Put simply, head is the height at which a pump can raise fluid up and is measured in metres or feet. It is a crucial specification, especially when dealing with centrifugal pumps.
Understanding Pump Head
In the context of water pumps, 'head' refers to the maximum vertical distance the pump can move a fluid against gravity. It's a measure of the pump's ability to overcome resistance in the piping system and deliver fluid to a certain height or pressure.
Key Aspects of Pump Head
Based on common definitions and the provided reference, here are the essential points about pump head:
- Definition: It represents the height the pump can lift fluid vertically.
- Measurement: It is measured in units of metres or feet.
- Application: It is particularly important when specifying centrifugal pumps.
- Fluid Property: For centrifugal pumps, the pumping characteristics (including head) tend to be independent of the fluid's specific gravity (relative density). This means the pump can lift water or a fluid twice as dense to roughly the same height, although the pressure generated will be different.
Why Head Matters
Understanding pump head is vital for selecting the correct pump for a specific application. You need to match the pump's total head capability to the system's total head requirement, which includes:
- The vertical distance the fluid needs to be lifted (static head).
- The pressure needed at the discharge point (pressure head).
- The energy lost due to friction in pipes and fittings (friction head).
The pump must be able to generate enough head to overcome these resistances and deliver the required flow rate.
Head vs. Flow Rate
Pump performance curves often show the relationship between head and flow rate. Generally, as the required head increases (meaning you're trying to pump higher or against more resistance), the flow rate the pump can deliver decreases.
| Head (metres/feet) | Flow Rate (Litres per minute / Gallons per minute) |
|---|---|
| High | Low |
| Low | High |
Choosing the right pump involves finding one whose performance curve meets your specific head and flow rate needs.
Practical Example
Imagine you need to pump water from a well to a tank 20 metres higher. You would need a pump capable of generating at least 20 metres of static head, plus additional head to overcome friction losses in the pipe and deliver water at the desired pressure and flow rate at the tank.
In summary, head is a fundamental measure of a pump's lifting power, expressed as a vertical height. It's a critical specification for ensuring a pump can move fluid effectively within a given system.
