Things to consider when choosing diaphragms

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Regarding the selection of diaphragms: Isolation diaphragms, when installed in conventional measuring instruments, help to address issues such as corrosion and clogging, thereby maintaining the accuracy and sensitivity of those instruments and extending their service life. During each maintenance session, only a new diaphragm needs to be replaced, **reducing the amount of work required for repairs. However, if the diaphragm material is not selected properly, it can cause the device to stop operating, leading to safety accidents. Below, the editor has compiled several suggestions regarding the selection of diaphragms; take a look~ 1. EPDM is suitable for sanitary applications where the operating temperature does not exceed 100°C. EPDM stands for Ethylene-propylene-diene monomer; its key features include excellent elasticity, resistance to oxidation, ozone, and corrosion. This type of diaphragm is suitable not only for polar substances and steam but also for hot water, cold water, alkaline media, and non-concentrated acids. EPDM does not have as wide a temperature range as PTFE; it is suitable for sanitary applications where the operating temperature does not exceed 100°C. For example, a purified water system. It should be noted that EPDM swells in the presence of organic substances; therefore, it is not recommended to use EPDM membranes in environments involving mineral oils, vegetable and animal fats, aliphatic or aromatic hydrocarbons, furnace solvents, or concentrated acids. 2. FKM is suitable for environments with high temperatures and high chemical stability. FKM is an abbreviation for fluororubber, referring to synthetic polymer elastomers in which carbon atoms in the main chain or side chains contain fluorine atoms. In addition to the high elasticity characteristic of rubbers, the incorporation of fluorine atoms endows fluororubbers with excellent properties such as heat resistance, oxidation resistance, oil resistance, corrosion resistance, and resistance to atmospheric aging. 3. PTFE is suitable for low- and high-temperature environments. Polytetrafluoroethylene (PTFE) is a fluoropolymer synthesized from vinyl fluoride, and it belongs to the category of fluoroplastics. The chemical inertness of PTFE prevents cross-linking; as a result, it has no \"memory,\" meaning it cannot return to its original shape like elastomers. This material undergoes creep and deformation under tension, a phenomenon known as \"cold flow.\" PTFE has a wide operating temperature range of (-200 to 260°C), and it possesses excellent properties such as resistance to compression, corrosion resistance, no aging issues, resistance to moisture and ultraviolet rays, and non-toxicity. A pure PTFE diaphragm will undergo significant deformation at temperatures above 130°C, resulting in its distortion and damage. 4. EPDM/PTFE composite diaphragms are widely used in high-temperature, sanitary applications such as water for injection or pure steam. As shown in Figure 3.135, these composite diaphragms effectively address the issues related to temperature resistance and toughness associated with PTFE; they possess both the high elasticity of EPDM and the corrosion resistance of PTFE. In the biotechnology and pharmaceutical industries, only EPDM and PTFE (TFMTM) are available as materials of choice; currently, only these two materials have obtained FDA approval and meet the various requirements of this industry. TFMTM is a second-generation improved version of PTFE; it possesses better diffusivity than traditional PTFE and has become the standard for some manufacturers. 5. The diaphragm is in direct contact with the working medium; before selecting a diaphragm material, a specific analysis of each application should be conducted. During the operation of the same device, different operating conditions often arise, which necessitates the use of various types of diaphragms made from different materials. The chemical properties of the medium and temperature can both lead to different interactions; the suitability of the products used must be determined through a product compatibility list or separate testing by quality experts. Only by going through this process can the equipment operate safely, cost-effectively, and for a long time.