The steam jacket practically considered as an efficient fuel economiser. A treatise on the economical use of steam for engine-builders, engine-drivers, mill-managers, and steam-users generally by Fletcher William mechanical engineer

Author:Fletcher, William, mechanical engineer
Language: eng
Format: epub
Tags: Steam-engines, Steam-jackets
Publisher: London, Whittaker & co.
Published: 1895-03-25T05:00:00+00:00

Fig. 45. —Draining pipe from jacket.

water knocked out of it—dry steam passing right and left to the admission valves. The water falls to the bottom of the jacket, and the result is such that drain-cocks are not needed." #

5. The jacket should be open to the boiler at all

times, and not affected by the stop-valve ; it will thus be

heated gradually as the steam is raised, and altvays hot

ready for work; therefore, no steam will be required

* The Engimer, 18th December 1885.

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for blowing through the cylinder for warming it. When the jacket steam is taken from the steam chest, as referred to previously, this fault obtains. In small engines it is not necessary to provide any means for shutting off the steam from the jacket, but large engines are generally fitted, so that the steam may be turned off; care, however, should be taken to arrange these cocks or appliances so that they may not be tampered with by being turned off or on, to suit the fancy of a meddlesome engine-driver. Fig. 62 shows

Fig. 46.—Portable engine cylinder.

the steam supply for the jacket independent of the stop-valve. Any water collecting in the steam pipe should pass into the jacket rather than into the cylinder, j

6. The steam-supply pipe should enter the jacket at such a point that a thorough circulation of the steam within may he secured and maintained, and the accumulation of air at any part made impossible.

Figs. 25 and 47 show sections of cylinders, the jacket of which is only taken partly round the cylinder; no circulation of the steam takes place in the jacket,

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and air collects at the top. The following incident occurred at a trial of portable engines, which appears to prove that air does sometimes accumulate at the highest point of the jacket, and prevent the jacket becoming heated by the steam, notwithstanding that some tell us that such cannot be the case.

A correspondent in Engineering says :—" The cylinder of one engine was steam-jacketed: being on the top of the boiler, the admission of the steam was direct to the jacket: it mjght be supposed that the

Fig. 47.—Traction engine cylinder—deficient circulation.

jacket would be heated as the steam rose; the jacket felt quite cold with sixty pounds pressure of steam in the boiler, until the safety-valve* (which was on the top of the cylinder, in communication with the jacket) being eased a little, a current was formed in the steam, showing clearly that the air must be expelled before they can be heated properly."

At the present time, there are hundreds of portable engines being sent out by celebrated makers, having the most worthless so-called steam-jackets, but, in

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reality, they are air-jackets, because no trouble has been taken to cause any circulation of the jacket steam.

The cylinders are bushed in the usual manner: a small hole is drilled into a pocket at one end of the cylinder at the lowest part of the annular space. Through this hole the steam supply

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