Gas control unit, gas control valve and system comprising such a gas control valve for error-free pressure control in a gas heater

Abstract

The invention relates to a gas control unit (10) for the fail-safe control of a gas, in particular in a gas heater (1) or a gas burner, wherein the gas control unit (10) has a communication interface (15), a first sensor assembly (11) and a second sensor assembly (12), wherein the first sensor assembly (11) is designed to acquire measured values ​​from which a signed first differential pressure (p11) between a process pressure (p1) of the gas and a reference pressure (p0) can be determined, and wherein the second sensor assembly (12) is designed to acquire measured values ​​from which a signed second differential pressure (p12) between the reference pressure (p0) and the process pressure (p1) can be determined, such that the signed first differential pressure (p11) and the signed second differential pressure (p12) are signed, mutually inverse differential pressures (p11, p12).and wherein the communication interface (15) is designed to send the mutually inverse differential pressures (p11, p12) and / or the measured values ​​to an external receiver.,

Description

[0001] The invention relates to a gas control unit, a gas control valve with such a gas control unit and a system with such a gas control valve for the fail-safe control of a gas on or in a gas heating device, in particular a gas boiler, as well as a method for the plausibility check of differential pressures which were detected by such a gas control unit, such a gas control valve and / or such a system.

[0002] Gas control valves for regulating a gas, and in particular for pressure control, are known in the prior art and, for example, from document DE 10 2018 102 866 A1. In gas heaters or gas burners in which a gas-air mixture is burned, a gas control valve is used upstream of a mixing device, in which gas is mixed with air to form the gas-air mixture, and further upstream of a main flow restrictor to adjust or regulate the gas flow, in particular the volume or mass flow, flowing into the mixing device.

[0003] It is often provided that the measured values ​​of a single differential pressure sensor are used for pressure control, which determines the pressure difference or the differential pressure between a process pressure of the gas, usually the pressure of the gas outflow or downstream of the gas control valve or the pressure of the gas at a first measuring point between the gas control valve and the main flow throttle, and a reference pressure, usually the pressure of the air in the vicinity of the pressure control valve, which flows into the mixing device.

[0004] Based on the measured differential pressure, the gas control valve or an actuator that determines the flow through the gas control valve is adjusted to a setpoint of 0 Pa by means of an actuator, for example a motor, usually with a so-called zero pressure control.

[0005] The fundamental problem here is that such gas control valves or gas control units for controlling such gas control valves are often not designed to be fail-safe. Even if they are designed to be fail-safe, the high costs associated with specially designed software, additional hardware, duplicate components, and necessary certifications are incurred, which is correspondingly disadvantageous.

[0006] The invention is therefore based on the object of overcoming the aforementioned disadvantages and of providing a gas control unit or a gas control valve comprising such a gas control unit, with which a fail-safe operation of a gas heater in particular is possible.

[0007] This problem is solved by the combination of features according to patent claim 1.

[0008] According to the invention, a gas control unit is therefore proposed for the fail-safe control of a gas, in particular in a gas heater or a gas burner, furthermore in particular in a gas boiler. For this purpose, the gas control unit has a communication interface, a first sensor module and a second sensor module. The first sensor module is designed to record measured values ​​from which a signed first differential pressure between a process pressure of the gas and a reference pressure can be determined or which is such a first differential pressure. Furthermore, the second sensor module is designed to record measured values ​​from which a signed second differential pressure between the reference pressure and the process pressure can be determined or which is the second differential pressure. The measured values ​​orDifferential pressures are determined by means of the sensor modules such that the signed first differential pressure and the signed second differential pressure are signed, mutually inverse differential pressures. Furthermore, the invention provides that the communication interface is configured to transmit the mutually inverse differential pressures and / or the measured values ​​to an external receiver, ie, to a receiver outside the gas control unit.

[0009] Because the differential pressure, on which the control of the gas is preferably based, is recorded not only twice but inversely to each other, the sign is available as additional information that can be evaluated in addition to the respective differential pressures. In addition, the gas control unit itself does not have to check the values ​​in a fail-safe manner, since these can be provided to an external receiver via the communication interface, for example the control unit, as explained below.

[0010] For clarification, it should be noted that the process pressure applied to or determinable with the first sensor assembly is the process pressure or corresponds to the process pressure applied to or determinable with the second sensor assembly. The same applies to the reference pressure. Neglecting measurement errors and tolerances, the first differential pressure and the second differential pressure are therefore equal in magnitude and, accordingly, inverse.

[0011] Although it can be provided that each sensor module is a differential pressure sensor, which can therefore directly detect the respective differential pressure, it can also be provided that each sensor module is a mass flow sensor, which can therefore detect the differential pressure via the mass flow, or that a sensor module is formed from two or more individual sensors, each of which can determine a pressure, so that the differential pressure can be determined from the individual pressures. Such sensors can be pressure or absolute pressure sensors, but also, for example, mass flow sensors.In principle, the different sensors can also be mixed, so that, for example, the first sensor assembly is a differential pressure sensor and the second sensor assembly has two sensors, of which a first sensor is a pressure sensor and a second sensor is a mass flow sensor.

