However, systems using HSE as the PCN backbone are few (ABB and Smar), and systems using Profinet as the PCN backbone arent a dominant fraction of bonafide, large-process applications. This means many users will bring in Wireless HART through gateways, which have limits. Hodson adds, Gateways may offer connectability, but they almost always have functional sacrifices and need some application configuration.
Large-process users all support open standards. One senior process control consultant from a major oil and gas firm, who is on the team that qualifies suppliers for their bid list, says that, With all things equal, the preference would be for an open PCN standard. However, the equals on the bid list dont show a strong leaning toward an open standard for their PCN, and this doesnt seem to affect any suppliers ability to win jobs. Whether large-system users will ever vote with their dollars remains to be seen. Until then, its reasonable to expect proprietary implementations of Ethernet, gateways, and OPC interconnection to remain the status quo.
For those of us in smaller I/O count facilities, where traditional PLC or hybrid architectures are the norm, the current environment may indeed look like its being taken over by Ethernet. Choices abound, and even intrinsically safe and out-of-the-box redundant Ethernet solutions are available. That numerous protocols and application layers exist doesnt seem to be slowing anyone down. As long as your business allows more diluted accountability for system troubles, end users or their system integrators may feel free to choose. But when an enterprise agonizes about lost production and call-outs at 3 a.m. on a holiday weekend, even network-savvy system integrators may be compelled to choose single-source accountability.
Perhaps todays increased network speeds and processing power will allow open protocols like OPC UA to make dissimilar connections appear seamless, but uptake by conservative users still may be slow. Proven-in-use would help, but it would probably end with the system having to be re-qualified [for its bid list] adds a long-time user at an oil and gas firm. Another fieldbus end user adds, To me, open standards are only useful when you want to have different vendors products talk. Its becoming more important, and we are dragging the vendors kicking and screaming along with us.
With many engineers working increasingly far from nitty-gritty process control networks, reliance on system integrators and vendors will remain the norm or increase. Our present mish-mash of networks and protocols will likely persist too. So it seems our suppliers are wise to claim to be all things to all people, like Micro Motion supporting every protocol it can afford.
The One Network may be a real possibility, but constraints on end users, their business and operations clients, and suppliers interests means every-bus, anybus, OPC and Modbus will be in our plants for years to come.
John Rezabek is a Control contributing editor