The glass water gauge column consists of an upright casting bolted to the front of the boiler, in which are fixed two cocks having stuffing boxes for receiving the gauge glass. The lower of these cocks is also fitted with a drain cock for blowing out the glass.
The try cocks are frequently placed on the above-mentioned standard or column.
The action of the gauge glass is to show the level of the water in the boiler by natural gravitation and the best position for it is in view of the engine room, as close to the boiler as possible and preferably in the middle line of its diameter, at such height that its lowest portion is about two inches above the highest part of the fire line of the boiler, and its centre, nine inches above that, making the total visible portion of glass eighteen inches long.
Glass water gauges sometimes have pipe connections top and bottom. The object of this arrangement is to have an undisturbed water level in the glass by carrying one pipe to the steam dome and the other near to the bottom of the boiler; the one position not being so liable to be affected by foaming and the other by the boiling of the water. Cocks should always be fitted to the boiler ends of these pipes, in order that in case of accident to the pipes, steam and water may be shut off.
The glasses are liable to burst and become choked up with dirt. The former defect is easily repaired by shutting off the cocks in connection with the boiler and putting in a new glass. The mud or sediment is cleaned out by opening the above-mentioned drain or blow-out cock and allowing the steam or water, or both, to rush through the glass, which will effectually blow out all sediment and leave the glass in good condition again to show the height of the water in the boiler.
In opening the cocks connected with the glasses, it should be done cautiously, as the glass is liable to burst.
A strip of white running the whole length of the glass on the side toward the boiler is a great help in observing the variations of the water line in the tube.
It is not needed to remove the gauge glasses to clean them. There are good fixtures in the market that by taking out the plug in the top, the glass may be cleaned with a bit of wicking on the end of a stick. A slight scratch will break the glass, hence do not use wire. Use soft rubber gaskets when setting the glass, screw up until all leaking stops. Don’t let the glass come in contact with the metal anywhere. Don’t try to reset the glass with an old hard gasket. Two glasses from the same bundle will not act alike.
The glasses used to show the water line are made of a soft glass known as “lead glass,” and are easily cut, or broken square across. Most of them can be broken by filing a notch at the point at which it is necessary to break them. After filing the notch, place the thumbs as if you would break the glass; it will crack easily, and the fracture be straight and clean. If the tube be brittle, as some are, to avoid cutting the hands wrap two pieces of paper around the glass, each side of the notch. If the ends are rough or uneven, they can be made smooth by filing or by the grindstone.
The Manchester, Eng., Boiler Association attribute more accidents to inattention to water gauges than to all other causes put together. It is, therefore, of much importance that these glasses should be kept clean. It is not an uncommon thing to go into a boiler room and find that a leaky stuffing box has allowed the steam or water to blow out, and, by running down the outside of the glass, leave a deposit of lime scale. After this deposit has been formed, it is sometimes difficult to remove—and more than a few glasses have been broken by the engineer attempting to remove the scale. After this scale has once been formed, unless it is soft enough to be wiped off with a piece of waste, it is best to take the glass out and soak or wash it in a solution of one-half muriatic acid and one-half water until it is clean or the scale so softened that it may be readily wiped off. To prevent the scale from again forming and hardening, the glass should be dipped in glycerine before replacing.