The mechanical engineering of collieries by Futers T. Campbell

Author:Futers, T. Campbell
Language: eng
Format: epub
Publisher: London : The Colliery guardian co., limited
Published: 1909-03-25T05:00:00+00:00

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1

FiOB 140b AND 1407.— Sqcabk Ghihmct.

Flos. 1404 AND 1405.—SquAKB Chihhbt.

Mr. Longridge gives the following rule:—

50 t* _ 1)

where D = diameter of flue in inches,

L = length in feet, i = thickness of plate in 32nds of an inch.

Boiler flues are made in short lengths, jointed together sometimes by flanging the rings and placing a stiffening ring between, as in Adamson's joint, the object being to strengthen the tube against collapse. Messrs. Hawksley Wild use two diameters in the tube, one being plain and the other flanged to fit inside the plain one, which make a vefy strong and reliable tube, as shown in fig. 1386.

Tubes for water-tube boilers should be of solid drawn steel, and not lap-welded.

The dimensions of a chimney depend, so far as height is concerned, very often upon local conditions, as a very high chimney is often merely required to carry away the products of combustion, and not to create a draught. The draught of a chimney depends upon

(? = H (o-0146 - Z^)

where

d =r draught in inches of water-gauge, n = height of chimney above firegrate level in feet, T = absolute temperature of gases in chimney.

The best temperature for T is about 1,060 dega Fahr.—or 600 degs. Fahr. (1,060 — 460) as the temperature of the hot gases in the chimney. The height H necessary to produce any required draught will be

d

H =

(0-0146 - 7|?)

and will depend upon the quality of coal being burned, inferior slack requiring a higher d than good small. From f in. to 1 in. water-gauge may be taken as necessary for good results with inferior coal generally used at collieries.

The area of the chimney, however, depends upon the coal consumption and may be determined from

A = —

16 X v^H

where A = area at top of chimney in square feet,

Q = pounds of coal consumed per hour, H = height of chimney in feet above firegrate level.

2u

Figs. 1404 and 1405 aod fi^. 1406 and 1407 show two chimneyu, one 126 fL high and the other 113 ft., both square and reating npon concrete foandationH, which dhould be designed to limit the pressure dae to the weight of the chimney to aboat 1 ton per square foot In the former the top portion is only one brick thick.

S

FtoB. 1408 AND 1409.— Squabb Chihnbt with Hoops.

while in the latter it is one and a-half bricks thick. As a rale the last 20 to 26 feet may be only one brick thick.

Another square chimney, 83 ft 6 in. in height, is shown in 6gs. 140S and 1409, which also shows the method of hooping square chimneys by means of corner angle irons and flat barn. Figs. 1410 and 1411 show a small square chimney about 47 ft high Square chimneys are probably not so good as round ones, though

Pio. 1*10. Pio. 1411.

i3F-n

I-

1 -

31

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FiOB. 1410 4N» 1411.— Sqxtaeb Chimnkt.

Fra. 1412.—CiRCTjLAE Chucnbt.

t

650

probably a little easier to build, an round chimneys should be built with properly shaped bricks. Fig. 1412 shows a chimney built by Messrs.

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