Patent Grant
7676287
This patent relates generally to performing diagnostics and maintenance in a process plant and, more particularly, to providing predictive diagnostics capabilities within a process plant in a manner that reduces or prevents abnormal situations within the process plant.
Process control systems, like those used in chemical, petroleum or other processes, typically include one or more centralized or decentralized process controllers communicatively coupled to at least one host or operator workstation and to one or more process control and instrumentation devices such as, for example, field devices, via analog, digital or combined analog/digital buses. Field devices, which may be, for example, valves, valve positioners, switches, transmitters, and sensors (e.g., temperature, pressure, and flow rate sensors), are located within the process plant environment, and perform functions within the process such as opening or closing valves, measuring process parameters, increasing or decreasing fluid flow, etc. Smart field devices such as field devices conforming to the well-known FOUNDATION™ Fieldbus (hereinafter “Fieldbus”) protocol or the HART® protocol may also perform control calculations, alarming functions, and other control functions commonly implemented within the process controller.
The process controllers, which are typically located within the process plant environment, receive signals indicative of process measurements or process variables made by or associated with the field devices and/or other information pertaining to the field devices, and execute controller applications. The controller applications implement, for example, different control modules that make process control decisions, generate control signals based on the received information, and coordinate with the control modules or blocks being performed in the field devices such as HART and Fieldbus field devices. The control modules in the process controllers send the control signals over the communication lines or signal paths to the field devices, to thereby control the operation of the process.
Information from the field devices and the process controllers is typically made available to one or more other hardware devices such as, for example, operator workstations, maintenance workstations, personal computers, handheld devices, data historians, report generators, centralized databases, etc. to enable an operator or a maintenance person to perform desired functions with respect to the process such as, for example, changing settings of the process control routine, modifying the operation of the control modules within the process controllers or the smart field devices, viewing the current state of the process or of particular devices within the process plant, viewing alarms generated by field devices and process controllers, simulating the operation of the process for the purpose of training personnel or testing the process control software, diagnosing problems or hardware failures within the process plant, etc.
While a typical process plant has many process control and instrumentation devices such as valves, transmitters, sensors, etc. connected to one or more process controllers, there are many other supporting devices that are also necessary for or related to process operation. These additional devices include, for example, power supply equipment, power generation and distribution equipment, rotating equipment such as turbines, motors, etc., which are located at numerous places in a typical plant. While this additional equipment does not necessarily create or use process variables and, in many instances, is not controlled or even coupled to a process controller for the purpose of affecting the process operation, this equipment is nevertheless important to, and ultimately necessary for proper operation of the process.
As is known, problems frequently arise within a process plant environment, especially a process plant having a large number of field devices and supporting equipment. These problems may take the form of broken or malfunctioning devices, logic elements, such as software routines, being in improper modes, process control loops being improperly tuned, one or more failures in communications between devices within the process plant, etc. These and other problems, while numerous in nature, generally result in the process operating in an abnormal state (i.e., the process plant being in an abnormal situation) which is usually associated with suboptimal performance of the process plant. Many diagnostic tools and applications have been developed to detect and determine the cause of problems within a process plant and to assist an operator or a maintenance person to diagnose and correct the problems, once the problems have occurred and been detected. For example, operator workstations, which are typically connected to the process controllers through communication connections such as a direct or wireless bus, Ethernet, modem, phone line, and the like, have processors and memories that are adapted to run software or firmware, such as the DeltaV™ and Ovation control systems, sold by Emerson Process Management which includes numerous control module and control loop diagnostic tools. Likewise, maintenance workstations, which may be connected to the process control devices, such as field devices, via the same communication connections as the controller applications, or via different communication connections, such as Object Linking & Embedding for Process Control (OPC) connections, handheld connections, etc., typically include one or more applications designed to view maintenance alarms and alerts generated by field devices within the process plant, to test devices within the process plant and to perform maintenance activities on the field devices and other devices within the process plant. Similar diagnostic applications have been developed to diagnose problems within the supporting equipment within the process plant.
Thus, for example, the Asset Management Solutions (AMS) application (at least partially disclosed in U.S. Pat. No. 5,960,214 entitled “Integrated Communication Network for use in a Field Device Management System”) sold by Emerson Process Management, enables communication with and stores data pertaining to field devices to ascertain and track the operating state of the field devices. In some instances, the AMS application may be used to communicate with a field device to change parameters within the field device, to cause the field device to run applications on itself such as, for example, self-calibration routines or self-diagnostic routines, to obtain information about the status or health of the field device, etc. This information may include, for example, status information (e.g., whether an alarm or other similar event has occurred), device configuration information (e.g., the manner in which the field device is currently or may be configured and the type of measuring units used by the field device), device parameters (e.g., the field device range values and other parameters), etc. Of course, this information may be used by a maintenance person to monitor, maintain, and/or diagnose problems with field devices.
Similarly, many process plants include equipment monitoring and diagnostic applications such as, for example, RBMware provided by CSI Systems, or any other known applications used to monitor, diagnose, and optimize the operating state of various rotating equipment. Maintenance personnel usually use these applications to maintain and oversee the performance of rotating equipment in the plant, to determine problems with the rotating equipment, and to determine when and if the rotating equipment must be repaired or replaced. Similarly, many process plants include power control and diagnostic applications such as those provided by, for example, the Liebert and ASCO companies, to control and maintain the power generation and distribution equipment. It is also known to run control optimization applications such as, for example, real-time optimizers (RTO+), within a process plant to optimize the control activities of the process plant. Such optimization applications typically use complex algorithms and/or models of the process plant to predict how inputs may be changed to optimize operation of the process plant with respect to some desired optimization variable such as, for example, profit.
These and other diagnostic and optimization applications are typically implemented on a system-wide basis in one or more of the operator or maintenance workstations, and may provide preconfigured displays to the operator or maintenance personnel regarding the operating state of the process plant, or the devices and equipment within the process plant. Typical displays include alarming displays that receive alarms generated by the process controllers or other devices within the process plant, control displays indicating the operating state of the process controllers and other devices within the process plant, maintenance displays indicating the operating state of the devices within the process plant, etc. Likewise, these and other diagnostic applications may enable an operator or a maintenance person to retune a control loop or to reset other control parameters, to run a test on one or more field devices to determine the current status of those field devices, to calibrate field devices or other equipment, or to perform other problem detection and correction activities on devices and equipment within the process plant.
