Electropneumatic positioner for a pneumatic actuator and actuator comprising an actuator and an electropneumatic positioner

Abstract

Electropneumatic position controller (1) for delivering at least one actuating pressure (Y1, Y2) for a pneumatic actuator for actuating a control valve, such as a control valve, of a process plant, comprising: an electropneumatic converter (3), such as a current-pressure converter; at least one amplifier stage for the pneumatic actuator, such as a pre-stage (4) and / or a main stage (6), with at least one pneumatic amplifier (5, 7, 9), to which a control pressure, in particular cascade pressure (P c ), is present, further comprising a pressure sensor (41, 61) for detecting the control pressure, in particular the cascade pressure (P C ), characterized by control and / or regulating electronics designed to generate an electrical control signal for the electropneumatic converter (3) so that the electropneumatic converter (3) causes the at least one pneumatic amplifier (7, 9) to deliver the actuating pressure (Y1, Y2), wherein the control and / or regulating electronics are configured to modulate the electrical control signal for the electropneumatic converter (3) based on the measurement of the pressure sensor (41, 61).

Description

[0001] The invention relates to an electropneumatic positioner for a pneumatic actuator for actuating a control valve, such as a control valve, of a process plant, such as a chemical plant, in particular a petrochemical plant, a power plant, a brewery, or the like. The invention also relates to a control device for a process plant, comprising an electropneumatic positioner and a pneumatic actuator.

[0002] DE 42 40 802 C2 discloses an electropneumatic converter consisting of a pilot stage and a main control stage. The pilot stage is electrically controlled and includes a nozzle-flapper system through which the supply air can escape at a throttled rate. Three discrete pre-pressure values can be generated with the nozzle. The pre-pressure actuates a pneumatically controlled valve in the main stage, which has three discrete switching positions for venting, venting, and deactivation, which are activated depending on the pre-pressure. This arrangement is only suitable for single-acting actuators.

[0003] EP 3 271 624 B1 relates to a fluid valve assembly and a process valve positioner, which is also suitable for double-acting actuators. The process valve positioner has a pre-stage for converting an electrical control signal into a pre-fluid pressure. The pre-fluid pressure, in turn, regulates a fluid valve assembly. The fluid valve assembly regulates the fluid supply of a hydraulic or pneumatic actuator for operating a control valve. The fluid valves of the assembly are mechanically coupled to one another by means of a shaft. Pressure relief reduces the switching forces, enabling reliable switching with low pre-pressure.

[0004] Positioners designed to deliver pneumatic control signals with high pressure and high volumes, for example for large actuators, are susceptible to disturbances. Furthermore, it has been shown that the control behavior of such positioners tends to oscillate, for example under unfavorable process conditions or with suboptimal dimensioning. If, for example, a very small volume flow of an electropneumatic converter is used for a large gain, the spring constants and friction in the system can result in undesirable behavior. To directly switch high actuating forces, the electropneumatic converter requires a correspondingly high power, which is generally incompatible with two-wire technology and Ex i requirements.

[0005] DE 10 2014 013 098 B3 describes a position controller for a pneumatic actuator of a process plant, which comprises a current-pressure converter with at least two I / P converters for generating at least two separate pneumatic control signals, microelectronics for generating at least two electrical control signals for the at least two I / P converters and a pneumatic signal switching valve.

[0006] DE 20 2016 106 017 U1 discloses an electropneumatic positioner and a field device with an electropneumatic positioner.

[0007] It is an object of the invention to provide an electropneumatic positioner and / or an actuator that overcomes the disadvantages of the prior art, in particular ensuring a fast, large-volume, and precise compressed air supply for actuators, especially at high actuating pressures. This object is achieved by the subject matter of the independent claims.

[0008] According to a first aspect of the invention, an electropneumatic positioner for a pneumatic actuator for actuating a control valve, such as a control valve, of a process plant, in particular a petrochemical plant, a power plant, a food processing plant, in particular a brewery, or the like is provided.

[0009] According to the first aspect of the invention, the electropneumatic position controller comprises an electropneumatic converter and at least one amplifier stage, such as a pilot stage and / or a main stage, with at least one pneumatic amplifier, to which a control pressure provided by the electropneumatic converter is applied. In particular, the control pressure, in particular the pilot pressure, is applied to a control input of the pneumatic amplifier of the amplifier stage, in particular the main stage. It is conceivable for the electropneumatic converter to have only a single amplifier stage, i.e. only one main stage. The pilot pressure set for the pneumatic amplifier of the main stage can correspond to the pilot pressure provided by the electropneumatic converter or, in other words, can be set directly by the electropneumatic converter.Optionally, the electropneumatic positioner according to the first aspect of the invention can comprise several, for example two, in particular cascaded, amplifier stages including a pilot stage and a main stage, wherein preferably the cascade pressure provided by the electropneumatic converter is applied to the pilot stage and / or the pilot pressure is applied to the main stage. In particular, the pilot stage sets the pilot pressure for the main stage using the pressure provided by the electropneumatic converter. An electropneumatic converter can comprise a valve with a piezoelectric or electromagnetic actuator for actuating this valve, in particular a needle valve, preferably with a very low maximum volume flow.The electropneumatic positioner preferably comprises a common supply line for both the electropneumatic converter and the at least one amplifier stage, in particular the supply input of the pneumatic amplifier or the supply inputs of the pneumatic amplifiers, for connection to the pneumatic source. The electropneumatic positioner is preferably designed and configured to provide a pneumatic control signal to a pneumatic actuator. In particular, the positioner is designed and configured to receive a preferably electrical and / or digital control signal from a higher-level control device, such as a central control room of a process plant, and to generate the pneumatic control signal based on the control signal.In addition, the electropneumatic position controller can preferably take into account at least one measurement signal relating to at least one disturbance or process variable, such as an actual position of a control valve and / or an actual pressure, for generating the pneumatic control signal.

[0010] An electropneumatic converter implements an electropneumatic component of a position controller. An electropneumatic converter is preferably designed and configured to adjust a converter pressure depending on an electrical signal. Preferably, an electropneumatic converter is designed and configured to adjust the converter pressure based on, on the one hand, a pneumatic source that provides a pressurized pneumatic medium, such as ambient air, nitrogen, or the like, at a supply pressure, and, on the other hand, a pneumatic sink, such as the atmosphere, which defines a reference pressure, for example, corresponding to the ambient pressure. Further preferably, an electropneumatic converter is configured to adjust the converter pressure taking into account an electrical signal, in particular an analog or digital one, such as a current signal or a voltage signal.For example, the electropneumatic converter can be implemented as a current-pressure converter and, in particular, adjust the converter pressure proportionally to or generally according to a control function of a current signal. The electropneumatic converter is preferably designed and configured to provide the converter pressure for at least one other pneumatic component, such as a pneumatic amplifier, at an active input or active output. For example, it can be provided that an electropneumatic converter is configured to adjustably close an opening of a pneumatic line fed by a pneumatic source with respect to the pressure sink, which may be implemented as atmosphere, in order to adjust the converter pressure at the transition of this pneumatic line to the converter, wherein a throttle or similar device is preferably provided in the pneumatic line between the transition and the pneumatic source.Preferably, an electropneumatic converter provides a converter pressure with a very low volume flow.

