control unit which can be used in the embodiments according to FIGS. 1 and 2.

According to the embodiment according to FIG. 1, MP are at a number of measuring points which are in the same or different

Rooms can be arranged, suction lines 1 connected. These branch out in lines 2 and 3, which are as short as possible in practice. SK selection valves are located at the branching points and consist of electrically controlled three-way valves. The lines 2 open into a first collecting piece (pipe branch) M1, while the branch lines 3 open into a second collecting piece M2. The first collecting piece M1 is connected to a discharge line 4, in which an electrically controlled main valve HK is arranged and which leads to the input of a detector D, which in this case is an ionization detector. The second collecting piece M2 has a discharge line 7 which leads to the line 4 between the main valve HK and the input of the detector D. The output of the detector is connected via a line 5 to a vacuum pump VP. A gas flow meter FL is also arranged in the discharge line 7. A bypass line 6, in which a manually adjustable control valve BK is arranged, connects the first collecting piece M1 directly to the pump VP.

A reagent gas container R is connected via a line 8 and a branch 9 directly to the second collecting piece M2 and via an electrically controllable control valve RK to the first collecting piece M1.

The detector D is connected to an electronic control unit from which the selection valves SK, the main valve HK and the reagent valve RK are controlled.

The operation of this device will now be explained when used as a fire safety device, the measuring points MP being in the vicinity of polyvinyl chloride, e.g. Insulating cables are arranged, which develops HCl gas when heated, and ammonia is used as the reagent gas, which reacts with HCl to form NH4C1 mist.

In normal operation, the position of the SK valves is such that connections 1-2 are open and connections 1-3 are closed. The main valve HK in line 4 is just as open as the reagent valve RK in line 8. The adjustable valve BK in the circulation line 6 is open at a set level. The vacuum pump VP is switched on continuously during operation.

As long as there is no MP HCl development due to local heating at any of the measuring points, the device remains switched in the aforementioned normal operating state. However, as soon as an inadmissible heating occurs at one or more of the measuring points, the HCl released from the heated polyvinyl chloride is sucked in with the air after the collecting piece M1, to which ammonia gas is also supplied from the reagent metering container via line 8. This forms NH4C1 mist, which passes through the supply line 4 to the detector D and is detected there. Accordingly, a detection signal is sent to the control unit (not shown), in which the alarm circuit for alarming and switching on the scanning circuit takes place, which then causes valve control in such a way that the main valve HK and the reagent valve RK are closed and the respective valves SK are cyclically switched to one another open connection 1-3 can be switched.

As a result, the measuring points MP are now scanned one after the other, each time such a measuring point being alternately connected via lines 1 and 3 to the second collecting piece M2, to which reagent gas is also supplied via lines 8, 9. The second supply line 7 leads the gas samples from M2 to the detector D, which, upon detection of NH4C1 fog (or smoke), forwards a detection signal to the control unit, which causes this signal to be registered and / or displayed.

In this way it is achieved that in the first phase a fire that has not yet been localized is quickly and non-selectively

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stove is detected and, after the alarm has been triggered, the position of this fire source is only determined more slowly. The advantage of this way of working, as already mentioned, is that the early alarm already enables you to take necessary measures, such as Calling a fire station to take measures, in particular measures that can already be taken without knowing the exact location of the identified fire source.

During the cyclical scanning of the measuring points MP, which follows the common scanning for a detection signal from the detector D, it is expedient to keep the suction power of the lines 1 and 3 at a predetermined level. This is not a problem with the lines 3, since these always remain in open connection with the detector D and thus with the pump VP. In order to keep the suction line in the lines after the main valve HK is closed, the bypass line 6 is provided, so that a direct connection between the first collecting piece M1 and the pump VP always remains open, so that via this bypass line also the main valve HK is still sucked off on the suction lines 1. As soon as one of the measuring points is switched after the open connection 1-3, the vacuum conditions in these two lines are already in place to ensure an instantaneous suction. In this way, the cyclic scanning for each measuring point MP can take place as quickly as possible.

For a good effect of the device, in which the suction lines have lengths of up to 30 meters and with line diameters on the order of a few millimeters, the VP pump can be a normal vacuum pump (backing pump) with sufficient capacity. Under these conditions, a suction speed of 2-3 meters per second can be obtained when suctioning the lines together, which ensures a quick first detection.

In order to check the various suction lines periodically, a gas flow meter 7 is arranged in the line 7 between the second collecting piece M2 and the detector D, which, when the various suction lines are selectively suctioned, registers a flow rate from which it can be determined whether the lines are free or blocked or are leaking. Such a check can be carried out periodically, as will be described in more detail with reference to FIG. 3.