While these various applications and tools are very helpful in identifying and correcting problems within a process plant, these diagnostic applications are generally configured to be used only after a problem has already occurred within a process plant and, therefore, after an abnormal situation already exists within the plant. Unfortunately, an abnormal situation may exist for some time before it is detected, identified and corrected using these tools, resulting in the suboptimal performance of the process plant for the period of time during which the problem is detected, identified and corrected. In many cases, a control operator will first detect that some problem exists based on alarms, alerts or poor performance of the process plant. The operator will then notify the maintenance personnel of the potential problem. The maintenance personnel may or may not detect an actual problem and may need further prompting before actually running tests or other diagnostic applications, or performing other activities needed to identify the actual problem. Once the problem is identified, the maintenance personnel may need to order parts and schedule a maintenance procedure, all of which may result in a significant period of time between the occurrence of a problem and the correction of that problem, during which time the process plant runs in an abnormal situation generally associated with the sub-optimal operation of the plant.
Additionally, many process plants can experience an abnormal situation which results in significant costs or damage within the plant in a relatively short amount of time. For example, some abnormal situations can cause significant damage to equipment, the loss of raw materials, or significant unexpected downtime within the process plant if these abnormal situations exist for even a short amount of time. Thus, merely detecting a problem within the plant after the problem has occurred, no matter how quickly the problem is corrected, may still result in significant loss or damage within the process plant. As a result, it is desirable to try to prevent abnormal situations from arising in the first place, instead of simply trying to react to and correct problems within the process plant after an abnormal situation arises.
There is currently one technique that may be used to collect data that enables a user to predict the occurrence of certain abnormal situations within a process plant before these abnormal situations actually arise, with the purpose of taking steps to prevent the predicted abnormal situation before any significant loss within the process plant takes place. This procedure is disclosed in U.S. patent application Ser. No. 09/972,078, entitled “Root Cause Diagnostics” (based in part on U.S. patent application Ser. No. 08/623,569, now U.S. Pat. No. 6,017,143). The entire disclosures of both of these applications are hereby incorporated by reference herein. Generally speaking, this technique places statistical data collection and processing blocks or statistical processing monitoring (SPM) blocks, in each of a number of devices, such as field devices, within a process plant. The statistical data collection and processing blocks collect, for example, process variable data and determine certain statistical measures associated with the collected data, such as a mean, a median, a standard deviation, etc. These statistical measures may then sent to a user and analyzed to recognize patterns suggesting the future occurrence of a known abnormal situation. Once a particular suspected future abnormal situation is detected, steps may be taken to correct the underlying problem, thereby avoiding the abnormal situation in the first place. However, the collection and analysis of this data may be time consuming and tedious for a typical maintenance operator, especially in process plants having a large number of field devices collecting this statistical data. Still further, while a maintenance person may be able to collect the statistical data, this person may not know how to best analyze or view the data or to determine what, if any, future abnormal situation may be suggested by the data.
Also, generally speaking, it is very cumbersome and tedious to configure a plant to collect and view all of the statistical process data generated by the SPMs, especially in large processes. In fact, at the present time, a user must generally create an OPC client that individually monitors each of the parameters of interest within the different field devices, which means that every field device must be individually configured to collect this data. This configuration process is very time consuming and is vulnerable to human errors.
In one aspect, a system for gathering data associated with a process plant, in which parameters are generated by a plurality of signal processing data collection blocks, automatically determines parameters to be monitored. The signal processing data collection blocks may generate data such as statistical data, frequency analysis data, auto regression data, wavelets data, etc. Then, the system monitors the determined parameters.
In another aspect, a system automatically determines signal processing data collection blocks implemented in a process plant. Data retrieved from these signal processing data collection blocks is analyzed to determine signal processing data collection blocks that are not enabled, if any. Then, signal processing data collection blocks that are not enabled are enabled to permit signal processing data collection.
Referring now to
Still further, maintenance systems, such as computers executing the AMS application or any other device monitoring and communication applications may be connected to the process control systems 12 and 14 or to the individual devices therein to perform maintenance and monitoring activities. For example, a maintenance computer 18 may be connected to the controller 12B and/or to the devices 15 via any desired communication lines or networks (including wireless or handheld device networks) to communicate with and, in some instances, reconfigure or perform other maintenance activities on the devices 15. Similarly, maintenance applications such as the AMS application may be installed in and executed by one or more of the user interfaces 14A associated with the distributed process control system 14 to perform maintenance and monitoring functions, including data collection related to the operating status of the devices 16.
The process plant 10 also includes various rotating equipment 20, such as turbines, motors, etc. which are connected to a maintenance computer 22 via some permanent or temporary communication link (such as a bus, a wireless communication system or hand held devices which are connected to the equipment 20 to take readings and are then removed). The maintenance computer 22 may store and execute known monitoring and diagnostic applications 23 provided by, for example, CSI (an Emerson Process Management Company) or other any other known applications used to diagnose, monitor and optimize the operating state of the rotating equipment 20. Maintenance personnel usually use the applications 23 to maintain and oversee the performance of rotating equipment 20 in the plant 10, to determine problems with the rotating equipment 20 and to determine when and if the rotating equipment 20 must be repaired or replaced. In some cases, outside consultants or service organizations may temporarily acquire or measure data pertaining to the equipment 20 and use this data to perform analyses for the equipment 20 to detect problems, poor performance or other issues effecting the equipment 20. In these cases, the computers running the analyses may not be connected to the rest of the system 10 via any communication line or may be connected only temporarily.
Similarly, a power generation and distribution system 24 having power generating and distribution equipment 25 associated with the plant 10 is connected via, for example, a bus, to another computer 26 which runs and oversees the operation of the power generating and distribution equipment 25 within the plant 10. The computer 26 may execute known power control and diagnostics applications 27 such a as those provided by, for example, Liebert and ASCO or other companies to control and maintain the power generation and distribution equipment 25. Again, in many cases, outside consultants or service organizations may use service applications that temporarily acquire or measure data pertaining to the equipment 25 and use this data to perform analyses for the equipment 25 to detect problems poor performance or other issues effecting the equipment 25. In these cases, the computers (such as the computer 26) running the analyses may not be connected to the rest of the system 10 via any communication line or may be connected only temporarily.
As illustrated in
Once the statistical data (or process variable data) is collected, the viewing application 40 may be used to process this data and/or to display the collected or processed statistical data (e.g., as stored in the database 43) in different manners to enable a user, such as a maintenance person, to better be able to determine the existence of or the predicted future existence of an abnormal situation and to take preemptive corrective actions. The rules engine development and execution application 42 may use one or more rules stored therein to analyze the collected data to determine the existence of, or to predict the future existence of an abnormal situation within the process plant 10. Additionally, the rules engine development and execution application 42 may enable an operator or other user to create additional rules to be implemented by a rules engine to detect or predict abnormal situations.
