阅读说明：本技术 控制头的操作安全替换 (Operationally safe replacement of control heads ) 是由 勒内·巴赫曼 拉里·库巴茨基 于 2021-06-18 设计创作，主要内容包括：提供了一种用于控制头的操作安全替换的方法。该控制头配置成对目标的运动进行致动并且至少限定第一操作位置,在将控制头更换为替换控制头之前,目标根据第一操作位置进行布置。在更换之后,替换控制头接收被更换的控制头的配置数据和参数。替换控制头至少限定第二操作位置。替换控制头的第二操作位置基本上对应于由被更换的控制头限定的第一操作位置。设置有感测装置以感测目标在更换过程之后的位置。指示装置用于提供状态指示符,其中,状态指示符至少取决于目标的位置与由替换控制头限定的第二操作位置之间的差。(A method for operational safety replacement of a control head is provided. The control head is configured to actuate movement of the target and to define at least a first operative position according to which the target is arranged prior to changing the control head to a replacement control head. After replacement, the replacement control head receives configuration data and parameters for the control head being replaced. The replacement control head defines at least a second operative position. The second operating position of the replacement control head substantially corresponds to the first operating position defined by the control head being replaced. Sensing means are provided to sense the position of the object after the replacement process. The indicating means is for providing a status indicator, wherein the status indicator is dependent on at least a difference between the position of the target and a second operational position defined by the replacement control head.)

1. A method for operational safety replacement of a control head configured to actuate movement of a target, the control head defining at least a first operative position according to which the target is arranged prior to replacement of the control head, the method comprising:

a) replacing the control head with a replacement control head;

b) receiving, by the replacement control head, configuration data and parameters of the control head being replaced, the replacement control head defining at least a second operational position, the second operational position of the replacement control head substantially corresponding to the first operational position defined by the control head being replaced;

c) sensing the position of the target relative to the replacement control head by means of a sensing device; and

d) providing a status indicator by means of a pointing device, said status indicator depending at least on a difference between said position of said target and said second operative position defined by said replacement control head.

2. The method of claim 1, wherein the control head comprises a communication device by means of which the control head is configured to receive configuration data and parameters.

3. The method of claim 2, wherein the control head is configured to communicate with at least one of a field device, a gateway, and a master device by way of the communication device.

4. The method of any one of the preceding claims, wherein the control head comprises a data processing unit, wherein the data processing unit is coupled to the sensing device, and wherein a difference between the position of the target and the second operational position defined by the replacement control head is determined with the data processing unit.

5. A method according to any of the preceding claims, wherein the status indicator can automatically have at least a first value and a second value indicating different situations of correspondence of the position of the target with at least one operating position defined by the replacement control head.

6. The method of any of the preceding claims, wherein the status indicator can have at least a first value and a second value, wherein the replacement control head defines a plurality of operating positions, and wherein the status indicator has the first value until a difference between the position of the target and a particular operating position of the plurality of operating positions defined by the replacement control head is determined for all of the particular operating positions.

7. A method according to claim 6, wherein the status indicator has a second value if the difference between the position of the target and the operating position defined by the replacement control head is less than or equal to a first distance for the particular operating position according to which the target is arranged when the control head is replaced and if the difference between the position of the target and the particular operating position for each of the remaining operating positions of the plurality of operating positions defined by the replacement control head is less than or equal to a second distance, the second distance being greater than the first distance.

8. A method according to claim 7, wherein the status indicator remains of the first value if the difference between the position of the target and the operating position defined by the replacement control head is greater than the first distance for the particular operating position according to which the target is arranged when the control head is replaced, or if the difference between the position of the target and the particular operating position is greater than the second distance but less than or equal to a third distance for any of the plurality of operating positions defined by the replacement control head, the third distance being greater than the second distance.

9. The method of claim 8, wherein the status indicator has a third value if, for any particular position of the plurality of operating positions defined by the replacement control head, a difference between the position of the target and the particular operating position is greater than the third distance.

10. A control head configured to perform the method of any one of claims 1 to 9.

11. The control head of claim 10, comprising at least one of a sensing device configured to sense a position of the target and an indicating device configured to provide a status indicator.

12. A process valve comprising a control head according to claim 10 or 11.

Technical Field

A method, control head and process valve for the operationally safe replacement of a control head are provided.

