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The average operational life of shield support systems in the German hardcoal industry is approximately ten years. During this time damage to hydraulic rams, controls and steel structures is quite frequent. The first objective of this project was to improve the corrosion resistance of hydraulic rams. In the course of the test activities three different anti-corrosive coatings were examined: hard chrome, gunited anti-corrosive layer no. 1 and gunited anti-corrosive layer no. 2. The following newly developed anti-corrosive layers led to longer operational lives on the test rig as well as underground: (1) bronzing with AlBz (approx. 0.5 mm thick layer), by electroplating or thermal application; (2) jacketing by approx. 1 mm thick chrome-nickel steel shell; (3) spiral wrapping with metal sheet strips (approx. 1 mm thick) with subsequent welding; (4) nickel-plating (approx. 0.1 mm thick) applied by melt-coating; (5) coating with special synthetic resins (development not yet completed). Different studies were carried out with a view to improving the hydraulic and electric components of electrohydraulic support controls. The functional efficiency of synchronised electrohydraulic controls in two coalfaces was examined. In one of them only 54% of the controls were operative and in the other one no more than 31%.

Additional information

Authors: MIGENDA P, Deutsche Montan Technologie, Essen (DE);GRÄWE F, Deutsche Montan Technologie, Essen (DE);HERWIG H, Deutsche Montan Technologie, Essen (DE)
Bibliographic Reference: EUR 14150 DE (1992) 40 pp., MF, ECU 4, blow-up copy ECU 6
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