The portion 50 of the process plant 10 illustrated in
In any event, one or more user interfaces or computers 72 and 74 (which may be any types of personal computers, workstations, etc.) accessible by plant personnel such as configuration engineers, process control operators, maintenance personnel, plant managers, supervisors, etc. are coupled to the process controllers 60 via a communication line or bus 76 which may be implemented using any desired hardwired or wireless communication structure, and using any desired or suitable communication protocol such as, for example, an Ethernet protocol. In addition, a database 78 may be connected to the communication bus 76 to operate as a data historian that collects and stores configuration information as well as on line process variable data, parameter data, status data, and other data associated with the process controllers 60 and field devices 60 and 66 within the process plant 10. Thus, the database 78 may operate as a configuration database to store the current configuration, including process configuration modules, as well as control configuration information for the process control system 54 as downloaded to and stored within the process controllers 60 and the field devices 60 and 66. Likewise, the database 78 may store historical abnormal situation prevention data, including statistical data collected by the field devices 60 and 66 within the process plant 10 or statistical data determined from process variables collected by the field devices 60 and 66.
While the process controllers 60, I/O devices 68 and 70, and field devices 60 and 66 are typically located down within and distributed throughout the sometimes harsh plant environment, the workstations 72 and 74, and the database 78 are usually located in control rooms, maintenance rooms or other less harsh environments easily accessible by operators, maintenance personnel, etc.
Generally speaking, the process controllers 60 store and execute one or more controller applications that implement control strategies using a number of different, independently executed, control modules or blocks. The control modules may each be made up of what are commonly referred to as function blocks, wherein each function block is a part or a subroutine of an overall control routine and operates in conjunction with other function blocks (via communications called links) to implement process control loops within the process plant 10. As is well known function blocks, which may be objects in an object oriented programming protocol, typically perform one of an input function, such as that associated with a transmitter, a sensor or other process parameter measurement device, a control function such as that associated with a control routine that performs PID, fuzzy logic, etc. control, or an output function, which controls the operation of some device, such as a valve to perform some physical function within the process plant 10. Of course, hybrid and other types of complex function blocks exist, such as model predictive controllers (MPCs), optimizers, etc. It is to be understood that while the Fieldbus protocol and the DeltaV™ system protocol use control modules and function blocks designed and implemented in an object-oriented programming protocol, the control modules may be designed using any desired control programming scheme including, for example, sequential function blocks, ladder logic, etc., and are not limited to being designed using function blocks or any other particular programming technique.
As illustrated in
Additionally, as shown in
Generally speaking, the blocks 80 and 82 or sub-elements of these blocks, collect data, such a process variable data, within the device in which they are located and perform statistical processing or analysis on the data for any number of reasons. For example, the block 80, which is illustrated as being associated with a valve, may have a stuck valve detection routine which analyzes the valve process variable data to determine if the valve is in a stuck condition. In addition, the block 80 includes a set of four statistical process monitoring (SPM) blocks or units SPM1-SPM4 which may collect process variable or other data within the valve and perform one or more statistical calculations on the collected data to determine, for example, a mean, a median, a standard deviation, a root-mean-square (RMS), a rate of change, a range, a minimum, a maximum, etc. of the collected data and/or to detect events such as drift, bias, noise, spikes, etc., in the collected data. The specific statistical data generated, nor the method in which it is generated is not critical. Thus, different types of statistical data can be generated in addition to, or instead of, the specific types described above. Additionally, a variety of techniques, including known techniques, can be used to generate such data. The term statistical process monitoring (SPM) block is used herein to describe functionality that performs statistical process monitoring on at least one process variable or other process parameter, and may be performed by any desired software, firmware or hardware within the device or even outside of a device for which data is collected. It will be understood that, because the SPMs are generally located in the devices where the device data is collected, the SPMs can acquire quantitatively more and qualitatively more accurate process variable data. As a result, the SPM blocks are generally capable of determining better statistical calculations with respect to the collected process variable data than a block located outside of the device in which the process variable data is collected.
As another example, the block 82 of
In one embodiment, each SPM block within the ADBs 80 and 82 can be either active or inactive. An active SPM block is one that is currently monitoring a process variable (or other process parameter) while an inactive SPM block is one that is not currently monitoring a process variable. Generally speaking, SPM blocks are, by default, inactive and, therefore, each one must generally be individually configured to monitor a process variable.
While certain statistical monitoring blocks are illustrated in the display 84 of
Referring again to
Still further, it is possible to place SPM blocks in host devices, other devices other than field devices, or other field devices to perform statistical process monitoring outside of the device that collects or generates the raw data, such as the raw process variable data. Thus, for example, the application 38 of
As the number of statistical data collection blocks or SPMs increases in a process plant, it is helpful to have an automated mechanism that gathers the statistical parameter data from the SPM blocks in the different devices, to trend the data and to provide detection results to an expert system for further data aggregation and decision making. In fact, at present time, it is very cumbersome and tedious to view all of the statistical process data for a large process. Currently, one must create an OPC client that individually monitors each of the SPM parameters of interest and, to do this, must individually configure every device for SPM collection. As indicated above, this configuration and viewing of statistical data is very time consuming and is vulnerable to human errors.
The configuration and data collection application 38 is adapted to automatically configure SPM blocks in devices, such as in valves, transmitters, etc., and to gather the SPM data available in a process from these SPM blocks during operation of the process.
In any event, at a first block 92, the application 38 scans the hierarchy of the process control network (e.g., the process plant) to determine a list of the devices within the process plant that include statistical data collection blocks (such as ADBs) therein. For the purposes of this discussion, it is assumed that the statistical data collection blocks are in the form of SPM blocks within Fieldbus ADBs as discussed above, although the block 92 could search for other types of statistical data collection blocks as well or in addition to Fieldbus type. SPMs in ADBs, and this method is not limited to use with Fieldbus ADBs or to SPM blocks within Fieldbus ADBs. In one embodiment, an OPC server (such as the server 89 of
To discover the ADBs and, therefore, the SPM blocks within the ADBs, the block 92 (
When searching the hierarchy or tree 94, there is generally a trade-off between speed and robustness. In particular, searching the hierarchy 94 will not generally be 100 percent reliable in finding all of the devices with an ADB and only the devices with an ADB. Typically, the more accurate the method of finding the devices with ADBs, the slower the method will be. For example, if a different manufacturer has devices that show up in the OPC tree 94 with blocks having the same name as the ADB blocks within the 3051F transmitter, then searching the hierarchy may falsely detect this device as having an ADB. Conversely, if the block 92 tries to eliminate this problem by searching too many sub-nodes to assure that only nodes with actual ADBs therein are located, then the speed of the method is reduced.
