Fieldbus moves into the mainstream

Ian Sully, managing director of Auma Actuators' UK operation, explains the advantages and applications of bus protocols

There has been a rapid and widespread switch to intelligent automation in the water and wastewater industry. Fieldbus has become the primary method of controlling many plants, and profibus is established as the most popular protocol for
European applications. The digital approach is used across all process applications.

Starting at field level, profibus is used in actuators, variable-speed drives, sensors and other field-based devices. The use of the protocol continues through to treatment control centres, and is now used in a large proportion of control-panel applications.

Today, much internal wiring at UK plants has been replaced by internal profibus systems, which communicate simply and effectively at a sophisticated level using just two cable cores. To the end user, specifying fieldbus technology at the treatment works or the operator on site, the move to the enhanced automation solution is straightforward, and considerable benefits are afforded.

Not only does bus technology decrease cabling at a field level, which eases the installation process, but the amount of cabling is also reduced within the control panel. This means the mass of wires previously linking valve and actuator systems are no longer required. This, in turn, leads to major cost-savings as there is no longer a requirement to install miles of cables.

Additionally, there is a significant reduction in wiring and commissioning time, which leads to further financial rewards and ensures that the potential for making any connection errors during installation is substantially decreased.

Actuation adopted
The widespread appreciation of the benefits of the intelligent approach to actuation within the water and wastewater sectors is such that most new contracts specify fieldbus. With installations around the globe, any doubts regarding the digital solution have been addressed.

When bus technology was first developed in the early 1990s, some engineers held reservations about its reliability. The main initial concern related to the problems which may result should a cable be accidentally cut.

Using the hard-wired solution that preceded bus technology, if a cable was severed, it was only likely to impact one or two actuators.

If a cable is hit at a fieldbus-led site, this could impact 30 devices downstream, which could lose communication.

With increasing numbers of utilities adopting bus technology, fears have been overcome with the many benefits of the digital solution far outweighing the likelihood of a cable being cut.

The prospect of a cable being penetrated is minimal. In the unlikely event of this happening, in an actuation system like Auma's, there is a straightforward command setting that ensures that the actuator will revert to a fail-safe position.

It is important to emphasise that actuator manufacturers take an independent stance regarding digital actuation options. From the manufacturer's perspective, there is no preferred protocol. It is simply the fact that, to UK users, profibus is popular because it is user-friendly and able to control a wide range of field devices.

Other protocols adopted around the world include Modbus RTU, DeviceNet and Foundation Fieldbus. And Auma can support whatever system the user specifies. It is essential that actuator manufacturers keep up to date with latest digital developments, and adopt an educational role to ensure that customers are advised of advancements in the field of actuator automation.

Time and resource is therefore devoted to active membership of bus system user groups to network on an international level. Involvement in user forums ensures the manufacturer keeps up to date with latest bus developments and the implementation of digital technology.

By participating in such groups, the supplier of actuation systems gets feedback on the most recent bus applications. The user forums are also an opportunity for the actuator manufacturer to act as a conduit, presenting development requests on behalf of customers. These are reviewed by the producers of bus systems, and can result in changes to bus solutions.

Knowledge partnership
Sharing knowledge and adopting an advisory role is key to developing long-term synergy between the actuator manufacturer and the end user.

It is not simply a case of specifying a certain number of actuators and ticking pre-determined boxes when responding to the utility organisation's brief. The actuator supplier needs to assess the long-term objectives of the site. And a depth of understanding is needed to enable them to respond with an appropriate actuation solution that addresses all requirements, including that of new-generation
bus systems.

In summary, the actuator manufacturer needs to take a proactive role in the supply of the automation solution. They need to continually invest time to keep informed of latest developments in the digital arena.

The actuator vendor also needs to be prepared to take an advisory role. By drilling down to the full requirements of the brief, and fully addressing the utility user's needs, the actuator manufacturer ensures the fieldbus actuation solution will communicate correctly without the need for many additional, retrospective hours on site.

Fieldbus technology is now widely recognised as the automation solution of choice for actuators at water and wastewater treatment works. It is rare that the actuator manufacturer has to sell the benefits of bus systems. But this does not mean there can be any cause for complacency. The manufacturer must strive for continuing professional development in the field of actuator automation.

It is essential that a proactive role is taken to impart news of the latest advancements, and that the bigger picture is considered before responding to individual site specifications. The benefits of fieldbus are many. It is here to stay, and it is essential that the actuator manufacturer goes beyond being a mere supplier of actuation products to providing technical sales and service support for the new generation bus protocols.

Auma supplied more than 100 actuators to the Margate and Broadstairs Urban Water & Wastewater Treatment Scheme in Kent.

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