It’s never too late to innovate

Pneumatic actuators have many advantages over their electrical counterparts for the water and wastewater process industries. These components are used extensively by the industry worldwide, except in the UK. Festo's Martin Hunt tries to pinpoint why, and sees an encouraging shift in attitudes.

Here in the UK, the water industry appears curiously indifferent to the benefits of pneumatics technology. This attitude is quite contrary to opinion worldwide, and its roots run deep.

Historically, when demand exceeded supply, water companies responded by simply increasing capacity, rather than improving processes – a reflection of more relaxed economic times.

Post privatisation, however, political, legislative and consumer pressure has grown. New imperatives, particularly the demand for more housing, mean water companies are under pressure to plug the leaks.

Today’s major utilities and smaller clean water companies operate in what is now a heavily regulated market. The consumer’s interests are looked after by Ofwat, while water quality is a matter for the Environment Agency among others. Both have legislative power to fine water companies for poor service or quality.

And with resources diverted to the urgent business of preventing wastage, fines for poor delivery or water quality can really hurt.

In terms of economic performance, the regulator now sets price limits based on demanding efficiency assumptions. This is to introduce an element of competition and encourage poorly performing companies to catch up with the more efficient ones.

From this stick dangles a carrot – cost-efficient companies are allowed to retain their savings for five years.

The result of this pressure is a distinct shift in corporate culture towards improving the efficiency of processes. Given the identifiable advantages of pneumatics, we would expect to see a shift towards this technology. So, why has this not happened?

Bad press

This grass-roots loyalty to electrical actuators, despite their inherent performance limitations, is due in part to the perceived unreliability of pneumatic actuators.

Thirty years ago, this perception may have had substance.

A number of first-generation pneumatic actuators did indeed suffer from unpredictable operation. This was caused primarily by lack of lubrication, poor maintenance and air preparation, and freezing due to moisture contamination.

Manufacturers of electrical drivers were quick elevate these problems the status of generic attributes.

Never mind that electrical drives suffered from issues such as water ingress, server drive bush wear, intermittent electrical failure, corrosion of electrical connections and overheating motors – they won the perceived quality war of words.

And it should be said that electrical drives still suffer from insufficient lubrication of drive bushes, rusty cover tubes leading to premature wear of drive bushes, complex valve-mounted electronics subject to vibration, and water ingress due to poor installation practices… so have they really improved?

Cracking torque

Pneumatic technology has evolved dramatically over the last 20 years. Pneumatic actuators now require little or no maintenance over a lifetime, which is typically ten times longer than their electrical counterparts.

The actuators that Festo produces for the process industry, for example, have 80% fewer parts than electrical actuators, resulting in higher reliability and a longer working life. Fewer moving parts, says Festo, mean they are inherently more robust and better suited to aggressive washdown environments. While electrical actuators often fail due to moisture ingress, pneumatics are also essentially immune to plant-induced vibration.

Festo says pneumatic has advantages over electrical that are of particular benefit to the water processing industry.

They can deliver the high, cracking torque required to open butterfly valves or operate penstocks that have become encrusted with solids. The motors in electrical actuators can trip out on torque or suffer motor overheating.

Furthermore, the gear trains of nearly all electrical actuators run in oil baths. This raises concerns about possible contamination of water supplies, whereas pneumatic actuators merely require a supply of unlubricated, dry air.

In addition, the performance of absorption dryers used in modern air preparation systems – down to a -40°C dew point – has also improved significantly in recent years. This enables remote pneumatic systems to be supplied with extremely dry air, eliminating the problem of the water content in the air freezing up.

The transformation of pneumatic actuation technology is mirrored by its electronics element. This has grown from near zero to the incorporation of fully integrated, high-performance closed-loop control systems.

Cost savings

Festo says it produces a wide variety of intelligent valve terminals and I/O modules, as well as the software to facilitate simple retrieval and interpretation of process-related data from individual valves.

The company says these types of products provide a particularly cost-effective solution for installations that cover a wide physical area. Festo says this makes them an attractive proposition for the water and wastewater industries.

By adopting a distributed control approach, instead of applying complex electronics to every single valve actuator, companies also save programming time. There is less I/O, meaning less cabling, and it all adds up to easier and quicker installation.

There are substantial cost savings to be had, too. By obviating the need for higher power electrical circuits, pneumatic actuators can reduce main contact breaker costs by about 25%, and site cabling costs by as much as 40%.

There are hopeful signs on the horizon. Engineers entering the utility industries are increasingly more open to pneumatics. And the utility companies now have a duty to investigate use of innovative technology to improve operating efficiency and reduce capital and life-cycle costs.

Festo says it was recently involved with the design of an aerobic digester for a UK water utility. which improved on the efficiency of the existing design by as much as 25%.

The new design uses Festo’s CPX programmable controller to independently control six digester gas valves, automatically sequencing their operation to ensure that all parts of the digester are receives sufficient air to maximise process efficiency.

Martin Hunt is process industry business development manager at Festo. T: 01604 667000

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