Safety device for boiler access

Abstract

A protection device for a boiler access point comprises a fan (10), a pressure sensor (20) and a check valve (30), wherein the fan (10) is connected, by means of an access point (5), to the surroundings in order to draw in ambient air, the pressure sensor (20) is connected downstream of the fan by means of a gas-tight connection (6), and a check valve (30) is connected downstream of the pressure sensor by means of an additional gas-tight connection (7). A control unit connected to the pressure sensor (20) has a data store, in which at least a lower first threshold value and a higher second threshold value for pressure values are stored. The existence of a malfunction can be detected by means of the control unit when a pressure sensor signal measured by the pressure sensor (20) and transferred to the control unit lies below the first threshold value or above the second threshold value.

Description

TECHNICAL FIELD

[0001] The present invention relates to a protective device for a boiler access through which an external device such as a boiler cleaning device is connected to a boiler through a boiler wall by introducing high-amplitude pressure waves. STATE OF THE ART

[0002] A device and method for generating high-amplitude pressure waves, particularly for boiler cleaning, is known from WO 2019 / 175736. The corresponding device has a discharge opening for the directed discharge of the gas pressure generated in a combustion chamber. This discharge opening usually ends in a hollow cylinder, which is guided through a boiler inlet in the boiler wall into the boiler to be cleaned. For the purpose of cleaning, the said high-amplitude pressure wave is generated in the device in a boiler, particularly one in operation, and introduced into the boiler volume.

[0003] The disadvantage here is that aggressive gases from the boiler can flow through the boiler inlet in the boiler wall into the hollow cylinder and through it to the drain opening and thus to the piston valve seat. These gases can impair the seal to the extent that the rapid pressure build-up, which is beneficial for boiler cleaning, is compromised by a deterioration in the quality of the valve seat.

[0004] DE 28 32 076 A1 discloses a protective device for a boiler access with the features of the preamble of claim 1. A similar protective device is known from CN 212 004 409 U.

[0005] CN 210 950 060 U discloses a hydraulic ultra-high-pressure safety valve with a check valve, wherein a pipeline access opening is formed in the valve seat. A pressure relief cavity is formed in the upper part of the valve body, with a drain hole in the side wall of the cavity. PRESENTATION OF THE INVENTION

[0006] Based on this prior art, the object of the invention is to provide a protective device for a boiler inlet which prevents such aggressive gases from flowing out of the boiler through the boiler inlet, in particular in a device for generating high-amplitude pressure waves with a hollow cylinder, to the discharge opening and thus to the piston valve seat, and which can be monitored for correct function with a simple control unit.

[0007] The object is achieved with a protective device for a boiler inlet comprising a fan and a check valve, wherein the fan is connected to the environment via an inlet for sucking in ambient air and wherein the check valve is connected downstream of the fan via a gas-tight connection, which check valve is then itself connected to the boiler inlet leading through a boiler wall via a pressure hose, wherein the check valve is installed in such a way that it blocks when there is a fluid pressure at the pressure hose if this pressure is greater than the fluid pressure at the fan, wherein an ambient outlet is provided in the gas-tight connection, in that a control unit with a data memory is connected to the pressure sensor, in which at least one lower first and one higher second threshold value for pressure values are stored.The control unit receives the pressure sensor signals measured by the pressure sensor and compares them with the stored threshold values. If the pressure sensor signal is below the first threshold, the presence of a malfunction in a malfunction range is determined.

[0008] If the pressure sensor signal measured by the pressure sensor and forwarded to the control unit exceeds the second threshold, the presence of a malfunction in an overpressure range is detected. A malfunction in the overpressure range corresponds to a closure of the check valve or a blockage of the pressure hose. If the control unit assigns the overpressure range to a closure of the check valve, a time interval is advantageously stored in the control unit so that a malfunction signal is only emitted if the pressure sensor signal in the overpressure range exceeds the specified time interval.When the device described here is used in a boiler cleaning facility by introducing pressure waves through the boiler inlet, this pressure increase can cause the check valve to close correspondingly for a time interval corresponding to the explosion shock, corresponding to a regular operating function, so that no malfunction occurs when this condition ends after a correspondingly predetermined time interval and the check valve opens again.