Background

A process valve for regulating a process medium includes a piston rod to determine an operating state of the valve. In order to move the piston rod between different operating positions corresponding to different operating states of the valve, the control head comprises an actuator. After installation, the control head needs to accommodate a particular range of travel of the process valve. Typically, this is accomplished using manual or automatic teaching functions.

When a (defective/damaged) control head is replaced (e.g. during a night shift), it is often not possible to activate the affected process valve, otherwise the process medium (e.g. milk) may flow accidentally. In such cases, it is common practice to replace a damaged control head with a replacement control head, and then teach only a single position (typically for the "closed" operating state of the process valve). The operational teaching for a single location is typically done via a manual teaching function so that the control procedure of the higher level system continues. However, in this case, the complete teaching of all the operating positions defined by the replacement control head is omitted in order to reduce as much as possible the down time of the higher-level system. Thus, the control head is not fully taught all operating positions of the piston rod.

Furthermore, the currently available replacement control heads fail to indicate (neither via a status display located on the device itself, nor via electronic communication with a higher level control system) that there is still a need to teach other operating locations. This "post-replacement" teaching is typically omitted until the next cleaning or maintenance of that part of the process system. Only then can the control head fully teach all operating positions. At the same time, where the worker does not have sufficient knowledge of the process or replacement control head, further production downtime may occur in the event that the control program of the process system does not receive the expected feedback (due to the lack of teaching of a particular operating position).

Even if tight manufacturing tolerances are maintained during the production process of the control head or a characteristic curve correction for the position sensing system is applied, statistical characteristic curve fluctuations occur for different control head samples. In the food and pharmaceutical industry, the operating position of the piston rod (process valve position) requires a very narrow tolerance range (feedback range) to ensure process reliability or product quality. In case no manual or automatic teaching function is performed after application of the replacement control head, there is always a risk that the piston rod position is eventually arranged outside the predefined feedback ranges or at least in the edge regions of those feedback ranges. Therefore, the consistency between the piston rod and the replacement control head is sub-optimal.

All known products require the activation of process valves to fully teach the replacement of all operating positions of the control head, which is not possible at any time without disturbing the production process. A different approach is to apply an operational tuning function of the process system. However, this operational tuning function is an indirect measure, since the control head does not teach all operational positions in its entirety, but rather uses additional components to compensate for differences in the flow of process media regulated by the process valve. In both methods, there is no limited teaching of automatically indicating the operating position of the replacement control head.

Disclosure of Invention

According to one aspect, a method for operational safety replacement of a control head is provided. The control head may be adapted for use with a process valve or may be a replaceable component of a process valve. A process valve may be a device configured to affect flow of a process medium. The process valve and/or the control head may be field devices within the process system.

The control head may be configured to actuate movement of the target. The target may be a piston rod of a process valve. The targets may be configured to control the operating state of the process valve. In particular, the operational state of the process valve may be any of an open configuration in which process medium flow is allowed, a closed configuration in which process medium flow is inhibited, a lower maintenance configuration (e.g., lower seat cleaning in the process), and an upper maintenance configuration (e.g., upper seat cleaning in the process). Thus, when the device/system is shut down, the lower and upper maintenance configurations will be understood to not refer to maintenance requiring disassembly of the process valve, but rather to represent a seat lift configuration during the process. This refers to, for example, cleaning the configuration (closed device/system) in the process after completion of a single batch process.

The targets may be configured to be capable of being arranged according to a plurality of operating positions. The plurality of operating positions may be defined by the control head. The plurality of operating positions may include different specific positions corresponding to various operating states of the process valve. For example, the piston rod can be arranged in a first operating position in which the process valve is open, a second operating position in which the process valve is closed, a fully retracted position according to the lower maintenance configuration and an intermediate position according to the upper maintenance configuration.

The control head may define at least a first operative position according to which the target is arranged prior to replacement of the control head. The first operating position may be any one of a plurality of operating positions defined by the control head according to which the target can be arranged.

The method may include replacing the first control head (either a damaged control head or a control head to be replaced) with a replacement control head.

