Pit prop

A pit props, also called stamping, is a supporting element which is used in the mining days to support the hanging wall. Props are made of wood, steel or light metal. Stamps are usually set in conjunction with caps, but it is also possible in certain areas stamp without using caps.

Basics

Each stamp can by design only carry a certain load. The insertion resistance produced mechanically or hydraulically in the continuous operation is referred to as a stamp support force. The stamp supporting force is the nominal power that provides the punch. The highest load bearing a stamp is called the carrying capacity. This capability is tested in advance with the 1.5 times the rated power fully extended punch length. From the data thus obtained can be determined, the stamp set density. The stamp set density is the number of stamps that must set the miner per square meter of exposed Hangendfläche in degradation. The stamp set density depends on the expansion array.

Wooden temple

Wood stamps are so placed that they are burdened by the hanging wall in the fiber direction. The stamps are, depending on local conditions, provided banking law at a distance of 0.8 to 2 meters between hanging wall and Lying. The stamps are holed with low ground pressure in the sole. Stronger pressure in Hangendbereich be short head woods, which is called the miner Anpfahl introduced between the punch and Hangendem. The Anpfahl is also used often in addition to the interception of the hanging wall. The length of the Anpfahls is here a little longer chosen as 2.5 times the stamp thickness, longer may not be the Anpfahl. Also, this length may be taken only in moderate rock pressure. For larger rock pressure may otherwise happen that the Anpfahl acts like a lever and punch umschiebt. In fractured hangingwall continuous joists are placed instead of several Anpfähle. For soft footwall are also placed under the stamp still Fußhölzer. Is achieved by the Anpfahl no sufficient flexibility of the stamp, the stamp can be sharpened in the foot area. The length of the sharpened piece must be 1.5 to 2.5 times the punch diameter between. By this sharpening the ram pressure can Shorten by up to ten percent of its original length without rupture. When ground conditions in which movements are transverse to the punch axis, are to be feared, the stamp must always be sharpened. Even in an inclined or steep storage, the stamp must be sharpened. When you set the ram the sharpened side in the direction of the strongest load must stand.

Stahlstempel

In the pit stamping of steel, a basic distinction of two types of rubber stamps, stamp friction and hydraulic ram. Steel columns are significantly more expensive than wood temple, they can, however, steal better and easier and can also be re-used much more often.

Friction props

Friction props consist of two telescoping tubes, whose primary is also called the inner temple. The lower tube, the lower punch, ie in accordance with outer temple. Both are connected by a plunger lock in the load in the case of stronger pushing together a grater resistance opposes. This is increased by wedges, which are equipped with linings made ​​of light metal. The wedges are pressed together and tighten the laid around it lock band that is stretched here. This allows the friction props accommodate an increased rock pressure by yielding to be destroyed without.

Friction props are used in the coal industry since the first half of the 20th century. From friction stamps, there are different versions. A disadvantage is the non-uniform supporting force of the individual stamps.

Hydraulic ram

Hydraulic ram, two - or multi-part stamp, in which the mesh displacement is controlled by a hydraulic system. Hydraulic ram be used as a single temple or at the roof supports. The stamp consists of an outer temple tube is attached to the upper part of a collar and at the lower end of the stem base. Outside Temple tube is an inner temple tube. The inner plunger tube is movable and is secured by a steel spring in the outer Temple tube. At the upper end of the inner temple tube is a specially shaped plate, the die head mounted. The inner plunger tube is pushed up by a hydraulic piston. Thus, the hydraulic cylinder is not overloaded, the hydraulic ram has a stroke limiter. To set the stamp are located on the outer temple pipe a release valve and bolts of the stamp a robbery valve. For the shield support, there are hydraulic ram in which the die head can be solved. The punch head is attached to the rod end of a piston rod which is moved out of the hydraulic ram.

Light metal temples

In longwall mining are used in single temple expansion for reasons of weight stamp made ​​of light metal, which consist of an alloy of aluminum, zinc and magnesium. The stamps are used in low coal seams in the flat and moderately sloped storage. With the exception of lock parts, these stamps are made completely of light alloy. There are also combinations of steel and light metal, in this case, the upper punch is made of light metal and the castle and the lower punch made ​​of steel. The upper temple consists of two semi-cylindrical shells, which are made coplanar. For the lower punch, medium-grade are used for cost reasons, steel pipes, steel because temples are cheaper than equivalent kink-resistant light alloy tubes. Light metal dies are manufactured as friction props.