Page 251 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Pumping of Liquids 221

Pump Selection H, = Head at no flow, or shutoff, ft
0
I-I"' = Head of viscous fluid, ft
Reciprocating pump selection follows the fundamen- H; = Water equivalent head, fl
tals of centrifugal pumps: hd = Discharge head on a pnmp, ft of fluid
h, = Suction head ( or suction lift) on a pump, ft of fluid
hsL, huL = Friction losses in pipe and fiuings., subscript SL for
1. Evaluation suction side head loss. suction line; and DL for discharge line, ft �f fluid
2. Evaluate discharge side head loss. h, = Velocity head, ft of fluid
3. Determine system static pressure. L = S = Static head, suction side, ft (Figure 3-38)
4. Determine total differential head across pump. I = Water depth in sump, ft (Figure 3-62)
N, = Specific speed, dimensionless
5. Determine the NPSHA available on suction of pump. NP = Number of pumps
6. From manufacturer's performance tables, select n = Ro �� ve speed, revolutions per minute = RP;\1 = rpm
pump nearest to GPM and head requirements. P = Positive external pressure on surface of liquid ( +)
7. Contact manufacturer for final recommendations , or partial vacuum on surface of liquid ( - )
give complete system requirements, and physical Pa = Atmospheric pressure or absolute pressure in ves-
sel, psia
properties of liquid. Figure 3-69 is convenient for Pso = Brake horsepower at shutoff or no flow
this purpose. P,d = Differential pressure between absolute pressures at
outlet and inlet to pump, psi
Nomenclature P,., = Vapor pressure of liquid at pumping temperature,
ps1a
a = Area of piston or plunger; sq in. p' = Absolute pressure, inches mercury abs
Bct = Bell diameter of vertical sump pump, ft p', = Atmospheric pressure or absolute pressure in ves-
BHP = Brake horsepower sel expressed as ft of fluid
(BHP)v,s = Brake horsepower when handling viscous material p'vp = Vapor pressure of liquid at pumping temperature
CE = Viscosity correction for efficiency to convert to expressed as ft of fluid
water performance Q = Flow rate, gal per minute
CH = Viscosity correction for head, to convert Lo water Q' = Capacity of rotary pump, fluid plus dissolved
performance gases/ entrained gases at operating conditions, GPM
CQ = Viscosity correction for capacity, Lo convert to Q�r = Minimum flow, GPM
water performance QN = Head at best efficiency point on pump curve, ft
cp = Specific heat of liquid, BTU/lb - °F Qm = Viscous liquid capacity, GPM
D = Height of liquid (static) above ( +) or below (-) Qw = Water capacity, GP'.\1
the centerline of the pump on discharge side, ft S = Suction static head, ft, or height of liquid (static)
D' = Incremental height of liquid (static) above normal above ( +) or below (-) the center line of the
D level, to establish "worst case" condition fr Fig- pump on suction side. fL, or,
i:re 3-38 ' ' ' S = Suction lift, negative suction head, ft
D" = Theoretical displacement volume displaced per S' L = Worst case suction side static lift, ft (Figure 3-39)
revo lutionrs) of driving rotors, cu in./rev S" = Slip, quantity of fluid that leaks through internal
d = Impeller diameter, in. clearances of rotary pump per unit time, GPM
dp = Diameter of piston or plunger, in. SpGr = Specific gravity of liquid at pumping temperature
referred Lo water = 1.0
d, = Diameter of piston rod, in. s = Stroke, in.
d' = Liquid displacement, cu ft/min
d" = Theoretical displacement, cu ft/min 1h = Temperature rise, °F
eHP = Electrical horsepower t.T, = Temperature rise, °F/min
t = Piston speed or travel, fl/min
E = Efficiency, percent V = Liquid velocity, ft/sec
En = Fraction entrained gas by volume al atmospheric v = Average velocity, ft/sec
pressure W = Width of channel with series pumo ft
E, = Volumetric efficiency, ratio of actual pump capaci- W1 = Weight of liquid in pump, lb r :
L;- to volume displaced per unit of time
Ew = Pump efficiency with water, percent whp = Water or liquid horsepower
Evis = Pump efficiency with viscous fluid, percent whp. = Power imparted by pump Lo fluid discharged (also
iiquid horsepower)
e = Pump efficiency, fraction
e., = Pump efficiency with water, fraction
evis = Pump efficiency with viscous fluid, fraction Subscripts
e, 01 = Volumetric efficiency, fraction
e\ 1 = Maximum safe flowing efficiency, overall pump, 1,2 = Refer to first and second condition respectively
fraction A = Available from pump system (NPSH)
g = Acceleration of gravity, 32 ft/sec/sec L = Liquid
H = Total head developed by a pump, fl of !1uid; or cl = Discharge side of pump
total head/stage, ft, 01� d, = Friction losses for pipe fittings and related items
H = Static head discharge ft (Figure 3-38, -39, -40) on discharge side of pump