13 rumours - 13 answers about remote I/O

Not necessarily – it depends on the product and certificates.
You have to check whether the remote I/O system itself is certified for operation in Zone 1. You can find this out, for example, from the Ex marking on the components or from the associated documentation (e.g. operating instructions, EC Type Examination Certificate). If the component marking includes "Ga" or "Gb" at the end, the remote I/O system can generally be used in Zone 0 or Zone 1. This refers to the equipment protection level. However, if "Ga" or "Gb" appears in brackets, only parts of the device are protected, e.g. the field circuits. This means that the devices require an additional type of protection to be installed in the zone, such as a flameproof d enclosure.
Here is an example: An I/O module has the IECEx marking "Ex ia [ia Ga] IIC T4 Gb" – the "Gb" at the end indicates that operation in Zone 1 is permitted. Although "Ga" relates to Zone 0, it is written in brackets here [ia Ga], which means that it is only partially suitable for Zone 0 – specifically for the intrinsically safe field circuits which may lead into Zone 0.
If the marking does not include "Ga" or "Gb", or if only "Gc" appears, a separately certified enclosure with a different type of protection, such as Ex d or Ex p, is required for use in Zone 1.

That has no longer been the case for some time now, as R. STAHL has offered remote I/O systems with Ethernet interfaces since as far back as 2009. And for some years, with IS1+ there have even been systems featuring both PROFIBUS DP and Ethernet protocols such as PROFINET, EtherNet/IP and Modbus TCP – both for Zone 2 and Zone 1 installations. Users can choose the protocol to use on the device themselves and also change it. This is ideal for migration concepts from PROFIBUS DP to PROFINET. In addition, an increasing number of IT-compatible connections are available for diagnostics and asset management data in remote I/O systems. IS1+ offers FDT/DTM, an OPC UA server and a web server for this purpose. This means there are no obstacles to prevent Ethernet from conquering process automation as well.
The installed basis with PROFIBUS DP is, however, large enough that most remote I/O systems will also continue to offer this interface over the next few years.

Certainly not. In fact, a combination of HART field devices and remote I/O is actually the ideal solution and enables you to take the first few steps towards modern digitalisation concepts. What's important is that remote I/O supports corresponding I/O modules for analogue sensors and actuators with HART. This is standard for modern systems nowadays, meaning that HART can be used up to version 7. Most analog multi-channel I/O modules function almost as HART multiplexers and transmit the HART commands from and to analogue field devices via the digital network. What's more, some systems like IS1+ can even incorporate HART variables into the cyclical data exchange with the control system, enabling the digital HART variables of the field devices to be used for control tasks too, as multi-variable field devices so to speak. 

This naturally depends on the requirements, but experience shows that remote I/O systems are fast enough for almost all tasks in process automation. In most cases, the limiting factor is actually the controllers of the control systems, which cannot process the data at the same speed that it is supplied by the remote I/O systems. There are different approaches here. For instance, some manufacturers assign fixed cycle times to their remote I/O systems, for example every 50 ms, every 100 ms, etc. The highest possible speed is always used for the Remote I/O IS1+. Here is an example of this: With 100 analogue input values, IS1+ takes less than 50 ms to transmit this data from the sensor to the control system via PROFIBUS DP. For 200 binary contacts, this takes just 20 ms. When using PROFINET, this time is further reduced to 40 ms or 15 ms, respectively. But you can see that the problem is not the actual network transfer rate but, in fact, the reaction time of the sensors and actuators. This means that, when compared to the usual cycle times of 200 to 500 ms in process automation, remote I/O is definitely fast enough.

It is a common misconception that remote I/O is always more expensive. Firstly, you have to consider what costs you mean. On the one hand, there are the costs for buying and installing a remote I/O system, also known as CAPEX (capital expenditure). On the other hand, you also have to look at the operating costs, i.e. what will it cost me to operate this system over the next 10 to 20 years? These costs are also referred to as OPEX (operational expenditure).
With CAPEX, the costs are highly depending on the number of signals, the installation location of the remote I/O and the scale of the system. To put it briefly, the system is cheaper with a higher number of signals, a shorter distance between the remote I/O and the field devices, and a greater distance from the control room. Example calculations prove that a remote I/O system can be cheaper than a conventional isolator solution starting from just 16 signals. In scenarios with, for example, 1000 field devices and distances to the field of approx. 200 m, remote I/O systems are typically up to 25% cheaper, with this figure rising to almost 50% for distances up to 1000 m. Potential savings are achieved by the lower number of cables to be installed, the space saving in the control room and, most importantly, the drastically reduced engineering costs.
Other factors influence the OPEX savings, making them harder to calculate. However, if we assume that using intelligent remote I/O solutions like IS1+ can prevent even just a single unplanned shut down through the integrated diagnostics and alarms, you will already have saved hundreds of thousands of euros or more, just like that.

