The frictional losses in a system of this description vary directly as the length of the pipe, and inversely as the fifth power of the diameter. Large pipes are therefore very desirable, not only because of their greater carrying capacity—which is very desirable—but also because such things as matches, hairpins, etc., are picked up every day by an installation as fitted in hotels, restaurants and theatres. Such material quickly clogs small pipes and causes endless trouble and delay.
The flexible hose should be as short as is consistent with ease of working, because the frictional losses in this class of tubing are very great. It would be preferable to increase the number of wall plugs, rather than have to use very long lengths of flexible hose.
Fig. 14.—Suction Nozzles for High Pressure Systems.
Suction Nozzles. Probably more patents have been taken out on new suction nozzles than on any other portion of a pneumatic suction plant. The chief desiderata for a nozzle on a high pressure system for wheat, coal, ashes, etc., are that it be of light construction to allow of easy manipulation by the operator, and that it have some means of allowing a “free air” inlet, making it impossible to choke the nozzle by burying the end. It is an advantage to be able to regulate the free air inlet according to the conditions existing with different materials. The same nozzle that will act best while dealing with a large bulk of material, may be quite unsuitable when it becomes necessary to “clean up” in the corners of the hold or waggon. Fig. 14 shows different types of nozzles for high pressure plants, but as the efficiency and capacity of the plant can be affected seriously by the design of this portion of the apparatus, it is highly advisable to allow the designer to have a free hand and to make use of the experience already gained.
Fig. 15.—Sturtevant Equipment Removing Wood Refuse from Double Tenoning Machine.
Nozzles designed for low pressure systems, dealing with dust, shavings, etc., have to be built to suit the machine to which they are attached, and they therefore vary indefinitely in details of design and construction. The same remarks apply to the nozzles for use on suction cleaning plants. Figs. 15 and 16 show how the suction nozzles are adapted to the machines.
Fig. 16.—Sturtevant Equipment Removing Dust from Sand-papering Machines.