Tyvek production machines under GE Fanuc control

Du Pont's Tyvek production machines are controlled by a triple-redundant PLC system as well as 1,500 distributed control blocks, with Cimplicity HMI software controlling and monitoring.

Protective clothing for dangerous missions, everybody has seen it before.

In order to produce the fleece material Tyvek, machines at Du Pont need to run, failure-free, for more than 100 days continuously, 24 hours a day.

They are controlled by a triple-redundant PLC system as well as 1,500 distributed control blocks, with Cimplicity HMI software controlling and monitoring.

Du Pont has been manufacturing this material for the European market in its Luxembourg plant since 1988.

Tyvek is also used for sterile medical packaging, roof lining, and envelopes.

Following a production changeover four years ago, the ecologically damaging chloro-fluorocarbons (CFCs) were replaced by easily flammable solvents, thus adding a 'high security' issue to the already very complex manufacturing process.

The control system also had to be adapted to these new requirements.

The production is now controlled by the triple-redundant GMR system, (Genius Modular Redundancy), and system-redundant Cimplicity HMI monitoring and control software.

The manufacturing process consists of three stages.

In the first stage, polyethylene is dissolved with a solvent.

64 injectors spin continuous strands of fibres which are then put together to form a fleece.

The machine runs for approximately 100 days, 24 hours a day, before being switched off for a short period in order to clean the injectors.

The analogue control function in the first stage is carried out by a Distributed Control System, while the digital detailed functions, such as the blending of raw materials, are controlled by the PLC system.

Due to the use of easily flammable materials, the Luxembourg legislator required the use of an approved redundant PLC system.

But also from a pure business economics point of view, redundancy has a major advantage: A short failure of the control system would lead to a production standstill of two to three days.

In the second stage, the fleece is carried over heated rollers in one of the three bonding machines where the fibres are bonded together by heat (at approximately 180C) and pressure.

The fleece rolls are then either stored in a high-rack warehouse or directly forwarded to one of three slitting machines.

In the third stage, the fleece is cut to size according to customer specifications.

Residues from the bonding and slitting machines are reprocessed in a recycling machine and can thus be reused.

All the machines are controlled by high-end PLCs, connected to 1,200 Genius I/O blocks via the GE Fanuc proprietary Genius Bus.

These blocks are located right next to the sensors/actuators.

The entire system controls approximately 20,000 I/Os.

The main advantage of this distributed I/O concept is that it requires very little cabling, which resulted in substantial savings.

In addition, the use of distributed I/O blocks made the entire control system more flexible, as expansion of the system is simple.

A further advantage is efficient and easy maintenance.

With their enhanced diagnosis functions, the blocks will detect errors, such as cable failures or short-circuit faults, and transmit this information immediately.

Due to the modular concept of the system, errors are located and eliminated quickly and easily.

The bonding, slitting and recycling machines are monitored and controlled from operator stations with the Cimplicity HMI software.

With 1,500 analogue and digital data points per system, Du Pont decided to implement a server-based redundant system.

The redundancy option offered by Cimplicity HMI was a decisive selection criterion.

Any information collected by the first server is automatically transmitted to the backup server.

If the first server fails, all the main functions, such as data processing or alarms, are automatically carried out by the second server.

The viewer stations are also connected to both servers and automatically switch to the backup unit in the event of a failure.

Claude Koch, technician at Du Pont, explained why this system was selected: "Cimplicity provides easy configuration, a wide variety of graphs, and an open architecture capable of handling products from other suppliers." The Du Pont control system is very reliable and ensures a high degree of availability while meeting all the safety requirements.

And if ever there is a problem or question, Du Pont has the GE Fanuc hotline to fall back on.

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