In any event, in one embodiment, the block 92 may search every node in the hierarchy or tree 94 to locate each node having a name known to be associated with an ADB in some device. While, in some cases such as in large process plants, this may take a significant amount of searching time, it will be the most accurate method of finding each of the ADBs and, therefore, each of the SPMs, within a process plant. On the other hand, the block 92 may search down a hierarchy until it reaches or finds a node having a name associated with known statistical monitoring block, such as TRANSDUCER800 or TRANSDUCER1300 or any other specific name known to be used by some device manufacturer to indicate a known statistical monitoring block. If such a node is found, then the parent node associated with that nodes may be detected as a device with an ADB. While this method is not as robust as searching every node within a particular OPC hierarchy or tree, it should be faster. None-the-less, if another manufacturer makes a device with an OPC node named TRANSDUCER800, this method will still falsely detect the other device as having an ADB.
Alternatively, the block 92 may search under each node that it finds having a name associated with a known ADB for an additional item within a device also known to be uniquely associated with or indicative of an ADB. Thus, the block 92 may, after locating a node having a name known to be used by at least one manufacturer to specify an ADB, search of sub-node to see if the item Characteristic/BLOCK TAG.STRING has a value “ADVANCED DIAGNOSTICS.” In this example, the Characteristic/BLOCK TAG.STRING OPC item has a value of “ADVANCED DIAGNOSTICS” only for devices with an ADB. While this method is very robust in locating only devices with ADBs, this method requires reading a value from a device via the OPC server, which takes significantly longer than just browsing the OPC hierarchy. Therefore, this method, while accurate, may be too slow for some circumstances.
Another method that may be implemented by the block 92 of
Of course, the block 92 could use any of these techniques, or any combination of these techniques or any other desired techniques to search for devices having ADBs therein (and therefore having SPMs therein). For example, one implementation may attempt to identify at least all ADBs known to be implemented by devices of at least one manufacturer, but may or may not be able to identify all the ADBs in a process plant. As another example, an implementation may attempt to identify all ADBs known to be implemented by devices of several different manufacturers. Furthermore, while this scanning step has been described as being performed using an OPC hierarchy, i.e., one generated by an OPC server, this method could be applied to or used on hierarchies generated by other devices, such as a controller, a data historian which stores a configuration hierarchy within a process plant, a workstation storing a device hierarchy, etc. Thus, other implementations need not utilize an OPC server and/or an OPC hierarchy, but could use a variety of other computing devices, communication protocols, and hierarchy protocols including, for example, known and later-developed computing devices, communication protocols, and hierarchy protocols. Other implementations may utilize web servers, XML, and/or proprietary computing devices and protocols, for example.
In the process of discovering or searching for the devices containing an ADB, the block 92 may store a list of devices detected as having an ADB, an SPM block or other type of data collection block, as indicated by the box 108 of
To read any of the SPM parameters from a device, it is generally necessary to know the OPC item ID for that parameter. Typically, i.e., in the case of Fieldbus SPM blocks, the OPC item ID for an SPM parameter includes a Device ID followed by the item specifier. To locate the Device ID, the block 92 may, for each device node which has been determined to contain an ADB, find the sub-node SPM_ACTIVE. Next, the block 92 may obtain the OPC Item ID for the leaf “CV”. For example, the OPC Item ID might be “DEVICE:0011513051022201100534-030003969/800/SPM ACTIVE.CV”. The Device ID is then the OPC Item ID minus the suffix “SPM ACTIVE.CV”. Thus, in this example, the Device ID is “DEVICE:0011513051022201100534-030003969/800/”. Of course, this is but one manner of determining a Device ID in an OPC system, it being possible to use other techniques as well or instead.
In any event, after the block 92 scans the hierarchy to determine the devices having an ADB, the application 38 knows or can easily determine the Device Tag, Device ID, and Device Location for each of these devices. An example of this data for a simple system containing 5 devices with ADB is shown in the table below.
Referring again to
After the block 114 determines if SPM is enabled in each of the devices listed in the box 108, a block 120 may check the status for each of the SPM blocks within each of the devices having SPM enabled, i.e., those devices listed or stored in the box 116. The block 120 basically performs this step to determine if each SPM block within the devices having SPM enabled is currently configured to monitor a process variable and, if so, to determine which process variable is being monitored. In this example, it is possible to determine if an SPM block is currently monitoring a process variable by reading the status of the SPM block. In Fieldbus SPM blocks, the status may be checked by reading the SPM[n] STATUS.CV item from the OPC server. Thus, for example, to read the status for SPM Block 1 in device PT-101 from the table above, the block 120 may read the OPC Item ID DEVICE:0011513051022201100534030003969/800/SPM1 STATUS.CV.
Generally speaking, the value of status is an 8-bit number ranging from 0 to 255. The status is a combination of 8 different bits that can be on or off. The bits are: Inactive (1), Learning (2), Verifying (4), No Detections (8), Mean Change (16), High Variation (32), Low Dynamics (64), and Not Licensed (128). All SPM Blocks that are licensed, but have not been configured, have a Status of Inactive. If the Status of an SPM Block is Inactive or Not Licensed, the block 120 may determine that this block will not be monitored because it is not generating any useful information. However, if the Status is any of the other possibilities, the block 120 may monitor the SPM block.
In a similar manner, a block 122 may automatically configure each device not having SPM enabled (i.e., the devices listed in the box 118) to thereby enable at least one SPM block within those devices to detect or monitor a process variable to thereby produce statistical data with respect to that process variable. In many cases, such as with the Rosemount 3051F and 3051S transmitters, the devices are shipped from the factory with the SPM not yet configured, which generally requires a user to manually configure SPM in each device. In a plant with hundreds or thousands of devices with ADB, this would be a very tedious process. To alleviate this manual configuration, the block 122 automatically configures at least one SPM block for each device. To perform this configuration, the block 122 may determine or store an indication of the particular process variable to be monitored within a device. This variable could be the main process input, a PID block output, or any number of other function block variables (inputs or outputs) that are available in the Fieldbus device. The indication of which variable to monitor may be set during a configuration process, may be specified by the user on a case by case basis or may be generally specified by the user before operation of the routine 38.