[0011] A pneumatic amplifier can generally be defined as a pneumatic component, preferably designed without electronics. A pneumatic amplifier is preferably designed and configured to adjust an amplified output pressure and / or an amplified output volume flow depending on a pneumatic control pressure, which can preferably be referred to as a pilot pressure. It is conceivable to connect several pneumatic amplifiers to the same pneumatic source. Pneumatic amplifiers can, in particular, be connected in inverted parallel and / or in series with a pneumatic source.A pneumatic amplifier may have a pneumatic control input for receiving the pneumatic control pressure, a supply input (amplifier input) connectable to a pneumatic source for supplying pneumatic medium, and an amplifier output for delivering pneumatic medium with amplified output pressure and / or amplified output volume flow. The maximum amplified output pressure and / or amplified output volume flow that can be delivered by the pneumatic amplifier is generally limited by the supply pressure of the pneumatic medium available at the supply input and by the structural design of the pneumatic amplifier. Those skilled in the art will understand that the term "amplification" generally refers to a relationship to the pneumatic control pressure at the pneumatic control input of the pneumatic amplifier.Several pneumatic amplifiers, in particular different amplifier stages, of a positioner can be connected to the same pneumatic source at their respective supply inputs and, in particular, can be supplied with pneumatic medium at the same supply pressure. A pneumatic amplifier can, for example, be designed as a pneumatically actuated double-cone valve. In an electropneumatic positioner with several pneumatic amplifiers, it may be preferable for several, in particular all, pneumatic amplifiers to be designed as a pneumatically actuated double-cone valve, in particular a single-acting one.

[0012] An amplifier stage can, for example, refer to a part of a position controller in which an amplified output pressure and / or an amplified output volume is provided by at least one pneumatic amplifier based on a pilot control signal, in particular a pneumatic pilot control signal. Within an amplifier stage, several pneumatic amplifiers with parallel-connected supply inputs can be provided. Several pneumatic amplifiers of the same amplifier stage can, in particular, be supplied with the same control signal at their respective control input. A position controller can comprise several amplifier stages, in particular coupled in a cascade manner, wherein a first stage can be referred to as the pilot stage and a second stage as the main stage.If multiple pneumatic amplifiers are provided in different cascaded amplifier stages, the amplifier output of a first pneumatic amplifier is typically connected to the control input of a second pneumatic amplifier of the successively next amplifier stage. For example, the control input of the pneumatic amplifier of the main stage is connected to the amplifier output of the pneumatic amplifier of the preliminary stage. In positioners with multiple amplifier stages, the pneumatic amplifiers of the different stages are preferably designed for different, in particular successively increasing, maximum deliverable amplified output pressures and / or amplified output volume flows, in particular coordinated with one another. The pilot pressure at the control input of the first pneumatic amplifier of a system with multiple cascaded amplifier stages can be referred to as the cascade pressure.

[0013] According to the first aspect of the invention, the electropneumatic positioner comprises a pressure sensor for detecting the control pressure, in particular the pilot pressure. Preferably, the first or second pressure sensor of the electropneumatic positioner according to the first aspect of the invention is designed and configured to detect the control pressure, in particular directly at the pneumatic control input of at least one pneumatic amplifier of the amplifier stage, in particular the main stage. In particular, it can be provided that the electropneumatic positioner comprises only a single amplifier stage and the pressure sensor is designed and configured to detect the control pressure, in particular directly at the pneumatic control input of the at least one pneumatic amplifier of the single amplifier stage.

[0014] According to a preferred embodiment of the first aspect of the invention, the electropneumatic converter sets the control pressure, in particular the pilot pressure. Preferably, the electropneumatic converter is connected directly to the control input of the at least one pneumatic amplifier such that the converter pressure corresponds to the control pressure. For example, the control input can be directly connected to an active input or output of the electropneumatic converter. Preferably, a pneumatic connecting line between the electropneumatic converter and the control stage supplied with the control pressure is free of a pressure-reducing pneumatic component, such as a throttle. Without a throttle, the input behavior of the amplifier is particularly dynamic.Alternatively, the pneumatic connection line between the electropneumatic converter and the control stage, which is supplied with the control pressure, is equipped with a pressure-reducing pneumatic component, such as a throttle. A throttle dampens the input response of the amplifier.

[0015] According to another preferred embodiment of the first aspect of the invention, the electropneumatic converter comprises a pre-stage having a preamplifier and a main stage having at least one further pneumatic amplifier. The pre-stage sets the control pressure as the pilot pressure for the main stage. Preferably, the pilot pressure corresponds to the amplified output pressure at the amplifier output of the preamplifier. In particular, the electropneumatic converter is indirectly connected, in particular via the pre-stage, to the control input of the main stage. Preferably, the electropneumatic converter is connected, in particular directly, to the control input of the preamplifier such that the converter pressure corresponds to the control pressure of the preamplifier, and the amplifier output is connected, in particular directly, to the control input of at least one main-stage amplifier such that the amplified output pressure of the preamplifier corresponds to the pilot pressure.For example, the control input of the at least one amplifier of the main stage can be directly connected to the amplifier output of the preamplifier. According to a preferred development of the other preferred embodiment of the first aspect of the invention, the electropneumatic converter sets a cascade pressure as an additional control pressure for the preamplifier.

[0016] According to a second aspect of the invention, which can be combined with the first aspect of the invention, an electropneumatic position controller for a pneumatic actuator for actuating a control valve, such as a control valve, of a process plant, in particular a petrochemical plant, a power plant, a food processing plant, in particular a brewery, or the like is provided.

[0017] According to the second aspect of the invention, the electropneumatic positioner comprises an electropneumatic converter and at least two amplifier stages. The two amplifier stages are connected in series. The electropneumatic positioner can optionally have further amplifier stages, in particular connected in series. The amplifier stages comprise a pilot stage with a first pneumatic amplifier, which can be referred to as a preamplifier. A cascade pressure provided by the electropneumatic converter is applied to the pilot stage. In particular, the pilot pressure is applied to a control input of the pneumatic amplifier of the pilot stage. The amplifier stages comprise a main stage with at least one second pneumatic amplifier. A pilot pressure set by the pilot stage, in particular the first pneumatic amplifier, is applied to the main stage.In particular, the pilot pressure is applied to a control input of the pneumatic amplifier, in particular of the main stage. Preferably, the electropneumatic positioner comprises a common supply line for both the electropneumatic converter and the at least two amplifier stages, in particular the supply inputs of the pneumatic amplifiers of the various amplifier stages, for connection to the pneumatic source.

