Sewerage and Sewage Treatment

by Harold E. Babbitt

115 Pump body. 127 Brass liner. 129 Water piston head. 130 Water piston follower. 137 Cylinder head. 139 Valve plate. 140 Cap. 152 Suction flange. 161 Discharge flange. 162 Valve seat, suction or discharge. 163 Valve, suction or discharge. 164 Suction valve spring. 167 Discharge valve spring. 168 Valve plate, suction or discharge. 169 Valve stem, suction or discharge.

STEAM END

55 Crank pin. 56 Valve rod link. 61 Long rocker arm. 62 Short rocker arm. 63 Rocker arm wiper. 69 Cross head.

condensing or non-condensing, etc. Throttling engines or automatic engines refer to the method of control of the steam by the governor. In throttling engines the governor controls the amount of opening of the throttle valve, in automatic engines the governor controls the position of the cut-off.

The simple slide valve, low-duty, non-condensing, throttling engine, is the lowest in first cost and the most expensive in the consumption of fuel. The triple-expansion Corliss, or the non-releasing Corliss, high-duty pumping engine is the most expensive in first cost but consumes less steam for the power delivered than any other form of reciprocating engine. For pumps of very small capacity the cost of fuel is not so important an item as the first cost of the machine. For this reason and because of the lower cost of attendance low-duty pumps are more frequently found in small pumping stations.

Fig. 64.—Diagram Showing Rates of Steam Consumption for Different Size Units under Different Loads.

TABLE 27
Water Rates of Prime Movers at Full and Part Loads
Type of Engine	Power, K.W.	Per Cent of Full Load					Boiler Press. Lbs.
		25	50	75	100	125
Single cylinder, high speed, non-condensing	25	33	27	26.3	27.0	27.5	100 to 150
	250	42	37.5	35	34.0	34.0
Automatic, flat four valve, high speed	150		32	30	26.5	29.0	100 to 125
	250		33	31	28	30.0
Tandem compound condensing, high speed	125		23	19	17	18	100 to 150
			25	20	19.5	21
Cross compound, condensing, high speed		30	26	24	23	23.5	125
Cross compound, non-condensing, high speed		39	31	27	26	27.5	125
Single cylinder Corliss, condensing	120	23.7	20.4	19	18.5	19.0	100
	500	26.3	22.8	21.3	20.8	21.3	125
Compound Corliss, condensing		16.5	14	12.5	12.1	12.5	100
		22.2	19	17.0	16.5	17.0	150
Single cylinder, rotary four valve, non-condensing	75	26.2	22.3	21.3	21.6	22.8	100
	400	35.0	27.2	26.4	26.0	26.8	180
Rotary four valve, tandem compound non-condensing	125	32.0	22.0	20	18.25	18.5	100
	600	40.0	28.3	23.2	22.5	22.7	150
Cross compound, non-condensing rotary four valve	125	25	21	19.1	18.5	19.0	100
	600	39.4	28	22.3	20.6	20.7	150
Single cylinder, poppett valve, non-condensing	120	22.7	20.5	19.7	19.1	20.1	100
	600	28.5	26.0	25.0	24.3	25.5	150
Single cylinder, poppett valve, condensing	120	18.5	16.7	16.1	15.6	16.4	100
	600	24.6	22.3	21.4	20.8	21.9	150
Compound condensing, poppett valve	200	14.2	13.0	12.5	12.2	12.9	100
	1200	18.4	16.9	16.3	15.9	16.8	150
Uniflow	125	14.6	13.7	13.4	13.4	13.3	150
	600	15.0	14.3	13.7	13.5	14.0
Steam turbines, condensing, Allis-Chalmers	300		24	17	160	16.5	125
	2000		31.9	26.3	23.8	23.0	175
Steam turbines, condensing, Westinghouse	300		13.7	12.8	12.2	12.6	125
	2000		18.2	16.9	16.2	16.8	175
Steam turbines, high pressure, non-con., 12″ to 36″ wheel, 1000 to 3600 R.P.M.	4 to 8 stages				28 5
					116.5
Ditto. Condensing, 26–inch					17 3
					112.0

The steam consumption per indicated horse-power, better known as the water rate of the engine, for various types of engines at full and at part load is shown in Fig. 64. The steam consumption of other types at full load is shown in Table 27. The indicated horse-power (I.H.P.) of a steam engine is the product of the mean effective pressure (M.E.P.), the area of the steam pistons, the length of the stroke, and the number of strokes per unit of time. A common form of this expression is,

I.H.P = PLAN
33,000,