The process is actually simple: The further the I/O level is extended into the field, the less wiring is required for connecting the field devices to the control system of an installation. Normally a remote I/O station only requires one bus cable – or two with redundant designs – to be routed from it to the control system. Remote I/O solutions also normally save space in the control room because the I/O level is moved to the field. These solutions are also easy to plan.
Remote I/O system
Turck’s excom has been available for the past fifteen years to provide this kind of remote I/O system for use in zone 1. The system transmits the process and diagnostic data of the periphery and communicates, if necessary, with the HART field instrumentation.
However, not all users share the preference for I/O installations in the field. Some customers place importance on having their entire I/O technology directly in the control room and connected to the DCS solutions. The reasons for this are multiple. Wage costs for wiring the field devices are less expensive. The cost saving benefit resulting from the reduced wiring of a remote I/O solution is therefore less significant.
Flexible application scenarios with one series
The use of excom as a system I/O, like the use of excom in the Ex area, provides the benefit that a separate interface technology for galvanic isolation or Ex separation is unnecessary. The little planning and space required compared to conventional interface technology applications, therefore, also pays out here.
The functions and handling of the system are the same for both types of installation. There is a standard structure and operating philosophy, both for the integration in the DCS system as well as for DTM-based asset management. The system can in all cases be maintained and modified during operation. This applies both to adding individual measuring points as well as to extending a system with additional modules. The tried and tested redundancy options of excom are also fully supported.
A standard Ex-i periphery supports signal processing and field device control from zones 0, 1 and 2. If this periphery is installed in zone 1 and 2 in order to detect signals as closely as possible to the location of the instrumentation, a specially optimised power supply unit is available for this application, which generates an intrinsically safe system voltage. The interface to the fieldbus, in this case Profibus DP, is also intrinsically safe. This configuration enables the entire system to be fully maintained during use in the Ex area.
The identical Ex-i periphery can now, however, also be used in the non-Ex area. The high signal density of excom can offer here the possibility of operating up to 24 I/O modules, which further reduces the basic installation costs. The special power supply unit for this application area makes the entire system considerably more compact. A special gateway provides the necessary protection of the Ex-i periphery to the bus so that a separate segment coupler is not required for implementing the intrinsically safe physical bus characteristics of RS485-IS.
Extended portfolio for the safe area
Even with exclusively non-Ex area applications, the user benefits from the advantages of the excom family: Two modules for digital 24 VDC signals were recently added to the range. A separate module for this purpose in the safe area has not been available to date. The new modules now close this gap. The DO80-N is suitable for connecting 24 VDC 3-wire digital sensors in PNP or NPN versions. It is a suitable module for digital output signals in the safe area. The DO80-N 24 VDC output supplies 24 VDC with 0.5 A. It’s short circuit protection can be configured as locking or non-locking in order to adapt it optimally to the application at hand. Both modules are therefore ideal for migration projects since their switching behavior can be adapted to the application in the controller.
New firmware and new DTM
In terms of software, the company has expanded the functionality of the gateway firmware and the DTM. The GDPIS FW 2.3 firmware for excom in zone 1 now supports all new modules. Information and maintenance functions can now also be integrated in compliance with the profile. The new software now makes excom open for DD - based asset management, such as for the predictive maintenance of field devices. HART protocols are tunneled to the field device in compliance with the profile. The new DTM likewise supports all new modules. The overview of the system status was improved with an enhanced diagnostics view. General systems states are now supported better with a DTM - based access.
Compact module rack
The company is offering in the range a particularly compact module rack for smaller installations in the field. The MT08 offers space for eight electronic modules and like other module racks guarantees a high availability, thanks to a redundant power supply and redundant communication modules.
The housing series for the module racks has also been standardised. The depth of all variants is 260 millimeters with the corresponding widths of 460, 650 and 800 millimeters for excom installations with 8, 16 or 24 modules. The flange plate on the bottom can now be replaced in order to adapt the cable routing to individual customer requirements. The standard flange plates provide space for
up to 120 M16 or M20 cable glands and can now be replaced individually.