This was often the case in the initial phase of remote I/O technology. The technology is much more flexible nowadays thanks to the continuous development of communication protocols, the introduction of conformance tests designed by the field bus organisations and, last but not least, stringent requirements on the part of users. A remote I/O as a PROFIBUS DP device is connected to a control system, the PROFIBUS DP master, via a GSD and starts working without the need for further measures or tools. However, some control systems require additional drivers to clearly display certain functions for users and programmers. For instance, the IS1+ Remote I/O supports the APL driver libraries for Siemens PCS7, the device types for Siemens PCS neo, the FHX files for Emerson DeltaV and the add-on instructions (AOI) für Rockwell ControlLogix. Although an IS1+ coupling works without these special drivers, they make integration simpler and more convenient. This is why we are constantly investing in these special drivers to make this process as straightforward as possible for users or system integrators.

The complexity of project engineering is naturally highly dependent on the "intelligence" of the specific remote I/O solution, whether the manufacturer expects the user to carry out extensive power consumption calculations according to system structure and mounting position or whether proprietary tools must be used for project engineering. Or, as is the case with IS1+, the system structure in principle permits 16 I/O modules, regardless of whether it is Zone 1 or Zone 2, which may be installed in any configuration in every mounting position – it's as easy as that.
However, this also mainly depends on the capabilities and functions of the communication protocols. No additional tools are required when integrating remote I/O via PROFIBUS DP or PROFINET. In this case, integration via GSD or GSDML is used, which is available as standard in the engineering system, like with a field device. This allows all settings and functions to be configured and managed centrally using a single tool. Different protocols which are not tailored specifically for remote I/O may require other tools, but these are always based on industrial standards. For instance, an effective DTM is available for IS1+, which is compatible with all FDT applications such as PACTware (freely available) or FieldCare (Endress+Hauser). FDI (field device integration) specification work for the RIO working group is currently in progress to get FDI ready for remote I/O, thereby making another very effective standard tool available.

Industrial remote I/O systems which were primarily designed for factory automation and have only been additionally approved for a Zone 2 installation in the field can actually go on to cause problems here sooner or later. The situation is completely different for Zone 1 systems which were developed for hazardous areas and use in the field of process automation from the very outset. For instance, our IS1+ can be used for many years in a temperature range from -40 to +75 °C without any heating or cooling measures. The devices can withstand even high levels of vibration or shock loads and are certified especially for use on LNG tankers, for example, after having undergone the relevant tests with ship approvals. The offshore industry is one of the main users of remote I/O. On the one hand, the weight is greatly reduced because many cables are no longer necessary and, on the other hand, the systems work without any problems over many years, which is why they are used ever more frequently on unmanned platforms. Even customers who do not operate in hazardous areas repeatedly use this Zone 1 remote I/O system due to its robustness and reliability.

When used together with HART, remote I/O opens up completely new possibilities compared to a conventional installation. While the HART information is transmitted transparently with just an isolator installation, the control system is often not able to receive anything. The HART data is to be transmitted to engineering and plant asset management systems. HART multiplexers are often used for this purpose. These extract the HART data from the analogue signals downstream of the Ex i isolator and then pass this on via serial or Ethernet connections. With remote I/O, these HART multiplexers are already integrated into the corresponding I/O modules, doing away with the need for additional hardware. IS1+ transmits the HART data transparently, from and to the devices. At the same time, however, the four HART variables of each field device are read out as an option and incorporated into the cyclical communication with the control system. This means that the control system receives the analogue measured value once from a field device via the network, as is currently the case. At the same time, up to four additional variables are now available in purely digital form. This makes it possible to use field devices as multi-variable devices in a similar way to field bus devices. For HART 7 field devices, even more status information in accordance with NAMUR NE 107 can also be read cyclically by the remote I/O. This clearly offers added value compared to the conventional solution, without incurring additional costs.

