Double-Diaphragm Liquid Transfer Pump

What is the Double-Diaphragm Liquid Transfer Pump?

A double-diaphragm liquid transfer pump moves liquids and slurries with two opposing membranes for smoother flow and higher discharge pressure. It is used for transfer, filtration feed and dosing of particle-laden or viscous fluids.

Overview

The double-diaphragm pump uses two membrane chambers driven in opposition, so one side draws while the other discharges. Flow is smoother than a single head, and discharge pressures of 2 to 8 bar are possible depending on the model and head arrangement. Bodies are available in polypropylene, PVDF, PTFE or stainless steel, with diaphragms in PTFE, EPDM or Viton, which allows use with acids, bases and solvents. The pump is self-priming, can run dry and passes small solids without damage, since there are no close-fitting parts in the flow path. Air-driven versions need only compressed air and are suitable for hazardous areas because they have no electric motor. Applications include reagent transfer, filtration feed, sample circulation and dosing of suspensions and slurries where shear must be kept low and solids tolerated.

How does it work?

A diaphragm pump uses a flexible membrane that reciprocates inside a small chamber. On the suction stroke the membrane moves back, the inlet check valve opens and fluid fills the chamber. On the discharge stroke the membrane pushes forward, the outlet valve opens and fluid is expelled while the inlet closes. An eccentric cam or a solenoid drives the membrane, and the valves control direction. Because the fluid never contacts the drive, these pumps are oil-free and tolerate corrosive gases and liquids when the wetted parts are made from PTFE, EPDM or stainless steel. Multiple heads can be connected in series to increase pressure or in parallel to increase flow. In liquid service they are self-priming, can run dry and handle small solids. Typical parameters are flow rate, pressure or vacuum, wetted materials and number of heads.

What are the key features?

• Two opposing membranes for smooth flow
• Discharge pressure of 2–8 bar depending on model
• Body in polypropylene, PVDF, PTFE or stainless steel
• Self-priming and tolerant of small solids
• Air-driven versions for hazardous areas
• Low shear suitable for suspensions

What are the technical specifications?

A typical double-diaphragm liquid transfer pump configuration offers flow rate of 1–50 L/min, discharge pressure of 2–8 bar, suction lift of Up to about 5 m water, body material of Polypropylene, PVDF, PTFE or stainless steel, diaphragm material of PTFE, EPDM or Viton and max particle size of Up to 3 mm. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Double-Diaphragm Liquid Transfer Pump is used in reagent and solvent transfer, filtration feed, slurry and suspension dosing, sample circulation and waste liquid transfer. Across the wider Diaphragm Pumps class, laboratories also deploy it for vacuum filtration and aspiration, gas sampling and transfer and reagent and buffer transfer.

Which standards and certifications apply?

Relevant standards and methods include IEC 61010-1, IEC 61326-1, ISO 21360, ISO 9001 and GB 4793.1. Certification candidates for this model are CE, RoHS and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Install the pump so that the inlet line is short and wide, and keep the pump below the liquid level where possible to help priming. Fit a filter on the inlet to protect the valves from particles, and a trap when pumping condensable vapors. Replace diaphragms and check valves as consumables, because cracks or worn seats cause flow loss and premature failure. Clean wetted parts with compatible solvents and avoid abrasive cleaning. For hazardous gases, exhaust to a safe location. Follow IEC 61010-1 for electrical safety, and verify flow or vacuum against a reference when the pump is used in regulated methods. Record part numbers, service intervals and calibration data so that maintenance and results stay traceable.

How do I select the right Double-Diaphragm Liquid Transfer Pump?

Choose a double-diaphragm pump for particle-laden, viscous or corrosive liquids needing moderate pressure and dry-run tolerance. For precise low-volume dosing, use a metering pump. In the RFQ, state flow, pressure, solids content, material compatibility and drive preference.

How does it compare with other Diaphragm Pumps variants?

Decide first whether you need vacuum, gas transfer or liquid transfer, since the head design differs. For vacuum and aspiration, choose a diaphragm pump with adequate free-air flow and the ultimate pressure your process needs. For liquid transfer, check the maximum discharge pressure, suction lift and ability to run dry. Match wetted materials to the fluid: PTFE and EPDM suit most solvents and acids, while stainless steel or PTFE-lined heads handle aggressive media. Choose the number of heads for the required flow and pressure, and consider double-diaphragm designs for higher pressure and smoother flow. Confirm the control interface, noise level and duty cycle for continuous instrument use. Specify calibration or flow verification where the pump is part of a metering system.