The method may further include receiving, by the replacement control head, configuration data and parameters of the replaced control head after the replacement process. This means that the replacement control head may be configured to receive configuration data and parameters of the control head being replaced. The configuration data and parameters may include information related to the state of the control head and/or target and/or process valve being replaced prior to the replacement process. Thus, the replacement control head may adapt the control of the target to the state before the replacement process.

Due to the received configuration data and parameters, the replacement control head may be configured to define at least the second operative position. The second operating position defined by the replacement control head may substantially correspond to the first operating position defined by the control head being replaced. In other words, after the replacement process, the targets should be arranged according to the second operating position defined by the replacement control head. In other words, in the ideal case where there is no difference between the first control head and the replacement control head, the first operating position defined by the first (to be replaced) control head will coincide exactly with the second operating position defined by the replacement control head. However, due to tolerances and statistical fluctuations during the manufacturing process or installation, the first operating position and the second operating position are substantially different from each other.

In the context of the present application, the definition of the operating position by the control head (whether by the control head being replaced or the replacement control head) is to be understood as: the operating positions are set by the respective control heads such that a desired corresponding operating configuration of the process valve can be provided. In other words, the respective control head presets/provides an operating position for the target so that the process valve (in particular the shut-off device of the process valve) can be adapted to the desired operating configuration (operating state). The target may be directly or indirectly coupled to a shut-off device of the process valve. Thus, the operating configuration of the process valve can be determined by the position of the target. For example, the target needs to be arranged in a first position to provide a process valve that is open and allows flow of process medium. Conversely, if the process valve should inhibit the flow of process medium, the target must be placed in a second position, wherein the second position is different from the first position. Thus, different operating positions may be "defined" by the control head to provide different operating configurations/states of the process valve.

The method may further include sensing a position of the target with the sensing device after replacing the first control head with the replacement control head. The position of the target may be sensed relative to the replacement control head. The sensing device may be external to the replacement control head or may be part of the replacement control head. The sensing device may be configured to provide electronic information relating to the sensed position of the target. In particular, electronic information may be provided to the replacement control head.

The above mechanism may be considered as "transmission tuning". In conventional teaching functions, two, three or four valve position values are recorded. These values are stored as absolute values. This means that each value is recorded as a distance from absolute zero. When a control head (switch control head or proportional controller) is replaced, a new control head must be provided with new values for a different configuration. If it is assumed that the new control head has the same exact dimensions as the old control head and that the new control head is already mounted in exactly the same position as the old control head, a simple transmission of the absolute position values will be sufficient. However, these cases are not always likely to occur. Generally, the relative position of the process valves (the distance between specific positions) remains unchanged when the process valves are replaced with replacement valves. In other words, while the absolute closed position value may change from a first process valve to a different process valve, the relative distance between the closed position and the open position or any other position may be the same. In this regard, "transmission tuning" records the absolute positions of the original process valves and then converts these absolute positions to relative positions. If the original control head fails and it is assumed that the process valve was in the closed position at the time of the failure, the closed position of the new process valve becomes the new zero position. The other relative position of the process valve is then provided to the new control head so that the new control head and process valve are now ready for operation. This means that the process valve does not need to be opened and closed (not moved at all) to configure a new control head.

Further, the method may include providing a status indicator with the indicating device. The indicating device may be coupled to or may be part of the replacement control head. The status indicator may represent information dependent on the consistency of the position of the target relative to the second operational position defined by the replacement control head. The status indicator may also represent information related to the status of the process valve. In addition, the status indicator may represent information relating to a teaching of the (sensed) position of at least the second operating position of the replacement control head relative to the target. The status indicator may also represent information related to the teaching of the definition of multiple operating positions by the replacement control head relative to multiple (sensed) positions of the target. In particular, according to the method, the status indicator may be provided automatically. Additionally, status indicators may be provided to a user of the process valve.

The indicating device may include a status display disposed at the process valve and/or the replacement control head. The indicating device may also be configured to communicate the status indicator to a different component of the process system, in particular to one of a field device, a gateway, and a higher level control system (master). The field devices may also be different control heads.