While any of the process variables can be monitored, a logical variable to monitor for statistical purposes is the primary analog input of a device. For Rosemount 3051F/S transmitters, this variable is the measured pressure or flow (e.g., differential pressure). Thus, the block 122 may be configured to automatically configure one of the SPM blocks in an ADB of a device to monitor the primary analog input or output of the device. If desired, the user can still manually configure the other SPM blocks of the device. Alternatively, the block 122 may store a list of process variables to be monitored for each type of device and could use this list to select or determine which process variable(s) to monitor in any given situation. While the block 122 is described herein as configuring a single SPM block within a device to monitor one process variable, the block 122 could configure more than one SPM block within a particular device, to thereby monitor more than one process variable associated with that device.
In addition, the DeltaV OPC server allows a user (given sufficient administrative privileges) to write values to the certain items within devices. Thus, it is possible to change the SPM parameters in a device by writing to the appropriate item in the OPC server. The block 122 may therefore automatically configure a device to monitor SPM for the main process variables by writing a sequence of values to the OPC Server. In one particular example, the values that are written to the OPC Server are shown in the table below.
Here, [DeviceID] should be replaced with the Device ID as found in Table 2. So for the device PT-101, the first OPC Item that would be written to is DEVICE:0011513051022201100534-030003969/800/SPM MONITORING CYCLE.CV. After writing all of these items to the OPC Server, the device is configured to monitor the main pressure variable in the SPM 1 block. Of course, this is but one example of writing to a particular kind of SPM block in Fieldbus devices, it being understood that other methods of writing to other types of SPM blocks can be used as well or instead, with the write commands being determined by the communication protocol used by those SPM blocks.
In any event, the operation of the blocks 120 and 122 of
However, it may not be necessary to monitor all of these parameters for each SPM block being monitored. In fact, it is possible that the OPC server may become overloaded if too many items are being monitored. Therefore, the application 38 may provide a mechanism by which a user is enabled to select the set of SPM parameters to be monitored. An example of a screen that would allow for this selection is shown as
A block 128 uses the list of SPM parameters to be monitored (as identified by the box 126) and the list of SPM blocks to be monitored (as identified by the box 124) to construct the set of SPM OPC items to be monitored by the application 38 during operation of the process. The block 128 may store this set of OPC items, as indicated by the box 130, for use in later steps of the monitoring process. Generally speaking, the block 128 creates the SPM OPC items for each SPM parameter to be monitored (indicated by the box 126) for each of the SPM blocks to be monitored (indicated by the box 124). In other words, given a set of SPM blocks to be monitored, and a set of SPM parameters to be monitored for each such block, the block 128 constructs a set of OPC items to be monitored as the OPC items for every possible combination of SPM blocks to be monitored and SPM parameters to be monitored. Thus, for example, if there are ten SPM blocks to be monitored, and five, SPM parameters to be monitored per SPM block, the block 128 will create a total of 50 OPC items. In this example, the OPC Item ID is a combination of the Device ID and the OPC Suffix from the tables above. For example, to read the mean for SPM 1 in device PT-101, the OPC Item ID would be: DEVICE:0011513051022201100534030003969/806/SPM1 MEAN.CV.
After all of the OPC items have been identified and stored in the box 130, blocks 132 and 134 monitor the SPM parameters for changes during operation of the process. Some of the SPM parameters may change, for example, every 5-60 minutes depending upon the configuration of the SPM blocks, while other SPM parameters may change only when the SPM block is configured. As a result, the block 132 may first read the current value of all of the SPM parameters (specified by the OPC items of the box 130) when the process of monitoring the SPM parameters is started. In one embodiment, the block 132 may perform this read using a SyncRead function calling for a read of each of the OPC item IDs. Reading each of the SPM parameters produces a set of SPM data points, as indicated by the box 136 of
After the first read of the SPM parameters, the block 134 may wait for changes in the SPM parameters. That is, after the initial values of each of the SPM parameters being monitored are read from OPC server to obtain the first set of SPM data points, the block 134 receives or obtains additional data indicating changes in any of the SPM parameters being monitored. Depending upon the configuration of the SPM blocks, the parameters Mean and Standard Deviation may change, for example, every 5-60 minutes. None-the-less, when any of the SPM parameters changes, the OPC server raises a DataChange event, which event is captured by the OPC client, e.g., the application 38. Alternatively, the block 134 may periodically or at preset times poll or read each of the SPM parameters being monitored to obtain new data points (box 136). In this manner, the SPM parameter data is read even if it has not changed. Of course, the block 134 may operate continuously during operation of the process to receive new SPM parameters and to store this SPM parameter data in a database for viewing by a user, for use by a rules engine described in more detail below, or for any other purpose. Of course, if desired, the routine 90 of
In fact, at any time after any of the SPM data points of box 136 are read, a block 138 may store or save these data points in a local database (such as the database 43 of
Generally speaking, the viewing application 40 (which may be implemented by the block 140 of
If desired, the viewing application 40 may allow or enable a user to add or reconfigure one or more SPM blocks within a field device or even within a host or other device in which these blocks are located.
Still further, the viewing application 40 may enable a user to navigate through a hierarchy to obtain a view of certain kinds of data either directly from the SPM blocks (or other monitoring blocks) or data generated therefrom by for example, the application 40. For example,
At a fast glance, the graph of
In a similar manner, the application 40 may plot any other of the SPM parameters (e.g., Standard Deviation, Mean Change, Standard Deviation Change, etc.) versus time as well as any mathematical combination of the SPM parameters (e.g., Standard Deviation divided by Mean, etc.) Also, the application 40 may place any combination of any of these plots on the same graph or page, to make comparisons between the different statistical data easier for the user.
Statistical process control is often used in the process control industry to determine whether or not a certain process variable is outside of the allowable limits. There are typically both upper and lower control limits (UCL, LCL) and upper and lower specification limits (USL, LSL), which can be calculated based on the SPM data collected by the application 38. The control limits may be, in one example, expressed as UCL=μ+3σ and LCL=μ−3σ where μ and σ are the baseline mean and baseline standard deviation, respectively. Additionally, the specification limits may be expressed as:
wherein Δμ is a user-specified mean limit, in percent. Of course, the viewing application 40 may calculate these values directly or may allow a user to input these values.
