General pump types

Centrifugal pumps
Centrifugal pumps operate at relatively low pressure. They will pass abrasives and bits of solid material without binding or appreciable wear, and require minimal maintenance. Pump discharge can be restricted without damage to pump or motor. No relief valve necessary. Viscosity range up to 2200 SSU.

Gear pumps
Ideal for applications where consistently high pressure is required to feed lubricants, drawing compounds, heavy viscosity oils and other fluids which are free of abrasives and scale. Viscosity range up to 5000 SSU.

Diaphragm pumps
Air powered. Deliver variable flow rates up to 12 GPM. Can be used for pumping water, chemicals and corrosives of viscosities up to 10000 SSU.

What you need to Know

• Maximum flow required (GPM)
• Maximum pressure required (see total developed head below)
• Description of proposed piping installation (pipe diameter, height to which liquid will be pumped, number of fittings, total piping length)
• Type of liquid (water, abrasive, acid, slurry, etc...)
• Duty cycle (continuous, intermittent)
• Mounting requirements
• Voltage, hertz and phase.

Total developed head (TDH)
TDH is the total resistance against which pump is working. This resistance is comprised of three general factors: Dynamic Head, Static Head and Velocity Head.

Dynamic Head Is the flow resistance (head) created by friction in piping, valves, fittings and liquid viscosity.* To derive maximum flow from a pump, avoid using piping smaller than the pumps' discharge (increasing the size of the outlet piping will decrease flow resistance). Street "ells" and globe valves should be avoided because they restrict flow. When the size of the piping is smaller than the pumps' discharge, or when long runs are required (over 20 feet), plumbing friction may easily comprise 50% or more of the TDH.

Static Head is the height (head) required to which liquid must be raised. Note: When using the flow charts in the pump selection, both Dynamic Head and Static Head must be included in estimating the TDH against which the pump will operate.

Velocity Head is the pressure (head) required to accelerate the liquid to it's flow velocity. This is usually a negligible factor of TDH and can be disregarded unless piping is smaller than the pump discharge and/or flow velocities are greater than 15 feet per second.

*The higher the viscosity of a liquid, the more resistance it has to flow. Pump viscosities throughout this information given are stated in SSU's (saybolt second universal). 70° F water = 31 SSU. Light hydraulic oil = 350 SSU. #10 oil = 500 SSU. When choosing pumps, be sure to note the designated fluid viscosity.