Mechanical Stowing

These methods of stowing are not practised in India. They are definitely costlier than hydraulic stowing, but will have to be adopted at some collieries in the near future for nearly complete extraction.

In this system a high speed belt is used to propel the stowing material into the goaf to be packed. The stowing material is transported to the thrower belt in the same manner as for pneumatic stowing. The material has to be deflected on the thrower belt by deflection plates known as scraper ploughs, which drop the material into a hopper above the high speed stowing belt. The thrower belt is mounted on a travelling carriage and a 660 mm wide belt is considered adequate. The driving drum rotates at 1000 r.p.m. giving the belt a velocity of 600 m/min (nearly 36 kmph). Driving motor is 25 to 40 H.P. and stowing of 50 to 60 te/hour of stowing material is possible. Good results are achieved if the stowing material is delivered to the thrower belt at a high speed and in the direction of belt travel. Barricade of wire netting is required as in other methods of stowing.

Of all the methods of stowing, it is the cheapest (less capital cost) and the number of man shifts required for roof control per 100 te coal produced is the least. Energy costs are a fraction of the costs for pneumatic stowing (consumption 0.3 to 0.4 kWh/m³ materials). It however does not have the adaptability of pneumatic stowing. Its disadvantage is that a prop-free front cannot be planned; the installation of a belt solely for throwing requires careful consideration from the stand-point of economy and roof contorl; it is only applicable in thin flat seams or slices of 1.3 to 2.3 m thickness; the roof convergence is more compared to that in pneumatic stowing; coal getting and stowing cannot take place at the same time; installation of a conveyor in the tail gate for continuously feeding the machine is unavoidable. At the face, the operation creates a lot of noise and airborne dust and the risk of electrostatic sparks exists in this machine as the material is discharged at a high speed.

The method is popular in Germany and is used on a limited scale in Britain.

The pneumatic stowing, compared to this method, needs high initial cost for compressors, pipe lines for compressed air, and excessive power and air consumption.