. Electric railway journal . the handsof careless workmen. A number of years ago companies in several citiesattempted to keep their conduit lines free from gas byconnecting them with the chimneys of abandoned powerstations, on the theory that the draft up the chimneywould suck the gas out of the conduits. In practice theplan did not work out as well as had been expected, asit was found that although the gas was drawn up thechimneys out of the ducts, yet the same partial vacuumalso drew in more gas from the earth surrounding thedistribution system. The induced-draft plan having proved a failure
. Electric railway journal . the handsof careless workmen. A number of years ago companies in several citiesattempted to keep their conduit lines free from gas byconnecting them with the chimneys of abandoned powerstations, on the theory that the draft up the chimneywould suck the gas out of the conduits. In practice theplan did not work out as well as had been expected, asit was found that although the gas was drawn up thechimneys out of the ducts, yet the same partial vacuumalso drew in more gas from the earth surrounding thedistribution system. The induced-draft plan having proved a failure, thereverse of this, or the forced-draft system, is now beingused, and with success. Its application to individualmanholes is neither recent nor uncommon; instead, itis a standard practice with many companies. In itssimplest form, which is the only one in which powerin some form is not required, a blanket, coat, or otherpiece of cloth is hung over the manhole guard on theside away from the wind, thus forming a baffle which. FREEING MANHOLES OF GAS—MANHOLE HOOD FOR USE INPUTTING MANHOLE UNDER AIR PRESSURE January 1, 1916] ELECTRIC RAILWAY JOURNAL 45 changes the course of the air slightly and forces it downinto the manhole. While not a very effective method ofclearing the gas from the hole this is better than none. A much better plan involves the use of a fan to drivethe air through a tube down into the hole. An accom-panying illustration shows one of these blowers, a hand-driven one, at work. Whenever electric power is ob-tainable it is better to use a motor-driven fan, as manpower is more expensive and less effective. There are manholes so gassy that even a motor-drivenblower alone will not suffice to drive out the gas fastenough to insure safety and comfort to men workingin them. The best additional appliance for such casesis the cover shown in another illustration. This issimply a skylight or monitor made with an iron frameholding glass panes through which plenty of light
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