With these or similar points, the viewing application 40 may plot the distribution of a mean against the baseline mean and the control limits to thereby provide a visualization of when a mean limit is reached or exceeded during operation of the plant. The result is essentially a histogram graph that may look similar to the graph 166 of
If desired, the viewing application 40 may add the control and specification limits, such as those discussed above, to the plots of the mean, standard deviation or any other desired statistical measurement (such as a medium, etc.) versus time. When the limits are added to a mean versus time plot, the resulting plot is called an X-Chart. An example of an X-Chart 178 for a statistical mean is illustrated in
In this case, it may be desirable to make an adjustment to the calculation of the upper and lower control limits because the viewing application 40 is not plotting the actual process variable, but is plotting the mean, over a certain interval of time. Because the measurement noise is reduced, the same variation that one would see in a standard X-Chart that plots the values of the process variable does not exist. One possible adjustment that could be made to the upper and lower control limits is to divide the 3σ portion by the square root of the number of data points that are used to calculate each mean. According to this formula, the upper and lower control limits would be calculated as follows:
where N=(Monitoring Cycle)*(60)*(Samples per second)
Here, the monitoring cycle is the number of minutes over which the mean and the standard deviation are calculated. A default of 15 minutes may be used. Samples per second is based on the sampling rate of the device taking the measurements, which is, for example, 10 for a Rosemount 3051F transmitter and 22 for a Rosemount 3051S transmitter, although other sampling rates could be used.
Additionally, the application 40 may produce an S-Chart, in which the standard deviation versus time is plotted with the control and specification limits. In this case, the upper and lower control and specification limits may be defined as follows:
where ΔHV is a user-defined High Variation Limit, in percent, and ΔLD is a user-defined Low Dynamics Limit, with ΔLD<0.
An example of an S-Chart 190 is illustrated in
Still further, the application 40 could determine other statistical measurements or values from the collected data. For example, the application 40 could calculate a distribution index or measurement for a variable x, which can include any statistical variable, as:
The application 40 could calculate a capability index or measurement as:
and could calculate a correlation coefficient between two variables (which may include statistical variables), as:
In another example, a correlation coefficient between two variables can be calculated as:
Of course, the viewing application 40 could perform other calculations for any variable or variables (including statistical variables as well as process variables) as desired or needed within the system to determine one or more abnormal situations within a process plant. Thus, for example, the application 40 or some routine therein may perform principle component analysis, regression analysis, neural network analysis, or any other single or multi-variable analysis on the collected data to perform abnormal situation detection and prevention.
Generally speaking, the graphs of
Of course, the viewing application 40 is not limited to providing two-dimensional scatter charts such as that of
Again, the scatter charts of
If desired, and as generally noted above, the viewing application 40 may calculate or determine a correlation coefficient for any pair of SPM parameters using any standard or known correlation calculations. When the correlation coefficient is near 1 (or −1), there is a strong linear correlation (or negative linear correlation) between the two SPM parameters. For a set of more than two SPM variables, a correlation matrix can be determined, where each element in the correlation matrix defines the correlation coefficient between a different set of two of the SPM parameters.
From the correlation matrix 230 of
In one example, such as that shown in the screen display 241 of
Likewise, as illustrated in the screen 243 of
Still further, the application 40 can provide other views of the SPM data in addition or in the alternative to those discussed above. As an example, the application 40 may provide visualization graphs or charts in the form of three-dimensional trend plots with time along the X-Axis, and Mean and Standard Deviation of an SPM block along the Y and Z axes, three-dimensional histogram plots that plot the mean and standard deviation along the X and Y axes, and the quantity of each along the Z-axis, three-dimensional trend plots with time along the X-axis, and mean and standard deviation of an SPM block along the Y and Z axes and including upper and lower control and/or specification limits for one or both of the mean and standard deviations. Of course, there are almost limitless manners for visualizing the SPM data and this disclosure is not limited to the specific methods described above.
As another example, the viewing application 40 may produce a trend plot of two (or more) different SPM parameters on the same graph to enable a user to view expected or non-expected behavior of one of the SPM parameters with respect to the other(s) of the parameters.
It is believed that correlation of SPM parameters can give some indication of the overall health of a plant, a portion of a plant, a piece of equipment, etc. When a plant (or a portion of the plant, or a piece of equipment, etc.) is in its normal operating state, there may be some variables that are highly correlated with other variables. Over time, it might be possible that some of the correlation values change. A change in some of the correlation values might indicate that a plant is no longer operating at the same performance as it was previously. Therefore, some examples described below provide methods for visualizing how one or more correlation values change over time.
In order to view a change in a correlation value over time, the correlation value may be calculated at different times. An equation such as Equation 11 or Equation 12 could be used to generate a correlation value of data from an entire available range. Additionally, the data could be divided into segments of a specific length (for example, 30 minutes, 1 hour, 6 hours, 1 day, 7 days, a particular number of samples, etc.), then one or more correlation values can be calculated for each segment. Thus, if a correlation value changes from one segment to the next, this can be considered a change in the correlation value over time. As another example, correlation values could be generated based on a sliding window of data, the sliding window having a particular length (for example, 30 minutes, 1 hour, 6 hours, 1 day, 7 days, a particular number of samples, etc.).
In one example, a change in a correlation value is plotted. For instance, a change in the correlation value from an initial value, a previous value, a baseline value, a “normal” value, an expected value, etc., may be plotted. In this example the change could be expressed either as a relative change (e.g., a percentage) or as an absolute change.
A baseline value for a given correlation value typically should be calculated on an amount of underlying data that is based on the amount of process variable data needed to generate the data underlying the correlation value. For example, a mean value may be generated based on a segment of data that could be as short as 5 minutes or as long as 1 day. It is currently believed that a correlation value from the mean data using at least 30 mean data points will provide a statistically reliable sample. (It should be understood that in some implementations, less than 30 mean data points may provide a statistically reliable correlation value, or more than 30 mean data points may be required.) In this case, if mean data points are evaluated at 5 minute intervals, a correlation window is should be approximately 3 hours or more.
In some implementations, generating mean data includes a training period before a first mean value is saved. In these implementations, an algorithm for generating the mean value includes trying to determine a baseline mean for the process. The existence of a baseline mean may be determined by verifying that the mean and standard deviation of two consecutive blocks of data are within a certain tolerance of each other. This may help to ensure that the baseline mean value will be from a time period when the process is in a steady state, and not when the process is in a transient. After the baseline mean value has been determined, the algorithm begins calculating and providing mean values that can be used by other algorithms, processes, etc. These mean values can be used to calculate correlation values. Thus, the process may be in a steady state and at its normal operating condition when the first mean values are calculated by the algorithm.
In one example, the first correlation value calculated after the baseline mean has been determined is chosen as the baseline correlation. As discussed above, the process may be, in many cases, in a steady state and at its normal operating condition when the first correlation value calculated.