With the above method, the state of the process valve in relation to the teaching of the (sensed) position of the at least one operating position defined by the replacement control head relative to the target can be clearly and unambiguously provided to the user or to a higher level system (control system). Since statistical fluctuations between different samples of the control head are unavoidable, differences in the operating positions defined by these different samples cannot generally be ruled out. However, based on the above method, a high reliability of the process system is provided, since the user is provided with clear information about the status of the replacement control head with respect to the target. Thus, the risk of accidental shutdown of the system may be reduced.

In particular, the first operating position of the piston rod may represent a position in which the process valve is closed. The piston rod with the position in which the process valve is closed can be highly relevant so that the flow of process medium controlled by the process valve is prevented with high reliability. In this regard, a piston rod having a position such that the process valve is closed may be considered more important than having a remaining position. In other words, if the offset is adjusted to zero for the closed position of the process valve, it may be less important if the open position (slope) of the process valve deviates slightly.

The control head may include or may be coupled to a communication device. With the communication device, the control heads may be configured to receive configuration data and parameters of different control heads. The control header may be configured to communicate its configuration data and parameters to field devices, gateways, or higher level control systems such as the master device of a process system. The configuration data and parameters may also include specific information related to the target and/or process valve to which the corresponding control head is applied. After the control head is replaced, the replacement control head may be configured to receive such stored configuration data and parameters for the control head being replaced. Alternatively, an external memory may be used to store the configuration data and parameters. Thus, a replacement control head can in principle be provided with the possibility of being configured similarly to a control head removed from the system. Thus, using such a communication device, the replacement control head may be configured not only similarly to the previous control head, but also similarly to the target and/or process valve.

The communication device may be particularly suitable for use in an industrial communication system, such as a fieldbus system, which may provide the possibility of automatically writing configuration data and parameters of a control head into a newly installed control head after replacement. The fieldbus system can be an industrial fieldbus system, such as a bus of the burkert system. A memory may be coupled to the fieldbus system to provide the possibility of storing configuration data and parameters of the control head. Thus, various criteria (e.g., device type, version) may be considered. The industrial communication system may be implemented, for example, via a field device, a gateway, or another higher level control device that manages configuration data and parameters. Alternatively (and often associated with more effort by the user), this process may also be performed manually through a "file transfer" using suitable tools. In this respect, a process valve and/or a control head represents a field device of such a fieldbus system.

The control head may comprise a data processing unit. The data processing unit may particularly be configured to receive information from the sensing device. Thus, the data processing unit may be configured to determine a difference between the sensed position of the target and the operational position defined by the replacement control head.

The data processing unit may also be coupled to the pointing device. In this way, the status indicator provided by the indicating means may be based on the difference determined by the data processing unit.

The status indicator may have at least a first value and a second value. The first value and/or the second value may depend on whether all of the operational positions defined by the replacement control head have been performed with respect to the teaching of the target. This means that the status indicator can indicate to the user that a complete parameterization relating to a specific target (piston rod) and/or process valve of the replacement control head has not been performed. Further, the status indicator may also be configured to indicate to the user whether emergency mode using the replacement control head is possible. For example, the status indicator may have a first value until a difference between the position of the target and the particular operating position is determined for all particular positions of the plurality of operating positions defined by the replacement control head.

The first value and/or the second value and optionally also the third value may also depend on the magnitude of the difference in the position of the target relative to the at least one operating position defined by the replacement control head. The status indicator may be switched from a first value to a second value if, for a particular operating position according to which the target is arranged when the replacement process takes place, the difference of the position of the target from a second operating position defined by the replacement control head is smaller than or equal to a first distance and the difference is smaller than or equal to the second distance for all remaining operating positions defined by the replacement control head, wherein the second distance may be equal to or greater than the first distance. Preferably, the second distance is greater than the first distance. The position at which the target is disposed when the replacement process occurs may be most important for replacing the control head. Thus, the position of the target should be more consistent with this "change" of target-the operating position, than the remaining operating positions defined by the replacement control head. Thus, the first distance, which per se may be considered to define a tolerance range with respect to the "replacement" operating position, may be a minimum range. For the remaining operating positions defined by the replacement control head, the consistency should then be within an acceptable range. However, this range may be larger than the "change" operating position. Thus, the second distance, which may be considered to define a different but still acceptable tolerance range with respect to the respective remaining operating positions defined by the replacement control head, may be greater than the first distance. The status indicator having the first value may indicate the following mode of operation of the replacement control head: in this mode of operation, maintenance (teaching) of the replacement control head is recommended. This may be due to a residual difference between the position of the target and the corresponding operating position defined by the replacement control head, which should be balanced by the "full" teaching of the replacement control head. "full" teaching may be performed to adapt configuration data and parameters and/or characteristics of the replacement control head to a particular setting. If the status indicator has a second value, the replacement control header may be configured to perform its usual control and/or feedback functions.