[0012] Accordingly, the first sensor assembly can be a first differential pressure or mass flow sensor or can comprise at least two sensors, each configured as a pressure sensor or a mass flow sensor. Furthermore, the second sensor assembly can be a second differential pressure or mass flow sensor or can comprise at least two sensors, each configured as a pressure sensor or a mass flow sensor.

[0013] In general, the gas control unit preferably has exactly one first and exactly one second sensor assembly, although alternatively, more than two sensor assemblies may be provided. If more than two sensor assemblies are provided, they are preferably grouped in pairs, and accordingly, several pairs of sensor assemblies are provided.

[0014] Based on two differential pressure sensors, an advantageous embodiment provides that the first sensor assembly is a first differential pressure sensor and the second sensor assembly is a second differential pressure sensor. The differential pressure sensors each have a first pressure input and a second pressure input and are designed to determine a differential pressure by subtracting a pressure present at the second pressure input from a pressure present at the first pressure input. If the pressure at the second pressure input is higher than the pressure at the first pressure input, a negative value results for the differential pressure determined by this differential pressure sensor. If the pressure at the second pressure input is lower than the pressure at the first pressure input, a positive value results for the differential pressure determined by this differential pressure sensor.It is provided that the process pressure is applied to the first pressure input of the first differential pressure sensor, and a reference pressure is applied to the second pressure input of the first differential pressure sensor. Conversely, it is further provided that the reference pressure is applied to the first pressure input of the second differential pressure sensor, and the process pressure is applied to the second pressure input of the second differential pressure sensor, so that the differential pressures determined by the two differential pressure sensors are signed and inverse to each other, or have an opposite sign if the differential pressures are not equal to 0 Pa.

[0015] Alternatively, it is provided that the same pressure, which can be referred to as process pressure, is present or can be applied to the first pressure input of the first differential pressure sensor and to the second pressure input of the second differential pressure sensor, and the same pressure, which can be referred to as reference pressure, is present or can be applied to the second pressure input of the first differential pressure sensor and to the first pressure input of the second differential pressure sensor, so that the differential pressures determined by the two differential pressure sensors are inverse to one another, ie the pressure values ​​representing the respective differential pressure have an opposite sign to one another.

[0016] If the sensor modules are each a differential pressure sensor, each having two pressure inputs, a separate pressure channel can be provided for connecting or applying the pressures (process pressure, reference pressure) to the pressure inputs, so that from a process pressure measuring point a pressure channel can lead to the first pressure input of the first differential pressure sensor and to the second pressure input of the second differential pressure sensor and / or from a reference pressure measuring point a pressure channel can lead to the second pressure input of the first differential pressure sensor and to the first pressure input of the second differential pressure sensor.

[0017] Alternatively or additionally, the pressure channels leading from the respective measuring points to the differential pressure sensors can also be formed integrally with one another, at least in sections, so that a single pressure channel can lead from the process pressure measuring point, at least in sections, to the first pressure input of the first differential pressure sensor and to the second pressure input of the second differential pressure sensor and / or from a reference pressure measuring point, at least in sections, a single pressure channel can lead to the second pressure input of the first differential pressure sensor and to the first pressure input of the second differential pressure sensor.

[0018] If a sensor assembly with pressure or absolute pressure sensors is assumed, one pressure sensor can essentially be equated with one pressure input of a differential pressure sensor.

[0019] The process pressure is preferably a gas pressure of a gas regulated by the gas control unit or the gas pressure of a gas flowing through the gas burner / gas heater and in particular the gas boiler. With regard to a gas heater or a gas burner, the process pressure measuring point is preferably located on the outflow side of the gas control valve, but upstream of any mixing device or upstream of any main flow throttle, so that the process pressure corresponds to the gas pressure of a fuel gas on the outflow side of the gas control valve. If the process pressure measuring point is upstream of the mixing device, the process pressure can also be referred to as the suction pressure. If a Venturi mixer is used as the mixing device, the process pressure can be referred to as the Venturi suction pressure.

[0020] The reference pressure can also preferably be an ambient or air pressure in an environment of the gas control unit or in an environment of the gas control valve or system mentioned below, so that the reference pressure measuring point is arranged accordingly in or on the respective environment. Furthermore, the reference pressure preferably corresponds to the pressure or air pressure at an air inlet of the mixing device. In principle, however, other reference pressures are also possible, so the reference pressure does not necessarily have to be the ambient pressure or the air pressure at the air inlet of the mixing device.

[0021] Furthermore, it is clarified that the sensor modules can determine the respective measured values ​​or the respective differential pressure within a mostly known accuracy or tolerance, so that the differential pressures in reality and in border areas (close to or at 0 Pa) do not necessarily have to have an opposite sign and there may be a deviation in the amounts of the differential pressures determined with the sensor modules.

