Controller keeps track of viscosity

Leading viscosity control company Fullbrook Systems has chosen to use Eurotherm control and data acquisition products for maximum flexibility.

Leading viscosity control company Fullbrook Systems offers a wide range of high accuracy solutions to measure, control and record the viscosity of printing inks and other coatings.

In large-scale multiple-viscometer installations, such as those found in the packaging and printing industries, the company has chosen to use Eurotherm control and data acquisition products for maximum flexibility.

This approach allows systems consisting of six, eight, ten or more linked viscometers to be operated from one central touch screen control unit.

Viscosity control in printing and coating is important for a number of reasons, including product consistency, quality and consumption of raw materials.

During a production run, solvent or water will naturally evaporate, often aided by dryers and heaters on the machine and as a result, viscosity of the coating will naturally increase over time.

This gradual increase manifests itself as an increase in coat weight and colour strength.

By accurately controlling the viscosity of the coating, colour strength and coat weight will remain consistent throughout the run.

Traditional manual methods of control rely on the machine operator picking up a colour change by eye, or by using a flow cup and stopwatch to check viscosity.

To correct the viscosity the operator will manually add solvent or water into the ink or coating, which often has the effect of dramatically reducing the shade.

Over time the effect of manual control can often be a series of seesaws in viscosity, and the resulting colour of the finished product.

Accurate viscosity control using precision viscometers enables solvent to be added in discreet amounts and avoids large swings in the fluid viscosity.

This approach not only ensures that product is printed or coated consistently during a run and from run to run, but also avoids shade variations and saves material.

The approach has been proved to save as much as 20% on ink and coating costs.

In large-scale systems a number of such viscometers may be used to monitor the various reservoirs containing different coatings.

For large-scale systems, Fullbrook have chosen to incorporate a combination of Eurotherm's Visual Supervisor controllers, 2500 System I/O controllers, 5000 Series data recorders and 2000 Series PID controllers, depending on the application.

This choice was made on the basis of product flexibility, system compatibility and ability to provide high accuracy solutions to different customer requirements.

Eurotherm systems are also supported by a comprehensive applications and engineering infrastructure.

The combination of powerful display and control functions offered by Visual Supervisor, supported by the modular, expandable 2500 PID controller, was recognised early on as an exceptionally cost-effective solution, offering great versatility for a number of large scale control requirements.

Combined with some unique intuitive continuous self tuning software developed in house by Fullbrook, the result is a viscosity control solution that is simple to operate but is far superior to manual methods.

Visual Supervisor is a powerful multifunction control and display product, which in effect is a process controller, data logger, setpoint programmer and interactive touch screen display in one unit.

It is compact, simple to use and is capable of performing both continuous and sequential control functions.

The unit features comprehensive alarm and event management, powerful trending, setpoint programming as well as local data logging facilities.

Because of its open network architecture, it may be connected to a wide range of third party process interface I/O modules as well as the proprietary Eurotherm 2500 System.

The touch-sensitive screen offers a simple configurable "pop-up" navigation menu, which enables users to access its wide range of functionality.

The system can be configured to show a hierarchical view of plant or machine using area/group/point displays.

The well-proven 2500 System is a high performance multiple loop PID controller which provides simple loop, cascade, override and ratio control functions as standard.

It can perform combinational logic, remote data acquisition, monitoring and alarm functions on its analogue and digital inputs and outputs.

Eurotherm's 5100V data acquisition unit (DAQ) is the latest member of the 5000 Series of data recording instruments, and is an advanced type of graphic recorder, which also acts as a process viewer.

The 5100v features a high-visibility quarter-VGA TFT colour screen which functions as both a touch-screen user interface and a display for bar graph, digital and chart information representing both current and historical data values.

The instrument provides a seamless interface between any monitored process and the IT environment.

In conjunction with Brookfield Viscosel VTA120 pneumatic viscometers, a recently installed 5100 is offering control and recording on a critical coating of board used for cigarette boxes.

To avoid customer rejections the shade of the coating has to be closely monitored.

The manufacturers require the viscosity to be controlled to +2mPas or 1 cup second.

In practice the specially written control algorithm in the 5100 is proving that control better than +0.5mPas or 0.25 cup seconds is achievable.

Factors other than viscosity can also affect the coating process, but the ability of the 5100 to accurately control and record process data enables the printer to quickly identify and rectify process problems.

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