Pumps by Type
TO SELECT THE RIGHT PUMP
The more data you can identify, the more quickly and precisely an appropriate pump can be specified.
- Maximum flow required (GPM).
- Maximum pressure required (see TDH).
- Description of the proposed piping installation (pipe diameter, height to which liquid will be pumped, number of fittings, total piping length).
- Type of liquid being pumped (water, acid, slurry, etc).
- Mounting/installation requirements.
- Voltage, hertz, and phase.
TOTAL DEVELOPED HEAD (TDH)
TDH is the total resistance against which the pump is working. This resistance is comprised of three general factors: Dynamic Head, Static Head, and Velocity Head.
- Dynamic Head is the flow resistance created by friction in piping, valves, fittings and by liquid viscosity*. To derive maximum flow from a pump, use the largest piping possible and minimize any restrictive components such as 90 degree elbows, reducers or valves.
- Static Head is the height to which the liquid must be raised. Note: When using the Flow Charts in the pump section, both Dynamic Head and Static Head must be included in estimating the TDH against which the pump will operate.
- Velocity Head is the pressure required to accelerate the liquid to its 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 thicker the viscosity of a liquid, the more resistance it has to flow. Most pump viscosities throughout this catalog are stated in SSUs (Saybolt’s Second Universal). 70°F water = 31 SSU. Light hydraulic oil = 350 SSU. #10 oil = 500 SSU. When using Pump flow charts, be sure to note the designated fluid viscosity.
HEAD FEET/PSI CONVERSIONS
Pump curves throughout the pump section are based on (TDH) feet of water pressure. Here are the formulas to convert head feet and pounds per square inch (PSI).
Head feet = PSI x 2.31 ÷ Specific Gravity
PSI = Head feet x Specific Gravity ÷ 2.31
(Specific gravity of water = 1)