[0022] Based on the process pressure p1 and the reference pressure p0, the first differential pressure p11 of the first sensor assembly is p 11 = p 1 − p 0 and for the second differential pressure p12 of the second sensor assembly p 12 = p 0 − p 1

[0023] If an ambient pressure of 1 bar is assumed for the reference pressure p0 and a suction pressure of 0.02 bar for the process pressure, the result is, for example, p 11 = p 1 − p 0 = 0 , 02 bar − 1 , 0 bar = − 0 , 98 bar p 12 = p 0 − p 1 = 1 , 0 bar − 0 , 02 bar = + 0 , 98 bar

[0024] Since - as explained below - it is known and stored, for example, in the form of target or threshold values, that a negative value must be set for the first differential pressure p11 and a positive value that is (essentially) identical in magnitude for the second differential pressure p12, it can be concluded whether the sensor assemblies or the differential pressure or mass flow sensors are correctly connected, are working correctly and whether the first differential pressure p11 assigned to the first sensor assembly is actually the differential pressure determined by the first sensor assembly or whether the second differential pressure p12 assigned to the second sensor assembly is actually the differential pressure determined by the second sensor assembly.

[0025] The pressure values ​​are merely the differential pressures represented as signed values, so that the first signed pressure value, which represents the first differential pressure p11 that can be determined by means of the first sensor assembly, can be referred to as pressure value p11 and the second signed pressure value, which represents the second differential pressure p12 that can be determined by means of the second sensor assembly, can be referred to as pressure value p12.

[0026] An advantageous development of the proposed gas control unit provides that it further comprises control electronics that are signal-connected to the first sensor assembly and the second sensor assembly. Furthermore, such a variant provides that the control electronics are configured to detect the mutually inverse differential pressures, in particular as a respective signed pressure value, or to determine them from the measured values ​​detected by the sensor assemblies.

[0027] Furthermore, a similarly advantageous embodiment of the gas control unit provides for it to have an actuator interface for controlling an actuator, wherein the actuator can be, in particular, a stepper motor. The actuator interface is connected to the control electronics for signaling purposes or is formed integrally with the control electronics. The actuator interface can be understood as a pure interface for connecting the actuator or, alternatively, as actuator control electronics.

[0028] Furthermore, the communication interface, which can also be understood as a pure interface or as communication electronics, can be connected to the control electronics for signaling purposes or be designed integrally with the control electronics. As already explained, the communication interface is designed to send the signed pressure values ​​to an external receiver. However, it can also be provided that the communication interface is also designed to receive control signals.

[0029] Although the sending and optional receiving is preferably done by wire and, for example, via a BUS system, the communication interface can alternatively be designed for optical signal transmission or for wireless sending and receiving, so that data can be transmitted, for example, via radio.

[0030] A further aspect of the invention relates to a gas control valve for fail-safe control of a gas and in particular pressure control or zero pressure control in a gas heater or a gas burner, in particular a gas boiler, wherein said valve comprises the gas control unit proposed according to the invention. In addition to such a gas control unit, the gas control valve further comprises an actuator for adjusting a flow rate of a gas flowing from an inflow side to an outflow side of the gas control valve, wherein the gas is preferably a fuel gas to be burned in the gas burner or the gas heater. The process pressure here is the pressure of the gas on the outflow side of the gas control valve or the pressure in the gas control valve on the outflow side of the actuator.

[0031] The flow of gas through the gas control valve can also be referred to as gas flow, whereby the gas control valve is intended to regulate in particular the volume flow and / or the mass flow of the gas.

[0032] It should also be pointed out that the gas control valve or actuator and gas control unit are not just a system of several components connected to one another, for example by cables, but they preferably form an integral unit.

[0033] Furthermore, the reference pressure is, in particular, an ambient pressure at the gas control unit and / or the gas control valve, whereby the reference pressure can also be measured at other points or correspond to the ambient pressure at other points. For example, the reference pressure can also correspond to the ambient pressure or the air pressure at an air inlet of the mixing device of the gas burner or gas heater.

[0034] The gas control valve can also have an actuator that is signal-connected to the actuator interface of the gas control unit or an actuator controlled via the actuator interface, which actuator is preferably a stepper motor. The actuator or stepper motor is designed to adjust the control element to adjust the flow rate and thereby regulate the volume and / or mass flow of the gas through the gas control valve.

[0035] Preferably, the control electronics of such a gas control valve are also designed to adjust the actuator for adjusting the flow rate by controlling the actuator or stepper motor until at least one of the differential pressures or measured values ​​corresponds to a predetermined value and, for example, at least one of the differential pressures is 0 Pa, so that zero-pressure control can be implemented directly by the control electronics or the gas control valve. The predetermined value can be stored in the control electronics or specified or transmitted to the control electronics via the communication interface. For example, the predetermined value can be transmitted to the control electronics via the communication interface from a control unit explained below.

