268

MODERN STEAM PRACTICE.

tion. The packing of the bücket is a plaited gasket, or gutta-percha rings may be adopted, and kept to the circumferential sur-face of the barrel by the hydraulic pressure of the water, a smallhole being bored at the top in communication with the recessesleft in the bücket. The pump rod is connected to the cross shaftplaced at the centre length of the back link, passing through an eyeformed on the shaft at the bottom end. The water is pumped intoa cistern provided with an overflow pipe, the exhaust steam passingover the surface of the water and then escaping through another pipe

into the atmosphere; by this meansthe feed water is heated before it isforced into the boiler by a plungerpump, the rod for working it beingconnected directly to the beam by agudgeon passing through it, and to theplunger with a pin joint. The valvesand their seatings are of brass; anda relief valve should be fitted, loadedwith a weight, to return the waterinto the well or pond from which it isdrawn by the cold-water pump. Thisof course is only required when a re-gulating valve is placed on the boiler;but should the valve for regulatingthe supply to the feed pump be placedon the suction pipe, a relief valve maybe dispensed with. In either case,however, it is desirable to have onefitted close to the pump, so that in thea, Pump . B , piunger. c, Suction valve. e vent of the water in the feed pipes

D, Delivery valve. e e, Brackets. , . .

freezmg the line of pipmg may notbe damaged; and to guard against this evil, a small plug tapshould be fitted to the line of feed pipes, and so placed that all thewater may be run off between the check valve on the boiler andthe pump.

The steam-regulating valve fitted to the nozzle ehest should beplaced so that the attendant can reach it easily when starting theengine. It consists of a sluice valve of brass, fitted on a cast-ironface, accurately planed and scraped to a true surface,.—the valveehest being fitted with two covers to facilitate the Operation of

Fig. 178.—Feed Pump.