Never touch the inside of the water gauge glass with iron or wire, as while the glass may be cut on the outside with a file, the slightest touch of steel or iron on the inside will cause an abrasion, the result of which is that the glass will crack and become useless.
Water gauge glasses frequently break because the steam and water connections are not in line, because the stuffing boxes are screwed down too tight, and sometimes in cold weather when struck by a cold draught of air admitted through an open door or window.
An engineer or fireman should never fill a boiler with cold water while the boiler is hot, as the injurious effect produced by contraction is similar to that produced by blowing out at a high pressure, and if persisted in will result in permanent injury to the boiler.
Exhaust steam will heat water to 212° Fahr. under atmospheric pressure.
Ten degrees extra heat in feed water means one per cent. saving in fuel.
Before blowing out the boiler the engineer or fireman should remove all the fire from the furnace, as a small quantity left in the corners, or attached to the bridge wall, might spring a seam or cause a plate to bulge.
Every engineer should know that unequal expansion and contraction is one of the evils which limit the longevity and endanger the safety of all classes of steam boilers; consequently the blowing out, the refilling, the starting of fires and the regulation of the draught should be done with judgment.
It is not necessary to fill a boiler with cold water above the second gauge cock, as the water expands under the process of the formation of steam and it will be found that there is a sufficiency of water in the boiler when steam is raised.
Single riveted seams are equal to 56% of the original strength of the sheet; double riveted seams are equal to 70%, and triple riveted seams are equal to 85%. Triple riveted seams, however, are very seldom used unless for some special purpose, as they are too heavy and thick, and would burn out rapidly if exposed to fire.
In making calculations on the strength of boilers, the factor 56 should be employed instead of 100, as 44% of the strength of the plate is lost by punching the holes for the rivets.