Reciprocating pumps move fluid with a back-and-forth motion. A piston or plunger draws fluid into a chamber on the suction stroke and pushes it out on the discharge stroke, with check valves controlling the direction. They are a major family of positive displacement pumps, built for high pressure and accurate flow.
Piston pump vs plunger pump
- Piston pump: the sealing rings travel with the piston inside the cylinder. Good for medium pressures and clean fluids.
- Plunger pump: a solid plunger moves through a fixed packing or seal. The seal does not move with the plunger, which makes it better for very high pressure and for more demanding fluids.
- Diaphragm pump: a flexible diaphragm does the pumping instead, so the fluid never touches the moving seals. This is the base of most metering pumps.
Simplex, duplex and triplex
The number tells you how many pistons or plungers the pump has. One (simplex) gives strongly pulsating flow. Three (triplex) gives much smoother flow and is common in high pressure duties.
Where they are used
- High pressure injection and pressure testing.
- Chemical metering and dosing, where accuracy matters.
- High pressure cleaning and descaling.
- Transfer of clean fluids against high pressure.
Strengths and weaknesses
- Strengths: high pressure, good efficiency, accurate and repeatable flow, flow almost independent of pressure.
- Weaknesses: pulsating flow, more moving parts, not suited to abrasive fluids or fluids with solids, regular maintenance of valves and seals.
Practical points
- Fit a pulsation dampener on the discharge to protect the pipework and smooth the flow.
- Always fit a pressure relief valve on the discharge line.
- Choose seal and valve materials for the actual fluid and temperature.
- Keep spare valves and seals on site.
For precise chemical injection, see our chemical dosing and metering pumps, and our guide to choosing a dosing pump.
Power Energy Gulf supplies metering and reciprocating pumps in Saudi Arabia and the GCC. Contact us with your fluid, flow and pressure details and we will recommend a suitable pump.