FIG. 73. SECONDARY SEPARATOR USED BY THE SANITARY DEVICES MANUFACTURING COMPANY.
FIG. 74. TYPE OF DRY SEPARATOR USED AS SECONDARY SEPARATOR.
The separator used by the Sanitary Devices Manufacturing Company differs from those already described in that the air and water are mixed before they enter the separator and the air comes into the separator above the water line. The air enters the pipe “a” ([Fig. 73]) and passes to the aspirator “b,” which is connected to the separator by the pipe “d” below the water line and the pipe “e” above the water line. The excess of vacuum in the separator draws the water out of the aspirator and its pipe connections until the water line in this pipe is lowered below the top of the horizontal portion of the piping, when the air bubbles up through the demonstrator glass “c” and passes into the separator through the pipe “e.” The filling of the vertical pipe leading to “c” with air causes the static head of the water in the separator to produce a flow of water through the pipe “d” into the aspirator “b.” This is formed in the shape of a nozzle and the water enters in the form of a spray and thoroughly mixes with the air. The cleansing action of this water spray has been found to be very effective in removal of all fine dust and this separator has been found to be the most effective wet separator ever produced.
While the wet separator when properly designed will effectively remove the finest of dust, greasy soot will not emulsify with the water and its removal is practically impossible. Fortunately, this form of material in the finely-divided condition in which it passes the primary separator is not gritty and does not produce injurious effect on the vacuum producer.
The wet separator is also at a disadvantage in that there is a loss of vacuum in passing through same equal to the head of water that is carried between the inlet and the surface of the water. This generally amounts to nearly 2 in. mercury.
Means must be provided to observe the height of the water in the wet separator. For this purpose a glass window in the side of the separator has been found to be the most effective. The use of an ordinary gauge glass such as is used on boilers has been tried, but it has been found that they readily become so clouded by the action of the muddy water as to render them useless while the constant agitation of the water against the window when the system is in operation tends to keep the glass clean.
Dry separators have been used for secondary separators to a limited extent. All of these contained a bag made of canvas or some other fabric. The separator illustrated in [Fig. 74] contains a bag made of drilling which is slightly smaller than the inner diameter of the cylindrical casing of the separator. The air enters the inside of the bag, inflating it, and passes through the bag and out through the opening in one side of the casing. A wire guard is placed over this opening to prevent the bag being drawn against the opening and thus rendering only a small portion of it effective.
These bags offer very little resistance to the passage of the air when they are clean but they soon become filled with dust and produce an increased resistance which, if neglected, may result in so great a difference in pressure as to hinder the action of the system and result in the rupture of the bag, letting the dust into the vacuum producer.
Some trouble has been experienced in finding a suitable material through which the dust will not pass. Hush cloth, such as used on dining tables, has been found to be the best material for this purpose. Better results are obtained by passing the air from the outside of the bag towards the inside than when the air is passed as indicated in [Fig. 74]. When this arrangement is adopted, it is necessary to stretch the bag over a metal screen or frame in order to prevent collapse.