[0009] The aforementioned malfunction range can usually be divided into two different malfunction ranges, with a third, lower threshold for a pressure value than the first, preferably stored in the control unit. The control unit then divides the aforementioned malfunction range into two sub-ranges when a pressure sensor signal is measured by the pressure sensor and forwarded to it. If the pressure value is below the third threshold, the presence of a malfunction in the lower part of the malfunction range is determined as a fan failure or sensor failure; otherwise, a leak or a filter problem is assumed.In the drawing linking the pressure measurement with the volume flow, only the fan failure is shown for the malfunction in the lower part of the malfunction area, since a sensor failure shows the same measured value, but this does not correlate with the actual volume flow in the still existing air flow.

[0010] With a pressure sensor arranged in this otherwise gas-tight connection, the function of the fan and check valve can be easily monitored.

[0011] The term fan refers to all forms of fans such as axial fans and blowers that have an intake side and an exhaust side on which the air coming from the intake side is released in a compressed manner.

[0012] This makes it possible to protect a boiler inlet from the ambient air without access to an external gas supply, preventing fluids from it from reaching an external system that needs to be protected, such as a boiler cleaning device.

[0013] The ambient outlet can, for example, be a hole in the wall of the gas-tight connection.

[0014] Further embodiments are specified in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Preferred embodiments of the invention are described below with reference to the drawings, which are for illustrative purposes only and are not to be construed as limiting. In the drawings: Fig. 1 shows a schematic block diagram of a device according to an embodiment of the invention; Fig. 2 shows a fan characteristic curve for the operation of a device according to Fig. 1; and Fig. 3 shows sensor value ranges of a control unit for the operation of a device according to Fig. 1 . DESCRIPTION OF PREFERRED EMBODIMENTS

[0016] Fig. 1 shows a schematic block diagram of a device according to an embodiment of the invention. An intake pipe 5 is connected to a fan 10, which is installed in such a way that it compresses the ambient air of the boiler cleaning device drawn in from the intake pipe 5 and forwards it to the connection 6. The fan 10 can be a design that can build up an overpressure of 80-200 mbar in the further connection 6.

[0017] The connecting element 6 is designed as a hollow cylindrical element, which has a minimal influence on the airflow. An outlet 16 is provided on the side, which divides the airflow generated by the fan 10. Part of the airflow is released back into the environment through the outlet 16, and the remaining part is fed via this connection 6 to a pressure sensor 20.

[0018] The pressure sensor 20 can, in particular, detect a pressure difference between 0 and 1 bar. The lower limit is crucial, and the upper limit is advantageously chosen to be a value that cannot be reached by the fan 10.

[0019] Behind the pressure sensor 20, the compressed ambient air is fed into the interior of the aforementioned hollow cylinder via a check valve 30 and a pressure hose 8 in the area between the valve seat of the aforementioned device and the boiler wall. In other words, the supply via, for example, a pressure hose 8 takes place outside the boiler inlet, so that the ambient air introduced under pressure flows through this inlet and the boiler wall, counter to the gases in the boiler.

[0020] The only requirement is that the fan 10 is powerful enough to blow the ambient air into the boiler in this way, whereby the overpressure generated by the fan 10 must be higher than the pressure prevailing in the boiler.

[0021] When cleaning explosions occur, the check valve 30 prevents the entry of reaction gases from the cleaning explosion in the discharge opening in the boiler into the Fig. 1The device in question. Due to the sudden pressure buildup, a column of air will also remain in front of the check valve 30 in the supply line of the pressure hose 8.

[0022] The Fig. 2 shows a fan characteristic curve for the operation of a device according to Fig. 1. The x-axis shows the volume flow 50 in volume per unit of time, here between 0 and 1,000 liters / minute (0 and 1 m³ / min), while the y-axis shows the overpressure 60 measured by the pressure sensor 20, here between 0 and 140 millibars. Both the volume flow 60 and the overpressure 50 are given for one exemplary embodiment. In other applications, by using a fan 10 with a higher flow rate, a volume flow 60 of up to 10 or up to 100 m³ / min can be generated. The overpressure at which this volume flow 60 is applied to the boiler, ie at the boiler passage, depends on the geometry of the connections and the geometry of the orifice plate 16. This pressure can be up to 1 bar, but generally an overpressure of up to 200 or up to 500 millibars is sufficient.