[0018] According to the second aspect of the invention, the electropneumatic positioner comprises a pressure sensor for detecting the cascade pressure. Preferably, the first or second pressure sensor of the electropneumatic positioner according to the second aspect of the invention is designed and configured to detect the cascade pressure, in particular directly at the pneumatic control input of the pneumatic preamplifier. In a preferred embodiment of the electropneumatic positioner that combines the first and second aspects of the invention, the positioner comprises a first pressure sensor for detecting the cascade pressure and a second pressure sensor for detecting the pilot pressure. Optionally, the electropneumatic positioner can comprise at least one further pressure sensor for detecting pressures in or on the electropneumatic positioner.

[0019] Using a pressure sensor to detect the control pressure, the electropneumatic positioner can achieve shorter control times and / or smaller control tolerances than a conventional electropneumatic positioner with one or more amplifier stages. Using at least one pressure sensor, malfunctions in the amplifier stage(s) can be reliably and early detected to initiate countermeasures. In particular, using at least one control pressure sensor can prevent undesirable behavior. It may be sufficient or, for cost reasons, preferable to provide only one pressure sensor for either the cascade pressure or the pilot pressure.Alternatively, it may be preferable, in particular for a particularly precise and / or robust control quality, to provide several control pressure sensors in different amplifier stages of the electropneumatic positioner, in particular a cascade pressure sensor and at least one pilot pressure sensor.

[0020] In a third aspect of the invention, which can be combined with the first and / or the second aspect of the invention, an electropneumatic positioner for a pneumatic actuator for actuating a control valve, such as a control valve, of a process plant, in particular a petrochemical plant, a power plant, a food processing plant, in particular a brewery, or the like is provided.

[0021] According to the third aspect of the invention, the electropneumatic positioner comprises an electropneumatic converter and at least one amplifier stage. The at least one amplifier stage of the pneumatic actuator comprises a first pneumatic amplifier for providing a first actuating pressure for the pneumatic actuator. The same at least one amplifier stage further comprises a second pneumatic amplifier for providing a second actuating pressure for the pneumatic actuator. In particular, the electropneumatic positioner has a main stage that comprises both the first and the second pneumatic amplifier.

[0022] According to the third aspect of the invention, it is provided that the same control pressure, in particular the same pilot pressure, provided by the electropneumatic converter, is applied to the first pneumatic amplifier and the second pneumatic amplifier, and that the first and second pneumatic amplifiers are free of any mechanical coupling. Preferably, both the control input of the first pneumatic amplifier and the control input of the second pneumatic amplifier are subjected to the same control pressure. Preferably, the control input of the first pneumatic amplifier and the control input of the second pneumatic amplifier are fluidically connected to one another, so that, in particular, pressure equalization between the first and second control inputs is ensured.The first pneumatic amplifier and the second pneumatic amplifier preferably each contain individual movable mechanical components, including, for example, a return spring, valve member, valve seat, valve rod, diaphragm, and / or poppet, so that they are free from any mechanical coupling. The mechanical components of the first pneumatic amplifier and the second pneumatic amplifier are preferably movable independently of one another. It should be understood that a rigid frame and / or housing of the electropneumatic positioner can support both the first and second pneumatic amplifiers. The first pneumatic amplifier and the second pneumatic amplifier are pneumatically but not mechanically coupled to one another.

[0023] A pneumatic coupling has the advantage over a mechanical coupling that, when used with a double-acting pneumatic actuator with two opposing pneumatic chambers, the respective actuating pressure in the two pneumatic chambers of the actuator is essentially identical, each amounting to 50% of the actuator supply pressure provided by the preferably same pneumatic source. This makes the pneumatic system more rigid and less susceptible to disturbances.

[0024] According to a preferred embodiment of the electropneumatic positioner according to the second and / or third aspect of the invention, and optionally additionally to the first aspect of the invention, the first amplifier has a venting valve for providing the actuating pressure to the pneumatic actuator. Optionally, the first pneumatic amplifier and the second pneumatic amplifier can each have a venting valve for providing the respective actuating pressure to the pneumatic actuator. The first amplifier further has a venting valve for venting the pneumatic actuator to a pressure sink, such as the atmosphere. Optionally, both the first and the second pneumatic amplifier can each have a venting valve for venting the pneumatic actuator to a pressure sink, such as the atmosphere.Preferably, the first amplifier and the second amplifier are pneumatically coupled in such a way that in a first actuating state, with a first pneumatic control signal, the first amplifier provides the first actuating pressure to the pneumatic actuator, in particular a first pneumatic chamber of the pneumatic actuator, by means of its venting valve and the second amplifier vents the pneumatic actuator, in particular a second pneumatic chamber of the pneumatic actuator, by means of its venting valve.Alternatively or additionally, the first amplifier and the second amplifier are pneumatically coupled such that in a second actuating state, with a second pneumatic control signal, the second amplifier provides the second actuating pressure to the pneumatic actuator, in particular the second pneumatic chamber of the pneumatic actuator, by means of its venting valve and the first amplifier vents the pneumatic actuator, in particular the first pneumatic chamber of the pneumatic actuator, by means of its venting valve.

[0025] In a further development of the electropneumatic positioner, the first pneumatic amplifier and optionally the second pneumatic amplifier is / are designed and configured to assume a blocking state in which the venting valve and the venting valve are closed when a control pressure, in particular pilot pressure, is applied at a predetermined average pressure level, in particular between a first, in particular lower, pressure threshold value and a second, in particular upper, pressure threshold value. The average pressure level can be referred to as the neutral pressure level. The neutral pressure level is preferably defined by a first and a second, in particular structurally predetermined, pressure threshold value. The neutral pressure level is preferably between a lowering pressure level and a raising pressure level.

[0026] Alternatively or additionally, in another development, the first pneumatic amplifier is designed and configured to assume a lowering state when a control pressure, in particular pilot pressure, is applied at a predetermined low pressure level, in particular below a first, in particular lower, pressure threshold. In the lowering state, the vent valve of the first pneumatic amplifier is open and its venting valve is closed. In particular, in the lowering state, the vent valve of the second pneumatic amplifier is closed and its venting valve is open. The low pressure level can be referred to as the lowering pressure level. The lowering pressure level is preferably limited by a first, in particular structurally predetermined, pressure threshold.

