Today we can connect a laptop or wireless handheld and you can access all the information, screens and intelligence that exists in any DCS network. This capability, combined with self-tuning and optimization features, make starts easier and more efficient operation, among others.
The operator training for the start of a plant or start-up, operation and shutdown can also be simplified thanks to the capabilities of process simulators. If the simulation model integrates the process itself and its control system, then you can train operators without the risk of errors in the learning process while the plant is running, in conclusion all benefit.
But this is only part of the story, on the other side of the coin that some DCS providers (vendors) sell their products without "strings" (software is extra) and expect users to do the work for them same, I mean to prepare control algorithms, faceplates, and environment HMI). Furthermore, of these hidden costs, the problems include the lack of standardization due to commercial competition between vendors and limitations of connectivity between systems.
Connectivity and Integration
At present, about 80% of all industrial production still continues to be controlled by analog systems, but modern control systems installed in new plants have capacities of intelligence and self-diagnostics of field devices (sensors, valves, motors, safety devices), a number of network buses or "data highways" that serve to integrate these devices Workstations field with DCS (serving for control / operations, engineering, history, maintenance) in addition to the network serving to plant and business planning functions, and not forgetting external PC for process modeling and simulation capabilities.
Figure
The trend seems to be that HART (today) would take the standard interface to analog and Ethernet is still handling most office solutions. Well SCADA is used to combine field data and control and provide the operator with an overview of the whole plant.
A protocol is a language that computers speak, if two black boxes (computers) in a refinery not speak the same language, the consequences can be serious. To avoid this, even though every manufacturer wants to assert a proprietary protocol, the IEC (International Electrotechnical Commission) has standardized eight protocols listed below:
Although there is a fieldbus protocol common in the DCS, and use all converge at the physical layer Ethernet and TCP / IP as transport layer. Generally MODBUS TCP is used as an interface between different protocols of DCS.
Organizing the Project
Integration of field instrumentation: a new plant, the first step should be to specify all the sensors, transmitters, control valves, actuators, positioners, local controllers, motors, solenoid valves, and other field equipment that needs to communicate information or receive commands from the DCS on the networks.
When the project is a modification of an existing plant, all interfaces between existing and new facilities must be specified (drawing). There are three types of interfaces that are the Object Linking Embedding (OLE), gateway-to-highway serial (low speed to high speed) and serial port-to-serial (link between low-speed protocols). Since digital transmitters, analyzers intelligent digital actuators, motors and starters use a wide variety of communication protocols, manufacturers interface cards to provide standardized protocols. These protocols are standardized HART, DeviceNet, Foundation Fieldbus, AS-Interface, Profibus, Modbus or AB's Data Highway Plus. This integration is not as simple as one might think, because there is no international standardization and some intelligent field devices are proprietary.
Secure integration: The second step is to specify the network requirements in terms of the physical layer needs redundant and also in terms of number and type of required network levels. Even here, where the safety instrumented system (SIS) is already defined for the plant and where it is decided whether the SIS and the control system are separated, then we define the type of integration interface to use. Even if the security system and control are not separate, we must make decisions to prioritize logic, redundancy, wiring, etc..
Some manufacturers provide redundancy, two of each component implementing a standard system, while others only provide redundancy for some components like power supplies, network, remote controllers, etc.. And with the redundancy there are different methods of performing the swithover (change in case of failure) which can be automatic or manual.
Maintenance Integration and Simulation: The third step is to specify the interface requirements between the control and maintenance systems and decide on optimization tools, simulation, training and commissioning that will be used and it needed to be integrated into the entire automation package of the plant.
Regarding the simulation of the process, there are a lot of variety of software packages for modeling the process and they may reside on a separate PC. Importantly, these software have access to the communication bus to control access to information without interrupting the control functions.
