Modern Gasworks Practice

672 MODERN GASWORKS PRACTICE spections should be made, and slight imperfections should be dealt with in the incipient stage. (a) Worn pins in the carriages should be replaced. As the wear develops the lifts will be thrown out of level, with the result that additional stresses will be set up. (b) The guide rails should be examined, and should be greased periodically. According to some designers the best preparation to use for the purpose is a mixture of blacklead, oil and tallow. (c) The bottom row of plates and the cup plates should be carefully examined at the level of the normal water-line. Corrosion occurs most actively at these points, and it is as well to paint or tar these portions of the holder every year. In Order to reach the seat of the trouble effectively a few inches of water should be syphoned out of the cups. (d) Roller carriages require oil or grease, and should be attended to every two months. The majority of carriages are fitted with some arrangement for adjustment of the rollers against the guide rail. Therefore, when. a roller is running free it should be brought back again on to its rail. (e) The overflow pipe for tank water must be kept clear. If the water- level (through, rain) is allowed to exceed the normal depth the gas inlet and outlet may become flooded. (f) Leaking cups are a continual source of trouble as, if the leak is serious, it may necessitate a constant supply of water to the cup in order to make good the water lost through, leakage. Such leaks are not easy to deal with during working, and one of the chief difiiculties is that of locating them. One successful method of determining the exact spot is to ground the lower lifts of the holder, and to maintain the top lift in such a position that it is sealed in the tank water to a depth. just sufficient to ensure that the gas will not blow. The water is then pumped out of the cup, when it will be possible to see where the tank water is coming in through the leak. A similar procedure may be followed with intermediate cups which may be leaking. (g) Leaks in crown and side plates and seams. There are several methods of dealing with these, and as a temporary expedient the author has found that brown paper and tar may be employed with considerable success while preparing for a more permanent remedy. A patch is tarred extending about 8 inches around the hole and a sheet of brown paper is pressed over this. The paper is thentarred and another sheet pressed overit, the outer surface of the second sheet also being tarred over. A comparatively permanent treatment is to clean and scrape the plate around the leak, apply a coat of red-lead paint, and then press red-lead putty into the leaking seam or hole, afterwards painting over with a good coat of red-lead paint. It is interesting to note that in Germany the practice of oiling gasholders in lieu of painting them is becoming populär. The treatment is said t.o be just as effective, while the saving in expenditure is considerable. Any light oil, so long as it is free from acid, may be employed, the oil being poured on to the water in. the tank and into the cups. In tliis way, as the bell rises and falls, the oil automatically forms a thin protecting film on the plates, but the crown must be treated by hand. In 1910 eight large holders in Vienna were treated in this way, and nothing has been done