[0027] Further alternatively or additionally, the electropneumatic positioner is such that the first pneumatic amplifier is designed and configured to assume a lifting state when a control pressure, in particular pilot pressure, is applied at a predetermined high pressure level, in particular above a second, in particular upper, pressure threshold. In the lifting state, the vent valve of the first pneumatic amplifier is closed and its venting valve is open. In particular, in the lifting state, the vent valve of the second pneumatic amplifier is open and its venting valve is closed. The high pressure level can be referred to as the lifting pressure level. The lifting pressure level is preferably limited by a second, in particular structurally predetermined, pressure threshold.

[0028] The electropneumatic position controller according to the first, second, and third aspects of the invention for delivering at least one actuating pressure for the pneumatic actuator according to one of the preceding claims comprises control and / or regulating electronics. The control and / or regulating electronics are designed to generate an electrical control signal for the electropneumatic converter so that the electropneumatic converter causes the at least one pneumatic amplifier to deliver the actuating pressure. The control and / or regulating electronics are further configured to modulate the electrical control signal for the electropneumatic converter based on the measurement of the pressure sensor, in particular the first pressure sensor for detecting the pilot pressure and / or the second pressure sensor for detecting the cascade pressure.

[0029] Preferably, the electropneumatic position controller is designed and configured to generate a pneumatic control signal for at least one pneumatic actuator based on a control signal and to modulate the pneumatic control signal based on the measurement of the at least one pressure sensor, in particular the first pressure sensor that detects the pilot pressure, and / or the second pressure sensor that detects the cascade pressure. For example, the electropneumatic position controller can be equipped with a PID controller for determining the pneumatic control signal, wherein the I component, the P component, and / or the D component of the controller are adapted or determined depending on the measurement signal of the at least one pressure sensor.Preferably, the electropneumatic positioner is designed and configured to additionally take into account a subordinate pneumatic control loop, which contains the pilot pressure and optionally the cascade pressure, in order to improve the control quality, for example to prevent oscillation, when controlling the higher-level control loop in which the control pressure is determined on the basis of the control signal and at least one measured process variable, such as an actual position of a control valve.

[0030] In one embodiment of an electropneumatic positioner according to the first, second, and / or third aspect of the invention, the electropneumatic positioner comprises at least one further pressure sensor for detecting a pressure in or at the electropneumatic positioner. The further pressure sensor is preferably designed to detect the first actuating pressure, the second actuating pressure, or a supply pressure at a supply input of the electropneumatic positioner, which can also be referred to as the main supply input. The electropneumatic positioner can comprise a plurality of further pressure sensors in order to detect a corresponding number of different pressures in or at the electropneumatic positioner.In a combination of this and the above-described embodiment with control and / or regulation electronics, the control and / or regulation electronics can be designed to process the pressure measurement value(s) of the at least one further pressure sensor for monitoring and / or diagnosing the position controller.

[0031] According to one embodiment, the electropneumatic positioner can have a housing that comprises at least two compartments. In particular, the first housing compartment of the positioner housing preferably houses exclusively purely pneumatic components. A purely pneumatic component is implemented, for example, by the at least one pneumatic amplifier. Other examples of purely pneumatic components are a pressure reducer and / or a flow limiter. A second housing compartment of the positioner housing preferably houses exclusively electronic, electrical and / or electropneumatic components, such as the electropneumatic converter, a sensor such as a pressure sensor, control and / or regulation electronics, or the like. The first compartment and the second compartment are arranged in the same, in particular integral, housing of the positioner.Preferably, the first compartment is pneumatically separated from the second compartment, in particular by a solid partition wall.

[0032] According to a preferred development of the electropneumatic positioner, the positioner housing has a housing cover that is or can be detachably connected to the housing. It may be preferred that the housing cover is at least partially insertable into the first housing compartment, wherein in particular the housing cover is adapted to the first housing compartment for closing an opening, in particular against the environment, such as the atmosphere. The housing cover is preferably equipped with at least one amplifier stage, in particular the pre-stage and / or the main stage. The pneumatic separation of the housing, in particular the solid partition wall, preferably comprises at least one interface for pneumatically coupling the cover-side pneumatic components, in particular the amplifier stage, to electropneumatic components in the second housing compartment.

[0033] In a particularly preferred development of the electropneumatic positioner, it comprises at least one ignition barrier, preferably a plurality of ignition barriers, in particular a sintered filter, in a pneumatic line. For example, an ignition barrier can be provided in at least one pneumatic line assigned to the electropneumatic converter, in particular a pneumatic line assigned to the active input or a pneumatic line assigned to the active output. Alternatively or additionally, an ignition barrier can be arranged in at least one pneumatic line assigned to a pressure sensor, in particular the first pressure sensor, the second pressure sensor, and / or optionally a respective further pressure sensor.

[0034] According to the invention, an actuator can be provided that comprises a pneumatic actuator and an electropneumatic positioner according to the first, second, and / or third aspect of the invention. The pneumatic actuator of the actuator according to the invention is connected to the electropneumatic positioner for receiving an amplified output pressure and / or an amplified output volume flow provided by the electropneumatic positioner.

[0035] In a further development of an actuating device according to the invention, the pneumatic actuator is designed to be pneumatically single-acting, in particular with a return spring, and the electropneumatic positioner in the amplifier stage, in particular the main stage, comprises only one, preferably pneumatic, amplifier. Preferably, both the electropneumatic converter and the at least one amplifier stage are connected or connectable to the pneumatic source via the common supply line.

[0036] In another development of an actuating device according to the invention, the pneumatic actuator is designed to be pneumatically double-acting, and the electropneumatic positioner comprises, particularly in the main stage, precisely two preferably pneumatic amplifiers. Preferably, this embodiment of an actuating device according to the invention implements the third aspect of the invention, with the first pneumatic amplifier and the second pneumatic amplifier constituting precisely two pneumatic amplifiers of the main stage. The pneumatically double-acting actuator comprises a first pneumatic chamber and a second pneumatic chamber. In a pneumatic actuator with an actuating rod or actuating shaft, the first pneumatic chamber and the second pneumatic chamber act in opposite directions on this actuating rod or actuating shaft.Particularly preferably, the actuator has a common supply line for both the actuator supply air pressure of both pneumatic chambers and for supplying the electropneumatic positioner from the same pneumatic source. Preferably, both the electropneumatic converter and the at least one amplifier stage are connected or connectable to the pneumatic source via the common supply line.