Network Integration and Bus: The fourth step is to select the network to use. Profibus and Foundation Fieldbus is supported by Siemens, Endress & Hauser, Yokogawa, Rosemount, Invensys, ABB, Emerson, Honeywell (others too). Most manufacturers accept DCS fieldbus standard IEC1158-2 to integrate their systems, as well as IEC-61804 standard specifies the function blocks for interfaces between technologies, while in other cases blocks can be integrated through "proxy" which map the data from one system to another (control or monitoring data and further diagnostics, maintenance and security). MODBUS interface can be used to integrate existing and new DCS.
In this fourth step the user must evaluate the best option for the requirements of the three steps above.
Selecting the DCS, the fifth and final step of this process of designing a control system for a plant is to send all the "package" to receive the respective proposals. Only DCS manufacturers which support the selected network should be invited to contribute. In the specifications it is important to list all intelligent field devices and external systems that are integrated within the overall control system. This proposal should require the manufacturer of DCS include everything needed, both in terms of hardware and software to integrate external devices and systems within the entire control system. Similarly, it is essential to specify which software packages (advanced management tools, maintenance, graphics, simulation, training, etc..) Are included in the proposal.
In terms of graphics requirements, the software package should be in accordance with the IEC61131-3. In addition to the list of screens (graphics, details, faceplates, alarm and event summary, trends, tuning, diagnosing, reporting, etc..) Which the provider is responsible for delivering DCS and construction standards of the same .
The specification must also contain the responsibilities and obligations between you, the engineering firm, systems integrator, and provider of advanced DCS control, graphics, simulation, training and commissioning. With regard to the implementation, responsibilities should be very specific in relation to training, procurement, testing, instrumentation and field bus, security system, advanced control testing, commissioning and tuning of controllers.
Probably, if the above recommendations are taken into account, the extra costs and delays will be minimized. And with that reduce delays in implementations, problems in implementation and security.
The future:
It will take at least a couple of decades, I hope, for proprietary networks disappear and only has a single industry standard communication network. I hope the time that all devices can connect to any network and any software that can be embedded into any DCS system this coming.
The trend, as happened with the PC and the Internet is global standardization and that any software package can be installed on any computer. What is needed to achieve this global standardization in the field of process control is a commercial pressure from users. Professional societies and groups play an important role in accelerating this process.
Today we can connect a laptop or wireless handheld and you can access all the information, screens and intelligence that exists in any DCS network. This capability, combined with self-tuning and optimization features, make starts easier and more efficient operation, among others.
The operator training for the start of a plant or start-up, operation and shutdown can also be simplified thanks to the capabilities of process simulators. If the simulation model integrates the process itself and its control system, then you can train operators without the risk of errors in the learning process while the plant is running, in conclusion all benefit.
In this article we will discuss the consideration that we have to integrate DCS systems in new plants and / or existing.
Connectivity and Integration
At present, about 80% of all industrial production still continues to be controlled by analog systems, but modern control systems installed in new plants have capacities of intelligence and self-diagnostics of field devices (sensors, valves, motors, safety devices), a number of network buses or "data highways" that serve to integrate these devices Workstations field with DCS (serving for control / operations, engineering, history, maintenance) in addition to the network serving to plant and business planning functions, and not forgetting external PC for process modeling and simulation capabilities.
The trend seems to be that HART (today) would take as a standard interface for analog systems. A protocol is a language that computers speak, if two black boxes (computers) in a refinery not speak the same language, the consequences can be serious. To avoid this, even though every manufacturer wants to assert a proprietary protocol, the IEC (International Electrotechnical Commission) has standardized eight protocols listed below:
Although there is a fieldbus protocol common in the DCS, and use all converge at the physical layer Ethernet and TCP / IP as transport layer. Generally MODBUS TCP is used as an interface between different protocols of DCS.
Organizing a Project
Integration of field instrumentation: a new plant, the first step should be to specify all the sensors, transmitters, control valves, actuators, positioners, local controllers, motors, solenoid valves, and other field equipment that needs to communicate information or receive commands from the DCS on the networks.
