The production of plastic film packaging includes several processes that use flammable liquids (such as paints, solvents, etc.). Filling and draining of tanks (handling), mixing of liquids or cleaning of receptacles may cause electrostatic charging.
The level of electrostatic charging depends first on the electrical conductivity of concerned liquids, the materials of receptacles and tanks, and the flow rates of liquid materials. If it occurs in an explosion hazard zone, electrostatic discharge may trigger ignition. The explosion risk of flammable liquid vapours mixed with air is caused by the electrostatic charging of the liquid surface by the processing in place, the electrostatic charges developing on the surfaces of processing equipment, or the electrostatic charging of the personnel present and working in an explosion hazard zone.
Reference standards and laws state that equipment users are liable for explosion prevention and assurance of protection against the consequences of explosion. The regulations in place also provide guidelines for countering the hazards from electrostatic charges. The largest manufacturers of plastic film packaging materials have decided to raise the safety level at their production plants and turned to the specialists at the WOLFF GROUP for a supply of electrical bonding systems that would assure safe discharge of static electricity.
According to the project investors’ preferences for specific plants, the WOLFF GROUP has been successively delivering the Bond-Rite grounding control systems, self-testing electrical clamps with warning LED indicators, or simple, certified grounding clamps. All these solutions are applied for electrical bonding and grounding of mobile and stationary components of industrial installations located in explosion hazard zones (such as paint mixing plants). The deliverables have been used to provide grounding of mixers and metal drums for holding of paints and solvents. The Bond-Rite systems and self-testing clamps help monitor the status of electrical grounding. The simple grounding clamps do not offer this functionality.
The customers’ plants have been provided with mains-powered and battery-powered versions of the Bond-Rite systems. The mains-powered bonding systems operate 24/7, while the battery version are engaged when self-testing terminals will not be connected to protected system components for more than 6 hours. The ground bonding clamps feature sharp tungsten carbide jaws that easily penetrate all paint coats, layers of rust or dirt which might have been deposited for long enough to form electrical isolation from the ground. The bonding terminals are connected with spiral cables in Hytrel sheaths which resist chemical attacks and mechanical abuse. The monitoring unit of an electrical bonding system features a LED indicator which tells when the grounding circuit is complete or broken.
Another deployment version of the bonding solutions is to apply a portable kit of self-testing clamps, comprising a pair of ground bonding clamps. One clamp is attached to the device being grounded (here these include metal drums or mixers), and the other clamp is connected to a part which discharges electricity to the ground (e.g. hoop iron, other grounded equipment, or steel structures). The clamps have LEDs which turn green if the bonding circuit is properly made. The problem with this version is that the LED indicators may become obscured by deposits of pollutants.
The last of the solutions chosen by packaging manufacturers are simple, certified grounding clamps made of stainless steel, each with two tungsten carbide teeth. These can be used in either of two possible configurations. A kit of two simple grounding clamps can be deployed and interconnected with a spiral bonding cable (with the clamps attached to the equipment listed in the previous deployment example). Another option consists in connecting one of the clamps to a container being grounded and connecting the lug clamp at the other end of the bonding cable to a groundclamp strip. The grounding terminals are available in two sizes (a small 12 cm clamp and a large 24 cm one), and the exact size selection depends on the size of the container or device being grounded. The bonding cables are available in different lengths (usually it is 3, 5, 10 or 15 m). A weakness in this case is the lack of any feedback on the current status of the installed grounding system.
SCOPE OF WORKS: successive deliveries of electric grounding and bonding systems for the largest manufacturers of plastic film packaging
LOCATION: Poland, Łódź Province, Wielkopolska Province
