Thirty years of Remote I/O at R. STAHL

Stahl’s explosion-protected Remote I/O systems: IS1

At the turn of the new millennium, R. STAHL presented the IS1 system, its second generation of explosion-protected Remote I/O solutions. IS1 is the most frequently used Zone 1 Remote I/O worldwide and is considered the standard in hazardous areas. It is based on an intrinsically safe system platform with Ex i fieldbus and intrinsically safe control of the I/O modules for connecting Ex i and non-Ex i field devices.
Installation, maintenance or extensions are thus permitted in hazardous areas without disconnecting power (hot work). Adding or replacing I/O modules and Ex i field devices is likewise permitted in Zone 1 (hot swap). The internal intrinsically safe system wiring uses a single, robust BusRail embedded in a top hat rail. In Zone 1, thus up to eight I/O modules (64 analogue / 128 digital signals) can be used and in Zone 2, up to sixteen I/O modules (128 analogue / 256 digital signals). HART and extensive diagnostics are transmitted transparently.

The CPU & power modules generate the intrinsically safe internal supply of the system. IS1 allows for setting up field stations in Zone 1 or Zone 2 without requiring Ex d or Ex p enclosures. GRP or stainless steel enclosures suitable for the respective application range are sufficient. IS1+ with new functions.
In 2010, R. STAHL presented IS1 Ethernet, the first Remote I/O for Zone 1 installation with Ethernet connectivity.

For easy implementation of Ethernet installations in hazardous areas and in order to ensure interference-protected transmission, IS1 Ethernet uses explosion- protected optical transmission through fibre optics in the “inherently safe op is” type of protection (IEC 60079-28).
The protection concept works by means of optical energy limitation similar to intrinsic safety.
Alongside offering robust transmission and independence from shielding and earthing quality, it allows for very long distances up to 30 km. Thanks to this, installations with Modbus TCP, EtherNet/IP and PROFINET are possible even in Zone 1.
The new development of the I/O level in 2013 was the next logical step in the evolution of Remote I/O. Multifunctional I/O modules allow mixed operation of inputs and outputs for analogue and/or digital field signals and of resistance sensors and thermocouples.
They enable compact and less expensive systems even with lower and inhomogeneous signal mixtures as well as savings in stocking spare parts.

The new low-power design is configured for use in extreme environments with temperatures of -40 °C to +75 °C. At the same time, energy consumption of the system was reduced by up to 50 %, and an extended service life time of up to 15 years was achieved. For each channel, the modules have LED status indications for faults and switching states. The “blue LED” is an innovative improvement for the “maintenance requirement” status indication, which is triggered by excess heat. The LED corresponds to the NAMUR (User Association of Automation Technology in Process Industries) recommendation NE107, “Self-Monitoring
and Diagnosis of Field Devices.” All indications are likewise transmitted to the control system (DCS / PLC) and plant asset management system over the process bus and ServiceBus.

Recently, R. STAHL presented a new IS1+ generation for Zone 2 with Ethernet connectivity. The new CPU module has one RS485 interface and two Ethernet interfaces and is multi-protocol capable. It supports PROFIBUS DP and the Ethernet protocols PROFINET, EtherNet/IP and Modbus TCP.

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