Doseuro High-Pressure Piston/Plunger Metering Pump: Solution for High-Concentration Chemical Dosing

A metering pump (metering/dosing pump) is a positive-displacement pump that delivers each precise dose of fluid per cycle. In the piston/plunger type, the piston moves reciprocally in the cylinder and is in direct contact with the liquid, without an intermediate diaphragm. As a result, energy is transmitted directly to the fluid, enabling the pump to reach pressures significantly higher than diaphragm types — the Doseuro AP-A variant operates up to 230 bar.

Flow rate is adjusted via two parameters: piston stroke length and cycle frequency. When increasing or decreasing the dose, the operator adjusts the stroke manually or via a control signal, while the frequency is determined by the motor and variable frequency drive. The dosing accuracy of positive-displacement pumps typically falls within ±1–3%, depending on the type and operating conditions.

Plunger metering pumps are selected when the working pressure exceeds the threshold of diaphragm pumps. Examples include: chemical dosing into high-pressure pipelines, boiler systems, demineralization systems, or petrochemical processes requiring injection against high process pressure. In these cases, diaphragm types cannot generate sufficient pressure, while the piston/plunger handles the task with the AP-A variant up to 230 bar.

The SS316L pump head of the SR type A handles a wide range of high-concentration chemicals. Depending on the fluid, Doseuro also offers PVC, PP, PVDF, and PTFE pump head materials for specialized corrosion resistance. Selection of the pump head — seal — ball valve material combination must be based on a specific chemical compatibility chart.

The SR type A series is Doseuro’s piston/plunger metering pump, positioned for the high-pressure segment of the product range. The main specifications below are drawn from the manufacturer’s technical documentation; exact figures for each order depend on the model and actual operating conditions.

For lower flow rates or rapid on/off switching, the electromagnetic SDP type S series (≤22 l/h, ≤20 bar) may be considered. Conversely, if the fluid is prone to leakage and leak-proof operation at high pressure is required but piston-level pressure is not yet needed, the hydraulic diaphragm SR type B series (108–1,068 l/h, standard ≤20 bar, AP-B variant up to 60 bar) offers a practical intermediate option.

Since the piston is in direct contact with the fluid, care must be taken to prevent wear with particle-laden liquids, and a safety relief valve should be installed on the discharge side to protect the pump against sudden pressure spikes. The suction line should be kept short, adequately submerged, and fitted with a coarse filter to prevent ball valve jamming. For high-concentration chemicals, the system must include a safe discharge area and a scheduled maintenance procedure for the seals and piston.

For automated dosing according to process demand, the SR type A accepts a 4-20mA control signal, which can be combined with pH/ORP/flow sensors to close the control loop. For oil & gas and petrochemical applications requiring high accuracy and standardization, Doseuro also offers the PDP series meeting API 675 and ATEX standards — the process metering pump standard with ±1% accuracy at steady state.