[0037] Preferred embodiments of the invention are described in the dependent claims. Further properties, advantages, and features of the invention will become clear from the following description of preferred embodiments of the invention with reference to the accompanying drawings, in which: Fig. 1 is a schematic block diagram of an embodiment of a pneumatic system of an electropneumatic positioner according to the invention; Fig. 2 a sectional view of an embodiment of an electropneumatic positioner according to the invention in a blocking state; Fig. 3 a sectional view of the electropneumatic positioner according to the invention according to Fig. 2 in a lifting state; Fig. 4 a sectional view of the electropneumatic positioner according to the invention according to Fig. 3 in a lowering state; Fig. 5 a schematic representation of an actuator with an electropneumatic positioner according to the invention; and Fig. 6 a schematic representation of the control of an actuator with an electropneumatic positioner according to the invention.

[0038] In the following description of preferred embodiments with reference to the figures, the same or similar components are provided with the same or similar reference numerals to simplify readability.

[0039] In the following illustrations of preferred embodiments of the invention, an electropneumatic positioner is generally designated by reference numeral 1. The electropneumatic positioner 1 according to the invention comprises an electropneumatic converter 3 and at least one amplifier stage with a pneumatic amplifier. The positioner preferably comprises a position measuring device and a control device (not shown).

[0040] Fig. Figure 1 shows a schematic block diagram of the pneumatics of an electropneumatic positioner 1 with an electropneumatic converter 3 and two cascade-coupled amplifier stages 4, 6. The first amplifier stage 4, which may also be referred to as a pre-stage, is equipped with a pneumatic amplifier 5. The second amplifier stage 6 contains two pneumatic amplifiers 7, 9.

[0041] Those skilled in the art will understand that, according to one embodiment (not shown), the main stage 6 can be equipped with only one pneumatic amplifier, either 7 or 9. Furthermore, those skilled in the art will understand that, in an alternative embodiment (not shown) of an electropneumatic positioner according to the invention, in particular according to the first aspect of the invention, the electropneumatic positioner comprises only a single amplifier stage, the actuation of which takes place by means of the transducer pressure in accordance with the actuation of the illustrated preliminary stage 4, as described below, and which provides the actuating pressure for a pneumatic actuator, such as a pneumatic actuator 110, as described below with respect to the main stage 6.

[0042] The electropneumatic positioner 1 is supplied with compressed air or another pneumatic medium from a pneumatic source 101. The electropneumatic positioner 1 has a main supply input 10 for connection to a pneumatic source 101. The electropneumatic positioner 1 comprises a supply line 11 through which the pneumatic medium is provided to the pneumatic or electropneumatic functional components of the positioner 1. The supply line 11 leads into the first amplifier stage 4 and is connected to the supply input 51 of the preamplifier 5. The supply line 11 leads into the main stage 6. In the main stage 6, the pneumatic supply line 11 is connected to the supply input 71 of the first pneumatic amplifier 7 and the supply input 91 of the second pneumatic amplifier 9.The electropneumatic converter 3 of the electropneumatic positioner 1 is also supplied with the pneumatic medium via the supply line 11. The electropneumatic converter 3 is designed to receive an electrical control signal and to provide a control pressure corresponding to the electrical control signal for at least one pneumatic amplifier operatively connected to the electropneumatic converter 3.

[0043] At the Fig. In the embodiment shown in Figure 1, the electropneumatic converter 3 is implemented as an analog current-pressure converter, which, for example, sets a converter pressure proportional to a current signal. In the embodiment shown, the electropneumatic converter is connected to the pneumatic source 101 at its pneumatic input 31 via the supply line 11 and has a pneumatic output connected to a pneumatic sink (here: the atmosphere 109).

[0044] At the Fig. In the embodiment shown in Figure 1, a flow limiter 32 and a pressure reducer 30 are provided between the active input 31 of the electropneumatic converter 3 and the pneumatic source 101. The electropneumatic converter 3 is connected to the pneumatic preamplifier 5 in such a way that the converter pressure present at the active input 31 corresponds to the control pressure (here: cascade pressure) present at the control input 33 of the preamplifier 5.

[0045] The electropneumatic converter 3 adjusts the converter pressure at the active input 31 according to the electrical control signal by selectively venting the pneumatic medium provided to the electropneumatic converter 3 by the pressure reducer 30 and the flow restrictor 32 to the pressure sink. If the electropneumatic converter 3 is implemented as an analog electropneumatic converter, as shown, the selective venting can be achieved, for example, by a clocked (e.g., pulse-width modulated) actuation of the converter, i.e., by clocked opening of the converter. The clocking can, for example, be constant, with each clock consisting of a closing period and an opening period. With constant clocking, the sum of the closing period and the opening period is always the same length. The length of the closing and opening periods can be varied using the electrical signal.A relatively long opening duration then results in a low converter pressure at the active input, possibly corresponding to or close to the pressure of the pressure sink. A relatively long closing duration results in a converter pressure at the active input closer to the maximum possible control pressure, which is preferably defined by the pressure reducer 30. When the electropneumatic converter is continuously closed, the converter pressure at its active input 31 corresponds to the maximum control pressure provided by the pneumatic source 101 through the pressure reducer 30 to the electropneumatic converter 3. Other embodiments are conceivable; for example, the electropneumatic converter 3 can be designed and configured to provide a control pressure corresponding to the electrical control signal, for example according to an open / close function.

[0046] In the illustrated version of an electropneumatic positioner 1 with two amplifier stages 4, 6, the control pressure, the control pressure provided by the electropneumatic converter 3 at the pneumatic amplifier 5, can be used as cascade pressure P C be designated.

[0047] The electropneumatic positioner 1 comprises a pressure sensor 41 for cascade pressure detection. The control pressure provided by the electropneumatic converter 3 (here: cascade pressure P C ) is detected by this pressure sensor 41. The pressure sensor 41 used to detect the cascade pressure P C The pressure sensor 41 installed can be referred to as a cascade pressure sensor. In the above-mentioned embodiment with only one amplifier stage (not shown), the electropneumatic converter 3 would directly provide the converter pressure as the control pressure for this single amplifier stage, which could be referred to as the pilot pressure (not shown).

[0048] At the Fig. In the embodiment shown in Figure 1, the pneumatic amplifier 5 of the first amplifier stage 4 is connected to the supply line 11 in order to supply the pneumatic medium from the pneumatic source 101 (cf. Fig. 5). The pneumatic control input 53 of the pneumatic amplifier 5 is connected to the electropneumatic converter 3 for receiving the pneumatic control signal. The preamplifier 5 receives the cascade pressure P at its control input 53. C . The pneumatic amplifier 5 is connected in the first amplifier stage 4 through its amplifier output 59 to a pneumatic line 15 vented to the pressure sink, in particular the atmosphere 109, through a further pressure reducer 50 and a further flow limiter 52. The pneumatic amplifier 5 provides a control pressure for the main stage 6 at its amplifier output 59, which is known as the pilot pressure P PThe electropneumatic positioner 1 comprises a pressure sensor 61 for detecting the pilot pressure. The preamplifier 6 is connected to a pressure sensor 61 for detecting the control pressure P P connected to the amplifier output 59 of the pneumatic amplifier 5.

