Intrinsically safe in-line viscometers from Hydramotion Ltd are playing a critical role in the production of polymer-coated cellulose films by a major UK manufacturer.

Cellulose films are used worldwide in speciality packaging, labelling, graphic arts and security products.  During the manufacturing process, the film is coated with a solvent-based lacquer which controls the barrier properties of the finished product (e.g. permeability to aromas, gases or moisture).  Maintaining the correct viscosity of the lacquer is vital for ensuring a constant and controllable coating laydown by the gravure coater.

In this case, a Hydramotion XL7 viscometer is mounted at the entry to the lacquer storage tank on each line.  As lacquer circulates between the tank and the applicator, the temperature-corrected viscosity signal from the XL7 is used by the process PLC to modulate the addition of virgin solvent, maintaining lacquer viscosity at the correct level and minimising costly downtime.

Hydramotion was initially selected because it could supply intrinsically safe instruments certified for Zone 0 (Class 1 Div 1 Group A) Hazardous Area operation.  In addition, the XL7 inline viscometer has no moving parts, simplifying maintenance.   As one of the Engineering Managers at the site commented, “The construction is robust and easy to install and maintain”.

The Hydramotion viscometers were first installed ten years ago, when the customer opened a new lacquer production facility.  The aim was to streamline production and reduce the number of shifts from three to two, with consequent savings in labour costs.  At that time, the customer was relying for viscosity measurement on a crude timed falling plunger system, which was described as “vastly inferior in terms of accuracy, reliability and operability”.  The old system suffered from numerous defects: it had no temperature compensation, calibration was regularly affected by mechanical wear, and the equipment required frequent cleaning and maintenance.  Moreover, it could not be totally enclosed, which led to health and safety concerns as well as problems caused by gelling of the lacquer when exposed to air.

The old system would not have been practical in the new production facility.  But with the Hydramotion viscometers in place, viscosity control was smoothly integrated into the manufacturing process, leading to “real, obvious and sustainable benefits”.  Ten years later they are still going strong.