Chapter IV: Typical Installations for Grain

The pneumatic principle has been applied to the handling of grain in bulk to a much greater extent than to any other material. As previously stated, the original successful plant invented and designed by Mr. Frederic Duckham was for the handling of wheat for the Millwall Docks Co., and the success of this plant was such that it was imitated by engineers in this country and abroad with equally satisfactory results.

Grain lends itself admirably to pneumatic transport because it is easy of flow, regular in size, and practically self-feeding. Also, the removal of dust, which is incidental to pneumatic conveying, is a special advantage where grain is concerned. Figs. 17 and 18 show clearly the advantages of pneumatic conveying in point of simplicity and labour saving.

=Typical Quayside Plant.= Fig. 19 shows a typical lay-out for a comparatively small plant handling 50 tons per hour. The diagram is almost self explanatory.

_A_ represents the special suction nozzle through which the grain enters the system, together with the “free air” which acts as the conveying medium.

_B_ is a length of flexible pipe to enable the nozzle to sweep the width of the barge, the length being dealt with by moving the boat to within the radius of the swivel arm _E_.

_C_ is a permanent pipe carried on the jib arm which is mounted on a swivel joint; _B_ is another short flexible pipe to permit of the swivelling already mentioned.

_F_ indicates the receiver into which the grain is deposited, and _G_ the special rotary valves, for releasing the material from the system without interfering with the vacuum of the conveying line.

_H_ illustrates the twin air filters which are provided with valves, so that each of the filters can be isolated in turn from the rest of the plant for cleaning of the fabric tubes, without interrupting the continuous working of the plant.

_J_ indicates the connecting pipes between the receiver, air filters, and pump, and it should be noted they are considerably larger than those on the suction end _C_, this being necessary to allow for the expansion of the air under vacuum.

_K_ is the reciprocating air pump, driven electrically by the motor _M_ through large helical gear wheels, which act as flywheels and are helpful in equalizing the torque required by the pump.

_L_ is the outlet pipe for the air as it is exhausted from and by the pump.

This plant is simple, but every possible modification can be added that circumstances make desirable; such as discharging on to a belt conveyor, for feeding the silos or other storage bins.

Where grain is bought by bulk it would be necessary to check the weight, and in this case an automatic weigher would be installed, into which the material would be discharged from the receiver. With a bag filter the collected dust can also be weighed, the total weight being then obtained by addition.

=Typical Floating Plant.= The most popular development of the above type of plant is the floating plant, designed for erection on a hulk, or barge, and intended to suck grain from an ocean-going steamer and discharge it into barges or lighters on the other side of the discharging plant, as indicated in Fig. 20. The plant shown is one of many in actual operation and its construction may be followed by reference to the description of the plant shown in Fig. 19, the same index letters being used in each case. One great advantage of floating plants is that the difference in height due to tides is of no consequence.

=Portable Plants.= Still another modification consists of a complete quay-side plant mounted like a travelling crane, so that it can be moved longitudinally along steel rails on the quay-side. This plant is particularly useful where large cargo ships have to be emptied and then allowed to remain at their berth until reloaded with another cargo.

Complete plants have also been mounted on railway trucks, the engine and pump in this case being on a second waggon (see Figs. 21, 22). In such a case the plant has to be mounted very low, and it is necessary to lift from the under-side of the truck to, say, a railway waggon, by means of an adjustable belt or bucket elevator (shown at the extreme left of Fig. 21).

Many other applications will suggest themselves to the reader, and sufficient has been said to prove that for the handling of wheat the pneumatic system is distinctly flexible and convenient; also, it effects a great saving in labour, which is an important consideration nowadays. “Bushelling,” conveying, and weighing by hand used to cost well over a shilling per ton, which figure was reduced to just over 1½d. per ton by pneumatic conveying; these are pre-war costs in both instances, but the relative saving effected by pneumatic conveying is certainly not less under present conditions.

All the previous remarks also apply to linseed and cotton seed in bulk, maize, oats, and in fact all cereals. Such materials have to be accepted as and when the ships arrive irrespective of convenience, and it is an important advantage of pneumatic conveying that the material can be lifted and discharged in the most convenient position; also, when the barge or ship has departed the same apparatus can be utilized to lift the material from its position in store to the cleaning or grinding plant.