[0036] A further aspect of the invention relates to a system for the fail-safe control of a gas in a gas heater or a gas burner, in particular a gas boiler. The control is further preferably a pressure or zero-pressure control. The system comprises a control unit for controlling combustion and a gas control valve proposed according to the invention or at least one gas control unit proposed according to the invention. According to the proposed system, the control unit, as an external receiver, is connected to the communication interface of the gas control unit and is designed to receive and process the signed and mutually inverse differential pressures and, additionally or alternatively, to send control signals to the gas control unit, its control electronics, or its communication interface.

[0037] The control unit can assume fail-safe process monitoring in the gas heater or gas burner and, for this purpose, controls individual components of the gas heater / gas burner. In particular, the gas control unit can be switched and / or controlled to various operating modes by the control unit, particularly via the aforementioned control signals.

[0038] Preferably, such a control unit is a Class C safety system certified according to IEC EN 60730 or EN 298, so that safe operation of the gas heater / gas burner is possible through the software measures required by Class C and a fail-safe or fault-detecting hardware circuit.

[0039] However, this is not the case for the gas control valve or gas control unit. Gas control valves and gas control units are preferably neither certified according to the aforementioned standards nor fail-safe, which accordingly reduces costs.

[0040] However, the entire system or system comprising the gas control unit / valve and control unit can be operated in a fail-safe manner by the measures provided according to the invention.

[0041] Basically, starting from a system with two differential pressure or mass flow sensors, it cannot be ruled out that the first differential pressure determined by the first differential pressure or mass flow sensor and the second differential pressure determined by the second differential pressure or mass flow sensor are swapped during transmission from the differential pressure or mass flow sensors to the control unit, whereby the control unit conventionally has no possibility of checking the plausibility of the differential pressures or pressure values, ie of checking for certain possible errors.

[0042] Because the differential pressures can be determined with a sign according to the invention, the control unit can derive from the sign whether the differential pressures are assigned to the correct sensor modules, particularly in the case of a differential pressure not equal to 0 Pa.

[0043] Accordingly, a variant of the system provides that the control unit is designed to check the plausibility of the mutually inverse differential pressures by comparing the differential pressures with setpoint values ​​or threshold values ​​stored in the control unit.

[0044] The target or threshold values ​​can also simply correspond to a respective sign, so that it is easy to query whether the signed differential pressures - regardless of their actual value - have an expected or predetermined sign.

[0045] For example - and as explained below - the differential pressure can be changed to a value other than 0 Pa by appropriately controlling the actuator or another component of the gas heater / gas burner, which results in two inverse pressure values ​​or differential pressures, one of which is positive and the other negative, and which - neglecting any measurement tolerances and taking into account a predetermined tolerance - are equal in their magnitude. Since the control unit stores in the form of threshold or setpoint values ​​whether the first pressure value should be positive or negative and whether the second pressure value should be positive or negative, it can be determined from this, i.e.It must be checked whether the first pressure value corresponds to the pressure value of the first sensor module and the second pressure value corresponds to the pressure value of the second sensor module or whether these were transmitted incorrectly and, in particular, swapped and are assigned to the wrong sensor module, so that the system can then display an error, be switched off or switched to a safe mode.

[0046] Additionally or alternatively, the control unit can be configured to check the plausibility of the mutually inverse differential pressures by comparing the absolute values ​​of the differential pressures. This allows conclusions to be drawn – taking a tolerance into account – as to whether the sensor modules are delivering correct measured values ​​or differential pressures. If, for example, one of the differential pressures deviates (in absolute value) from the other differential pressure by more than a predetermined tolerance, one of the sensor modules is defective or the transmission is faulty, so the system can then indicate an error, be shut down, or switch to a safe mode.

[0047] Additionally or alternatively, it can further be provided that the control unit is designed to check the plausibility of the application of the process pressure and the reference pressure at the sensor assemblies. If, for example, a differential pressure sensor is assumed as the sensor assembly, the plausibility of the application of the process pressure and the reference pressure at the first pressure inputs and the second pressure inputs can be checked. If the pressure values ​​are, for example, the same in terms of their signs and - within a tolerance - also in terms of their magnitudes, the same pressure is present at both first inputs of the differential pressure sensors, i.e. process pressure or reference pressure, and the same pressure is also present at the two second inputs of the differential pressure sensors, i.e. reference pressure or process pressure, so that the system can in turn indicate an error, be switched off or switched to a safe mode.

[0048] Furthermore, one aspect of the invention relates to a method for checking the plausibility of differential pressures which can be or have been detected with a system for fail-safe pressure control proposed according to the invention and / or a pressure control valve proposed according to the invention and / or a pressure control unit proposed according to the invention.

[0049] It is advantageous if a differential pressure other than 0 Pa is present for plausibility check, ie for checking the differential pressures for possible errors, since measurement tolerances then have no or at least no significant influence on the plausibility check.

[0050] To achieve this, the actuator of the gas control valve or a safety valve provided upstream of the gas control valve is controlled, in particular by the control unit, to change the process pressure, so that the signed pressure values ​​change inversely to each other due to the change in the process pressure.

