Boiler Accessories Water Gauges

BOILER ACCESSORIES: WATER GAUGES It is of great importance that the level of the water in the boiler can easily be ascertained at all times. Should the level be too low, there is danger o f overheating the furnace plates or tubes. If it is too high, there is likely to be an undue amount of priming. The water-level is usually indicated by gauge-cocks or try-cocks or water gaugeglasses. Sometimes a float is provided, which is connected to a small whistle, and if the water-level falls below a certain point, an alarm is sounded. Such a device can readily be used in conjunction with the ordinary water-gauge.

Try-Cocks. Try-cocks are very generally used. They are of widely different forms, and may be either like the general type shown in Fig. 31, which is the ordinary 1ocomotive form, constructed in two parts so that they can be separated for the purpose of repacking without detachment from the boiler; or they may be of the lever type shown in Fig. 32. There are usually three cocks, one at the highest desired water-level, one at the lowest, and one midway. More cocks may, of course, be used if desired. The water-level can be determined by opening the cocks in succession and observing whether dry steam or hot water flows out. If the boiler is encased in brickwork, as is customary for externally-fired boilers, the gauge-cocks are placed outside the brickwork, and are connected to the boiler by nipples of the proper length.

Gauge-Glasses. In order that the fireman may know the water-level without trying the cocks, a water gauge-glass is used. It consists of a strong glass tube about one foot in length, having the ends connected to the boiler by suitable fittings.

As both ends of the tube are in communication with the boiler, the water-level in the glass will be the same as in the boiler. and is always in sight. Fig. 33 shows a good form of gauge.

glass. The glass is protected by rods which are parallel to it. As the glass frequently needs cleaning, repacking, or renewing, cocks are provided for shutting off communication with the boiler. A drain-cock is also placed at the lower end to empty the glass when the attendant wishes to ascertain whether the glass is working properly or not. The drain-cock is often provided with a drain-pipe. The

steam and water passages should be at least one half-inch in internal diameter.

The glass is likely to break because of accident or of changes in temperature. To prevent serious injury to the fireman and loss of water as a result of the breaking of the gaugeglass, automatic valves may be placed in the passages. In Fig. 34 the ball-valve is shown in detail. If the glass breaks, the pressure of the steam drives the ball outward, filling the conical passage. When a new glass is put in, the balls are forced back by slowly screwing in the stems. This, like other safety devices, is very likely not to work when it should.

In boilers where the steam space is small, as in locomotives, the allowable variation of water-level is slight; but the greater care with which the glass is watched makes up for the small margin of safety. If dirty water is used, or if the water foams, the level in the glass will be unsteady and unreliable, since dirt clogs the passages, unless they are large, and the foaming causes a fluctuation of the water-level. A small pipe connecting with the steam space where no ebullition occurs, will insure a steadier water-level. If the steam and water connection are long, the pipes should be made large.

The chief objection to the gauge-glass—namely, its breaking— may be to some extent overcome by attaching the gauge-glass to a gauge-column, which is usually made of brass and stands quite clear of the boiler itself. In such an arrangement as this, the temperature in the gauge-glass cannot vary so widely as if it were attached directly to the boiler. The "Klinger Patent" water gauge-glass is not easily broken, and possesses many advantages over the common glass. Fig. 35 illustrates both these devices.

The water gauge is not absolutely reliable, for the water in the gauge, being cooler than that in the boiler, may not indicate the true level, and the small passages leading to it may become choked with sediment. If the gauge-glass is frequently blown out by the engineer and kept clean, this difficulty will be reduced to a minimum.