A Safe Future with Pepperl+Fuchs Remote I/O
Profibus in hazardous areas
LB/FB Remote I/O is a cost-effective instrumentation solution and is comparable to a pure field bus solution. In plant retrofits and and system expansions it is even better, since the existing field instrumentation can be used. LB/FB also enables HART communication from intelligent field devices via the PROFIBUS. At the operator workstation, the FDT-based PACTware framework application is available. With LB/FB, even a bus-independent functional safety feature is already "inside".
LB and FB Remote I/O collect numerous field signals in an intelligent field junction box. Conventional input and output signals are linked to the control system via Remote I/O. Up to 80 analog input and output loops can be handled in a single sub-station. More than 10 such stations can be operated on a single bus line. The savings are considerable, compared with conventional cabling. HART communication with intelligent field devices is also possible via the same 2-wire bus.
HART communication – an additional benefit
The Remote I/O stations, LB for Zone 2 and FB for Zone 1, offer the user additional benefits, at no extra cost. All HART-enabled field devices can be addressed from a central position, making use of the HART on PROFIBUS profile. They no longer require handheld communication devices to be linked to them individually as in the past. Instead a FDT-based framework application, such as PACTware, is used at the operator workstation.
The FDT concept creates open systems by setting the environment for the incorporation of software drivers for peripheral devices and communication components. This is to integrate them into the process control system. The software drivers, the DTMs (Device Type Managers), transfer the functionality of the HART field devices and the LB and FB Remote I/O Systems to the FDT-based (Field Device Tool) engineering tool of the control system, so that the user can configure and parameterize the HART field devices and the Remote I/O via the PROFIBUS. The Remote I/O systems themselves are represented by a modular DTM, which allows bus coupler or gateway to be parameterized from a central position. The DCS´s own engineering tool or a separate configuration tool such as PACTware can be employed to configure all the I/O modules.
The Pepperl+Fuchs Remote I/Os process the HART information in conformity to standards and function as a HART modem by receiving the HART telegrams from the PROFIBUS class 2 master. Subsequently the data is modulated onto the 20mA current loop of the connected transmitter power supply units and output isolators. Conversely, the response of the field devices is sent back to the control system via the PROFIBUS. The cyclical data traffic of the PROFIBUS communication is not affected by this. HART field devices, which have a dedicated DTM are operated via the PROFIBUS with their device-specific HART parameters.
The FDT concept creates open systems by setting the environment for the incorporation of software drivers for peripheral devices and communication components. This is to integrate them into the process control system. The software drivers, the DTMs (Device Type Managers), transfer the functionality of the HART field devices and the LB and FB Remote I/O Systems to the FDT-based (Field Device Tool) engineering tool of the control system, so that the user can configure and parameterize the HART field devices and the Remote I/O via the PROFIBUS. The Remote I/O systems themselves are represented by a modular DTM, which allows bus coupler or gateway to be parameterized from a central position. The DCS´s own engineering tool or a separate configuration tool such as PACTware can be employed to configure all the I/O modules.
The Pepperl+Fuchs Remote I/Os process the HART information in conformity to standards and function as a HART modem by receiving the HART telegrams from the PROFIBUS class 2 master. Subsequently the data is modulated onto the 20mA current loop of the connected transmitter power supply units and output isolators. Conversely, the response of the field devices is sent back to the control system via the PROFIBUS. The cyclical data traffic of the PROFIBUS communication is not affected by this. HART field devices, which have a dedicated DTM are operated via the PROFIBUS with their device-specific HART parameters.
Class 2 master communicating with HART field devices via the Profibus
Remote I/Os simplify planning for retrofits in plants with hazardous areas. With this, the well-proven principles and methods of explosion protection are used. Current loops with increased safety are thus as easy to handle as intrinsically safe loops, while providing more energy for the field devices at the same time. Remote I/Os embrace an overall concept for installations in explosive atmospheres, for which the use of HART communication not only ensures savings in terms of hardware, but also over the entire life-cycle of the system (cost of ownership).
Safety Integrity Level (SIL 2)
In the past, applications with Remote I/O always required additional discrete loops, when it came to applications involving functional safety, as the bus was frequently not able to fulfill the safety requirements. For this reason, we have developed a bus-independent, functional safety concept using a separate shut-down input. With this, outputs can be shut off by overriding the bus commands. Pepperl+Fuchs offers output modules that are controlled via the bus but whose output current can also be driven to zero via a separate shutdown input.
SIL 2 valve shutdown
In order to avoid unnecessary diagnostic messages, we do not simply switch off the power supply for the module, but rather disable the output current loop. Modules without shutdown inputs can be combined with modules with a shutdown input, on a single backplane. The latter modules are under the constant control of the control system via the bus, and are independent from the switching position of the shutdown contact. In contrast, modules with a shutdown input are only controlled by the bus, when the shutdown contact is closed.