Page 249 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Pumping of Liquids 221

p seaectjion H,, = Head at no flow, or shutoff, ft
H,,, = Head of viscous fluid, ft
eciprocating pump selection follows the fundamen- H, = Water equivalent head, ft
tals of centrifugal pumps: hd = Discharge head on a pump, ft of fluid
h, = Suction head (or suction lift) on a pamp, ft of fluid
hsL, h,, = Friction losses in pipe and fittings:, subscript SL for
1. Evaluation sucl ion side head loss. suction line; and DL for discharge he, ft of 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. 1 = Water depth in sump, ft (Figure 3-62)
N, = Specific speed, dimensionless
5. Determine the NPSHA available on suction of pump. N, = Number of pumps
6. From manufacturer’s performance tables, select n = Rotative speed, revolutions per minute = RPM = 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 oi ’liquid. Figure 3-69 is convenient for P,, = Brake horsepower at shutoff or no flow
this purpose. Ptd = Differential pressure between absolute pressures at
outlet and inlet to pump, psi
PVT = Vapor pressure of liquid at pumping temperature,
psia
a = Area of piston or plunger, sq in. p‘ = Absolute pressure, inches mercury abs
B, = Bell diamleter of vertical sump pump, ft = Atmospheric pressure or absolute pressure in ves-
BHP = Brake horsepower sel expressed as ft of fluid
=
(BHP),+ = Brake horsepower when handling viscous material P‘~ Vapor pressure of liquid at pumping temperature
6, = Viscosity correction for effficiency to convert to expressed as ft of fluid
water performance Q = Flow rate, gal per minute
6, = Viscosity correction for head, to convert to water Q‘ = Capacity of rotary pump, fluid plus dissolved
performance gases/entrained gases at operating conditions, GPM
CQ = Viscosity correction for capacity, to convert to QhI = Minimum flow, GPM
water performance 0, = Head at best efficiency point on pump curve, ft
cp = Specific heat of liquid, BTU/lb - “F QiS = Viscous liquid capacity, GPM
D = Height of liquid (static) above (+) or below (-) Qw = Water capacity, GPM
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
I4 level, to establish “worst case” condition, ft; Fig- pump on suction side, ft, or,
ure 3-38 S = Suction lift, negative suction head, ft
D” = Theoretkal displacement volume displaced per = Worst case suction side static lift, ft (Figure 3-39)
revolution(s) 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
d, = Diameter of piston or plunger, in. SpGr = Specific gravity of liquid at pumping temperature
referred to water = 1.0
d, = Diametei- of piston rod, in.
d’ = Liquid displacement, cu ft/min s = Stroke, in.
d” = Theoretical displacement, cu ft/min At = Temperature rise, “F
eHP = Electrical horsepower ATr = Temperature rise, “F/min
t = Piston speed or travel, ft/min
E = Efficiency, percent
E, = Fraction entrained gas by volume at atmospheric V = Liquid velocity, ft/sec
v = Average velocity, ft/sec
press-ure
MT = Width of channel with series pump, ft
E, = \blumetric efficiency, ratio of actual pump capaci- W1 = Weight of liquid in pump, lb
ty to volume displaced per unit of time
E, = Pump efficiency with water, percent whp = Water or liquid horsepower
E,<, = Pump efficiency with viscous fluid, percent whpl = Power imparted by pump to fluid discharged (also
liquid horsepower)
e = Pump efficiency, fraction
e, = Pump efficiency with water, fraction
e~s Subscripts
= Bump efficiency with ~4scous fluid, fraction
eval = Volumetric efficiency, fraiction
eM = 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
II = Total head developed by a pump, ft of fluid; or d = Discharge side of pump
total heatd/stage, ft, or, dl = Friction losses for pipe fittings and related items
= Static head discharge ft l(Figure 3-38, -39, -40) on discharge side of pump