ing. If too much water is delivered, some of it will escape through O into C, and, pressing on the piston N N, will move the combining-tube away from the delivery-tube, thus throttling the watersupply; and if sufficient water is not admitted, a partial vacuum will be formed in C, and the unbalanced pressure on the upper side of the piston, N N, will move the combining-tube towards the delivery-tube, thus enlarging the orifice for the admission of water. The injector, once started, will continue to work without any further adjustment, delivering all its water to the boiler, the waste-valve being kept shut. By placing the hand on the starting-lever, it is easy to tell whether or not the injector is working; and if desired, the waste-valve can be opened momentarily by pushing the rod L, a knob on the end being provided for the purpose.

TABLE

SHOWING STEAM-PRESSURE REQUIRED TO LIFT AND DELIVER WATER WITH SELLERS' FIXED-NOZZLE LIFTING INJECTOR.

Sellers' Non-Adjusting Fixed-Nozzle Injector with Lifting Attachment, for Stationary Boilers.

The cut on page 413 represents Sellers' Non-Adjustable Injector with fixed-nozzle and lifting attachment. As will be ob served, a steam-ejector or siphon is attached to the side of this instrument, which draws the water, when lifted by the admission of the steam, through the combining-tube, and discharges it through the orifice of the lifting attachment, through which, also,

the waste water or overflow escapes. This injector has a checkvalve connected to it, also a steam stop-valve, which can be opened wide by half a revolution of the lever on the stem. In connecting the injector, since it has fixed nozzles, a water-supply valve must be provided, and, as al

ready remarked, a second check-valve in the delivery - pipe and another steam-stop valve are desirable.

In starting this injector, steam is first admitted to the lifting-nozzle, the water-supply valve being adjusted so as to deliver about the maximum amount of water corresponding to the steam-pressure; and as soon as solid water issues from the liftingnozzle, the steam-valve is to be opened slightly until the jet is established, when the full steam-pressure is to be admitted, and the valve that admits steam to the lifting-nozzle is to be closed.

D

Some little dexterity Section of Sellers' Non-Adjustable FixedNozzle Lifting Injector. is required to start the

injector for a maximum lift, but the manipulation is readily acquired, while for all ordinary lifts no special care is required. As the velocity of steam escaping from an orifice varies greatly with

the pressure, other things being equal, the lifting-nozzle must have proportions depending on the minimum steam-pressure to be employed, since it can readily be adapted to higher pressures by partially closing the steam-admission valve.

Directions for operating Sellers' non-adjustable fixed-nozzle

Lifting Injector.

injector, with lifting attachment. First, close the steam-spindle, A, by means of the handle, B. Second, open the lifting-jet by backing the wheel, C, one-quarter turn. Third, when the water escapes at the overflow, D, run out the spindle, A, by backing it quickly; then close the lifting-jet, C, as the injector will then be feeding the boiler, and the water-supply may be regulated by means of an ordinary globe-valve placed between the injector and the water source. If this valve is set to admit the required quantity of water, there will be no drip from the overflow. When required, a special regulating valve, which re

quires but one turn, and which indicates the required opening, is attached to the injector, so that those having it in charge may de

termine the actual amount of opening by a glance at the handwheel on the valve-spindle.

Duty of Sellers' injectors, or the foot-pounds of useful work performed by the consumption of 100 lbs. of coal in the boiler supplying steam to the injector, may be of interest. When the evaporation of the boiler is known, this duty can readily be computed from the data obtained in connection with the maximum delivery of the injector. This can be illustrated by an example. Assuming the boiler evaporation at 9 lbs. of steam per lb. of coal, a result which, though rather above the average, is occasionally exceeded in good practice. Using the data recorded in the table on page 416 for the maximum delivery at a steam-pressure of 130 lbs. per square inch, it appears that 150-66- 84 units of heat were imparted to each pound of water delivered by the injector, and, the weight of a cubic foot of water at a temperature of 66° Fah. being about 62.3 lbs., that the total weight of water delivered per hour was 161.2 × 62·3 = 10,042.76 lbs., so that the total amount of heat imparted to the water per hour was 10,042.76 × 84843,591.84 units.

=

The total heat above 32° in a pound of dry steam, at a pressure of 130 lbs. per square inch, is 1187-8 units, and the heat remaining in a pound of steam above 32°, after condensation, is 150 -32118 units, so that each pound of dry steam imparted 1187.8-118: 1069-8 units of heat to the feed-water, and the

weight of dry steam required per hour was

843,591.84
1069.8

=

788.6 lbs.

The height of a column of water equivalent to the pressure against

the useful work performed per hour was 10,042·76 × 300·5= 3,017,049.38 foot-pounds. The weight of coal required to do this

work, on the assumed boiler evaporation, was

788.6
9

87.6 lbs.,

so that the duty of the injector, per 100 lbs. of coal, was 3,017,049-38 × 100

3,455,536 foot-pounds.

The term range is frequently used in connection with injectors, and means the difference between the maximum and minimum delivery.

TABLE

SHOWING THE MAXIMUM AND MINIMUM DELIVERY OF SELLERS' SELFADJUSTING, 1876, INJECTOR NO. 6; TEMPERATURE OF DELIVERED

WATER; PRESSURE AGAINST WHICH INJECTOR DELIVERS WATER, AND HIGHEST TEMPERATURE OF FEED ADMISSIBLE; WATER FLOWING TO INJECTOR UNDER 15 INCHES HEAD; WASTE-VALVES SHUT.

The table of capacities shows the maximum delivery, but the injector can be regulated so as to reduce the amount about 60 per

cent.