Conversely, if the position of the target differs from the second operational position defined by the replacement control head by more than the first distance but less than or equal to the third distance, the status indicator may remain at the first value. The third distance may be equal to or greater than the second distance. Preferably, the third distance is greater than the second distance. In this regard, the third distance may be considered to define yet another tolerance range corresponding to the emergency mode of the process valve. In other words, the process valve can still be operated according to the emergency mode. However, a status indicator having a second value may indicate that maintenance (teaching) of the replacement control head is required. If the status indicator has a first value, the replacement control head may be configured to perform its usual control and/or feedback functions.

The status indicator may also remain to have the first value if, for any of the remaining operating positions defined by the replacement control head (not the "replacement" operating position), the difference between the position of the target and the corresponding operating position is greater than the second distance but less than or equal to the third distance. In this case, there is a high degree of correspondence of the position of the target with the second operating position defined by the replacement control head (which corresponds to the "replacement" operating position). However, at least for one of the remaining operating positions defined by the replacement control head, consistency is only acceptable within the scope of the emergency mode of the process valve.

The status indicator may also have a third value. The third value may indicate that a difference between the position of the target and the particular operational position defined by the replacement control head is greater than a third distance of the at least one operational position defined by the replacement control head. In this case, at least for the single operating position defined by the replacement control head, according to which the targets should be arranged, the targets are misaligned to such an extent that it is no longer acceptable. Thus, the status indicator having the third value may be considered to indicate an error condition of the replacement control head and/or the process valve. If the status indicator has a third value, further actuation of the replacement control head and/or target may be disabled to avoid danger throughout the process.

Thus, status indicators having different values may be used to identify different instances of correspondence between the location of the target and the at least one operating location defined by the replacement control head.

In the context of the present application, the difference between the position of the target and the specific operating position defined by the control head is always to be determined if the target should be arranged according to this operating position. For example, if the control head defines a first operating position and a second operating position and it is assumed that the target is arranged according to the first operating position, only the difference between the position of the target (piston rod) and the first operating position is determined. If the target should not be arranged according to the second operating position, the evaluation of the difference between the position of the target and the second operating position is omitted.

Due to statistical fluctuations between different specimens of the control head, the first operating position defined by the first control head before the control head is replaced does not coincide with the second operating position defined by the replacement control head after the replacement is performed. Thus, after application of the replacement control head, the position of the target is typically not coincident with the second operational position. In this regard, the status indicators described above provide a clear indication as to the reliability of the operational position defined by the replacement control head relative to the target position. Thus, with the absolute position of the target, the status indicator provides clear information that suggests or requires a degree of maintenance work on the replacement control head or whether the replacement control head/process valve is in an error state.

According to another aspect, a control head configured for performing the above method is provided.

According to yet another aspect, a process valve is provided. The process valve may include a control head configured to perform the above-described method.

The control head may comprise at least one of a sensing device configured to sense a position of the target and an indicating device configured to provide the status indicator.

Those skilled in the art will certainly appreciate that any of the above aspects may be combined with each other in any meaningful combination as required by the particular control head and/or process valve and/or the method to be performed by the control head.

Drawings

Other aspects and features will emerge from the following description of a preferred embodiment with reference to the accompanying drawings, in which:

figure 1 shows a simplified schematic view of the operating position of the control head,

FIG. 2 shows a simplified schematic of a control head and an alternative control head, an

Figure 3 shows a simplified schematic of a method for the operationally safe replacement of a control head.

Detailed Description

FIG. 1 shows a simplified schematic model of a process valve 100 according to four different configurations A through D. The process valve 100 is implemented as a field device in a process system. The process valve 100 includes a housing 110, a shut-off device 120, a control head 130 that is a replacement control head 130b, and a piston rod (target) 140. The piston rod 140 includes a front end 142. The position of the piston rod 140 within the replacement control head 130b is defined by the forward end 142 of the piston rod 140. Actuating the piston rod 140 causes the shut-off device 120 to change its position such that the flow of the process medium can be influenced. The replacement control head 130b is used to actuate the piston rod 140.

