Giving networks broader scope

A fieldbus is much more than a data pipeline. It’s real value lies ability to provide an unprecedented richness of data to applications and services

Fieldbus today is incapable of replacing distributed control systems for sophisticated, highly demanding purposes, because the set of functions in fieldbus devices is incomplete (transmitters have transmitter-oriented functions; valves have valve-oriented functions), so sophisticated controllers are still very necessary. A state-of-the-art DCS can integrate all the devices needed for specific applications into a unified architecture which is easy to maintain.

Overall in a plant, you will not only see fieldbus networks being used, but a combination of point-to-point wiring with conventional instruments, point-to-point wiring with smart transmitters, field-mounted I/O, and smart transmitters on fieldbus networks. A system vendor should be capable of providing solutions for all these needs. And rather than asking for a particular technology, the end user should look for the best solution for a particular application.

However, a fieldbus is much more than a data pipeline. Its real value lies in its ability to provide an unprecedented richness of data to applications and services, enabling manufacturers to lower product cost and improve quality. Foundation Fieldbus is one of the eight bus protocols defined by IEC 61158, but no one single fieldbus protocol can meet all application needs. This is why typically more than one protocol will be utilised on several networks in one plant. Profibus DP for instance can be applied in a discrete manufacturing environment, while Foundation Fieldbus is the protocol of choice for continuous process automation systems.

Consider how Honeywell has risen to this challenge. To provide the right solution for a particular application, in addition to Foundation Fieldbus technology Honeywell supports other open technologies such as Fast Ethernet (mainly for the operation and supervisory domain integration), ControlNet (for process control integration), Profibus DP (for distributed peripherals integration) as well as other proprietary network technologies. Industrial strength plant networks are made open and secure by including the workstations in an NT domain dedicated to process automation functions. Communication between domains typically uses open standards such as OLE for Process Control (OPC).

For the present, Honeywell currently has several field installations of the low-speed H1 standard of Foundation Fieldbus and preparations are being made to support 100 Mbps High-Speed Ethernet (HSE). Here HSE will serve as the high bandwidth backbone carrying digital information and lower bandwidth H1 Foundation Fieldbus segments are branched off this to carry data and also field devices power if required.

Honeywell's networked structure will evolve into an architecture where high performance controllers exchange data over fieldbus networks with smart field devices and field I/O. The controller in its turn will communicate with other controllers and the business domain over redundant, deterministic High-Speed Ethernet. This network-oriented structure is in line with architecture proposed by the NAMUR organisation for future control systems, and provides the scalability, flexibility and integration end users require.

Honeywell refers to its implementation of the redundant deterministic High-Speed Ethernet as Fault Tolerant Ethernet. This 100 Mbps redundant Ethernet is fully compatible with the Fieldbus Foundation standard and is currently already used in one of Honeywell's TPS Solutions, TPN Bridge, which links two or more process networks through a Fault Tolerant Ethernet. As the HSE standard is endorsed, more HSE products and applications will be released.

Honeywell is adopting current and future network technologies as enablers for the networked structure of state-of-the-art process automation systems. TotalPlant Solution (TPS), TotalPlant Alcont (TPA) and PlantScape systems already offer open solutions, with determinism, robustness and guaranteed performance equal to or even exceeding that of former proprietary systems.

• Honeywell
  a157@industrialnetworking.co.uk