In some cases, however, problems can arise if one tries always to use the first correlation value as the “normal” value. For example, the process might be such that even in the normal operating condition, the correlation coefficient is irregular from one correlation block to the next. This is especially true if two variables naturally have a very low correlation. Also, if the monitoring cycle of an SPM block that generates the mean value is configured too high or too low, or if the process was not in the normal state when the algorithm for generating the mean was trained, the first correlation value may not be a good estimate of the normal value.
Therefore, in some situations, it may be useful to use a correlation value different than the first correlation value as the baseline correlation value. Additionally, it may be determined that no baseline correlation value will be selected, or the baseline correlation value is to be selected as some absolute value (e.g., 0), when, for example, correlation values are relatively small and/or irregular.
Some example methods are described below for determining whether to use the first correlation value as the baseline value. In one example, differences between the first correlation value and one or more subsequent correlation values may be generated to see if the first correlation value is consistent with the subsequent correlation values. If the first correlation value differs from subsequent correlation values by a certain degree, it may be that the first correlation value should not be used as a baseline value. In one particular example, the first correlation value is compared to a second correlation value. If the first correlation value differs from the second correlation value by less than a certain degree (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, etc.), then the first correlation value may be selected as the baseline correlation value. If the difference is greater than the specified degree then the first correlation value is not selected as the baseline correlation value. Many other methods could be used to determine whether the first correlation value should be used as the baseline value.
In one example, the baseline value could be generated based on a plurality of generated correlation values (e.g., averaging the correlation values, taking the median correlation value, etc.). In other examples, the baseline value could be generated based on one or more generated correlation values from another similar process, based on a simulation, based on a model, etc.
Once the initial value, a previous value, the baseline value, the “normal” value, the expected value, etc., has been determined for each correlation value, a correlation change array can be calculated. The correlation change array could include the difference between each correlation value and the corresponding initial value, baseline value, “normal” value, expected value, etc.
The difference could be expressed as either a relative change (e.g., a percentage) or an absolute change. Because typical methods for calculating correlation values generate correlation values between 0 and 1, the absolute change would also be between 0 and 1. If a percent change is used, however, the percent change could potentially become very large, especially if the baseline correlation is near 0. There may be situations, however, when using the percent change is useful and/or preferable as compared to using the absolute change.
The displays 266 and 268 of
Additionally, multiple correlation difference values could be combined to generate a value indicative of the differences of the multiple correlation values. This value could be plotted versus time. The multiple correlation difference values could be combined in a variety of ways. For example, a set of correlation difference values could be considered as a vector, and the norm of the vector could be indicative of the differences in the correlation values. Three equations are provided below for calculating the norm of a Vector. The norm could be calculated according to any of these equations, or a different equation.
where ΔCi is the ith correlation difference value, and N is the number of correlation difference values. The
factor in equation 13 and the
factor in equation 14 can be omitted if desired. Additionally, other equations could be used as well.
As mentioned previously, a correlation value may indicate a measure of the degree of linear correlation between two variables. A correlation value may be determined when linear regression is done on a set of data. Generally, linear regression determines a line that “best” fits the set of data. The results of a linear regression fit often are the slope of the line and the Y-intercept of the line. The slope of this line and/or the change in the slope of this line over time may be useful in monitoring the health of a process plant, a portion of the process plant, a process, a piece of equipment, and/or detecting an abnormal situation. Given two sets of data X and Y, the slope of the best-fit line may be calculated by the following equation:
where xi is an ith sample of the X data set, yi is an ith sample of the Y data set,
A correlation value and a corresponding slope can be visualized by plotting them on a polar coordinate plot. In particular, the absolute value of the correlation value would correspond to a radius, and an angle could be determined as
θ=tan−1 m (Equ. 17)
where m is the slope determined by the equation 16, or some other equation. The range of the arctangent function is
Thus, using this method only one half of the polar coordinate plane would contain correlation points. Optionally, in order to utilize the entire polar coordinate plane, one could use the equation:
θ=2·tan−1 m (Equ. 18)
In this case, the angle shown on the plot would not show the exact slope of the line. However, this might be a desirable trade-off if a user finds it more visually appealing.
In another example, a difference between the correlation value and the baseline may be plotted on a polar plot. In this example, the magnitude of a correlation change is computed as the absolute value of the difference between the correlation value and its baseline, and the angle is simply the angle of the correlation value computed using, for example, Equation 18. Thus, correlation values that are near their baseline value will tend to result in correlation change values located in the center of the plot. If a correlation value significantly changes from its baseline, it will tend to result in a correlation change value located away from the center of the plot.
In some instances, a polar plot such, as in
Displays such as the displays of
The statistical data described above with respect to
While the viewing application 40 may provide a user or an engineer with some or all of the views discussed above to enable the user or engineer to manually detect the presence of or the suspected future existence of an abnormal situation within the process plant, the rules engine development and execution application 42 may also be used to automatically detect abnormal situations based on the SPM data. One possible embodiment of the rules engine development and execution application 42 of
The rules engine 290 applies the rules 292 to the SPM and other data to determine if a condition exists that indicates, according to at least one of the rules 292, that an alert or alarm should be sent to a user, as indicated by a block 296. Of course, if desired, the rules engine 290 may take other actions, besides providing or setting an alarm, if a rule indicates that a problem exists. Such actions may include, for example, shutting down or more components of the process, switching control parameters to alter the control of the process, etc.
Additionally, a rules development application or routine 298 enables a user to develop one or more expert system rules (e.g., to be used as one of the rules 292) based on statistical data patterns and their correlations, to thereby detect known plant, unit, device, control loop, etc. abnormalities. Thus, while at least some of the rules 292 used by the expert engine 290 may be preset or preconfigured, the rules development application 298 enables a user to create other rules based on experiences within the process plant being monitored. For example, if a user knows that a certain combination of SPM abnormal conditions or events indicates a certain problem in the process, the user can use the rules development application 298 to create an appropriate rule to detect this condition and, if desired, to generate an alarm or alert or to take some other action based on the detected existence of this condition.
Of course, during operation of the process plant, the rules engine 290, which is configured to receive the SPM data (and any other needed data), applies the rules 292 to determine if any of the rules are matched. If a problem in the process is detected based on one or more of the rules 292, an alert can be displayed to a plant operator, or sent to another appropriate person. Of course, if desired, various rules for detecting various abnormal conditions within a plant and process operation could be part of the expert system runtime engine 290, which may look for patterns, correlations of data and SPM parameters to detect developing abnormal conditions.
