THE DRY PURIFICATION OF COAL GAS
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Thus, with a 40-feet square purifier we get—
40 +.å° X 0-7 = 80 X 0-7 = 28 inches.
2 2
Tn such a case it would be decided to put in the next largest standard size of main, i.e. a 30-inch pipe.
Ordinary water-lute purifiers are constructed from side plates ha ving the lute made as portion of the plate itself, or with the lute as a distinct casting (Fig. 360). From the economical standpoint the former type is preferable, first, owing to the initial outlay being less, and secondly, on account of the greater ease with. which it is erected. With both types the most costly section is the corner plate. The depth of the water lute (usually half the depth of the box) is an important consideration,
Fig. 361.—Milbourke’s Cover Fasteneb.
and it must be ensured that the depth. of water obtainable will be sufficient to with-stand the heaviest pressure which is likely to prevail inside the vessel. Covers for purifiers may be éither flat or curved. In either case some form of trussing or stifien-ing will be required, and strong curbs sliould be provided wlien the vessel is of any size. So far as lifting is concerned, the cover, when of the domed type, is usually provided with a stout lifting-eye attached to straps, which are in turn riveted to the side plates and again. to the bottom curb. With the flat cover, which is invariably employed with dry lutes, the lifting is frequently carried out by means of eyes attached to tlie external stillening sections or trussing. The floor plates of purifiers should, when possible, have internal flanges, thus avoiding local stress on the bottom plates. The box, moreover, when of the ground-level type, obtains a level bearing on the