Water and electricity are a critical combination, especially where industrial processes are concerned. Dangerous or even fatal electrical accidents occur not only in the high-voltage range ("hot zone"), but many occur also with low voltages. In moist or wet process environments it must hence be ensured that an insulation fault does not cause a serious accident. A suitable IT system (unearthed system) and monitoring equipment that is especially designed or adapted for such conditions can achieve this.
How the protection of persons, processes and equipment of a large industrial installation employing wet processes can be safeguarded is described in the following.
Many industrial processes, be it in the paper industry, in food production or in cleaning applications, require the use of water or other electrically conductive liquids in combination with electricity. Water plays a major role especially in the case of automatic or semi-automatic washing or cleaning installations. The requirements for the protection of their operators against electric shock are correspondingly high. With many industrial processes involving moving components and high dynamics, such as e. g. electrical drive systems, insulation faults are often only a matter of time. What usually is a limited, easy to manage risk in a dry environment, quickly becomes a real hazard in wet process environments, as the permanent contact with water and moistness also affects the electrical insulation, can result in material fatigue and therefore in insulation faults. Constant and continuous insulation monitoring of the production plant therefore helps to minimise the dangers it entails.
However, the combination of water and electricity is problematic not only in terms of the protection of people. The consequences of an insulation fault may be considerable, also when there is no damage to persons. Failures of the power supply system can reduce the availability of an installation to such an extent that also all downstream processes and installations will stand still. In the best case, this results only in a short-term reduction of a company's productivity and the consequent decrease in profitability. The outcome will be worse when an insulation fault damages the installation to a larger extent and time-consuming repairs are needed. A further danger looms for the products: These may be damaged in the defective installation or may have inferior quality due to an insulation fault.
For many years now Bender has been a proven specialist when it comes to unearthed systems (IT systems). When Bender experts are asked for the best protection of persons, installations, and processes in wet environments, they name an unearthed system in many cases. They recommend it in the clear knowledge that the choice of power-supply system is crucial for safety. And IT systems, as opposed to the (earthed) TT or NT systems, offer two decisive advantages: The low fault currents entailed reduce the risk of an electric shock endangering human health to practically zero. And, in the event of a first insulation fault, the installation does not shut down as with other supply system types, but it can continue to operate also while the fault is being located.
For a Spanish customer in the recycling sector, plant manufacturer Krones AG, designed and realised a plastic washing system with corresponding shredders. Since cleaning the used plastic requires much water, the requirements for electrical safety were correspondingly high. As a specialist for IT systems, Bender was asked to deliver standard-compliant insulation monitoring with a fault locating system for two IT systems. In each system, insulation monitoring is performed by an ISOMETER® iso685. Altogether 27 EDS440 insulation fault locators and roughly 250 current transformers were installed for fault location.
Bender supported Krones plastic washing plant project with consultancy, engineering, and it built the control cabinets. Also, Bender specialists were on site during the commissioning of the plant. In this manner, the experts were able to test the IT systems when the plant was ready for operation and with the voltage applied, and they were able to ensure that commissioning took place without a glitch – which completely satisfied the customer. (Read the full story here.)
If your company has wet or moist ambient conditions, contacting Bender will be worth your while. Regardless of whether you are dealing with designing a plant from scratch, redesigning a plant, or modernising one: Bender specialists will be happy to advise you on the possible applications of an IT system and its advantages, on safe processes, on the highest degree of personal protection, and on safe plants.