Electrostatics

Many factors contribute to creation of static electricity: a) Contact and separation (friction) Whenever two dissimilar materials come in contact with each other and separate, one of the materials loses electrons and the other gains electrons. This phenomenon is called “triboelectric effect”. Static charges are developed on the surface of one of the materials depending on its relative position in triboelectric series. b) Changes in temperature Changes in temperature cause separation of charge in the atoms or molecules of certain materials. This is called “pyroelectric effect”. c) Changes in pressure Applied mechanical stress generates a separation of charge in certain types of crystals and ceramic molecules. This is called “Piezoelectric effect”. d) Induction A charged object brought close to an electrically neutral object causes a separation of charge within the neutral object. This results in static charges.

It is difficult to measure static charges in Coulomb – the SI unit of electric charge (equal to the quantity of electricity conveyed in one second by a current of one ampere).  An easier method is to measure static charges in terms of surface voltage in kilo volts (kV) using a static charge meter. Valstat static charge meters measure ±20 kV at 25 mm distance from the surface of substrates and higher voltages at proportionally higher gaps.

Static charges are less in humid conditions and more in dry atmosphere.

Active static eliminators are the ones which rely on AC or DC power supply which generate high voltages. This high voltage in turn helps in generating ions of positive and negative polarities which will help to neutralise excess charges present on the surface of the target substrate. They are best suited to eliminate static charges from fast moving webs, sheets, films and such.

A passive static eliminator is one which does not depend on an electric power supply to function. These are generally in the form of a brush or pad connected to ground. They help to drain excess charges from the substrate to the ground. These are best suited to considerably reduce the high static charge levels from substrates such as moving sheets, films, as they do not completely eliminate static charges.

AC static eliminating systems work on AC power supply. They contain a set of electrodes generating positive and negative ions during respective cycles of AC supply. DC static eliminating systems work on DC power supply. They contain two separate sets of electrodes. The electrodes connected to positive DC supply generate positive ions and the electrodes connected to negative DC supply generate negative ions.

All the static eliminating systems do the same job of generating ions. It is the application which decides the appropriate system to use.

Valstat static eliminators are shock-less and spark-free. Though the operating voltage is in the order of kilo volts, the current is limited to a few milli amperes and hence it will not yield any shock upon touching the electrode.

No. The Valstat bars are not recommended to be installed against metal rollers as the ions generated by the static bars tend to get earthed through the metal rollers which are attached to the machine frame, rendering them ineffective.

Regular static eliminating bars cannot be used in explosion prone areas like print stations of a printing machine. Separate ATEX certified explosion proof Valstat static eliminating systems are available for such applications. Please consult our product office to know more.

Only some specialised applications involve handling metallised inks/films. It is not recommended to use active bars in such applications. We suggest using passive discharging systems in such cases.

Valstat static eliminators are easy to operate and require very less maintenance. The electrode tips must be cleaned regularly using a nylon brush. The bars must be cleaned to remove dust, dirt and scales regularly. Details have been covered in our instructions manual regarding the same.

The passive brushes are made up of 35 micron-controlled resistivity fibres. The fibres are extremely soft and durable and are housed in a powder coated aluminium section. When positioned very close or just about touching a charged web, Valstat passive brushes will minimise the static charges and send it to ground. Hence, they are ideally suited for applications in hazardous areas.

Antistatic touch pads help to drain off the static charges present on human body. Valstat antistatic touch pads contain a static dissipative layer which will conduct the static charges safely to ground and keep the humans safe of unwanted static charge build up.

Just opposite to static elimination, here, a controlled level of static charges is transmitted on non-conductive surface that provides temporary bonding between the materials. The static charging is useful in applications such as stacking, printing, edge pinning, in-mould labelling.

Valstat electrostatic charging electrodes generate a controlled static charge that create a temporary adhesion between surfaces. Valstat VC series static charging electrodes are available in two variants; point static chargers and linear static charging bars. Both are supplied with high voltage cable enclosed in a flexible conduit. Point static chargers are suitable for applications that require localised charging, like edge pinning, in-mould labelling etc. Linear charging bars are used to generate electrostatic charges in linear applications like sheet stacking, pinning tracking etc.

Valstat static charging bars are easy to operate and require very less maintenance. The electrode tips must be cleaned regularly using a nylon brush. The bars must be cleaned to remove dust, dirt and scales regularly. Details have been covered in our instructions manual regarding the same.

Static monitoring system is measuring and monitoring equipment to identify the location of static charges and its magnitude and polarity. The Valstat V205 static charge meter is an offline, compact, digital, non-contact, electrostatic surface voltmeter, designed to locate and measure surface voltage on stationary and moving objects. AxisValence also offers cloud based and real-time static charge monitoring system Valstat SM20 for accurate and continuous monitoring. In this system, electrostatic sensor is fixed at the location where the charge level on a moving target is to be monitored. Each sensor is connected to the respective Valstat field station controller, which in turn are connected to a common touch panel. Depending on needed sensing points, the application and requirements of the user, the common touch panel is suitably located for monitoring and control purpose.

The distance range of Valstat V205 hand-held static meter is 50 mm from the object. The distance range of Valstat SM20 is 25 to 75 mm from the object.