The various forms of vacuum cleaning apparatus with mouthpieces designed to aspirate the dust from different surfaces are sure to be increasingly used. In our opinion, wherever electric power is available, they will obviate barbarous methods involving use of hand-brushes to collect dust from machines, such as those for litho-dusting or for sweeping lead dust from benches and floors, or use of bellows to blow out the dust from compositors’ cases.
Finally, the carrying out of lead processes by automatic methods and with the interior of the casing under a negative pressure, so that the material is transported from one process to another by means of worms or conveyors, is everywhere to be aimed at. Or, again, it has been found possible on a commercial scale, by means of compressed air in a closed system of receivers and pipes, to force material in very fine state of division from one place to another, as, for instance, of litharge from the cask into the mixing machine for preparation of the paste for manufacture of accumulator plates, without risk of contact.
Indication of the efficiency of the draught may be gained by holding smoke-paper at the orifice of the hood. The definition of efficient exhaust in some regulations for the removal of fumes, as in the Tinning Regulations, is that it shall not be deemed to be efficient unless it removes smoke generated at the point where the fume originates. Accurate gauging, however, of the draught can only be done with an anemometer, so as to determine the number of linear and cubic feet passing through the throat per minute. Only rarely does one find an occupier alive to the value of the use of such an instrument. The importance of this point has been recognized in the Regulations for Heading of Yarn, by the requirement that the speed of each exhaust opening shall be determined once in every three months at least, and recorded in the general register. We prefer to use Davis’s[A] self-timing anemometer, which gives readings in feet per second without the need of a watch. Other useful anemometers—Casella’s or Negretti and Zambra’s—require to be timed.
[A] It is not available for velocities exceeding 1,200 linear feet per minute.
The details of all routine observations on localized exhaust ventilation might well be entered on a card hung up in the workroom. Such a card drawn up by our colleagues, Miss Lovibond and Mr. C. R. Pendock, has the following headings:
| FIRM .......... | PROCESS .......... | ||
| Fans: No. .......... | Kind .......... | Size .......... | Maker .......... |
| Motive power .......... | H.P. .......... | Method of driving .......... | |
| Other load .......... | Condition of driving .......... | ||
| Screen .......... | Dust collection .......... | ||
| Direction .......... | |||
| Periodic cleaning .......... | |||
| Hoods: No. .......... | Kind .......... | Size .......... | |
| Structure .......... | |||
| Distance between each .......... | |||
| Ducts: No. .......... | Kind .......... | ||
| Size .......... | Length .......... | Section .......... | |
| Structure .......... | |||
| Periodic cleaning .......... | |||
| Fresh-Air Inlets: No. .......... | Kind .......... | ||
| Position .......... | |||
| Size .......... | |||
| Fixed or temporary .......... | |||
| Hood: | Position of Anemo- meter. | Date ..... | Date ..... | Remarks. | ||||
|---|---|---|---|---|---|---|---|---|
| Reference Number. | External Conditions ..... | External Conditions ..... | ||||||
| Area of Throat. | Speed F. p.m. | Volume C.F. p.m. | Area of Throat. | Speed F. p.m. | Volume C.F. p.m. | |||
Frequent cleaning and inspection of exhaust installations are very important, as accumulation of dust greatly impedes the flow of air at all points of the system. The person employed in cleaning the fan should wear a respirator. Hoods and ducts should always be cleaned with the exhaust in full action.
REFERENCES.
[1] Annual Report of the Chief Inspector of Factories for 1910, p. 172.