Borehole submersible pump
A long, narrow multi-stage submersible sized to fit a borehole casing, for water supply, irrigation abstraction and groundwater control. Selected on casing diameter before anything else.
Features
- Outside diameter has to clear the casing with room for the rising main and cable, so the borehole log determines the pump before the duty does.
- Motor cooling depends on water flowing past the motor at a minimum velocity, which is why a flow sleeve is needed in an oversized casing.
- Setting depth is chosen below the drawdown level at full pumping rate, not below the rest water level.
- Sand content is measured, not assumed: even a few tens of mg/l abrades stages and shortens life dramatically.
- Dry-run and over-current protection are essential because the pump is inaccessible and a failure is a rig visit.
- Cable, rising main, well head and control gear are all part of the specification and usually cost more than the pump.
Specifications
| Figure | Typical range | Unit | Why it matters |
|---|---|---|---|
| Outside diameter | 98 / 145 / 195 | mm | Must clear the casing with the rising main. |
| Maximum flow | 2 - 80 | m³/h | Must not exceed the borehole's sustainable yield. |
| Maximum total head | 40 - 300 | m | Setting depth plus surface delivery head. |
| Minimum flow past motor | 0.08 - 0.16 | m/s | Below it the motor overheats; a flow sleeve fixes it. |
| Permissible sand content | < 25 | mg/l | Above it, stage life collapses. |