This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 Excerpt: ...blow-off equipment. 349. The surface blow-off apparatus (Figs. 281 and 282) is for the purpose of blowing off scum from the surface of the water. The scum is formed by impurities in the water which rise to the top. It is detrimental in that it does not allow the Fig. 2 7 6.--The Crosby automatic water-gage valve. steam ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 Excerpt: ...blow-off equipment. 349. The surface blow-off apparatus (Figs. 281 and 282) is for the purpose of blowing off scum from the surface of the water. The scum is formed by impurities in the water which rise to the top. It is detrimental in that it does not allow the Fig. 2 7 6.--The Crosby automatic water-gage valve. steam bubbles to escape freely. Thus it causes a violent agitation of the water. Part of the scum may rise with the steam into the mains and thus be transmitted to the engine or other equipment. Scoring of valves, cylinders and pistons, an impairment of lubrication and a racing of the engine may result. The racing is due to the inability of the relativelyweak governor mechanism to overcome the excessive valve Fig. 277.--Reliance water col-.fig. 278.--Working umn showing inside and outside mechanism of Reliance high fittings, and low-water alarm. friction induced by the scum and deposits which are carried into the engine. Explanation.--The skimmer, S, in Fig. 281, is funnel-shaped and square in cross-section. It should be located about H the length of the boiler from the back head and at a height such that the outlet from the funnel will be submerged at the lowest stage of the water level. The upper edge of the funnel should project above the surface of the water at its highest level. These conditions are necessary for proper collection of the scum and impurities. 350. Surface blow-off piping should not exceed % in. pipe size. When inside and outside pipes are used, they should form a continuous passage. This may be accomplished by using bushings or a flange similar to those of Fig. 248. The material for the bushings may be brass or steel (A.S.M.E. Code, Par. 307). 351. The bottom blow-off apparatus is for the purpose of blowing-off the sludgy sedim...
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