The four different configurations A-D of the process valve 100 represent four different operating positions 150, 152, 154, 156 defined by the replacement control head 130 b. In each of the different configurations a to D, the front end 142 of the piston rod 140 is arranged differently. Configuration a corresponds to a closed configuration of the process valve 100, according to which the front end 142 of the piston rod 140 is arranged at the operating position 152. Configuration B corresponds to an open configuration of the process valve 100 according to which the front end 142 of the piston rod 140 is arranged at a different operating position 150. Configuration C corresponds to an upper maintenance configuration of the process valve 100, according to which the front end 142 of the piston rod 140 is arranged at a further operating position 154. Configuration D corresponds to a lower maintenance configuration of the process valve 100 according to which the front end 142 of the piston rod 140 is arranged at a further operating position 156.

Replacement control head 130b may also include a position sensing system 132. The position sensing system 132 may be configured to sense the position of the forward end 142 of the piston rod 140 within the control head 130 b.

Furthermore, the replacement control head 130b may comprise a data processing unit 134, a communication device 136 and a pointing device 138.

For simplicity, the position sensing system 132, the data processing unit 134, the communication device 136 and the pointing device 138 are only shown for configuration D. However, for the remaining configurations a through C, these components are also part of the replacement control head 130 b.

Based on the communication device 136, the replacement control head 130b may be configured to communicate with a different field device, such as the control head 130 of a different process valve 100, a gateway, or a higher level component of a process system. In general, the replacement control head 130b may also be configured to communicate with several devices using a single communication device 136. The communication device 136 can also be configured to communicate with an industrial fieldbus system, such as the burkert system bus, for which the process valve 100 and/or the control head 130 can be field devices.

The replacement control head 130b can receive configuration data and parameters to accommodate the particular use of the process valve 100. For example, after replacing a particular control head 130 with a replacement control head 130b, the replacement control head 130b receives the configuration data and parameters of the replaced control head 130. To this end, each control head 130 may be configured to communicate its configuration data and parameters to some device having a memory.

Accordingly, replacement control head 130b may define operating positions 150, 152, 154, 156 such that these operating positions generally correspond to the operating positions of the control head 130 being replaced. However, due to statistical fluctuations between different specimens of the control head 130, the operating positions between different specimens will differ at least slightly from one another. Thus, if the front end 142 of the piston rod 140 is arranged at a specific operating position before the control head 130 is replaced, the front end 142 of the piston rod 140 will substantially no longer coincide with the specific operating position after the replacement control head 130b is applied. In this case, replacement control head 130b may utilize position sensing system 132 to sense the position of forward end 142 of piston rod 140 relative to the operating position defined by replacement control head 130 b.

Data processing unit 134 may be used to evaluate data received from position sensing system 132 regarding the operational position defined by replacement control head 130 b. Thus, by means of the data processing unit 134, it is possible to determine the difference between the position of the front end portion 142 and the specific operating position according to which the front end portion 142 should be arranged. The data processing unit 134 can then determine whether the difference is within any of certain tolerance ranges. These tolerance ranges may include any of a first tolerance range, a second tolerance range, and a third tolerance range that are acceptable. The data processing unit 134 may also be configured to evaluate whether the difference is outside any of the tolerance ranges. In this regard, the first and second tolerance ranges may correspond to configurations in which the process valve 100 may be used despite the recommendation for servicing the replacement control head 130 b. The third tolerance range may correspond to a configuration in which the replacement control head 130b and/or the process valve 100 may be further used only in accordance with the emergency mode. If the difference between the position of the forward end 142 of the piston rod 140 and the particular operating position defined by the replacement control head 130b is outside of the third tolerance range, the replacement control head 130b and/or the process valve 100 may be in an error state.

The indicating device 138 may be configured to indicate a status indicator to a user that represents the status of the process valve 100 as determined by the data processing unit 134 as described above. In this regard, the indicating device 138 may include a display located at the replacement control head 130 b. Additionally or alternatively, the indicating device 138 may be configured to indicate status indicators to different field devices, fieldbus systems, gateways, or higher level control systems.

