The Locomotive Of Today

38 The Boiler : Regtdators, Priining, Safety Valves. case, of course, the pipe is parallel ; this joint is shown in section at G. A common form of stuffing box through which the regu- lator rod has to pass at the tirebox end of the boiler is shown at H. It consists of a cast iron box, with flange and a projec- tion at the top of it forming a guide and stop for the handle ; a neck ring fits at the base of the inside of the box, and a giand at the outside, the joint around the rod being usually made with hemp packing. The handles are either double or single, a usual form of a single one is shown at H, one end of which fits upon a square at the end of the regulator rod where it is held in position by means of a nut. A particularly neat form of double handle is shown at I, consisting of a round bar with a boss to lit the square on the rod as before, and a rectangular portion to engage the stops on the stuffing box flange. A double handle, of course, gives the driver more power over the regulator than a single one, this being very useful in .the case of a “sticking” valve. At J is shown a clouble håndled “ pull out ” arrangement. The rod end has a fork which is connected to the centre of the lever, a hinge for this lever being on one side of the stuffing box flange, and on the other a sector through which a screw affixed to the lever passes with a thumb nut at the top, so that the driver can clamp it in any position he may wish. A securing device of some kind is necessary for the forms of regulator shown at E and F, as they have no tendency to keep closed by their own weight as the vertical patterns have. Priming or foaming is caused generally by the presence of greasy matters in the water, and it may be remedied, if so caused, by the addition of a lunip of unslaked lime to the feed water in the tank, or a piece of bluestone (sulphate of copper), but the two should not be used together. Water carried too high will also cause priming; this is not always because the level is nearer to the point at which the steam is drawn off, but because the higher the water is carried the less will be the area from which the steam has to escape. Safety valves are provided to prevent the pressure of steam in the boiler exceeding the precletermined limit arranged for by the designer. The valves are adjusted to lift and permit the surplus steam to escape as soon as the pressure attains the appointed figure, and close when the necessary reduction is accomplished. Every boiler should be fitted with at least two valves, three are provided at times to reduce to a minimum the possibility of explosion through valves sticking and con- sequent excessive pressure.