Small diaphragm pumps—How to choose the diaphragm?

small diaphragm pumps

Small diaphragm pumps rely on the reciprocating motion of the diaphragm in the small diaphragm pumps body to inhale and discharge gas. Therefore, the diaphragm is a very important component of the pump body. Its performance has a great impact on the small diaphragm pumps. The life of the diaphragm is mainly reflected in several aspects, including bending life, Corrosion resistance, high and low temperature resistance. Therefore, the range of diaphragm materials that must meet the above requirements has been greatly reduced. Currently, the following rubbers are most commonly used and mature in the diaphragm industry: EPDM, PTFE, FKM, NBR, etc.

1.EPDM (ethylene propylene diene rubber) for small diaphragm pumps

EPDM rubber is a copolymer of ethylene, propylene and a small amount of non-conjugated diene. The main chain is composed of chemically stable saturated hydrocarbons. It is a commonly used rubber with the lightest raw rubber density.

Performance characteristics:

Aging resistance: ozone resistance, UV resistance, and other aging properties. When copolymerized with other unsaturated dienes, the oxidation resistance and anti-aging are significantly improved.

Chemical resistance: good resistance to weak acids, alkalis, alcohols, and ketones; excellent water and water vapor resistance, radiation resistance;

Insulation: high volume resistivity and breakdown voltage of 30-40MV/m, which can effectively reduce the effects of static electricity caused by friction;

Applicable temperature: minimum operating temperature -40~-60℃, can be used under 130℃ for a long time. (The diaphragm material can be used at this temperature, but it does not mean that the small diaphragm pumps can also be used at this temperature. The operating temperature of the small diaphragm pumps are comprehensively affected by other components such as the motor, diaphragm, and cavity material)

Application fields: It is widely used in automobile parts, building materials, seals and other fields.

2.PTFE (polytetrafluoroethylene) for small diaphragm pumps

Polytetrafluoroethylene, also known as “Teflon“, is a polymer compound made of polymerized tetrafluoroethylene. It is one of the best corrosion-resistant materials in the world today.

Performance characteristics:

Aging resistance properties: non-hygroscopic, non-flammable, extremely stable to oxygen and ultraviolet rays, and has excellent weather resistance;

Chemical corrosion resistance: It can withstand aqua regia and most organic solvents. Even if it is boiled in aqua regia, its quality and performance will not change. It has excellent corrosion resistance, but it is not resistant to radiation. It can easily cause degradation after radiation. Polymers The electrical and mechanical properties have significantly declined, so the diaphragm used in the exhaust gas sampling small diaphragm pumps of the nuclear power plant is mainly made of EPDM;

Insulation: High breakdown voltage, volume resistivity, and arc resistance, making it an ideal insulating material; Applicable temperature: Maintaining excellent mechanical properties within a wide temperature range of -196 to 260°C, and does not work well at low temperatures becomes brittle but still maintains good flexibility;

Volume deformation rate: It is a typical soft and weak polymer. The mutual attraction between macromolecules is small, the stiffness, hardness, and strength are small. It will deform under long-term stress.

Note: According to the list of carcinogens from the World Health Organization’s International Agency for Research on Cancer, polytetrafluoroethylene is a Category 3 carcinogen, which means its carcinogenic effect on humans is not yet known. It is recommended to take protective measures when using or coming into contact with such materials.

Application areas: In the petrochemical and metallurgical industry, pipes, small diaphragm pumps, valves and other equipment that require anti-corrosion are widely used. As coatings and impregnation materials, it is widely used in textile, medical, chemical, electrical and other fields.

3.FKM (fluorine rubber) for small diaphragm pumps

Fluorine rubber is polymerized into a polymer material by containing fluorine atoms in the carbon bonds of the main chain or side chain. There are many derivatives of fluorine rubber with widely different properties. This type of material can be seen in all walks of life.

Performance characteristics:

Aging resistance: excellent weather resistance, can be used for a long time in environments with high ozone concentration;

Chemical corrosion resistance: relatively stable chemical properties, resistant to most organic and inorganic solvents, and most petroleum-based oils, but not resistant to low-molecular ketones, ethers, esters, ammonia, etc.;

Not resistant to radiation, easily cracked after irradiation, and the structural strength is significantly reduced;

Insulation: low hygroscopicity, good insulation;

Applicable temperature: Resistant to a certain high temperature, can still maintain high mechanical strength at 200°C; but has a certain volume deformation;

Application areas: used as seals in the chemical industry, can be used to seal various organic solvents, used as insulation materials for wires and cables in the petrochemical industry, have high oil resistance and wear resistance, and are also widely used in the automotive engine industry.

Our diaphragm types:

The diaphragms of our air small diaphragm pumps and liquid small diaphragm pumps are mainly made of EPDM, which has good tolerance to low-corrosive, weak acid and weak alkali media. When pumping media with serious corrosion or needs to meet the specified anti-corrosion level, it is recommended to use For PTFE diaphragms, FKM material diaphragms can also be customized according to needs for special media. For customization requirements and procedures, please contact our sales manager for details.

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