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01 03 02a 02b Cable carriers with chemical-resistant plastic deal with high acid exposure MOTION AND DRIVES On the pre-treatment line of a hot dip galvanizing plant, working conditions are harsh, as the work-pieces have to be cleaned in diluted hydrochloric acid. As a result, the concentration of hydrogen chloride in the air around the pre-treatment line is around 2 percent. This means that the indoor crane and the components on it are subjected to exceptional acid exposure. Plastic energy chain systems from the motion plastics specialist igus along with plastic troughs made of a chemical-resistant material have been dealing with these aggressive conditions easily for years now. Since 1986, Meissner Krane GmbH has been offering customized solutions and services for crane systems and hoisting technology. One of the areas of supply for the company is the equipment used in hot dip galvanizing plants. In 2015, Meissner Krane equipped the first process crane in the pre-treatment line of a hot dip galvanizing plant of Wiegel Group, one of the largest and most important hot dip galvanizers in Europe. Bathing in acid Hot dip galvanizing is the most effective corrosion protection method that is used on an industrial scale to protect steel from corrosion. By immersing the work-pieces in metallic molten zinc, a zinc coating is applied. Iron-zinc alloys of different composition are formed on the steel surface. On the outside, the surface is closed by a coating of pure zinc. However, for a permanent and complete iron-zinc reaction, the work-pieces must be pre-treated. By immersing in a series of pre-treatment baths, the work-pieces are cleaned before the actual hot dip galvanizing, to remove production residues such as oils and other characteristic impurities such as rust and scale. This is followed by two rinses in order to minimise the carryover of acid 22 WORLD OF INDUSTRIES 2019
01 The chains move in plastic troughs made of the chemically resistant material igumid EG+, as a result of which the system easily copes with the difficult conditions 02 In the pre-treatment lines of the galvanizing plants of the Wiegel group, energy chain systems from igus supply the process cranes with energy and data 03 Before the actual galvanizing, the work-pieces must be pre-treated to rid the work-pieces of grease, rust and scale. In the enclosed pretreatment line there is an HCL condensate of about two percent in the air and salt residues with the galvanizing material as far as possible. In the penultimate step, the work-pieces are immersed in a flux bath, which is intended for the very fine cleaning of the steel surface. Thereafter, the parts are dried before being immersed in the molten zinc. The operating temperature of a galvanizing bath is between 440 - 460°C, where the steel surface enters into a solid bond with the zinc achieving excellent quality. Thereafter, workpieces are air-cooled. Harsh environment around the pre-treatment line Due to the open process baths, which are completely enclosed by the surrounding environment, an HCl condensate of about 2 % prevails in the air in the area of the pre-treatment line, which corresponds to a technical environment of 20 g/l hydrochloric acid. This means that it is important to use chemically-resistant components inside the pre-treatment line. In the past, a cable festoon was “The use of an acid-resistant energy chain was the right decision.“ used at all Wiegel locations for the energy supply of the process cranes. Cables and hoses are suspended and moved with small trolleys. A disadvantage of this technology, is that at the end of the travel, a cable station takes up a lot of space and the rollers of the cable trolleys also quickly wear out, because the C-profiles in which they are guided become corroded and sharp-edged due to the acid exposure. Peter Zorn, Project Manager at Wiegel Verwaltung GmbH & Co KG, explains the development at that time: “Two things were very important to us: A tightly sealed area for material preparation, which was previously not the case with a festoon system, as well as high wear resistance. At that time Meissner Krane proposed to try out something different, and our answer was: ‘Yes, gladly!’ What ultimately convinced me of the igus energy chain systems were the pictures from composting plants or cement plants, where the chain could hardly be recognised due to the pollution, but the system was still running.” By the end of 2014, igus had presented the products to Meissner Krane, and the company was immediately ready to test this approach. In 2015, the first energy chain from igus was used in the Wiegel’s Lauchhammer plant. A year later, the next application followed at the location in Feuchtwangen, where igus supplied both the E4/4 series energy chain and the new plastic trough made of the chemical-resistant igumid EG+ material. This ensures a high resistance to chemicals, so that the use of the guide trough is ideal for use in hot dip galvanizing or, for example, fertilizer production. Lightweight and chemically resistant: guidelite plus from igus The material igumid EG+ is characterised by a very low water absorption. This offers an increased resistance to aggressive chemicals. The material can be used in a temperature range of 0 - 100 °C with its clearly optimised gliding properties for the guide trough and also for most series of e-chains. Since both the e-chain and the trough in the complete system consist of the chemically resistant material, they prove to be very good gliding partners. The complete system, consisting of chain and trough called ‘guidelite plus EG’, is now used in 4 Wiegel plants. “We are currently modernising about 2 Wiegel plants per year, using energy chain systems from igus,” explains Ronny Horn, Project Manager at Meissner Krane GmbH. “Another big advantage of the energy chain is that we have more options to safely guide the cables and hoses - even with larger cross-sections. Or to be able to add and change them later.” Wiegel, Meissner and igus: a successful tripartite co-operation The first systems have been in use at Wiegel for several years now. The relatively moderate crane speed of 40 m/min does not pose a big challenge to the igus energy chain system. The company has already successfully implemented applications with speeds of approx 10 m/s. Much more crucial here is the durability in the aggressive environment. Peter Zorn explains: “Of course we had to be bold to a certain extent and rely on the new solution from igus. Prior to this, we tested the chain made of the chemically resistant material by using it on the crane for just six to eight weeks to see if the material could cope with the environment. Now we expect a service life of at least 10 years, so that the higher initial cost pays off compared to a festooning system.” So far it has become clear that the energy chains from igus are doing reliably well at Wiegel. “The experience gained since 2015 shows that the use of an acid-resistant energy chain in the area of the pre-treatment line for energy and signal transmission was the right decision,” concludes Ronny Horn from Meissner Krane. “In all factories, the systems have been running trouble-free since their commissioning.” And Peter Zorn from Wiegel adds: “The plastic trough was very important to us. Neither 304 nor 316 stainless steel would have withstood these environmental conditions. Equally important to us was the fact that the wall around the pre-treatment line can now be completely closed and we also have much less maintenance with the new system.” These requirements have so far been fully met. Energy chain systems from igus will also be installed at the next Wiegel plants that will be retrofitting Meissner cranes. Photographs: igus GmbH www.igus.com WORLD OF INDUSTRIES 2019 23
