Utilities follow the bus route

Ian Sully, managing director of Auma Actuators, reports on digital control technology and why bus systems have recently experienced growing popularity within the UK water sector

After over a decade of the water industry keeping a watching brief on bus systems, the sector is now recognising the scope of benefits such systems offer. As a result, we are currently witnessing a wave of interest from the market.

With the ability to substantially decrease field wiring costs, while at the same time improving information feedback, digital systems first entered the UK market in

the early 1990s.

watch and learn

However, the water industry was cautious. It was not until 1995 when one utility broke away from the pack to spearhead a Profibus application that the rest of the industry began to embrace bus technology.

After one initiator demonstrated the benefits of the digital solution, growth in demand snowballed. The strongest interest has been shown in the Profibus protocol. As the most common digital control system, supported by a large range of UK manufacturers, Profibus is a particularly user-friendly option that controls a comprehensive range of field devices.

Auma has experienced a phenomenal increase in sales of Profibus actuator systems in the water sector and the thousands of reference sites catalogued on Auma’s global Profibus customer listing reflect the popularity of this solution.

Profibus installations are to be found in a wide range of applications including potable treatment plants, filtration plants and WwTWs.

Setting the standard

Due to the popularity of Profibus, Auma predicts that within the next five years the technology will become standard within the water sector. The take up of the technology is such that hard wiring solutions are already widely being superseded by digital systems.

Cost savings are a major benefit to customers when adopting the new approach to actuation. Traditionally, a 20-core, multi cable would be connected to each actuator at the plant. However, with a simple twisted pair replacing multi cable costs, the requirement is for substantially less cabling and this is reflected in significant cost reductions. With just two wires instead of 20, commissioning becomes considerably easier with less chance of wiring errors.

In addition, digital technology substantially increases the feedback of process information. Bus technologies provide almost unlimited data feedback and the user can obtain precise information relating to the processes within the WTW. Furthermore, a recent Profibus DP V1 breakthrough enables the user to change the settings of field devices without leaving the control room. This technological initiative enhances site management, processes and logistics.

Case study

Avonmouth WwTW provides one example of a Profibus actuator application. Located on over 45ha of reclaimed marshland, Avonmouth is Wessex Water’s largest WwTW supporting a 1M PE. Considered a flagship site for the utility, the technology at the works incorporates Profibus open fieldbus actuator solutions from Auma, contracted and installed by MJ Gleeson.

The works treats up to 300Ml/d, but originally only 30Ml/d was treated to full secondary standard, mainly for industrial use. A major extension of secondary treatment plant, undertaken to meet the Urban Wastewater Treatment Directive and completed in 2000, increased secondary treatment capacity to 213Ml/d.

A final extension to the works currently being undertaken is set to treat all flows to full secondary standard. As a result of this expansion, the site will incorporate 11 sequencing batch reactors (SBRs) taking capacity to over 300Ml/d, which equates to 3,472 litres/s.

Chosen for their modular extension capabilities and efficient use of land, the SBR’s play a key role in the successful operation, management and logistics of the works — this modular approach gives Wessex Water the option to potentially add a twelfth SBR to the site.

Due to the complex nature of the highly automated computer control and monitoring technology of the SBR’s, actuators play a key role in valve operation.

Recognising that traditional hard wire systems would not be appropriate, Auma’s Profibus solution was chosen as it provided cost savings on cabling and a substantial increase in feedback from the field, thereby ensuring optimum performance. In a unique position to provide a plug socket connection for Profibus, Auma’s solution gives Wessex Water the ability to remove an actuator from the line while maintaining continuity downstream.

With a track record at the works proven during Avonmouth’s first expansion phase, Auma was also selected to provide actuators for the storm tank element of the current scheme which is to improve compliance with the Bathing Water Directive as part of AMP3 quality output.

Water industry growth in digital control applications extends far wider than the UK market and, as a global organisation, Auma can cite case-study sites around the world.

Sales procedures

With the benefits of digital technology clearly recognised by the water industry, changes are needed within the actuator supplier organisation to respond to the new generation of customer needs. First, the company needs to provide a guru-style consultancy service to customers. Keeping its finger on the pulse of latest developments in the digital field, the actuator supplier should be positioned to offer the latest, most informed and comprehensive independent advice.

Digital control systems are widely recognised as the way forward for flow control solutions. However, the range of options can be confusing to the user and, with this in mind, a dedicated support function is needed to provide market application advice. In Auma’s case this means a company-wide informed knowledge base throughout its sales personnel and the appointment of a Profibus product specialist.

Second, as bus systems are considerably more technical than the traditional actuator solution, the sale becomes considerably more complex for the system provider. As such, Auma is experiencing increased involvement with contractors and end-users to effectively convey the full picture of fieldbus benefits.

The technical nature of the installation also means that more detailed pre-application discussions are required at the concept stage to ensure that, as a supplier, Auma fully understands the customer’s requirements and, in turn, the user comprehends the full scope of the system including installation, management and benefits. For example, with each actuator comes the possibility of 40 status feedbacks but it should be understood this is the maximum potential of the solution and tailoring is required to meet specific customer needs.

Decade of progress

Having positioned our organisation to support new generation fieldbus technology, the rapid rise in popularity of Profibus is the most significant market development Auma has experienced over the last decade.

We are now witnessing a turning-point in the water industry’s willingness to implement and execute

wide-ranging digital control actuator solutions

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