[0051] If the safety valve is closed, the process pressure corresponds in particular to a suction pressure, which is generated by a fan arranged downstream of the gas control valve and / or by a mixing device, particularly designed as a Venturi mixer. Since the safety valve is closed, in particular, during a burner ventilation before or after burner operation, for example, during a pre-purge phase and / or during a post-purge phase of the gas heater / gas burner, the plausibility check can be performed during ventilation and in particular during the pre-purge or post-purge phase.

[0052] If the flow through the safety valve is varied to change the process pressure, even a small differential pressure may be sufficient for plausibility testing. Such a change in process pressure can occur during operation of the gas heater / gas burner, i.e., after the pre-purge phase or during burner operation.

[0053] Preferably, it is provided in each case that the change in the process pressure exceeds at least a predetermined measurement tolerance of the sensor assemblies, so that measurement tolerances can be essentially neglected for the plausibility check.

[0054] The signed differential pressures determined by the sensor modules after the change in the process pressure are then compared with a respective setpoint or threshold value.

[0055] As already explained, the comparison makes it plausible whether a first differential pressure of the two signed differential pressures, which is assigned to the first sensor assembly, is the differential pressure determined by the first sensor assembly, and / or whether a second differential pressure of the two signed differential pressures, which is assigned to the second sensor assembly, is the differential pressure determined by the second sensor assembly, and / or whether the process pressure is present at the first pressure input of the first sensor assembly designed as a differential pressure sensor or at a first pressure sensor of a sensor assembly having at least one pressure sensor and / or whether the reference pressure is present at the second pressure input of the first sensor assembly designed as a differential pressure sensor or at a second pressure sensor of a sensor assembly having at least one pressure sensor and / or whether the reference pressure is present at the first pressure input of the second sensor assembly designed as a differential pressure sensor orwhether the reference pressure is present at a first pressure sensor of a sensor assembly comprising at least one pressure sensor and / or whether the process pressure is present at the second pressure input of the second sensor assembly configured as a differential pressure sensor or at a second pressure sensor of a sensor assembly comprising at least one pressure sensor.

[0056] If it is determined that the signed differential pressures are not plausible, ie they do not have the expected sign or magnitude, the system can indicate an error, be shut down or switched to a safe mode.

[0057] Accordingly, a further development of the method provides that an error is detected and output if the signed differential pressures do not correspond to the respective target values ​​or do not reach the respective threshold values.

[0058] The features disclosed above can be combined as desired, as long as this is technically possible and they do not contradict each other.

[0059] Other advantageous developments of the invention are characterized in the subclaims or are presented in more detail below, together with the description of the preferred embodiment of the invention, with reference to the figures. They show: Fig. 1 shows a schematic block diagram of a gas heater; Fig. 2 shows a schematic block diagram of a gas control valve; Fig. 3 shows a first pressure diagram for plausibility check in a first operating mode; Fig. 4 shows a second pressure diagram for plausibility check in a second operating mode.

[0060] The figures are schematic examples. Identical reference numerals in the figures indicate identical functional and / or structural features.

[0061] In Figure 1a section or part of a gas heating device 1, in particular a gas boiler, is shown schematically and by way of example, wherein the gas control valve 2 shown in Figure 2 and the gas control unit 10 contained therein each represent the gas control valve 2 and the gas control unit 10 according to Figure 1 However, they can also be considered independent of the gas heater 1 or installed in other systems or devices. Although the components and functions of the Figures 1 and 2 described together here, in particular the Figure 2 Also disclosed independently of the exemplary embodiment according to Figure 1 be considered.

[0062] Figure 1schematically shows a part or section of a gas heater 1 and, more precisely, the schematic structure of a gas-air system of a gas heater 1, wherein a Venturi mixer is shown as the mixing device 7, into which air is sucked from the environment by a fan 8 through an air inlet L at an air pressure p0. In the mixing device 7, the inflowing air and a fuel (gas) flowing in through the fuel supply G are mixed to form a gas-air mixture.

[0063] The gas flowing in from the fuel supply G flows to the mixing device 7 through a safety valve 5 with an actuator 40 adjustable by an actuator 50, a gas control valve 2 with a valve or actuator 30 designed, for example, as a proportional valve, and a main flow throttle 6.

[0064] The safety valve 5 or its actuator 40 preferably has a pass-through position and a blocking position, between which the actuator 50 can switch. The flow of fuel or gas is permitted in the pass-through position and blocked in the blocking position. The safety valve 5 can additionally or alternatively also be manually operable.

[0065] The gas control valve 2 is designed to control the volume or mass flow of the gas, so that the gas or the flow of the gas through the gas control valve 2 to the mixing device 7 can be adjusted or controlled.

[0066] By adjusting or regulating the flow of the gas with the gas control valve 2 and by a main flow throttle 6 provided between the gas control valve 4 and the mixing device 7, the mixing ratio of the gas-air mixture in the mixing device 7 can thus be regulated or adjusted.

