___________________________
600 MODERN GASWORKS PRACTICE
Purifiers up to 10 feet square __________________________...... f inch plates.
„ „ 20 „ ,_______________________________....... H »
„ above 20 „ ___________________________% „ „
Flanges are cast Jg- inch or J inch thicker.
The common methods of jointing cast-iron plates together are described and illustrated on page 523. Side plates are usually cast with a widtli of four or five feet for Standardization.
The smallest purifiers are usually three feet deep, and the largest sizes vary from six to eiglit feet deep. Intermediate sizes are four to six feet in deptli. As a rule for ascertaining the required deptli for a purifier, the author suggests the following:—
Depth in. feet = -^Total superficial area X !•!.
The depth may then be taken to the nearest foot—portions of a foot being neglected owing to the general practice of casting these plates in lengths divisible by a foot. For smaller purifiers, that is boxes with. an area up to 300 square feet, multiply by 1-3 instead of 1-1.
Thus, considering a purifier 30 feet X 30 feet—
Total area = 900 square feet
V9ÖÖ = 5-47 and 5-47 X 1-1 = 6 017 feet.
Tlierefore the required depth is six feet.
Again, with a smaller purifier, say 12 feet X 16 feet—
Total area = 192 square feet.
^192 = 3-725 and 3-725 X 1-3 = 4-84 feet.
Accordingly required deptli is 5 feet.
PURIFIER CONNECTIONS
The size of the gas main working in Connection with purifiers may be best calculated as follows :— _____________________________
Diameter of pipe in. inches = Varea of eacli box in square feet. For small purifiers (up to 60 square feet area) the result can be taken as it stands, but for medium-size boxes deduct one-sixth. and for large boxes one-fourth. As an example, consider a square purifier with. 40 feet sides, then— ____
Diameter of pipe in inches = Vl,600 less one-fourtli
= 40 —(1 of 40)
= 40 — 10 = 30 inches
i.e. a 30-inch main would be used.
Another rule which may be conveniently employed is that due to Milbourne:— Diameter of pipe in inches =
Length and breadth of purifier (in feet)
2