Hydraulic Diaphragm Metering Pump: Leak Prevention for Corrosive Chemicals

A mechanical diaphragm uses a cam or eccentric mechanism to act directly on the diaphragm, while a hydraulic diaphragm inserts a layer of oil between the piston and diaphragm so the oil transmits pressure to drive the diaphragm. With pressure balanced on both faces of the diaphragm, the hydraulic configuration handles higher pressure and reduces stress on the diaphragm. In Doseuro’s range, SR type D is the mechanical diaphragm (3–14 bar), while SR type B/BR is the hydraulic diaphragm (up to 20 bar, AP-B up to 60 bar).

The diaphragm completely separates the fluid chamber from the drive mechanism, so there is no rotating shaft passing through the casing to contact the chemical as there is with shaft seals — which are common leakage points. The oil cushion also reduces local diaphragm deformation; some variants use a double diaphragm for a backup layer. The Doseuro BR variant adds a safety valve to protect the diaphragm in case of overpressure.

The SR type B series (comprising B and BR) meters 108–1,068 l/h. The standard variant operates up to 20 bar; the high-pressure AP-B variant extends up to 60 bar. The series is available in ATEX configuration for hazardous areas. Parameters outside this range depend on the specific model and operating conditions.

Doseuro pump heads are selected based on the fluid’s chemical properties: SS316L for most industrial solutions, PVC/PP for common acids and bases, PVDF and PTFE for strongly corrosive chemicals. Selecting the correct wetted material determines pump service life, so it is necessary to provide the chemical name and concentration when seeking advice.

Yes. The flow rate is adjusted via stroke length and frequency, and can be controlled manually or via a 4–20mA signal. When integrated with pH/ORP/flow sensors, the system can automatically adjust the dosing rate based on the measured parameters, maintaining metering accuracy typically within ±1–3%.

When very high pressure and high-concentration chemical dosing are required, the piston/plunger configuration (Doseuro SR type A, up to 230 bar with the AP-A variant) is more appropriate as the piston contacts the fluid directly and can handle high pressure. In return, the hydraulic diaphragm has the advantage of sealed isolation against leakage. The choice depends on pressure requirements, fluid characteristics, and the application’s acceptable leakage tolerance.