[0067] The gas-air mixture is further conveyed by the blower 8 into a burner 9 or its combustion chamber, in which the combustion of the gas-air mixture takes place.

[0068] To regulate the gas flow or the flow through the gas control valve 2, the latter has an actuator 30 - as shown, for example, designed as a proportional valve - whose position can be adjusted by an actuator 20 designed in particular as a stepper motor, as well as a gas control unit 10.

[0069] The gas control unit 10 itself is not designed to be fail-safe, but in addition to a control electronics unit 13, an actuator interface 14 connected to the control electronics unit 13 for signaling purposes, and a communication interface 15 connected to the control electronics unit 13 for signaling purposes, it comprises two sensor assemblies 11, 12, each of which is designed as a differential pressure sensor 11, 12.

[0070] It is essential for the illustrated embodiment, on the one hand, that the respective differential pressure p11, p12 is detected by the respective differential pressure sensor 11, 12 not merely as an absolute value (i.e., unsigned), but rather as signed pressure values ​​or signed differential pressures. The differential pressures are obtained, for example, by subtracting a pressure applied to the respective second pressure input 11B, 12B from a pressure applied to the respective first pressure input 11A, 12A, so that—depending on the respective pressures present—signed pressure values ​​can result for the differential pressures.

[0071] On the other hand, it is essential for the illustrated embodiment that the same pressure, which can be referred to as process pressure p1, is present or can be applied to the first pressure input 11A of the first differential pressure sensor 11 and to the second pressure input 12B of the second differential pressure sensor 12, and that the same pressure, which can be referred to as reference pressure p0, is present or can be applied to the second pressure input 11B of the first differential pressure sensor 11 and to the first pressure input 12A of the second differential pressure sensor 12, so that the differential pressures p11, p12 determined by the two differential pressure sensors 11, 12 are inverse to one another.

[0072] As in the Figures 1 and 2As shown, it is provided here that a separate pressure channel leads to the first pressure inlet 11A of the first differential pressure sensor 11 and to the second pressure inlet 12B of the second differential pressure sensor 12 to the measuring point of the process pressure, whereas the pressure channels from the second pressure inlet 11B of the first differential pressure sensor 11 and from the first pressure inlet 12A of the second differential pressure sensor 12 to the measuring point of the reference pressure are formed integrally with one another in sections.

[0073] The process pressure p1 is a gas pressure in the gas control valve 2 on the downstream or outflow side of the actuator 30 and the reference pressure p0 is an air pressure at the gas control valve 2 or at the air inlet L, which, however, can deviate from the ambient pressure p∞.

[0074] Although the gas control valve 2 itself is not designed to be fail-safe, the gas heater 1 must be capable of fail-safe operation. For this purpose, the differential pressures p0, p1 are transmitted from the gas control valve 2 via the communication interface 15 to a control unit 3, which can use these values ​​to check whether a measurement error has occurred. However, in the prior art, such control units 3 cannot verify whether the differential pressures assigned to the first differential pressure sensor 11 and the second differential pressure sensor 12 were actually measured by the respective differential pressure sensor 11, 12.

[0075] In order to form a system 4 comprising control unit 3 and gas control valve 2 which is fail-safe overall, the signed pressure values ​​are transmitted from the gas control valve 2 or via the communication interface 15 of the gas control unit 10 to the control unit 3.

[0076] Since zero-pressure control is usually desired during normal combustion operation of gas heater 1, the process pressure p1 essentially corresponds to the reference pressure p0, so that the differential pressures p11, p12 fluctuate around 0 (e.g., 0 Pa or 0 bar). Due to measurement inaccuracies, the respective sign usually cannot reliably indicate an error.

[0077] Therefore, the control unit 3 is designed to check the differential pressures p11, p12 for plausibility in certain operating modes or within the framework of certain procedures, ie to check for errors, whereby a pressure diagram is generated in each case according to the Figures 3 and 4 results.

[0078] Since the plausibility check cannot usually be carried out reliably during normal combustion or burner operation, according to a first process variant - the pressure curve in Figure 3shown - it is provided that the plausibility check is carried out during or parallel to ventilation and in particular in a pre-purge phase, in which the burner 9 or its combustion chamber is purged or ventilated with air. For this purpose, the safety valve 5 and / or the gas control valve 2 is controlled to completely block a gas flow or a gas flow to the mixing device 7 during ventilation and here in the pre-purge phase, wherein the fan 8 continues to suck in air, so that a suction pressure of the fan 8 is established at the process pressure measuring point. As an alternative to the pre-purge phase, the described method can also be carried out in a post-purge phase.

[0079] The resulting pressure curve is in Figure 3shown, wherein at time T1 the fan 8 is switched on with the safety valve 5 and / or gas control valve 2 closed and at time T2 the closed valves (safety valve 5 and / or gas control valve 2) are opened to allow flow.

[0080] Based on the exemplary course, during the aeration and here, for example, in the pre-purge phase (in particular between the times T1 and T2), a signed maximum pressure value of - 4 is established for the first differential pressure p11 and a signed maximum pressure value of + 4 is established for the second differential pressure, whereby these are represented and assumed to be unitless in the present case.

