Overdrive protection

from Wikipedia, the free encyclopedia

The overdo assurance is special part of the tray guide , which serves to slow the funding for it when overdo possible before the sheaves comes to a halt. The braking effect may, however, only start outside the end position of the conveying means and after the limit switch. For safety reasons, the maximum delay of the conveying means should not exceed the value of 9.81 m / s². Excessive protection must be checked at regular intervals by competent and responsible personnel.

Basics and history

In the course of the 19th century, the speed of the conveyors could be increased significantly due to the increased performance of the conveyors . This made it possible to increase the effectiveness of the shaft conveyance, but also increased the risk that the conveying cage would overdo it . Towards the end of the 19th century, exaggeration led to an increasing number of minor accidents on the cable car . In 1898, 17 miners had a fatal accident at the General Blumenthal colliery because the conveyor cage was pulled up to under the sheaves. For this reason, the Minister of Commerce and Industry approved the formation of a commission made up of representatives from private industry and the mining authority . The purpose of this commission was to examine the existing safety devices of the shaft hoisting systems. In order to stop the hoisting cage from exaggerating, there are options either to intervene in the control of the hoisting machine by means of appropriate safety devices, or to then brake it through mechanical safety devices that act on the hoisting pan.

Necessity of exaggeration protection

In the case of shaft conveyor systems, it is possible that the conveyor may move over the uppermost stop in the event of a defect in the control. In this case, a safety device that acts directly on the control of the machine ensures that the machine is stopped. The hoisting machine is then switched off by the limit switch and braked by the safety brake. In the event that the limit switch does not work properly or even fails completely, a mechanical device must greatly reduce the speed of the conveying means for safety reasons. If the conveying device drives underneath the bumper beam without braking , this can have serious consequences, including the rope breaking . In this case, the conveyor cage must be secured against falling using the safety supports . Even at a low speed of a conveyor cage , it can have serious consequences for those driving on it if the cage moves unchecked under the bumper beam. The overdoing measures reduce the consequences of overdoing it.

construction

The overdrive protection consists of the end section of the shaft guide and a device for braking on the shaft guide, which slows down the conveying means. In the first half of the 20th century, specially shaped brake shoes were used to decelerate the conveyor vessels. In today's shaft conveyor systems with guide rails , thickened or mutually inclined guide rails are used. The widened or contracted guide rails must always be made of wood . In systems with rail guides, the braking devices can also be made of steel. In the case of shaft conveyor systems with a conveying speed of up to one meter per second, elastic buffer devices with a buffer path of at least 200 millimeters can also be used as a device for braking.

Track lath thickening

The thickening of the guide rails is carried out in such a way that the guide rails are widened above and below the outermost operating position of the conveying means. This widening is carried out symmetrically on each side of the guide rails. In the case of shaft conveyor systems with a conveying speed of more than 4 , the widening must be carried out with a gradient of 1: 100, for systems with a lower speed a gradient of 1:40 is sufficient. The maximum thickness of the thickening is fifty millimeters per side, which means that a maximum thickening of 100 millimeters is achieved. The widening may extend a maximum of five meters. The thickening is created either by cutting the guide rails to size or by spreading two halves of the guide rails apart by means of hammered-in wedges . The wedges are driven into the guide rails from the rear, as wedges driven in from the front could easily be stripped off. The widening must not be created by nailing, screwing or gluing on wedges. If a conveyor cage is driven into the thickened guide rail, it will be damaged by the cage's guide shoes.

Contracted guide rod strands

With this form of the device for braking, the distances between the guide rod strands below the filling point are reduced in their clear space. Here, each lane is given an incline to the vertical. For systems with a travel speed of more than 4 , the gradient is 1:50, for systems with lower travel speeds 1:20. The slope may extend a maximum of five meters. The maximum reduction in the distance is 200 millimeters. In this area, the guide battens must be stiffened particularly strongly against the shaft wall. After reducing the width of the gauge, the guide surfaces of the gauge must again run parallel to one another. Since a strong pressure acts on the guide rails, contracted guide rails cannot be installed above the suspended bench in the headframe . The outward pressure would bend the headframe. In the case of laterally guided conveying means, due to the construction, the contraction of the guide rails cannot be used in the shaft sump , since the guide rails attached to the center lines cannot be adequately supported here. The disadvantage of contracted guide rails is also the negative effect on the conveying means, since it is deformed when it enters the narrowed area.

Individual evidence

  1. ↑ a b c d Excessive protection for the shaft conveyance . Patent No. 73616, online (accessed January 19, 2012; PDF file; 220 kB).
  2. ↑ a b c d e f g h Technical requirements for shaft and inclined conveyor systems (TAS). Verlag Hermann Bellmann, Dortmund 2005
  3. ↑ Mining Ordinance for Shaft and Inclined Conveyor Systems (ThürBVOS) . Thuringian Online ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (accessed on January 19, 2012; PDF file; 222 kB). @1@ 2Template: Webachiv / IABot / www.tlba.de
  4. ↑ a b c Hans Bansen (Ed.): The mining machines . Fourth volume, The shaft production. Published by Julius Springer, Berlin 1913, pp. 289–294.
  5. ^ Report of the ropeway commission for the Oberbergamtsiertel Dortmund . In: Glückauf, Berg- und Hüttenmännische magazine. Association for mining interests in the Oberbergamtsiertel Dortmund (Ed.), No. 18, 41st year, May 6, 1905, pp. 557-574.
  6. ↑ Fritz Heise, Fritz Herbst: Textbook of mining science with special consideration of hard coal mining. Second volume, fifth increased and improved edition, published by Julius Springer, Berlin 1932, pp. 660–662.
  7. ↑ a b Horst Roschlau, Wolfram Heintze: Bergmaschinentechnik . VEB German publishing house for basic industry, Leipzig 1977, pp. 266-267.
  8. ↑ a b c d e f g h i j Carl Hellmut Fritzsche: Textbook of mining science. First volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1961.
  9. ↑ Shaft hoisting system . Patent specification, document identification DE2944515C2 January 14, 1988, online (accessed January 19, 2012).