Fig. 2 shows a simplified schematic of control head 130a and alternate control head 130 b. Based on this figure, the evaluation difference with respect to the position of the front end portion 142 of the piston rod 140 due to the replacement process will be described in more detail.

The first control head 130a will be replaced. For simplicity, the first control head 130a defines only the first and second operating configurations 160 and 170. For each operating configuration 160, 170, a particular operating position is defined by the control head 130 a. For example, the operating position 161 corresponds to a position at which the front end 142 of the piston rod 140 is disposed when the process valve 100 is in the first operating configuration 160.

If the control head 130a is replaced with a replacement control head 130b, the replacement control head 130b may receive configuration data and parameters for the replaced control head 130 a. This may be accomplished using a communication device 136 that replaces control head 130 b. Thus, based on the received configuration data and parameters, the replacement control head 130b may likewise define two operational configurations 180, 190, which two operational configurations 180, 190 may substantially correspond to the operational configurations 160, 170 of the replaced control head 130 a. Due to statistical fluctuations during the production process or during installation, the operating positions of the corresponding operating configurations do not need to coincide. For example, although the respective operating configurations correspond to each other, the operating position 161 of the replaced control head 130a does not necessarily coincide with the operating position 181 of the replacement control head 130 b. Therefore, even if the leading end portion 142 of the piston rod 140 is arranged at the operation position 161 of the control head 130a being replaced, the leading end portion 142 may be misaligned with respect to the operation position 181 of the replacement control head 130b after the replacement is performed.

To automatically indicate to the user the extent of such misalignment and the status of the replacement control head 130b (in terms of recommended and required maintenance or error status), the replacement control head 130b defines a first tolerance range, a second tolerance range, and a third tolerance range for each operating position. For the operative position 181 of the replacement control head 130b, a first tolerance range is determined by the lines 182, 183. The first tolerance range is less than a second tolerance range defined by lines 184, 185, which itself is less than a third tolerance range defined by lines 186, 187.

The replacement control head 130b may then be configured to indicate with the indicating device 138 the extent to which the position of the tip portion 142 differs from the operating position 181 based on the various tolerance ranges 182, 183, 184, 185, 186, 187. Furthermore, differences with respect to other operational positions defined by the replacement control head 130b may also be considered during this evaluation.

In this regard, the indication device 138 may provide a status indicator. Further, the determination of the difference between the front end 142 and the respective operating position may be based on the position sensing system 132 and the data processing unit 134.

The status indicator may have a first value before the difference between the position of the front end 142 of the piston rod 140 and each respective operating position defined by the replacement control head 130b is determined. The first value may indicate that maintenance is required. In other words, the status indicator will have a first value until the difference is determined for all operating positions, i.e., until the process valve is enabled to have at least once each of the operating configurations defined by the replacement control head 130b such that the degree of misalignment can be evaluated.

Since the control head 130a is replaced when a higher level processing system is in operation, consistency between the position of the front end 142 of the piston rod 140 and the "replacement" operating position 181 (i.e., the operating position in which the front end is disposed when replacement occurs) is most relevant. Accordingly, the replacement control head 130b may be configured to determine whether the difference between the front end 142 and the particular operating position 181 is within a first tolerance range defined by the lines 182, 183. Due to the dependence of the operating position, the tolerance ranges 182, 183 can be small.

If replacement control head 130b finds leading end 142 within first tolerance range 182, 183, replacement control head 130b may be configured to determine whether the position of leading end 142 relative to all remaining operating positions defined by replacement control head 130b is at least within second tolerance range 184, 185 for each of the remaining operating positions. The second tolerance range 184, 185 may be greater than the first tolerance range 182, 183. If the replacement control head 130b finds that the condition is met for all remaining operation positions (except for the "swap" -operation position for which the difference is within the first tolerance range 182, 183), the status indicator switches from the first value to the second value. The second value may indicate that maintenance is not required but recommended. According to this situation, the consistency between the front end portion 142 and the operation position defined by the replacement control head 130b is very good. However, the difference is still not negligible. To balance the remaining differences, a full teaching of the position of replacement control head 130b with respect to front end 142 may need to be performed.