[0081] Since it is known that p11 is the result of p1 - p0 and p12 is the result of p0 - p1, and since the ventilation results in a value for p1 lower than p0, it can be determined directly from the respective sign whether the values ​​transmitted to the control unit 3 are correctly assigned to the differential pressure sensors. The relationships and necessary assumptions do not necessarily have to be stored in the control unit 3. For example, it is sufficient to assume an error if p11 is > 0 during ventilation or p11 at a specific time during ventilation or an average value of p11 during ventilation and / or if p12 is < 0 during ventilation or p12 at a specific time during ventilation or an average value of p12 during ventilation.

[0082] If the differential pressure p12 is positive and the differential pressure p11 is negative, the differential pressure p12 is correctly assigned to the second differential pressure sensor 12 and the differential pressure p11 is correctly assigned to the first differential pressure sensor 11, so that the differential pressures or pressure values ​​have been verified. If this is not the case, an error has occurred, so an error message is issued and / or the gas heater 1 can be shut down and / or switched to a safe mode.

[0083] Since a plausibility check by this variant is only possible during ventilation and, for example, in pre-purge operation (or post-purge operation), it can alternatively or additionally be provided that during combustion operation or burner operation the control unit 3 briefly switches to a plausibility check mode in which no zero pressure control takes place for a short time, but - as in Figure 4shown - a target pressure difference X of, for example, 2 is adjusted, whereby other predetermined target pressure values ​​X are also possible, which, however, should exceed a measurement tolerance of the differential pressure sensors 11, 12. In the plausibility mode, a deliberate short-term stimulation of the differential pressure sensors 11, 12 takes place, whereby the plausibility can be carried out from their behavior or the signed pressure values ​​determined thereby.

[0084] Accordingly, a target differential pressure of 2 can be specified to the control electronics 13 via the communication interface 15 by the control unit 3, so that the control electronics 13 regulates the actuator 20 via the actuator electronics or actuator interface 14 such that the new target differential pressure X is established at least briefly at at least one of the differential pressure sensors 11, 12 or both differential pressure sensors 11, 12. Subsequently, and in particular if no error is detected, it is possible to immediately switch back to normal combustion operation.

[0085] If the new target differential pressure X of, for example, 2 has been reached, it can again be immediately determined whether the signed pressure values ​​are assigned to the correct differential pressure sensor 11, 12. It should be noted that during ventilation, ie here in the pre-purge phase, only a suction pressure can be set for the process pressure, so that during ventilation or here in the pre-purge phase, p1 <p0 gilt. In dem genannten Plausibilisierungsbetrieb bzw. -modus kann jedoch frei bestimmt und vorgegeben und durch Ansteuerung des Stellgliedes 30 des Gasregelventils 2 eingestellt sein, ob der Durchfluss des Gases erhöht oder reduziert werden soll, sodass abhängig von der gewünschten Ansteuerung p1<p0 (Unterdruck) oder p1> p0 (overpressure). The pressure curve corresponds to Figure 4 the variant p1>p0, so that p 11 = p 1 − p 0 > 0 and p 12 = p 0 − p 1 < 0 .

[0086] If the differential pressures p11 and p12 do not show the required pressure for the respective case (p1<p0 oder p1> p0) has a previously known and stored sign or the previously known and stored setpoint or threshold value, an error has occurred, so that an error message can be issued accordingly and / or the gas heater 1 can be switched off and / or switched to a safe mode.

[0087] The invention is not limited to the preferred embodiments described above. Rather, a number of variants are conceivable that utilize the presented solution even in fundamentally different embodiments.

Claims

1. Gas control unit (10) for the fail-safe control of a gas, in particular in a gas heater (1) or a gas burner, wherein the gas control unit (10) has a communication interface (15), a first sensor assembly (11) and a second sensor assembly (12), wherein the first sensor assembly (11) is designed to record measured values ​​from which a signed first differential pressure (p11) between a process pressure (p1) of the gas and a reference pressure (p0) can be determined, and wherein the second sensor assembly (12) is designed to record measured values ​​from which a signed second differential pressure (p12) between the reference pressure (p0) and the process pressure (p1) can be determined, so that the signed first differential pressure (p11) and the signed second differential pressure (p12) are signed, mutually inverse differential pressures (p11, p12), and wherein the communication interface (15) is designed,to send the mutually inverse differential pressures (p11, p12) and / or the measured values ​​to an external receiver.

2. Gas control unit according to claim 1, wherein the first sensor assembly (11) is a first differential pressure sensor (11) or a first mass flow sensor or has at least two sensors, each designed as a pressure sensor or as a mass flow sensor, and / or wherein the second sensor assembly (12) is a second differential pressure sensor (12) or a second mass flow sensor or has at least two sensors, each designed as a pressure sensor or as a mass flow sensor.

