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Diaphragm Pump Technology

Learn about the Gas and Liquid Diaphragm Pumps and Compressors

Diaphragm Working Principle

Gas Diaphragm Pumps and Compressors

Technical Overview

Diaphragm pumps are a type of positive displacement pumps. A flexible diaphragm in the pump head is moved up and down via the conrod and through the action of an eccentric on the motor shaft.

On the downstroke, the medium is drawn into the pump chamber and expelled on the upstroke. Internal valves mounted within the pump head function as check valves and control the direction of flow.


Gas Diaphragm Pumps
Equally suitable for use as a vacuum pump or compressor, they are characterized by low sound level, high efficiency and gas tightness. Models are available with AC or DC drive. They are available in single and multiple head models, which can be configured in series or parallel, with vacuum to 1 mbar abs, pressure to 3,0 bar and flow rate in the range from 0,3 to 90 liters per minute.

Most of Thomas’s diaphragm pump product lines feature several motor options ranging from low cost DC up to brushless DC solutions. The sealed air path is inherent to the design itself. Chemical resistance is addressed with different pump head and elastomer materials such as PPS (Ryton) or FKM (Viton). Other attributes include operational water vapour tolerance, working point controllability and a very good size to performance ratio.

Typical applications profiting from above mentioned features are handheld or portable gas detectors and analyzers. Here, leak tightness and chemical resistance comes into play. Dental autoclaves or Negative Pressure Wound Therapy (NPWT) rely on pump controllability, a low sound level or pump lifetime and efficiency due to brushless DC configurations. Various laboratory applications or wherever efficient, compact vacuum pumps or compressors are required round off target applications.


Gas Diaphragm Pumps Technology Benefits

  • Suitable for pressure and vacuum or combined
  • Gas tightness to the outside
  • Durable plastic or corrosion resistant coated aluminum
  • Long-life diaphragms
  • Balanced for low vibration
  • Low noise level
  • Permanently lubricated bearings
  • Flow rates up to 3.2 cfm (91 l/min), end vacuum 29.2 in.Hg (-990 mbar), pressure 44 psi (3.0 bar)

Liquid Diaphragm Pumps

Technical Overview

Diaphragm pumps for gases and fluids might look very similar on the outside. Due to the contrary nature of gases and liquids, significant differences in the construction of pumps for both types of media can be seen.

The main impact on pump design is that liquids cannot be compressed and therefore create higher forces on the pump components and inducing pulsation. This leads to pump designs with smaller diaphragm strokes, stiffer diaphragm materials and more robust bearings.


Liquid Diaphragm Pumps
Thomas is one of the few manufacturers of dedicated liquid diaphragm pumps. Flow rates are ranging from 0.18 to more than 1.8 liters per minute and operating pressures up to 6 bar. Similar to our gas diaphragm portfolio single head and multiple head configurations can be offered depending on the flow requirements as well as an extensive range of brushed and brushless DC motors.

Pressure pulses are a common problem in positive displacement pumps for liquids. In order to reduce those pulses an additional resonating diaphragm is implemented in our pumps to allow more gentle pumping of fluids. This also reduces the effect of cavitation and air bubble formation.

Liquid diaphragm pumps are remarkably robust and made for heavy-duty applications. They offer long-term suitability with high media temperatures, and superior resistance to chemical or mechanical damage by fluids. Depending on the type of liquid, you can choose pump components in the most suitable material, such as EPDM, FKM, PTFE or FFKM.

Liquid diaphragm technology stands out due to its excellent ratio between cost and pump lifetime. This makes it the prime solution for applications requiring continuous operation without the need of maintenance. With the range of brushless DC motors (BLDC) lifetimes of over 10,000 hours can be achieved with liquid diaphragm pumps.

Many applications benefit from liquid diaphragm pump. For example digital inkjet printers use liquid diaphragm pumps for ink handling. Digital inkjet printer manufacturers rely on the resistance against aggressive inks as well as the ability to gently move inks for up to 2 years without maintenance. Diagnostic equipment (IVD) such as hematology analyzers require pumps for cleaning the fluid handling system. In these applications pumps need to operate with high pressure levels or need to aspire residue liquids in a fast and thorough way.


Liquid Diaphragm Pumps Technology Benefits

  • The highest pressure capacities and highest chemical compatibility among all pump technologies
  • Provides smooth flow and minimized pulses
  • Deliver bubble-free transfer of media
  • Self-priming pumps
  • Flow rates up to 0.064 cfm (1.8 l/min), maximum suction height up to 10 m H2O,and max pressure height up to 40 m H2O,

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