i86

MODERN STEAM PRACTICE.

bottom of the barrel, and the delivery valve at the top. The annularspace round the plunger is equal to the area of the plunger. Withthis arrangement no air can collect at the under side of the gland,as when the delivery valve is placed at the bottom of the barrel.

The main pump for this engine is of the plunger type, the rodsbeing cottered to the plunger, instead of the wooden rod passing

Fig. 118.—Pump.

a, Plunger. b, Stuffing box and. gland. c, Suction valve. d, Delivery valve.e, Stand pipe with air vessel. f Pump rod.

down through it, as has been already explained. The diameter ofthe plunger is 18 inches, with an annular space all round equal to thearea of the rams. The suction and delivery valves, of the flap type,are placed at the top of the pump barrel—this arrangement gettingrid of the air that collects in a barrel having the valves arranged atthe bottom. On the stand pipe an air vessel is fitted, to relieve theshock on the ram in the act of forcing the water. This arrangement of