The governor is not only intended to maintain a uniform water pressure in the mains, but to prevent the pump from racing whenever a greater quantity of water is demanded than the pump is capable of delivering, as in the case of bursted mains or hose, or any other contingency whereby the pressure upon the discharge pipe is suddenly relieved.
Examples of pump governors or regulators follow.—
The Mason Pump Governor. This pump governor, shown in Figs. [566] and [567], is attached directly to the rock arm of the pump, and operates a balance valve placed in the steam pipe, thereby exactly weighing the pressure of steam to the needs of the pump. As all the working parts are immersed in oil, the wear is reduced to a minimum.
Fig. 567.
The Mason governor consists mainly of a cylindrical shell, or reservoir, as shown in sectional view, filled with oil or glycerine. The plunger, A, is connected with the arm, I, to some reciprocating part of the pump and works simultaneously with the strokes of the pump, thereby drawing the oil up through the check valve, DD, into the chambers, JJ, whence it is forced alternately through the passages, BB, through another set of check valves into the pressure chamber, EE. The oil then runs through the orifice, C, the size of which is controlled by a key inserted at, N, into the lower chamber, to be re-pumped as before. In case the pump or engine works more rapidly than is intended the oil is pumped into the chamber, EE, faster than it can escape through the outlet at, C, and the piston, GG, is forced upward, raising the lever, L, with its weight, and throttling the steam. In case the pump runs more slowly than was intended, a reverse action takes place, the weight on the end of the lever, L, forces the piston, GG, down and more steam is admitted. As the orifice at, C, can be increased or diminished by adjusting the screw at, N, the governor can be set within reasonable limits to maintain any desired speed. The piston, GG, fits over the stationary piston, forming an oil dashpot, thereby preventing dancing of the governor. This dashpot is fed from the pressure chamber, E, through a passage which is controlled by an adjusting screw, K, which is set with a screwdriver, after removing the cap screw, T. It requires no further attention after being once adjusted.
For duplex pumps up to 2-inch steam pipe, inclusive, this governor is fitted with a duplex valve, which prevents the escape of oil from the pressure chamber through the orifice, C, and thereby prevents the steam valve from opening wide during the momentary pause of the pump piston.
This governor should be placed on the pump at some point where the requisite motion can be obtained for operating it, and also in such a way that a rod can be run from the knuckle joint on the top lever, I, to the valve in the steam pipe, as shown in the engraving. Place the valve in the pipe, so that the stem shall be in a direct line with the knuckle joint on the lever, and pull out the valve stem to its full extent. With the ball on the governor in its lowest position, connect the valve rod to the lever. The governor is then ready to be filled with oil. Remove the plug on top of the gauge glass, and fill the governor about half full with a good, clean, light grade of mineral oil. The governor is then ready to work.
Start the pump at about its maximum speed; place the key in the keyhole on the side of the governor and turn to the right until the speed of the pump has diminished slightly. Open the throttle valve wide, and the pump will be under full control of the governor. Should there be much dancing or fluctuation of the ball, remove the screw, T, insert a small screwdriver, and screw the adjusting screw in, at K, until the irregular motion ceases. After the governor has run a little while, it will be found that the oil in the glass gauge has dropped considerably. It should then be refilled, so that the glass will be about half full when the governor is at work. Under no circumstances should the gauge be full, as too much oil will prevent the ball from coming down and opening the valve when the steam pressure falls. As there is no glass pressure upon the glass gauge the governor may be filled while in motion by removing the plug on the top of the gauge.