20Coal handling plant

20.1Rail-borne reception and discharging

The annual coal consumption of a 2000 MW station, depending on its load factor, amounts to approximately 5 million tonnes, i.c., 20 000 tonnes daily over 250 days. To achieve this delivery rate of coal, trains to large modern power station utilise hopper-bottom wagons on a permanently coupled basis. Permanently coupled working means the keeping together of the main line locomotive and its train of wagons as a single unit, from entering to leaving the site, including discharge over a track unloading hopper.

The advantages of this system are a fast turnround of the train at the power station. It is expected that trains will achieve at least 3.5 trips per week between colliery and power station, thus giving greater wagon utilisation together with capital economy in track work and associated savings in operational costs.

A design of hopper wagon has now been adopted having rapid self-discharging characteristics. This wagon is the 32 tonne capacity. 2-axle wagon with six bottom doors operated automatically by lineside equip­ ment. It discharges the coal whilst travelling at a speed of approximately 0.24 m/s.

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The largest train at present envisaged by British Rail is 2070 tonnes gross load, with a payload of 1440 tonnes. The size of the train for this payload will be 45 wagons plus locomotive giving an overall length of 425 m. Accommodation in the sidings layout should

lengths, if site space allows, to provide for longer trains should BR wish to introduce them at some later date. Introduction of light wagon bodies offering lower tare weights, and hence higher payload potential, is also currently being considered.

Depending on the space available and the volume of traffic to be handled, the choice lies between the merry- go-round (MGR) loop system or the run round system. The latter, although necessitating the main line loco­ motive running round its train, is accepted by BR as permanently coupled working. Figure 2.75 shows the merry-go-round system at a 2000 MW coal-fired station and Figure 2.76 shows the run round system at a 2000 MW coal-fired station.

The CEGB now accepts the weekly delivery of coal over 5 days. Consequently, two sevenths of the daily coal intake is put out to store for reclamation at weekends, when coal is not being delivered. Normally the stations are coaled over two shifts (i.e., 16 hours). However, BR have the right to request the CEGB to