When the project is a modification of an existing plant, all interfaces between existing and new facilities must be specified (drawing). There are three types of interfaces that are the Object Linking Embedding (OLE) or OPC, gateway-to-highway serial (low speed to high speed) and serial-to-serial (link between low-speed protocols). Since digital transmitters, analyzers intelligent digital actuators, motors and starters use a wide variety of communication protocols, manufacturers interface cards to provide standardized protocols. These protocols are standardized HART, DeviceNet, Foundation Fieldbus, AS-Interface, Profibus, Modbus or AB's Data Highway Plus. This integration is not as simple as one might think, because there is no international standardization and some intelligent field devices are proprietary.
Secure integration: The second step is to specify the network requirements in terms of the physical layer needs redundant and also in terms of number and type of required network levels. Even here, where the safety instrumented system (SIS) is already defined for the plant and where it is decided whether the SIS and the control system are separated, then we define the type of integration interface to use. Even if the security system and control are not separate, we must make decisions to prioritize logic, redundancy, wiring, etc..
Some manufacturers provide redundancy, two of each component implementing a standard system, while others only provide redundancy for some components like power supplies, network, remote controllers, etc.. And with the redundancy there are different methods of performing the swithover (change in case of failure) which can be automatic or manual.
Maintenance Integration and Simulation: The third step is to specify the interface requirements between the control and maintenance systems and decide on optimization tools, simulation, training and commissioning that will be used and it needed to be integrated into the entire automation package of the plant.
Regarding the simulation of the process, there are a lot of variety of software packages for modeling the process and they may reside on a separate PC. Importantly, these software have access to the communication bus to control access to information without interrupting the control functions.
Network Integration and Bus: The fourth step is to select the network to use. Profibus and Foundation Fieldbus is supported by Siemens, Endress & Hauser, Yokogawa, Rosemount, Invensys, ABB, Emerson, Honeywell (others too). Most manufacturers accept DCS fieldbus standard IEC1158-2 to integrate their systems, as well as IEC-61804 standard specifies the function blocks for interfaces between technologies, while in other cases blocks can be integrated through "proxy" which map the data from one system to another (control or monitoring data and further diagnostics, maintenance and security). MODBUS interface can be used to integrate existing and new DCS.
In this fourth step the user must evaluate the best option for the requirements of the three steps above. Here is a table of characteristics of the main bus systems:
Select the manufacturer DCS: the fifth and final step in the process of designing a control system for a plant is to send the entire "package" to receive the respective proposals. Only DCS manufacturers which support the selected network should be invited to contribute. In the specifications it is important to list all intelligent field devices and external systems that are integrated within the overall control system. This proposal should require the manufacturer of DCS include everything needed, both in terms of hardware and software to integrate external devices and systems within the entire control system. Similarly, it is essential to specify which software packages (advanced management tools, maintenance, graphics, simulation, training, etc..) Are included in the proposal.
In terms of graphics requirements, the software package should be in accordance with the IEC61131-3. In addition to the list of screens (graphics, details, faceplates, alarm and event summary, trends, tuning, diagnosing, reporting, etc..) Which the provider is responsible for delivering DCS and construction standards of the same .
The specification must also contain the responsibilities and obligations between you, the engineering firm, systems integrator, and provider of advanced DCS control, graphics, simulation, training and commissioning. With regard to the implementation, responsibilities should be very specific in relation to training, procurement, testing, instrumentation and field bus, security system, advanced control testing, commissioning and tuning of controllers.
Probably, if the above recommendations are taken into account, the extra costs and delays will be minimized. And with that reduce delays in implementations, problems in implementation and security.
The future:
It will take at least a couple of decades, I hope, for proprietary networks disappear and only has a single industry standard communication network. I hope the time that all devices can connect to any network and any software that can be embedded into any DCS system this coming.
The trend, as happened with the PC and the Internet is global standardization and that any software package can be installed on any computer. What is needed to achieve this global standardization in the field of process control is a commercial pressure from users. Professional societies and groups play an important role in accelerating this process.
