HIGH HEAD, LOW CAPACITY PUMPS H017
We sometimes need a low capacity pump that can put out a high pressure or large head. Here are some ways to get those features:
- High speed centrifugal pumps are the most popular choice. There are centrifugal pump designs that run at 30,000 rpm and above. Narrow width impellers may give you the low capacity you are looking for.
- Multistage vertical and horizontal pumps are another option.
- Regenerative turbine pumps work well, but the necessary close clearances dictate only clean fluids.
- Gear or rotary positive displacement pumps work well, but they have slippage problems in low viscosity service and their very low capacities may not be sufficient for the application.
- Metering pumps are good for very low flow, but the inherent pulsations can damage some instrumentation.
- You can connect single stage centrifugal pumps in series if a single pump cannot meet the head requirements.
- Partial emission pumps can operate at a specific speed of as little as two (2).They utilize a “Baske” straight vane impeller with a diffuser that allows flow from a small section of the impeller channels to pass to the pump discharge at any time (hence partial emission). This pump was developed during World War II to handle the high head low flow rate requirements of the German ram jet fuel pump.
- Throttling a centrifugal pump to get a high head will cause some problems:
- The resultant shaft deflection can damage the seal or break the shaft.
- Internal recirculation can overheat the volute and cause cavitation problems.
- A high differential pressure across the pump can damage close internal clearances.
- The power loss can be expensive.