[0049] The pneumatic amplifier 5 is designed and arranged to generate a pilot pressure P at its amplifier output 59 P which is fed from the pneumatic pressure of the pneumatic source 101 and dependent on the cascade pressure P C As can be seen from the Fig. 2-5 below, the pneumatic preamplifier 5 is implemented by a pneumatically actuated valve with spring return. The restoring force of the spring return acts on the cascade pressure P C at the pneumatic control input 53 in order to set an opening width of the pneumatic amplifier 5.

[0050] The second amplifier stage receives the pneumatic medium from the pneumatic source 101 via the supply line 11. A control line 16 is connected to the amplifier output 59 of the pneumatic amplifier 5 of the pre-stage 4. The control line 16 is connected to the pneumatic control input 73 of the first pneumatic amplifier 7 and the pneumatic control input 93 of the second pneumatic amplifier 9. The pneumatic supply line 11 is connected to the supply input 71 of the first amplifier 7 and to the supply input 91 of the second amplifier 9 of the main stage 6. The amplifier output 79 of the first amplifier 7 of the main stage 6 is connected to a first signal pressure output 17 of the electropneumatic positioner 1 for supplying a first pneumatic chamber or drive chamber of a positioning actuator 110 with the first signal pressure Y1.The amplifier output 99 of the second amplifier 9 of the main stage 6 is connected to a second control pressure output 19 of the electropneumatic positioner 1 for supplying a second pneumatic chamber of the actuator 110 with the second control pressure Y2. The electropneumatic positioner 1 can have one or more additional pressure sensors 72, 92 at the amplifier output(s) 79, 99 for detecting the control pressure Y1 or Y2 provided there. Alternatively or additionally, the electropneumatic positioner 1 also comprises a further pressure sensor 12 for detecting the supply pressure P. S in the supply line 11.

[0051] The pneumatic amplifiers 7, 9 or the pneumatic amplifier of the main stage 6 are designed essentially according to the amplifier 5 of the pre-stage 4 described above. It may be expedient for the pneumatic amplifiers 7, 9 of the main stage 6 to be designed for significantly larger flow volumes than the amplifier 5 of the pre-stage 4 and the electro-pneumatic converter 3. For example, the pre-amplifier 5 can be designed for flow volumes that are at least 10 times, preferably 100 times, larger than the nominal flow volume of the electro-pneumatic converter 3 during operation. Further alternatively or additionally, it can be provided that the nominal flow volume of the main stage amplifiers 7, 9 is at least 10 times, preferably at least 100 times, larger than the nominal flow volume of the pneumatic pre-amplifier 5. According to an expedient embodiment, it can be provided that the main stage amplifiers 7, 9 are of the same size, in particular of identical construction.It should be understood that, as an alternative to the illustrated embodiment, an electropneumatic positioner according to the invention may comprise more than two pneumatic amplifier stages coupled to one another in cascade. Furthermore, those skilled in the art will understand that in a specific embodiment according to the first and / or third aspect of the invention, the electropneumatic positioner has only a single pneumatic amplifier stage (not illustrated). In this embodiment, the converter and control pressure provided by the electropneumatic converter 3 would be connected directly to the pneumatic control input 73 and / or 93 of the pneumatic amplifier 7 or 9 or of the single amplifier stage 6 without an intermediate pre-stage 4.Thanks to the inventive design of an electropneumatic positioner with one or more pneumatic amplifier stages, a pneumatic actuating pressure Y1 and / or Y2 can be provided for a pneumatic actuator with a large volume flow and high control pressure. The electropneumatic positioner 1 is capable of particularly precise and robust controllability. It may be particularly preferred that the preamplifier 5 and / or the at least one main amplifier 7, 9 are filled without any respective pressure compensation.Surprisingly, it has been found that, contrary to common prejudices according to which pneumatic amplifiers with pressure compensation would be necessary for stable control with the aid of an electropneumatic positioner, by utilizing the design disclosed here, preferably with several amplifier stages, a particularly stable control can be realized even without pressure compensation of one and / or several, in particular all, pneumatic amplifier components 5, 7, 9.

[0052] As detailed in the Fig. As shown in Figures 2 to 4, the multiple pneumatic amplifiers 7, 9 of the main stage 6 act in opposite directions. The first pneumatic amplifier 7 opens its vent valve 74 at increased pilot pressure P P' , in particular above a first threshold value, whereas the second pneumatic amplifier 9 opens its vent valve 95. If a low pilot pressure P P, in particular below a second threshold value which is lower than the first threshold value, the first pneumatic amplifier 7 opens its vent valve 75 and the second pneumatic amplifier 9 opens its vent valve 94. The pneumatic amplifiers 7 and 9 of the main stage 6 are optionally further designed such that in a medium pressure range of the pilot pressure P P , in particular below the first threshold value and above the second threshold value, all ventilation valves 74, 94 and vent valves 75, 95 are closed, so that a blocking state is established, as in Fig. 2 shown.

[0053] A low cascade pressure P acts on the pneumatic control input 53 of the preamplifier C . The cascade pressure P Cacts on the control diaphragm 151 against the return force of the return spring 152. A vent valve seat 155 for the vent valve 55 of the preamplifier 5 is held on the diaphragm 151, which is actuated by the cascade pressure P C is pressed against a valve cone 156 of a double cone 150. The return spring 152 presses both valve cones 153, 156 of the double cone 150 against the corresponding valve seat 154, 155.

[0054] Fig. 3 shows the amplifier stages 4, 6 at increased cascade pressure P C and correspondingly increased pilot pressure P P . The increased cascade pressure P acting on the control diaphragm 151 C lifts the double cone 150 by means of the vent valve seat 155 and releases the vent valve cone 153 from the vent valve seat 154. The supply pressure P available at the supply inlet 51 Scan be communicated through the open vent valve 54 to the amplifier output 59. The amplifier output 59 of the preamplifier 5 is fluidically connected to the control inputs 73, 93 of the pneumatic amplifiers 7, 9 of the main stage 6. The vent valve 55 remains closed. As long as the pneumatic preamplifier 5 remains in the vented state, the pilot pressure P P to its maximum, which is determined by the supply pressure Ps and, if applicable, an overflow valve 50, 52. Components 50, 52 implement an overflow valve that minimizes reversing errors of the preamplifier. The overflow valve can, for example, comprise a pressure reducer and / or a flow limiter.