3. Gas control unit according to claim 1, wherein the first sensor assembly (11) is a first differential pressure sensor (11) and the second sensor assembly (12) is a second differential pressure sensor (12), wherein the differential pressure sensors (11, 12) each have a first pressure input (11A, 12A) and a second pressure input (11B, 12B) and are designed to determine a differential pressure (p11, p12) by subtracting a pressure present at the second pressure input (11B, 12B) from a pressure present at the first pressure input (11A, 12A), wherein the process pressure (p1) is present at the first pressure input (11A) of the first differential pressure sensor (11) and the reference pressure (p0) is present at the second pressure input (11B) of the first differential pressure sensor (11), and the reference pressure (p0) is present at the first pressure input (12A) of the second differential pressure sensor (12). and the process pressure (p1) is applied to the second pressure input (12B) of the second differential pressure sensor (12),so that the differential pressures (p11, p12) determined by the two differential pressure sensors (11, 12) are inverse to each other., 4. Gas control unit according to one of the preceding claims, further comprising control electronics (13) which is signal-technically connected to the first sensor assembly (11) and the second sensor assembly (12) and is designed to detect the mutually inverse differential pressures (p11, p12) or to determine them from the measured values.

5. Gas control unit according to the preceding claim, further comprising an actuator interface (14) for controlling an actuator (20), in particular a stepper motor, which is connected to the control electronics (13) in terms of signal technology or is formed integrally with the control electronics (13).

6. Gas control unit according to one of claims 4 or 5, wherein the communication interface (15) is connected to the control electronics (13) in terms of signal technology or is formed integrally with the control electronics (13), wherein the communication interface (15) is designed in particular to receive control signals.

7. Gas control valve (2) for the fail-safe control of a gas in a gas heater (1) or a gas burner, wherein the gas control valve (2) has a gas control unit (10) according to one of the preceding claims and an actuator (30) for adjusting a flow rate of a gas flowing from an inflow side to an outflow side of the gas control valve (2), wherein the process pressure (p1) is the pressure of the gas on the outflow side of the gas control valve (2).

8. Gas control valve according to the preceding claim, wherein the reference pressure (p0) is an ambient pressure at the gas control unit (10) and / or the gas control valve (2).

9. Gas control valve according to one of the two preceding claims and at least claim 5, further comprising an actuator (20) which is signal-connected to the actuator interface (14) of the gas control unit (10) and which is designed to adjust the actuator (30) to adjust the flow rate.

10. Gas control valve according to the preceding claim and at least claim 4, wherein the control electronics (13) are designed to adjust the actuator (30) for adjusting the flow by controlling the actuator (20) until at least one of the differential pressures (p11, p12) and / or measured values ​​corresponds to a predetermined value and / or is 0 Pa.

11. System (4) for the fail-safe control of a gas in a gas heater (1) or a gas burner with a control unit (3) for controlling combustion and a gas control valve (2) according to one of the preceding claims 7 to 10, wherein the control unit (3) as an external receiver is connected in terms of signal technology to the communication interface (15) of the gas control unit (10) and is designed to receive and process the mutually inverse differential pressures (p11, p12) and / or to send control signals to the communication interface (15).

12. System according to the preceding claim, wherein the control unit (3) is designed to check the plausibility of the mutually inverse differential pressures (p11, p12) by comparing the mutually inverse differential pressures (p11, p12) with setpoint values ​​or threshold values ​​stored in the control unit (3) and / or to check the plausibility of the mutually inverse differential pressures (p11, p12) by comparing the amounts of the mutually inverse differential pressures (p11, p12) with one another and / or to check the plausibility of the application of the process pressure (p1) and the reference pressure (p0) to the sensor assemblies (11, 12).

13. Method for checking the plausibility of differential pressures (p11, p12) which were detected with a system (4) for fail-safe pressure control according to one of the preceding claims 11 and 12, wherein the actuator (30) of the gas control valve (2) or a safety valve (5) provided upstream of the gas control valve (2) is controlled to change the process pressure (p1), so that the change in the process pressure (p1) causes the first differential pressure (p11) and the second differential pressure (p12) to change inversely to one another, the mutually inverse differential pressures (p11, p12) are each compared with a respective setpoint or threshold value after their change, and the comparison is used to check whether the first differential pressure (p11) assigned to the first sensor assembly (11) is the differential pressure detected by the first sensor assembly (11), and / or whether the second differential pressure (p12) assigned to the second sensor assembly (12) is assigned,the differential pressure detected by the second sensor assembly (12), and / or whether the process pressure (p1) is applied to the first sensor assembly (11) as intended, and / or whether the reference pressure (p0) is applied to the first sensor assembly (11) as intended, and / or whether the reference pressure (p0) is applied to the second sensor assembly (12) as intended, and / or whether the process pressure (p1) is applied to the second sensor assembly (12) as intended.

14. Method according to the preceding claim, wherein an error is detected and output if the mutually inverse differential pressures (p11, p12) do not correspond to the respective target values ​​or do not reach the respective threshold values.

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