Additionally, some of the data that may be used by the rules engine 290 are SPM conditions that may be detected within the devices in which the SPM data is generated. In this case, the rules engine 290 may be a client system or may be part of a client system that reads the SPM parameters and conditions from the devices via, for example, an OPC server. As discussed above, these SPM parameters may be stored to a database for future use, such as plotting the values of mean and standard deviation versus time. In any case, if the mean or standard deviation of a process variable changes by more than a user specified amount, the SPM block itself may detect an abnormal condition, such as Mean Change, High Variation, or Low Dynamics. These abnormal conditions can then be communicated to the client system, e.g., the rules engine 290, along with all the statistical monitoring data collected by these field devices.
Now, if a plant engineer or other user knows that, when a certain combination of process variables change in a certain manner, ascertain alarm should be triggered, or a certain action needs to be taken, the engineer can use the rules definition routine 298 to define a rule to detect this situation knowing that the application of the rule will trigger the alarm if that set of conditions occurs. In one example, the rules definition application 298 may create a configuration screen that enables the user to create one or more IF-THEN or Boolean type rules to be stored in the rules database 292. An example of one possible such configuration screen 300 is illustrated in
In the particular example of
Thus, in the example of
As illustrated in
It will be understood that, after a set of rules has been created and stored in the rules database 292 of
If desired, the system 42 may provide a viewing screen which provides a user with information about the current configuration and status of the rules engine 290 of
As will be understood, the main tree browser 110 and the summary 115 of SPM blocks available may be provided by the methods described with respect to
Still further, while the screens of
During operation, the rules engine 290 of
As will be understood, once the monitoring process starts, all of the rules are fed into the rules engine 292 via any appropriate interface. Thereafter, each time the SPM conditions change, such as would be detected by the blocks 132 or 134 of
Although a rules engine 292 was described above, other types of analysis engines could be used additionally, or alternatively. Other examples of types of analysis engines that could be used include a mathematical computing engine (e.g., Mathematical computing system from Wolfram Research, MATLAB® system from The MathWorks, etc.), a fuzzy logic analysis engine, a pattern matching engine, a neural network, a regression analysis engine, etc.
While the above described data collection technique, visualization technique and rules engine techniques may be used to collect, view and process SPM data in the plant configuration of
In a similar manner, the data collection and viewing applications may access the field devices or other devices via a remote viewing device. Thus, this software may reside in or be accessible through web servers like, for example, the Asset Portal and AMSweb provided by Emerson Process Management. Also, while the OPC server has been illustrated in
Additionally, the rules engine application 42 (or portions thereof such as the rules engine 290 of
While in the example of
Moreover, although the above description referred to blocks, such as ADB blocks and SPM blocks, that calculate statistical data, other types of signal processing data collection blocks that generate other types of signal processing data may be utilized as well. For example, signal processing data collection blocks that generate frequency analysis data (e.g., data generated based on a Fourier transform or some other transform of a process variable), auto regression data, wavelets data, data generated using a neural network, data generated using fuzzy logic, etc., could be used in an abnormal situation prevention system. Thus, the term signal processing data collection block as used herein is intended to refer to and to include any type of monitoring blocks, software routines, hardware, etc. which collect process data or variables and which perform some signal processing operation or monitoring thereon, such as generating statistical data, mathematically transforming (e.g., using Fourier transform, discrete Fourier transform, fast Fourier transform, short time Fourier transmform, Z-transform, Hilbert transform, Radon transform, Wigner distribution, wavelet transform, etc.) process data, extracting information from transformed process data, filtering, extracting information from process data using fuzzy logic, neural networks, auto regression techniques, etc.
Further, although examples have been described in which signal processing data from signal data collection blocks within a single process plant is gathered and analyzed, it will be understood that similar techniques can be used in the context of multiple process plants. For example, signal processing data from multiple process plants can be gathered, and then this data could be provided to an analysis engine and/or a viewing application.
Although examples have been described using particular communication protocols and techniques, a variety of other protocols and techniques, including known protocols and techniques, for accessing configuration data and signal processing data from signal processing data collection blocks can be used as well. For instance, other protocols and techniques besides OPC can be used to identify and/or configure signal processing data collection blocks, gather signal processing data, etc. Other techniques may include, for example, using Internet protocols, Ethernet, XML, proprietary protocols, etc., and other implementations may utilize web servers, and/or proprietary computing devices such as process controllers, I/O devices, workstations, field devices, etc. Similarly, other types of hierarchy data may be utilized including proprietary data.
While the abnormal situation prevention system and the applications described, herein as being associated with the abnormal situation prevention system are preferably implemented in software, they may be implemented in hardware, firmware, etc., and may be implemented by any other processor associated with the process control system. Thus, the elements described herein may be implemented in a standard multi-purpose CPU or on specifically designed hardware or firmware such as an application-specific integrated circuit (ASIC) or other, hard-wired device as desired. When implemented in software, the software routine may be stored in any computer readable memory such as on a magnetic disk, a laser disk (such as a DVD) or other storage medium, in a RAM or ROM of a computer or processor, in any database, etc. Likewise, this software may be delivered to a user or a process plant via any known or desired delivery method including, for example, on a computer readable disk or other transportable computer storage mechanism or over a communication channel such as a telephone line, the internet, etc. (which are viewed as being the same as or, interchangeable with providing such software via a transportable storage medium).
Thus, while the present disclosure has been described with reference to specific examples, which are intended to be illustrative only and not to be limiting, it will be apparent to those of ordinary skill in the art that changes, additions or deletions may be made to the disclosed embodiments without departing from the spirit and scope of the disclosure.
This application claims the benefit of U.S. Provisional Patent Application No. 60/549,796, filed on Mar. 3, 2004, and entitled “ABNORMAL SITUATION PREVENTION IN A PROCESS PLANT,” which is hereby incorporated by reference herein in its entirety for all purposes. This application also is related to the following patent applications: U.S. patent application Ser. No. 10/971,361, filed on the same day as the present application, and entitled “ABNORMAL SITUATION PREVENTION IN A PROCESS PLANT;” which has since matured into U.S. Pat. No. 7,079,984. U.S. patent application Ser. No. 10/972,155, filed on the same day as the present application, and entitled “DATA PRESENTATION SYSTEM FOR ABNORMAL SITUATION PREVENTION IN A PROCESS PLANT.” which has since matured into U.S. Pat. No. 7,389,204. The above-referenced patent applications are hereby incorporated by reference herein in their entireties for all purposes.
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| 60549796 | Mar 2004 | US |