The embodiment according to FIG. 2 mainly corresponds to that of FIG. 1. Corresponding parts are therefore provided with the same reference symbols. In contrast to the embodiment according to FIG. 1, the reagent gas metering container R is not directly connected to the second collecting piece M2. Rather, the metering container R is connected to the first collecting container M1 via a relatively long line 8 ', which again contains a reagent valve RK, while branches 10 of this line 8' lead to the suction lines 1 in the vicinity of the measuring points MP. Such a metering of the reagent gas is important in cases where the reagent gas has to react longer with the component to be detected or in cases where only low concentrations of the gas to be detected can be determined.

The embodiment of FIG. 2, like that of FIG. 1, can be used for HCl detection using NH3. The effect of the valves is in principle the same as in the previous embodiment. This training is particularly suitable for use in damp and / or cold environments.

Although in the above examples from an invented

According to the device designed according to the invention, with which smoke or HCl gas evolving from polyvinyl chloride with ammonia is detected, it is clear that numerous other applications are possible. It is also possible to detect undesirable ammonia gas, for example in cold rooms, using HCl as the reagent gas. Other devices based on a particular chemical reaction are also possible. In other cases, for example in CO detection, a reagent gas is not required. In these cases, the arrangement of a reagent metering container can be omitted.

FIG. 3 shows in a block diagram a possible embodiment of a control unit shown in FIGS. 1 and 2 and to be used in the detection devices. The most important individual parts of the unit shown are a clock circuit 11, a data input 12, an alarm circuit 13 and a sampling circuit 14, which controls a digital display circuit 18 and, via a binary decimal converter 15, a lamp display circuit 16 and a valve controller 17. The clock circuit 11 contains the clock circuit 11 a fixed oscillator and a frequency dividing circuit and can deliver synchronous pulses of different lengths. The clock circuit 11 is connected to a timer circuit 19, which determines the effect of the sampling circuit, as well as to a manually operable timer circuit 20, with which the sampling circuit 14 can be started for a selective measuring point, and to a timer circuit 21, which the sampling circuit 14 once in 24 hours can start for a measuring cycle to check the suction lines 1 by means of a current meter FL.

In the control unit there are also a number of locking circuits 22, 23 and 24 and a gate 25, the function of which is explained in the following description of the method of operation.

In normal monitoring operation, with the pump VP running, the valves SK having an open connection between lines 1 and 2 and the main valve HK and the reagent valve RK being open, the time switch ^ is switched off. Only the timer 21 is switched on once every 24 hours for a control cycle.

If the detector D connected to the data input 12 now generates a detection signal, this is forwarded via the data input to the alarm circuit, which converts this signal into an alarm. At the same time, the alarm circuit sends a start signal to the timer circuit 19 via the latch circuit 22, as a result of which the timer circuit 19 begins to run and drives the sampling circuit 14 for a selective measuring cycle, while at the same time the latch 22 causes the manually operated reset circuit 26 to be blocked. The alarm circuit 13 gives further signals to the locking circuits 23 and 24, whereby the eventual effect of the time circuits 20 and 21 is blocked. The sampling circuit 14 is essentially a digital counter, e.g. a four-bit digital counter, the count content of which is adapted to the number of valves SK to be controlled. Once the scanning circuit 14 is turned on. a control signal is also forwarded via the valve control 17 to the main valve HK and the reagent valve RK, as a result of which they close. Otherwise, the scanning circuit 14, via the binary decimal converter 15, ensures that the valves SK open the connections 1-3 one after the other and then close the connections 1-2. while the lamp indicator circuit indicates which of these valves is switched. These switchovers have a certain period of time, which is matched to the required measuring time for the respective suction line, which can be achieved by opening the valve, flushing the lines and the detector, i.e. Detecting and closing the valve determines v \ in!

If during the selective scan over a

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If the leakage of HCl gas is detected, the detector D introduces this signal into the data input 12, which forwards this signal to one input of the AND gate 25, the other input of which is connected to the timer circuit 19. Upon receipt of these two input signals and after a certain time course, the gate 25 opens and sends a signal to the digital display circuit 18 which records the current digital display thereon. A circuit built into the gate 25, e.g. a delay circuit, which is necessary because most of a measuring cycle consists of rinsing. If HCl determination had taken place at a previous measuring point, the detector and the relevant line must first be rinsed clean, which takes up a large part of the measuring time, for example 13 seconds with a measuring duration of 15 seconds, so that a delay of 13 seconds is necessary.

