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LITERATURE



 

PUMP ENERGY
                      INC. TOOLS

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Definitions

Capacity Flow rate required, i.e., GPM, BPH, etc.
Suction Pressure PSI or Head (ft.)
Discharge Pressure PSI or Head (ft.)
NPSH Available in absolute pressure
Product Type liquid & its conditions (temperatures, viscosity, specific gravity,
clean, solids, abrasive, corrosive)
Type Centrifugal, rotary, reciprocating--gear, lobe, screw--horizontal, vertical, in-line, submersible, self priming- etc.
Materials of Construction Desired materials and/or construction features, if any
Driver Electric/Air/Hydraulic motor - gas/diesel engine - gas/steam turbine

Formulas

  • Head (ft.) = (psi x 2.31) / sp. gr. = (in. Hg.) / (sp. gr. x .88)
  • PS1 = (head (ft.) x sp.gr) / 2.31 = (.49 x in. x Hg.)
  • Velocity (ft./sec.) = (0.4085 x gpm) / [i.d. (in.) of pipe] ^ 2
  • BHP (Centrifugal) = (GMP x head (ft.) x sp. gr.) / (3960 x pump eff)
  • BHP Positive Displacement = (GMP X PSI) / (1715 x pump eff.)

Conversions

Wt of Water 8.34 lb./gal. or 62.37 lb./cu. ft @ 60 degrees
1 lb./sq. in. 2.31 ft. water (1.0 sp. gr.)
BPH x .7 GPM
BPD x .0292 GPM
1 BBL. (petroleum) 42 gallons (U.S.)
1 ft. water .433 PSI
Atmospheric Press 14.7 psi or 33.9 fr. fresh water @ sea level
1 inch of mercury (Hg) vacuum 1.133 ft. water
Dynamic Suctions Lift (ft.) Vacuum in inches of Hg. / (0.883 x sp. gr.)


Net Positivie Suction Head (NPSH)

  • NPSHr = head required @ the eye of the pump's impeller to prevent cavitation, a function of pump design.
  • NPSHa = head available from the suction side of the system, must always equal or exceed the required (NPSHr) to prevent cavication.

NPSHa Factors Table

Positive Negative
1) Absolute pressure on liquid 1) Vapor pressure of the liquid, absolute
2) Static suction head 2) Friction & entrance losses
  3) Static suction lift

Affinity Laws

Effects on centrifugal pumps with limited change of speed (RPM) or impeller diameter.

  1. Capacity (Q) varies directly as the speed (N) or impeller diameter (D).
  2. Head (H) varies as the square of the speed or impeller diameter.
  3. BHP varies as the cube of the speed or impeller diameter.
  • Law 1 = Q^1/Q^2 = N^1/N^2 or D^1/D^2
  • Law 2 = H^1/H^2 = (N^1/N^2)^2 or (D^1/D^2)^2
  • Law 3 = P^1/P^2 = (N^1/N^2)^3 or (D^1/D^2)^3



 

 
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