I aad
CARGO HANDLING AT PORTS
Moreover, in dealing with a number of parcels of grain
»f different quality, or ownership, separated in the ship’s
hold by mats, the difficulty of feeding the elevator is very
marked, since each layer has to be cleared up in turn, and
his has to be done by hand labour.
Elevator speeds generally range from 200 to 400 feet
per minute, but may be as high as 600 feet per minute.
Band or belt conveyors run at 300 to 600 feet per minute,
but for light grain, such as oats, the speed should not exceed
300 feet per minute.
THE PNEUMATIC ELEVATOR.
The main advantage of the pneumatic elevator, or suction
apparatus, over the bucket elevator is that it requires no
manual feeding. The flexible intake pipe may be taken to
the furthermost parts of a ship’s interior, e.g. the lazarette,
so as to reach every parcel on board. Also, there are no
restrictions imposed on the use of the apparatus by varia-
Hons in freeboard, such as hamper, and, in certain cases,
prevent, the employment of bucket elevators. Moreover,
the suction method is a healthier process for the few men
required to attend to the plant. The dust stirred up by the
bucket machine becomes diffused throughout the atmos-
phere of the hold, and renders it unbreathable, in addition
to causing irritation to the eyes. In the case of the pneu-
matic tube, the dust is sucked up along with the grain. The
strong current of air is decidedly beneficial to the grain, as
it aspirates or aerates it, and so improves its’ condition,
aspecially in cases where its temperature has risen in con-
sequence of a prolonged voyage. :
An objection sometimes urged against the pneumatic
apparatus is that the surface friction of the pipes tends to
injure some of the more delicate classes of grain, such as
malting barley, but this drawback, for all practical purposes,
has been eliminated of late years by the easing of bends and
the removal of all internal projections in the pipes. The
obiectors overlook the fact that the cutting and driving