If the replacement control head 130b finds that the front end portion 142 is outside the first tolerance range 182, 183 for a particular operating position ("replacement" operating position), according to which the front end portion 142 is arranged during the replacement process, the replacement control head 130b enables the third tolerance range 186, 187 (enables the respective feedback mechanism). In this case, the replacement control head 130b determines whether the difference is within the third tolerance range 186, 187 for each of the operating positions defined by the replacement control head 130 b. If this is true for all of the operational positions defined by the replacement control head 130b, the status indicator remains at the first value. If the difference is outside of the third tolerance range for any of the operating positions defined by the replacement control head 130b, the status indicator switches to a third value that indicates an error status of the control head 130b and/or the process valve 100.

Fig. 3 shows a simplified schematic diagram of a method 200 for operational safety replacement of a control head.

At step 210, the damaged control head 130a is replaced with a replacement control head 130 b.

At step 220, the replacement control head 130b receives the configuration data and parameters of the replaced control head 130a by using the communication device 136. Based on the received data, the replacement control head 130b defines a corresponding operating configuration and operating position.

At step 230, replacement control head 130b senses, with position sensing device 132, the position of the leading end 142 of piston rod 140 relative to the operating position defined by replacement control head 130b according to which leading end 142 should be disposed when the replacement process occurs.

The remaining steps of the method 200 depend on a determination of the difference between the front end 142 of the piston rod 140 and the specific operating position 181, according to which the front end 142 should be arranged during the replacement process. Thus, step 240 includes several substeps 242, 244 and 246.

Generally, the data processing unit 134 of the replacement control head 130b is used to determine the relevant conditions at step 240. In this regard, the replacement control head 130b defines a plurality of operating positions i-1 to N. Further, as previously described, for each operating position i-1 to N, the difference Di between the front end 142 of the piston rod 140 and the respective operating position i-1 to N is determined individually. This means that the data processing unit 134 typically determines N difference values Di, where i equals 1 to N, each difference value corresponding to a separate operating position. In addition, for each operating position i-1 to N, typically three tolerance ranges T1, T2, and T3 may be defined by the replacement control head 130b, wherein typically T1 ≦ T2 ≦ T3, preferably T1< T2< T3.

At sub-step 242, the replacement control head 130b evaluates: for a specific operating position i ═ 1, according to which the front end 142 of the piston rod 140 is arranged during the replacement process, whether the difference D1 between the front end 142 and the operating position i ═ 1 is within the first tolerance range T1, i.e. whether D1 ≦ T1.

If sub-step 242 is found to be true, replacement control head 130b evaluates at sub-step 244: for each remaining operating position defined by the replacement control head 130b (i.e., for i >1 through N), whether the difference Di is within the second tolerance range T2, i.e., whether Di ≦ T2 for i >1 through N.

If either of sub-steps 242 or 244 is found to be false, the replacement control head 130b enables a third feedback mechanism corresponding to a third tolerance range T3 at sub-step 246. Subsequently, the replacement control head 130b evaluates at sub-step 246: for each operating position i-1 to N defined by the replacement control head 130b, whether the difference Di is within the third tolerance range T3, i.e., whether Di ≦ T3 for i-1 to N.

Based on the evaluation of the difference Di, the indicating means 138 provides a status indicator. If the evaluation procedure of step 240 has been completed, this is not only performed at step 250, but also during the evaluation procedure at step 240 itself. If during step 240 no difference in the difference Di for at least one operating position i-1 to N has been determined, the status indicator has a first value V-1. This is indicated by the dashed box 241 in step 240. The first value V ═ 1 can be described as requiring maintenance.

Once the evaluation procedure of step 240 is completed, the status indicator may remain to have a first value V-1. This is the case if sub-step 246 is performed and found to be true.

If substep 244 is performed and found to be true, the status indicator switches to a second value V2, which is described as a recommended maintenance.

If sub-step 246 is performed and found to be false, the status indicator switches to a further value, i.e., a third value V-3, which is depicted as the replacement control head 130b and/or the process valve 100 being in an error state.

Although the invention has been described above with reference to specific embodiments, the invention is not limited to these embodiments and, of course, other alternatives falling within the scope of the claimed invention will occur to those skilled in the art.