[0055] Fig. 4 shows the amplifier stages 4, 6 at reduced cascade pressure P C and correspondingly reduced pilot pressure P P . If a reduced cascade pressure P Cacting on the control diaphragm 151, the return spring 152 pushes the venting valve cone 153 against the venting valve seat 154 and closes the venting valve 54. The control diaphragm 150 and the associated venting valve seat 155 move away from the venting valve cone 156, so that the amplifier output 59 is pneumatically connected to a vent opening 58 of the pneumatic amplifier 5. While the preamplifier 5 is in the venting state, the pilot pressure P P down to the pressure of the pressure sink, for example the atmosphere 109.

[0056] The pilot pressure P P is applied to the control inputs 73, 93 of the pneumatic amplifiers 7, 9 of the main stage 6. The first pneumatic amplifier 7 has a control diaphragm 170, which is firmly connected to a vent valve seat 175, which is above a low pilot pressure P Pis forced against the double cone 170 and thus closes the vent valve 74. At increased pilot pressure P P the ventilation valve cone 173 opens the ventilation valve seat 174. The amplifier output 79 is then in fluid communication with the supply inlet 71, so that the first control pressure Y1 is raised.

[0057] In the first pneumatic amplifier 7 of the main stage 6, the vent valve seat 175 is pushed by a return spring 172 against the pilot pressure P P away from the vent valve cone 176. A second return spring 172' urges the vent valve cone 173 against the vent valve seat 174. The second return spring 172' can urge the double cone 170 against the vent valve seat 175.

[0058] The second pneumatic amplifier 9 has a control diaphragm 191, which is connected via a control rod 191' to a vent valve seat 195, which, at an increased pilot pressure PP is lifted off the vent valve cone 196 and thus opens the vent valve 95, as in Fig. 3. The second control pressure Y2 is then reduced by venting via the vent opening 98 to the pressure sink, such as the atmosphere 109.

[0059] In the second pneumatic amplifier 9 of the main stage 6, the vent valve seat 194 is moved by a return spring 192 in the direction of the pilot pressure P P away from the vent valve cone 196. Directed opposite to the pilot pressure P applied to the amplifier 9 P In a second working chamber, the supply pressure P S A second return spring 192' urges the ventilation valve cone 193 against the ventilation valve seat 194. The second return spring 192' can urge the double cone 190 against the vent valve seat 195. Conversely, with reduced pilot pressure P Pby opening the vent valve 94 in the second amplifier 9, the second control pressure Y2 corresponding to the supply pressure P S raised and by opening the vent valve 75 in the first amplifier 7, the first control pressure Y1 is reduced to the level of the pressure sink. At low pilot pressure P P the pneumatic medium is vented from the amplifier output 79 through the vent opening 78 to the pressure sink.

[0060] The one in the Fig. The pneumatics of the electropneumatic positioner 1 shown in Figures 1 and 2-4 can be expediently combined with a double-acting pneumatic actuator 110.

[0061] In Fig. Figure 5 schematically shows a control device 100 with a double-acting pneumatic actuator 110 and an electropneumatic positioner 1 connected thereto. The double-acting pneumatic actuator 110 has opposing working chambers, one of which is subjected to the first actuating pressure Y1 and the other to the second actuating pressure Y2, in order to provide an actuating force for actuating a control valve 120 through the difference between the actuating pressures Y1, Y2.

[0062] The actuator 100 is supplied with the pneumatic medium from a pneumatic source 101, which feeds the main supply input 10 of the electropneumatic positioner 1. The electropneumatic positioner 1 receives an electrical control signal x soll from a higher-level control and / or regulation unit of a process plant, for example a control room 201. The control signal represents a setpoint value x sollfor the positioner 1. The setpoint value x soll can, for example, specify a target position for the control valve 120. The control device 100 can be equipped with a position sensor 130 for detecting an actual position of the control valve 120 as a measurement signal x ist be equipped.

[0063] As in Fig. 6, the electropneumatic positioner 1 is designed and configured to determine the control value difference dx between the actual measurement signal x ist and the setpoint value x soll and according to a higher-level control routine 301 at least one target control pressure P soll to actuate the pneumatic actuator 110. In the positioner 1 described here, at least one pressure sensor 41, 61 is provided for detecting a control pressure P generated in the positioner 1 C , P Pfor at least one pneumatic amplifier stage 4, 6. The positioner 1 can also comprise one or more further pressure sensors 12, 72, 92, which measure the supply pressure P S , can generate a measurement signal representing the first control pressure Y1 and / or the second control pressure Y2. The person skilled in the art is familiar with numerous common control routines for determining a target control pressure P soll for electropneumatic actuators 100, for example in the form of a PID controller, a PI controller, a PD controller or similar.

[0064] A subordinate control routine 303 is designed and configured to provide an adjusted target control pressure P soll * based on the target control pressure P soll taking into account a positioner-internal control pressure P P , P C to generate 305. For this purpose, the cascade pressure P C recorded 304 and / or the pilot pressure P Pis detected 306. For example, the subordinate control routine 303 can determine the target control pressure P soll Alternatively or additionally, parameters of the higher-level control routine 301, for example weighting factors for a proportional, differential and / or integral control element, taking into account the cascade pressure P prevailing in the electropneumatic positioner C and / or pilot pressure P P be adjusted.

[0065] The features disclosed in the above description, the figures and the claims may be important both individually and in any combination for the realization of the invention in the various embodiments Reference symbols: 1 electropneumatic positioner 3 electropneumatic converter 4 Pre-stage 5 amplifiers 6 Main Level 7.9 amplifiers 10 Main supply entrance 11 Supply line 12 Pressure sensor 15, 16 Line 30 pressure reducers 32 flow limiters 50, 52 transfer ports 33 electrical control input 31 pneumatic active input 41, 61 pressure sensor 51, 71, 91 supply input 53, 73, 93 pneumatic control input 54, 74, 94 ventilation valve 55, 75, 95 vent valve 58, 78, 98 vent opening 59, 79, 99 amplifier output 72, 92 pressure sensor 100 actuator 101 Pneumatic source 109 Atmosphere 110 pneumatic actuator 120 control valve 130 Position sensor 150 double cones 151 Control diaphragm 152 return spring 153 Ventilation valve cone 154 Ventilation valve seat 155 vent valve seat 156 vent valve cone 170, 190 double cone 171, 191 control membrane 191' adjusting rod 172, 192 return spring 172', 192' return spring 173, 193 Ventilation valve cone 174, 194 Ventilation valve seat 175, 195 vent valve seat 176, 196 vent valve cone 201 Control Room 301 Control routine 303 subordinate control routine 304 Record cascade pressure 305 Generate control pressure 306 Record pilot pressure P P Pilot pressure P C Cascade printing P S Supply pressure P soll Target control pressure P soll* adjusted target control pressure Y1, Y2 control pressure x ist Actual control value x sollTarget control value dx control value difference