The received detection signal can also be forwarded to the lamp display circuit 16 via the alarm circuit 13 and the scanning circuit 14 in order to keep a lamp which is currently burning on.

When the total measuring cycle of all measuring points has ended, the scanning circuit 14 switches the timer circuit 19 off again, after which it is possible to restore the initial circuit conditions with the reset circuit 26 after the cause of the alarm has been eliminated, namely resetting the timer circuit 19 and switching off the alarm that Latches 23 and 24 and the digital and lamp anise show that the control circuit is again able to control the detection device in normal operation.

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3 sheets of drawings

Claims (11)

659 711 PATENT CLAIMS 1. Selective gas / smoke detection device with a plurality of suction lines (1, 2) connected separately at different measuring points (MP) in a room or rooms to be monitored for receiving air or gas samples at these measuring points, furthermore with a gas connected to these lines or smoke detector (D), which reacts to the presence of a certain gas or smoke in a sample and emits a detection signal when a specified threshold value is exceeded, which in turn controls a display and / or alarm circuit, and with shut-off valves arranged in the individual suction lines ( SK), which, controlled by a control circuit, can be actuated cyclically and periodically, characterized in that the detector (D) is connected to a control unit (FIG. 3) which, in the absence of a detection signal, adjusts the valves (SK) in such a way that all Suction lines (1,2) are at the same time in open connection with the detector, and which switches to a scan when a detection signal is received, the suction lines being connected cyclically one after the other or in groups to the detector. 2. Device according to claim 1, characterized in that the control unit (Figure 3) contains an alarm circuit (13) and a scanning circuit (14), of which the alarm circuit (13) generates an alarm signal upon receipt of a first detection signal from the detector (D) , which on the one hand triggers an alarm and on the other hand switches on the scanning circuit (14) for a cyclical actuation of the valves (SK) in the suction lines (1, 2), and that display and / or registration circuits (16 to 18) are also provided, which Display or register detection signals received during this cyclic scan. 3. Device according to claim 1, characterized in that each suction line (1,2) opens into a first collecting piece (Ml) and via a branch (3) into a second collecting piece (M2), which collecting pieces have separate feed lines (4,7 ) are connected to the detector, with a controlled main valve (HK) located in the first feed line (4) of the first collecting piece (Ml), which is open during normal operation and closes when switched to cyclic scanning, and that in the suction lines Controlled valves (SK) are arranged, which close the branch (3) during normal operation and open them one by one or in groups when switching to cyclical scanning. 4. The device according to claim 3, characterized in that the valves (SK) in the suction lines (1,2) are three-way valves. 5. The device according to claim 3, characterized in that a vacuum pump (VP) is connected for suction via the suction lines (1,2) on the output side of the detector (D). 6. The device according to claim 5, characterized in that a circulation line (6) with an adjustable valve (BK) connects the first collecting piece (Ml) directly to the vacuum pump (VP). 7. The device according to claim 3, characterized in that in the second feed line (7) between the second collecting piece (M2) and the detector (D) a gas flow meter (FL) for periodic control of the suction lines (1,2) is arranged. 8. Device according to claims 2 and 7, characterized in that the control unit (Figure 3) contains a timer (21) which periodically, about once every 24 hours, the scanning circuit (14) for periodic control of the suction lines turns on, and that a locking circuit (22) is provided which is controlled by the Alarm circuit (13), this circuit prevents when the alarm circuit has received a detection signal. 9. Device according to one of claims 3 to 8, wherein the detection of a specific gas in a gas or air sample by means of a reagent gas reacting with this gas, characterized in that a reagent gas metering container (R) directly (8 to 9) is connected to the second collecting piece (M2) and to the first collecting piece (M 1) via a controlled reagent valve (RK) (FIG. 1). io 10. Device according to one of claims 3 to 8, wherein the detection of a specific gas in a gas or air sample is carried out by means of a reagent gas reacting with this gas, characterized in that a reagent metering container (R) via a with a controlled reagent valve (RK) provided reagent line (8 ') with the first collecting piece (Ml) and that branches (10) between the reagent valve (RK) and the metering container (R) this reagent line (8') with the suction lines (1,2) connect 20 in the vicinity of their measuring points (MP) (FIG. 2). 11. The device according to claim 9 or 10 as a fire safety device, characterized in that the measuring points (MP) are arranged in rooms containing polyvinyl chloride, ammonia being used as the reagent gas, and in that the detector (D) is an ionization detector.