[0023] Reference numeral 51 represents the fan characteristic curve of the free-running fan 10, i.e. the generated overpressure at a corresponding air volume per unit of time. By installing the fan 10 in the device according to Fig. 1 different operating modes arise.

[0024] Reference numeral 61 designates the fan characteristic point at which the check valve 30 is open and thus, at the beginning of area 6, allows a volume flow 60 of 470 liters per minute directly at the fan, whereby an overpressure of approximately 80 millibars would be detectable by a pressure sensor directly behind the fan 10. In the area upstream of the check valve 30, however, only a lower volume flow 60 of approximately 220 liters / minute arrives, since a correspondingly remaining portion escapes from the connection through the opening or orifice 16. Since the pressure sensor measures the same air column, the pressure with the check valve 30 open is also approximately 80 millibars.

[0025] When the cleaning device is in operation, pressure waves are triggered which then find their way back into the pressure hose 8 in the boiler and on the way from the cleaning device to the boiler, causing the check valve 30 to close.

[0026] When the check valve 30 is now closed, a higher pressure measured by the pressure sensor 20 results, resulting in the characteristic point at the fan 62, which corresponds to a flow of 320 units per minute through the fan 10, since all of the ambient air being conveyed is now recirculated to the outside through the orifice plate 16. This leads to a pressure increase to approximately 110 millibars.

[0027] However, this corresponds directly to a reduction in the volume flow from approximately 220 liters / minute according to point 71 to a volume flow 72 of 0 liters / minute with the check valve 30 closed.

[0028] In other words, the decrease in the actual volume flow in pressure hose 8 changes from the value at point 71 to point 72, as shown by arrow 75. This is offset by the decrease in volume flow at pressure sensor 20 between points 61 and 62, as shown by arrow 65, with the pressure increasing from 80 millibars to just over 100 millibars. Here, too, the actual pressure at check valve 30 is equal to this measured pressure.

[0029] The orifice plate 16 as the ambient outlet can, for example, have a diameter between 3 mm and 7.5 mm. However, the orifice plate 16 can also have a diameter of 1 mm to 2 cm, depending on the desired discharge at a particular flow rate, and the desired pressure increase in front of the check valve 30 when the latter is closed. The choice of the orifice plate diameter and the type and length of the connection to the ambient also depend on the desired overpressure and volume flow. When using a control unit, the basic arrangement of the measuring points is essential. Fig.3 for their evaluation, as will be described below.

[0030] In the Fig. 2Three pressure threshold values 112, 113 and 114 of 10, 65 and 95 millibar are shown schematically and by way of example, which illustrate the pressure values that will be used when explaining the function of the control unit with the working and malfunction ranges.

[0031] The device according to Fig. 1 advantageously has a control unit with which the fan 10 can be controlled in its performance and in which the sensor values of the pressure sensor 20 can be converted directly into monitoring values, so that the result provides a direct indication of the function of the device.

[0032] The Fig. 3 shows sensor value ranges of a pressure sensor 20, which in a control unit have threshold values for the operation of a device according to Fig. 1for a display or, for example, stopping the cleaning device or the boiler function. The sensor value ranges extend according to the arrow 100 from 0 to, for example, 1 bar. The inventors have found that the measured values of the pressure sensor 20 can be converted into direct monitoring values. With a pressure value 101 of 0 bar up to a pressure value 102 of, for example, 20 mbar as the first threshold value 112 in Fig. 2 It is assumed that the pressure sensor or the fan has failed, so that there is a self-diagnosis of the device, which accordingly indicates a malfunction area 140.

[0033] Between the upper limit value 102 of the malfunction range 140 and the next higher limit value 103 of, for example, 90 mbar, a filter problem may be present if such an optional filter is installed in connections 6 or 7. This value range 130 characterizes either a filter problem or a leakage of connections 6 or 7. The upper limit value 103 is defined as the pressure threshold value 113 in the Fig. 2 A distinction between pressure thresholds 112 and 113 is useful for troubleshooting; for monitoring function, the higher of the two thresholds is sufficient.