Claims

[1] Electropneumatic position controller (1) for delivering at least one actuating pressure (Y1, Y2) for a pneumatic actuator for actuating a control valve, such as a control valve, of a process plant, comprising: an electropneumatic converter (3), such as a current-pressure converter; at least one amplifier stage for the pneumatic actuator, such as a pre-stage (4) and / or a main stage (6), with at least one pneumatic amplifier (5, 7, 9), to which a control pressure, in particular cascade pressure (P c ), is present, further comprising a pressure sensor (41, 61) for detecting the control pressure, in particular the cascade pressure (P C ), characterized bya control and / or regulation electronics which is designed to generate an electrical control signal for the electropneumatic converter (3) so that the electropneumatic converter (3) causes the at least one pneumatic amplifier (7, 9) to deliver the actuating pressure (Y1, Y2), wherein the control and / or regulating electronics are configured to modulate the electrical control signal for the electropneumatic converter (3) based on the measurement of the pressure sensor (41, 61). [2] Electropneumatic position controller (1) according to claim 1, characterized by that the electropneumatic converter (3) supplies the control pressure, in particular the pilot pressure (P P ), sets. [3] Electropneumatic position controller (1) according to claim 1, characterized bya pre-stage (4) comprising a pre-amplifier (5) and a main stage (6) comprising at least one pneumatic amplifier (7, 9), wherein the pre-stage (4) supplies the control pressure as a pilot pressure (P P ) for the main stage (6). [4] Electropneumatic position controller (1) according to claim 3, characterized by that the electropneumatic converter (3) has a cascade pressure (P C ) as an additional control pressure for the pre-stage (4). [5] Electropneumatic position controller (1) for delivering at least one actuating pressure (Y1, Y2) for a pneumatic actuator for actuating a control valve, such as a control valve, of a process plant, in particular according to one of the preceding claims, comprising: an electropneumatic converter (3), such as a current-pressure converter; two amplifier stages for the pneumatic actuator, comprising a pre-stage (4) with a first pneumatic amplifier (5), to which a control pressure, in particular cascade pressure (P C ), and a main stage (6) with at least one second pneumatic amplifier (7, 9), to which a pilot pressure (P P ) is present, further comprising a pressure sensor (41) for detecting the control pressure, in particular the cascade pressure (P C ), characterized by a control and / or regulation electronics which is designed to generate an electrical control signal for the electropneumatic converter (3) so that the electropneumatic converter (3) causes the at least one pneumatic amplifier (7, 9) to deliver the actuating pressure (Y1, Y2), wherein the control and / or regulating electronics are configured to modulate the electrical control signal for the electropneumatic converter (3) based on the measurement of the pressure sensor (41, 61). [6] Electropneumatic position controller (1) for delivering at least one actuating pressure (Y1, Y2) for a pneumatic actuator for actuating a control valve, such as a control valve, of a process plant, in particular according to one of the preceding claims, comprising: an electropneumatic converter (3); at least one amplifier stage to the pneumatic actuator, in particular a main stage (6), with a first pneumatic amplifier (7) for providing a first actuating pressure (Y1) for the pneumatic actuator and a second pneumatic amplifier (9) for providing a second actuating pressure (Y2) for the pneumatic actuator, wherein the same control pressure provided by the electropneumatic converter (3), in particular cascade pressure (P C ) and / or pilot pressure (P P ), and that the first and second pneumatic amplifiers (7, 9) are free from mechanical coupling, characterized bya control and / or regulating electronics which is designed to generate an electrical control signal for the electropneumatic converter (3) so that the electropneumatic converter (3) causes the at least one pneumatic amplifier (7, 9) to deliver the actuating pressure (Y1, Y2), wherein the control and / or regulating electronics is designed to modulate the electrical control signal for the electropneumatic converter (3) based on the measurement of the pressure sensor (41, 61). [7] Electropneumatic position controller (1) according to one of the preceding claims, in particular according to one of claims 3 to 6, characterized bythat the first pneumatic amplifier (7) and optionally the second pneumatic amplifier (9) have or have a venting valve (74, 94) for providing the actuating pressure (Y1, Y2) to the pneumatic actuator and that the first pneumatic amplifier (7) and optionally the second pneumatic amplifier (9) have or have a venting valve (75, 95) for venting the pneumatic actuator to a pressure sink, such as the atmosphere. [8] Electropneumatic positioner according to claim 7, characterized by that the first pneumatic amplifier (7) and optionally the second pneumatic amplifier (9) is / are designed and arranged to, when a control pressure, in particular pilot pressure (P P), with a predetermined average pressure level, in particular between a first, in particular lower, pressure threshold value and a second, in particular upper, pressure threshold value, to assume a blocking state in which the ventilation valve (74, 94) and the venting valve (75, 95) are closed. [9] Electropneumatic positioner according to claim 7 or 8, characterized by that the first pneumatic amplifier (7) is designed and arranged to actuate the first pneumatic amplifier (7) when a control pressure, in particular pilot pressure (P P), with a predetermined low pressure level, in particular below a first, in particular lower, pressure threshold value, to assume a lowering state in which the vent valve (75) of the first pneumatic amplifier (7) is open and its venting valve (74) is closed, wherein in particular in the lowering state the vent valve (95) of the second pneumatic amplifier (9) is closed and its venting valve (94) is open. [10] Electropneumatic positioner according to one of claims 7 to 9, characterized by that the first pneumatic amplifier (7) is designed and arranged to, when a pilot pressure (P P) with a predetermined high pressure level, in particular above a second, in particular upper, pressure threshold value, to assume a lifting state in which the vent valve (75) of the first pneumatic amplifier (7) is closed and its venting valve (74) is open, wherein in particular in the lifting state the vent valve (95) of the second pneumatic amplifier (9) is open and its venting valve (94) is closed. [11] Electropneumatic position controller (1) according to one of the preceding claims, characterized by at least one further pressure sensor (12, 72, 92) for detecting the first control pressure (Y1), the second control pressure (Y2) and / or a supply pressure (P S) at a supply input (10) of the electropneumatic position controller (1), wherein preferably the control and / or regulating electronics processes the pressure measured values of the at least one further pressure sensor (12, 72, 92) for monitoring and / or diagnosing the position controller. [12] Actuating device (100) comprising an electropneumatic position controller (1) according to one of the preceding claims and a pneumatic actuator (110). [13] Actuator (100) according to claim 12, characterized by that the pneumatic actuator (110) is designed to be pneumatically single-acting and that the electropneumatic position controller (1) comprises only one amplifier (7, 9) in the amplifier stage, in particular the main stage. [14] Actuator (100) according to claim 12, characterized bythat the pneumatic actuator (110) is designed to be pneumatically double-acting and that the electropneumatic position controller (1) comprises two amplifiers (7, 9) in the amplifier stage, in particular the main stage.

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