Newly developed brake system for applications with the production of high forces and adverse environmental conditions
- 11 June 2011
- Product News
Just like in so-called offshore applications, there are numerous applications in mining which make special demands on the characteristics of brake systems. In particular abrasive influences and corrosion are the two worst enemies of the technology used in mining and as a result of the brake systems.
Though brake systems, specifically in underground mining, are supposed to have small sizes due to a lack of space, whereas low weights are beneficial in the offshore range, since this makes less lifting force necessary with the assembly, as an example, on ships or platforms.
Demands on brake systems using the example of mining Brake systems basically have two different functions in mining:
- Use as a service brake.
- Use as an emergency stop system.
Usually the service brakes are mounted on the input shaft of a gearbox ensuring a corresponding deceleration when being activated.
In case of standstill of the plant the brake system ensures a safe stop of the load. For that purpose they are typically designed as spring-actuated brakes locking or remaining locked, respectively, with rated load in case of a voltage interruption. KTR-STOP is a newly developed floating caliper brake having numerous benefits in design compared to conventional brakes making them particularly sturdy, long-lasting and easy to maintain. As a result it is predestined for the use in mining.
Mining is subdivided into three ranges:
- Underground mining.
- Drill hole mining - considering offshore applications in particular.
The demands on the brake systems for the three aforementioned types of mining are extremely different. In surface mining, here in particular brown coal open cast mining, giant equipment is often used. Part of such equipment are, for example, bucket-wheel excavators or spreaders having daily outputs of up to 240.000 m³ Conveyor lines with a transport capacity of in part more than 30.000 t/h connect the machines with each other or with the downstream or inserted operations such as processing, mixing bunkers, drying plants or power stations. Special demands in surface mining are both dry and humid application conditions with a high claim on the abrasiveness resistance of the materials used, caused by the almost ubiquitous presence of sand with a more or less high content of crystal.
In contrast to that the equipment and plants used in underground mining are rather small. Here special demands result from the mostly humid and warm climate and the presence of abrasive material which is pressed into almost every small gap due to the permanent ventilation. In addition, corrosive influences, in particular resulting from the digging of potash, rock salt or sulphur compound, but almost always by pit water containing resolved minerals in a different composition, are present and produce heavy corrosion. Moreover, a lack of space requests for designs with high power density.
In offshore applications mainly the heavily corrosive influences of sea salt and the necessity to save weight, in particular in the range of swimming oil platforms, make high demands on the technology used. Anyway, high-tech is used in overall mining. Enormous masses are moved and big forces have to be controlled. Mining sets the highest demands on safety and reliability in almost every place of the world.
Thus, in addition to safety, reliability and economic efficiency of a brake system the following main claims have to be fulfilled in the aforementioned three different types of mining:
- Required space.
- Ease of maintenance.
Steel for load-bearing elements
With KTR-STOP load-bearing elements from steel instead of the usual nodular iron are used. In this way KTR has reduced the trend of a sudden failure of components compared to the use of cast iron due to the considerably higher elasticity module of steel. Apart from that the higher elasticity module ensures a considerably lower degree of deformation along with the resulting increase of the power potential of the brake systems. In addition, the generous use of steel allows the use of KTR-STOP for many mechanically critical components even with low temperatures, as this is often the case in open cast mining in polar areas, in northern and eastern mining regions or offshore applications.
By the selection of material and surface finishing processes for the different components, differentiated demands regarding abrasiveness and corrosion resistance can be realised.
Many different brake linings are available for the different applications, no matter whether linings with an organic support matrix for temperatures up to 1.100 °C and friction speeds up to 100 m/s or linings from powder metal for a higher service life are concerned. A wide range ensures the application under various environmental and operating conditions.
Higher power density
The new design of KTR-STOP results in a higher power density. In case of the brake described in here it is about 50 % higher than with usual brake designs having the same size. That is why it is in many cases possible to use the next smaller size for the application. The result are considerable benefits for underground mining and offshore applications by a reduction of space or weight, respectively.
In addition to a full encapsulation of the shafts of the floating caliper brake which are already state of the art in KTR, the piston guides of KTR-STOP are provided with guide rings. They serve as wear rings and make sure that the pistons which are the most expensive spare part of the brakes achieve a very high service life even with a high dirt load.
Longer service life of brake linings
The special design of KTR-STOP with its bigger piston stroke allows to use the brake linings down to the carrier sheet metal. This is a benefit which extends the maintenance intervals and which increases the service life of expensive brake linings significantly.
Oil flooding: Benefit for maintenance and the use with extreme cold
For KTR-STOP hydraulic power packs providing for an oil flooding of the brakes were used as a standard for the first time. A filter ensures the continuous cleaning of the oil and prevents deposits in the hydraulic part of the brake. In addition, the permanent flooding of the brake prevents a diesel effect which may cause burning of the seals. Both, in turn, extend the maintenance intervals and increase the functional reliability of the brake. With the use under extremely cold conditions the oil flooding offers significant benefits, too: Due to the oil circulation used for KTR-STOP as a standard easy design measures allow to keep the brakes ready for operation even with extreme cold. It is furthermore possible to install a heating in the oil circulation which is in a position to heat the oil and as a result the entire brake at standstill.
The use of the intelligent control system IntelliRamp allowing accurate braking processes controlled by a programme predestines the brake for the use in critical areas. As an example we should mention conveyor systems in surface mining which may suffer from considerable damages and resulting breakdowns in case of pile-up of a conveyor operation. The IntelliRamp-System with its large programme variety in combination with the high power density of KTR-STOP allows for an improved brake system which is better adapted to the subsequent conveyors than with conventional brakes.