Fig. 10.
Fig. 11.
Fig. 12.
Fig. 10.—Course taken by Material Round Bend.
Fig. 11.—Segment-Back Bend.
Fig. 12.—Lobster Bend.
With regard to the straight lengths of pipe, it is necessary to ensure a smooth internal bore, especially at the joints. It is therefore desirable that the joints should be self-aligning as, if this is not the case, eddies will be formed which will cause the material to deviate from the centre of the pipe, striking the side at one or more definite points where holes will eventually be worn through the pipe.
In vertical pipes the evidence of wear is negligible, in fact the conveyed material presumably does not touch the pipe at all, but travels up the centre of it as a core.
Capacity of Pipes. The velocity of the air passing up the pipe should be from 40 to 50 ft. per sec., equivalent to about 35 miles per hour.