4 Key Factors for Choosing a Best Pump Diaphragm

Four key factors user should consider when choosing a pump diaphragm for their applications

The pump diaphragm is a key component of the diaphragm pump. It changes the volume of the pump cavity through the reciprocating movement of the diaphragm. That’s how diaphragm pumps can transmit fluid. When selecting a diaphragm in pump, users need to pay special attention to the choice of the diaphragm.

  • Material of Diaphragm for mini pump
  • The life of the diaphragm and its test conditions
  • The shape and structure of the pump diaphragm
  • Pump Diaphragm price and replacement

The following are the 4 key factors for choosing a diaphragm for pump.

Material of diaphragm for mini pump

According to different application requirements, the diaphragm in pump will be made of elastic materials. EPDM rubber (ethylene propylene diene monomer rubber) has become the most commonly used material for diaphragms, which because of its good processing properties, elasticity, price and life. However, EPDM rubber also has certain limitations, for instance corrosion resistance and high temperature resistance. Therefore, in order to meet some specific application requirements, different manufacturers have introduced different materials for miniature pumps. Such as FKM (Fluoroelastomers). FKM is also called Viton, FPM or fluorine rubber. Fluorine rubber diaphragm has better corrosion resistance than EPDM rubber. It can work at higher temperature, and has good cost economy, so it is also widely used. In recent years, PTFE-based corrosion-resistant materials have been widely welcomed in industry. It is also used in the field of enhancing the chemical compatibility of diaphragms. By covering the surface of the diaphragm with a layer of PTFE membrane, the corrosion resistance of the diaphragm can be greatly enhanced. However, as a plastic material, its elasticity and softness are worse than rubber materials. PTFE materials cannot be used on diaphragms that require high elasticity. When selecting the diaphragm material, the user should comprehensively consider the application fluid properties. Vacuum, gas pressure and flow-rate is important for a pump. The chemical composition of the medium will be another key factors. Chemical resistance are very important to select the most suitable diaphragm material.

The life of the diaphragm and its test conditions

The life of the diaphragm is the core factor that affects the life of the diaphragm miniature pumps. Pump diaphragms in the diaphragm pump will realize thousands of reciprocating movements per minute. It moves with the operation of the motor. Each movement will stretch and compress the diaphragm once. The rubber material used in the pump is subjected to such frequent movement. If it is not specially designed, fatigue will easily occur. Those fatigues will cause damage to the diaphragm and the pumps. Therefore, the manufacturer of the diaphragm pump will test the life of the diaphragm in the laboratory. The life of the diaphragm pump is generally related to its working pressure. During the life test, some manufacturers will carry out the test under low pressure load, some others may choose to test under the highest pressure. The life values of pump diaphragm​measured under different load conditions will vary greatly. Therefore, in addition to understanding the life of the diaphragm, the test conditions are also key indicators. At present, in the industry, some basic products can achieve a diaphragm life of more than millions reciprocating motions. Some manufacturers can achieve hundreds of millions of reciprocating motions under no load, while some manufacturers such as Hilintec have achieved billions of reciprocating motions under the maximum load.

The shape and structure of the pump diaphragm

The  diaphragm in mini pump is not only used to drive fluid movement, but also needs to divide the inside and outside of the pump cavity. It play a key role in fluid sealing. Only a diaphragm with good sealing performance can ensure that the diaphragm pump has good air tightness. Its structure and shape have a great influence on sealing performance. Currently in the industry, there are generally two categories, one of which is the connecting rod built-in integral diaphragm. It wraps the metal parts of connecting rod in the rubber. The rubber material itself is a whole. Its center does not have a connecting hole. The medium is in contact with the rubber of the diaphragm, so the medium cannot leak from the central connecting hole.This kind of diaphragm has good air tightness. However, it needs to wrap and embed metal parts during the vulcanization process of the rubber, which is a complicated process and high cost.

connecting-rod-built-in-integral-pumpdiaphragm
Connecting rod built-in integral diaphragm

The second structure is a split diaphragm with a hole in the center. It uses a screw to connect the upper cover of the diaphragm to the connecting rod. This structure is simple and has the advantage of low cost, but the upper cover and the screw will come into contact with the medium. This structure brings the risk of contamination and corrosion. At the same time, the medium may leak out through the screw connection hole.

split-pump-diaphragm-with-center-hole
Split pump diaphragm with center hole

Pump diaphragm price and replacement

According to the above description, the price of the diaphragm has a strong correlation with the material used. The life of the diaphragm, and the structure of the diaphragm itself also affect product prices. Different manufacturers have different strategies on whether to provide diaphragm replacement kits. The different strategies adopted are mainly related to the repair service and life span. For example, some manufacturers can promise that the diaphragm pump motor can run continuously for 2 years, but the life of the diaphragm can work stably for one year under heavy load. In this case the user needs to replace the diaphragm in the middle of the pump life-time. When the diaphragm life is greater than or equal to the pump motor and other parts, the manufacturer generally chooses not to provide a diaphragm replacement kit.

The above are the four key factors for choosing a diaphragm for a pump. When selecting a diaphragm in diaphragm, the user will also conduct a comprehensive assessment of the medium temperature, surface treatment and cooperation with the pump. If you have other information that needs to be added, or any questions, you can also contact us. We are very happy to discuss with you about the technical issues of the diaphragm pump.