specific gravity of the liquid handled is 1.0. Then bhPi = (2000)(127)(1.0)/(3960)(0.70) =
91.6hp(68.4kW).
The theoretical or hydraulic horsepower hph = (gpm)(Ht)(s)/396Q, or hph = (2000) =
(127)(1.0)73900 = 64.1 hp (47.8 kW).
Related Calculations. Use this procedure for any liquid—water, oil, chemical,
sludge, etc.—whose specific gravity is known. When liquids other than water are being
pumped, the specific gravity and viscosity of the liquid, as discussed in later calculation
procedures, must be taken into consideration. The procedure given here can be used for
any class of pump—centrifugal, rotary, or reciprocating.
Note that Fig. 5 can be used to determine the equivalent length of a variety of pipe fit-
tings. To use Fig. 5, simply substitute the appropriate K value in the relation h = Kv^2 /2g,
where h = equivalent length of straight pipe; other symbols as before.
PUMP SELECTION FOR ANY
PUMPING SYSTEM
Give a step-by-step procedure for choosing the class, type, capacity, drive, and materials
for a pump that will be used in an industrial pumping system.
Calculation Procedure:
- Sketch the proposed piping layout
Use a single-line diagram, Fig. 6, of the piping system. Base the sketch on the actual job
conditions. Show all the piping, fittings, valves, equipment, and other units in the system.
Mark the actual and equivalent pipe length (see the previous calculation procedure) on
the sketch. Be certain to include all vertical lifts, sharp bends, sudden enlargements, stor-
age tanks, and similar equipment in the proposed system. - Determine the required capacity of the pump
The required capacity is the flow rate that must be handled in gal/min, million gal/day,
ft^3 /s, gal/h, bbl/day, Ib/h, acre-ft/day, mil/h, or some similar measure. Obtain the required
flow rate from the process conditions, for example, boiler feed rate, cooling-water flow
rate, chemical feed rate, etc. The required flow rate for any process unit is usually given
by the manufacturer or can be computed by using the calculation procedures given
throughout this handbook.
Once the required flow rate is determined, apply a suitable factor of safety. The value
of this factor of safety can vary from a low of 5 percent of the required flow to a high of
50 percent or more, depending on the application. Typical safety factors are in the 10 per-
cent range. With flow rates up to 1000 gal/min (63.1 L/s), and in the selection of process
pumps, it is common practice to round a computed required flow rate to the next highest
round-number capacity. Thus, with a required flow rate of 450 gal/min (28.4 L/s) and a
10 percent safety factor, the flow of 450 + 0.10(450) = 495 gal/min (31.2 L/s) would be
rounded to 500 gal/min (31.6 L/s) before the pump was selected. A pump of 500-gal/min
(31.6-L/s), or larger, capacity would be selected. - Compute the total head on the pump
Use the steps given in the previous calculation procedure to compute the total head on the
pump. Express the result in ft (m) of water—this is the most common way of expressing
the head on a pump. Be certain to use the exact specific gravity of the liquid handled