[0034] At a pressure in the range between the value 103 and the pressure value 104, the operating range 120 is present, which corresponds to the normal value of the system. The operating range refers to the operation of the boiler and not to the rest periods of the boiler function when cleaning is required. If this upper limit 104 is exceeded, an overpressure range 110 is reached, which corresponds to a blockage of the system, so that no gas flow through the Fig. 1 shown connections 5, 6, 7 and 8, so that there is no protective function by the device, usually triggered by an activation of the check valve 30. This can correspond to a correct function of the device for a short time interval if an explosion shock is triggered in a boiler cleaning device of the type mentioned at the beginning, which of course also enters the pressure hose 8 in front of the boiler wall if necessary.

[0035] Thus, by means of a simple pressure measurement with a differential pressure sensor 20, the operating state of the ventilation system can be monitored by a selection of monitoring areas 110, 120, and jointly or separately 130 and 140 via the above-mentioned threshold values 103, 104 and, if applicable, 102.

[0036] By using ambient air as the supply, the supply of protective gases from corresponding gas pressure vessels for industrial gases can be largely dispensed with. LIST OF REFERENCE SYMBOLS 5 intake pipe Check valve (open) 6 Connection 72 Characteristic point at 7 Connection Check valve (closed) 8 pressure hose 75 Change in measured value on 10 fan Check valve 16 Outlet / aperture 100 Pressure range (ascending 20 pressure sensor Values) 30 Check valve 101 Pressure value 0 bar 50 Volume flow 102 Pressure value third threshold 51 Fan characteristic curve free-running 103 Pressure value first threshold 60 Overpressure 104 Pressure value second threshold 61 Characteristic point on the fan / 110 Overpressure range Operating point open 112 Pressure level third threshold Check valve 113 Pressure level first threshold 62 Characteristic point on the fan / 114 Pressure level second Operating point closed Threshold Check valve 120 Workspace 63 Characteristic point at failure 130 Malfunction area fan Filter problem or leak 64 Characteristic point at leakage 140 Malfunction area or filter problem Sensor failure or 65 Change in measured value on Fan failure fan 71 Characteristic point at

Claims

1. A protective device for a boiler access point, comprising a fan (10) and a check valve (30), wherein the fan (10) is connected via an access (5) to the environment for drawing in ambient air, wherein the check valve (30) is connected downstream of the fan (10) via a gas-tight connection (6, 7), wherein the check valve (30) is connected via a pressure hose (8) to the boiler access point leading through a boiler wall, wherein the check valve (30) closes at a fluid pressure present at the pressure hose (8) if this is greater than the fluid pressure present at the fan (10), wherein the gas-tight connection (6, 7) has an ambient outlet (16), characterized in that a control unit connected to the pressure sensor (20) is provided with a data memory in which at least a lower first (103) and a higher second (104) threshold value for pressure values are stored, wherein the presence of a malfunction in a malfunction range (130, 140) is detected by the control unit when the pressure sensor signal measured by the pressure sensor (20) and forwarded to it is below the first threshold value (103) and wherein the presence of a malfunction in an overpressure range (110) is detected by the control unit when the pressure sensor signal measured by the pressure sensor (20) and forwarded to it is above the second threshold value (104).

2. The protective device according to claim 1, wherein the overpressure range (110) is assigned by the control unit to a closure of the check valve (30), a time interval being stored in the control unit, so that a malfunction signal is only emitted by the pressure sensor signal in the overpressure range (110) if the predetermined time interval is exceeded.

3. The protective device according to claim 1 or 2, wherein a third threshold value (102) for a pressure value, which is lower than the first threshold value (103), is stored in the control unit, wherein the control unit indicates the presence of a malfunction in the malfunction area (130, 140) by distinguishing between leakage or sensor failure or fan failure in the case of a pressure sensor signal below the third threshold value (102) measured by the pressure sensor (20) and forwarded to it.

4. The protective device according to any one of claims 1 to 3, wherein the ambient outlet (16) is a bore in the wall of the gas-tight connection (6, 7).

5. The protective device according to any one of claims 1 to 4, wherein the device further comprises a pressure sensor (20) arranged in the gas-tight connection (6, 7).

6. The protective device according to any one of claims 1 to 5, wherein the ambient outlet (16) is arranged in the gas-tight connection (6) between the fan (10) and the pressure sensor (20).

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