Sometimes breakdown of the smallest element in a production line can create costly problems. A broken valve can have a big impact on profitability if it halts the line. So the intelligent valve, which will predict its own impending failure, should be welcomed by industry. The development is being championed by pneumatic automation and control […]

Sometimes breakdown of the smallest element in a production line can create costly problems. A broken valve can have a big impact on profitability if it halts the line. So the intelligent valve, which will predict its own impending failure, should be welcomed by industry.

The development is being championed by pneumatic automation and control specialist IMI Norgren, based in Staffordshire.

While competitors offer a variety of ways to introduce microchip-based intelligence for fieldbuses (digital communications links which convey instructions to equipment around a factory, such as programmable logic controllers), Norgren proposes a more advanced option.

Recently Norgren combined its valve islands with an integrated programmable logic controller (PLC). Technical director Chris Bramley says this was the first step to revolutionising the pneumatics industry and could change the industry’s approach to intelligent systems.

‘Soon intelligent valves will not only be able to diagnose a system fault but will also be able to predict and prevent expensive breakdowns and system failures,’ Bramley says.

A new generation of intelligent valves will bring the development of pneumatics almost full circle, he says. Originally, when air pilot valves were controlled by pneumatic signals, individual valves were located close to the cylinder or actuator they were controlling. With electronic controls, individual valves were grouped and relocated in cabinets, to reduce wiring by placing them next to the PLC that instructed the valves when to open. Later, integrated valve islands replaced the valves in these cabinets. With the valves remote from the pneumatic cylinders they were controlling, however, response times increased.

No need for cabinets

Now Norgren has eliminated the need for valve cabinets and associated equipment by connecting the PLC to the valve island and protecting the unit against dirt and moisture to the IP65 standard for electrical equipment. The next step will be to move the intelligence from the integrated PLC into individual valves, by fitting each with a microchip. ‘So we will be able to take the valves away from the island and back to the machine,’ says Bramley.

In current systems, the fieldbus carries signals to different valves, using a two-wire system. With intelligent valves, systems will be able to communicate in both directions. Intelligent valves will be able to diagnose problems or give prior warning of breakdown, using the onboard microchip to measure data, process the measurements and communicate findings back to the controller.

‘Transferring PLC intelligence to an individual valve will allow it to measure, process and communicate on its own,’ says Bramley.

‘Once you have fieldbuses, then two-way communication is possible, but the system is still dumb. Adding intelligence to valves means valves will be able to be monitored directly and send signals back if there is a problem.’

He predicts that hard-wiring to valve islands will become a thing of the past, as Norgren is developing a technique in which a single two-wire cable will allow the chip on each valve station to communicate directly with the controller. With the valve situated on the machine, response times will also be faster.

There will be significant diagnostic and operational benefits. Current technology means that although fieldbuses or PLCs can tell a valve is not working, they cannot tell the operator what is wrong. Intelligent valves will communicate the nature of the problem to the controller, so they can take action at the next maintenance break. Should a valve’s response time increase above a predetermined threshold, its chip will alert the operator to a potential failure.

Bramley suggests the next stage is integrating the intelligent valve with the actuator. ‘With the benefit of an intelligent actuator, the operator will be able to tell the actuator how to act at any stage of a given stroke.’

For operations such as crimping, the actuator may need to move out quickly for the first part of its stroke, then increase pressure and slow down. At present a cumbersome array of several ordinary valves and a proportional valve driving a multiple-speed actuator is needed. An intelligent actuator achieves this with one assembly: the valve adjusts the speed and pressure is applied to the actuator electronically as it moves through its stroke.

‘This could result in benefits in cost, installation time, maintenance and operational performance,’ says Bramley. Ultimately, similar principles will be applied to any kind of pneumatic equipment.

Norgren promises to introduce its first intelligent valve products to the market next year. Bramley says the pneumatics industry is generally conservative, so he expects uptake to be slow and steady, rather than an overnight sensation. ‘The industry has even been slow to take up the fieldbus because of the lack of a standard protocol.’

Norgren’s enthusiasm for adding intelligence to valves is not shared throughout the industry. Cannock-based Parker Pneumatic has concentrated on developing fieldbus capability. It has developed a family of manifolded electrical and pneumatic valves in the Valvetronic Valve Island range, and earlier this year introduced a new range of AS-I modules, which allow connection to the AS-I fieldbus system.

The Valvetronic range takes existing pneumatic valves and enables them to be manifolded together in a modular form with the benefit of reduced cabling and faster installation time.

Two valve ranges are available in the Valvetronic family and a further two will be launched soon. The next stage will enable inclusion of a fieldbus module which will allow networking to a fieldbus system.

The UK’s largest installation of a Parker Pneumatic distributed valve island system is at the Ford manufacturing line in Enfield, which supplies instrument clusters for the Mondeo range. It was installed by Baar & Paatz Industrial Automation and incorporates manifold and pneumatic connections via a DeviceNet fieldbus.

According to Barr & Paatz director Stirling Paatz: ‘Using Parker Pneumatic valve islands on the DeviceNet network saved hundreds of hours of wiring time. It avoided the need for additional cabinets, which would have been difficult to accommodate because of restricted space. The flexibility of the DeviceNet addressing system also meant that changes and additions were easily managed.’

But a spokesman for Parker Pneumatic says most sales of the fieldbus versions of the Valvetronic range have been made in mainland Europe.

‘UK companies seem slow to pick up on fieldbus technology. Considering that using a fieldbus system allows you to connect industrial devices in a similar way to a PC network, many British companies are missing significant benefits in terms of control and diagnostics, as the system can tell operators which nodes aren’t operating.’

Lack of standards

He is concerned about the lack of generic standards in the electronic control field and believes this is inhibiting the take-up of intelligent valve islands. ‘Customers prefer to use a simple valve island connected to a PLC by a ribbon cable rather than using a fieldbus,’ he says.

Meanwhile, compressor manufacturer Atlas Copco is applying electronic intelligence in optimising multiple compressor set-ups.

Most factories have multiple compressors, to allow for fluctuating demand for pneumatic equipment. To have one compressor big enough to meet peak demand would be inefficient, so normally there will be several, with one in reserve for breakdowns.

Pressure control switches on the compressors are arranged so that they successively cut in if demand is such that the pressure in the system drops below a certain level known as a cascade system but this can only control the pressure within a relatively wide band of 1 2bar.

Atlas Copco has introduced a new programmable pressure band controller, the ES300, to regulate the air network pressure in multi-compressor installations to within 0.2bar.

Claimed to offer large energy savings compared with a pressure cascade system, the ES300 pressure controllers analyses network pressure and the rate at which pressure changes for two to 16 compressors on a network. It then switches the compressors on and off in the most economical combination and rotates them so that none is used more heavily than any other.

An ES400 remote compressor monitoring and control system has also been introduced. This can be operated from a single PC at a chosen location using a simple Windows-based package.

But how popular any of these developments will prove remains a moot point, however, with the prevailing attitude among UK companies apparently being ‘if it aint broke, why fix it?’