Unfortunately this is the case with some manufacturers, especially when it comes to systems for use in hazardous areas which require corresponding Ex certificates for the specific regions. The work required to provide users with advice is much greater than with industrial systems as, on the one hand, explosion protection is a very wide-ranging topic and, on the other hand, regulations which differ from one region to another must be complied with. This means that very few explosion-protected remote I/O systems are sold off the shelf. New explosion protection technologies and functions are also much more complex and expensive to integrate, usually requiring a very experienced development team to implement in an acceptable time frame.
If you compare the remote I/O systems that are currently available, it will quickly become apparent why IS1+ has become established as the technology leader. We have been developing remote I/O systems for Zone 1 and Zone 2 for over 30 years and implement currently available technologies for hazardous areas in a short space of time. For instance, in 1995 we developed an intrinsically safe version of the completely new PROFIBUS DP system, and have been using Ethernet in Zone 1 since back in 2009. Our Zone 1 systems already support "new" technologies such as PROFINET for PA, OPC UA, MTP, or concepts developed by the Open Process Automation Forum (OPAF) – technologies that are in some cases only at an initial stage in the industrial sector.
We can therefore assure our users that we are continuously working on our products and launch new functions on a regular basis.

That's certainly not the case. Rather, remote I/O is one of the driving forces behind the development of intrinsically safe and explosion-protected Ethernet solutions. The first users wanted to use Ethernet in hazardous areas back in 2009. At that time, we connected the conventional 4 to 20 mA and HART field devices to Ethernet via Remote I/O with an explosion-protected, optical fibre data interface ("op is" type of protection in accordance with IEC 60079-28). An intrinsically safe version of this solution by the name of 100BASE-TX-IS (IS for intrinsic safety) has since also become available for CAT cables. Ethernet-APL, a new, explosion-protected Ethernet interface, is now being launched. It has been optimised specifically for direct connection of Ethernet field devices, i.e. 10 MBit/s transfer rate, 1000 m cable length and integrated, intrinsically safe field device power supply up to Zone 0. Remote I/O will, however, continue to feature in these new systems. For economic reasons, it makes little sense to equip simple contacts, initiators or indicator lamps and temperature sensors with their own Ethernet interface. The available stock of field devices with conventional 4 to 20 mA and HART interface will not be replaced by Ethernet-APL devices from one day to the next. These are all applications where remote I/O will play an important role as an "intermediary" between the analogue world and the digital world of Ethernet.

This tendency to think in extremes is now outdated. Ultimately, the most effective and economical solution is worth it and in this case it can also make sense to use a remote I/O system centrally in the control room, even if this is not a typical application. The available space in the control room is usually very limited, especially in brownfield applications and system extensions. And this space is extremely valuable at the same time, meaning that extending a control room can quickly become very expensive – if it is possible at all. Ex i isolators, which are fitted in cabinets in the control room, are traditionally used for field device installation in hazardous areas. These isolators are often connected via cables to the control system's I/O cards using marshalling panels and are wired to the field devices in the direction of the field using marshalling panels and multicore cables. This means that you need space for cabinets with the I/O level of the control system, for the Ex i isolators, for the marshalling panels and lastly for all of the cables. If a remote I/O system is used, this replaces both the I/O level of the control system and the Ex i isolators, and is connected to the controller using one or just a few cables, doing away with the need for this marshalling panel level and cabling. Multicore cables or single cables are only used to connect the devices in the direction of the field. The only way to avoid this is a "true" remote I/O installation in the field. Example calculations show that a remote I/O system as a control room installation can save up to 60% of space in the control room, or even up to 90% as a field installation.

In actual fact, remote I/O offers the most advantages when it is combined with intrinsically safe field devices. This makes installation, replacement, maintenance work and modifications easy to perform during operation in Zone 1 without requiring special approval or monitoring devices. There are now so many intrinsically safe field device variants that a solution is available for any task. The I/O modules of the Remote I/O IS1+ are suitable for almost all Ex i field devices on the market, both in terms of their functions and Ex i interconnection. Despite this, every now and again there are devices that are only available with certain types of protection like "d" (flameproof enclosure), "m" (encapsulation) or "q" (powder filling) and therefore must have a connection with increased safety "e". IS1+ offers possible solutions for this too. On the one hand, there are special multi-channel I/O modules with non-intrinsically safe interfaces which may be installed mixed with the Ex i modules in the same system, for example for solenoid valves with 230 V AC/2 A control or for PNP initiators. On the other hand, single-channel signal-conditioning isolators are available, allowing one or more non-Ex i field devices to be operated on a single multi-channel Ex i module, such as 4-conductor transmitters or solenoid valves. The I/O modules can still be replaced during operation, allowing the advantages of intrinsic safety to be combined with those of non-intrinsically safe field devices. The required 50 mm clearances between intrinsically safe and non-intrinsically safe electrical circuits are achieved using partitions that are easy to lock on to the I/O module.

Do you have further questions? Feel free to use our comment function.