Unit 3.2 – Pumps

Pumps that impart velocity to fluid and convert it to pressure are called:

• Positive displacement pumps

• Dynamic pumps

• Reciprocating pumps

• Gear pumps

Single-stage centrifugal pumps are preferred for:

• High head, low flow

• Most general chemical industry service

• Slurries only

• Vacuum service

Positive displacement pumps are normally used when:

• High head at low flow rate is required

• Large flow at low head is needed

• Liquids are near boiling

• System curve is steep

For high head at large flow rate, which pump is typically selected?

• Single-stage centrifugal

• Multi-stage centrifugal

• Diaphragm

• Gear

Centrifugal pumps convert:

• Thermal energy to kinetic

• Rotational kinetic energy to hydrodynamic energy

• Pressure to electricity

• Potential to nuclear

The reverse of a centrifugal pump is:

• Vacuum pump

• Water turbine

• Air compressor

• Diaphragm pump

The pump head HH in feet can be calculated from pressure and specific gravity as:

• H=2.31P/SG

• H=0.433P×SG

• H=P×SG

• H=1.0P/SG

Velocity head developed by an impeller is given by:

• V^2 / (2g)

• 2g/V

• gV^2

• V / 2g

Relation between impeller speed (N), diameter (D) and velocity head:

• V=ND/229

• V=229/(ND)

• V=ND/144

• V=N^2 D

Pump capacity Q (gpm) from pipe cross-section and velocity is approximated by:

• Q=449AV

• Q=2.31AV

• Q=3960AV

• Q=144AV