Technical points of silicone sealing gasket for industrial equipment

1、 Material adaptation requirements 1. Safety and compliance matching The compliance of silicone sealing gaskets for industrial equipment is a prerequisite for selection, and different application scenarios require corresponding compliance standards, which should not be mixed arbitrarily. The sealing of equipment that comes into contact with food must comply with FDA 21 CFR 177.2600 and China's GB 4806.11-2016 standards. The sealing of medical equipment must meet ISO 10993 biocompatibility requirements. The sealing of outdoor chemical equipment must comply with RoHS 2.0 and REACH SVHC high concern substance restrictions. The sealing gasket for conventional industrial scenarios can be made of ordinary methyl vinyl liquid silicone, while special scenarios require additional modification of the material, such as adding fluorine modified groups for oil resistant scenarios, adjusting crosslinking density for high and low temperature resistant scenarios, and adding specific reinforcing fillers for low compression permanent deformation scenarios. Compliance verification requires the supplier to provide corresponding third-party testing reports, and hazardous substance sampling and review must be conducted before batch feeding.

2. Use performance adaptation The performance parameters of silicone sealing gaskets for industrial equipment need to be accurately matched with the equipment operating conditions, and the core matching parameters are concentrated in the following dimensions: Hardness: Conventional static seals use Shore A at 40-60 degrees, dynamic reciprocating seals use Shore A at 60-70 degrees, and high-pressure seals can be increased to Shore A at 70-80 degrees Temperature range: Ordinary LSR can work in an environment of -40 ℃~200 ℃ for a long time, while specially modified phenyl silicone can be extended to -60 ℃~250 ℃ Medium resistance: Fluorine modified silicone gel should be selected for contact with mineral oil and acid-base media to avoid short-term swelling failure Compression permanent deformation is a core parameter that affects the sealing life. The compression permanent deformation of high-quality industrial grade silicone (GB/T 7759.1125 ℃× 22h) can be controlled within the range of 15%~25%. The lower this value, the better the resilience of the gasket after long-term compression, and the higher the sealing reliability. During the selection stage, it is necessary to clarify the three core operating conditions of the equipment: pressure range, temperature fluctuations, and contact media, in order to avoid cost waste caused by parameter interference or early failure caused by insufficient parameters.

2、 Core manufacturing process 1. Selection of molding process The molding process of silicone sealing gaskets for industrial equipment needs to be selected according to the order quantity and dimensional accuracy requirements. The current mainstream processes are divided into two categories: compression molding and liquid silicone (LSR) injection molding. The adaptation scenarios of the two types of processes are significantly different: Process type, applicable size range, accuracy tolerance, suitable batch size Mold forming inner diameter of 50~500mm ± 0.10~± 0.20mm for small and medium-sized batches (up to 10000 pieces) LSR injection molding with an inner diameter of 5-300mm ± 0.05~± 0.15mm for large quantities (over 10000 pieces) For precision industrial sealing gaskets with complex cross-sections and positioning slots, LSR injection molding has better consistency and can achieve automated shearing gates, reducing dimensional deviations caused by manual trimming. For large-sized low-pressure sealing gaskets, the mold cost for molding is lower and the overall cost-effectiveness is higher. During the molding process, it is necessary to control the vulcanization temperature and cross-linking time to avoid insufficient hardness caused by under sulfur or material brittleness caused by over sulfur.

2. Mold accuracy control The dimensional accuracy of silicone sealing gaskets for industrial equipment is completely determined by the precision of the mold, especially the cross-sectional tolerance of gaskets used for dynamic sealing, which directly affects the matching of sealing gaps. The conventional precision sealing mold adopts S136 pre hardened mold steel, and the cavity is processed by CNC precision machining and mirror discharge treatment. The dimensional tolerance of the cavity needs to be controlled within IT7~IT8 levels, and the corresponding dimensional deviation should not exceed 1/3 of the part tolerance. The position design of the mold parting line can also affect the sealing performance: the parting line of the static sealing gasket should be set on the non-contact sealing surface to avoid the parting line flying edge scratching the equipment installation surface and causing leakage; The parting line of the dynamic sealing gasket should avoid the friction contact surface to reduce wear during long-term reciprocating motion. Before mass production, 3-5 trial molds need to be made, and only after passing the full-size inspection can they be put into mass production. For every 100000 molds produced, a cavity size re inspection is required to promptly correct wear deviations.

3、 Key points of quality verification 1. Sealing performance test The silicone sealing gasket for industrial equipment must undergo sealing performance sampling before leaving the factory. The core testing is divided into two categories: static leakage testing and dynamic performance testing. The static test adopts the pressure holding method. The gasket is installed in the standard testing fixture, and compressed air or water with 1.2 times the rated working pressure is introduced. After holding for 30 minutes, the pressure drop is detected. The qualification requirement is that the pressure drop does not exceed 2% of the initial pressure and there is no visible external leakage. For sealing gaskets used in dynamic reciprocating motion scenarios, additional friction coefficient testing and reciprocating life pre testing are required. The friction coefficient should be controlled within the range of 0.2~0.4 (under dry friction conditions), and there should be no obvious cracks after 10000 reciprocating motions, with wear not exceeding 5% of the cross-sectional size. The gasket in the food and medical scene also needs to undergo immersion precipitation testing to verify that there is no soluble harmful substance precipitation after contact with the medium.

2. Verification of lifespan aging The hot air aging test is the core method for verifying the service life of silicone sealing gaskets in industrial equipment. It is carried out in accordance with the GB/T 3512 standard, and the conventional testing conditions are 150 ℃ × 72h. After the test, the performance change rate is detected Hardness variation: not exceeding ± 5 Shore A Tensile strength change rate: not exceeding ± 20% Change rate of elongation at break: not exceeding ± 30% For gaskets used outdoors for a long time, ozone aging resistance testing and UV aging testing should be supplemented. After ozone aging (50pphm, 40 ℃ × 100h), the sample should not crack, and after UV aging for 1000 hours, the change in Shore A hardness should not exceed 6 degrees. In mass production, 3-5 pieces are selected from each batch for aging verification. Only when the performance meets the requirements can they be released from the factory to avoid batch material performance failure.

4、 Summary and Prospect The silicone sealing gasket for industrial equipment may seem like a small basic component, but deviations in material selection, manufacturing accuracy, and quality verification can directly affect the overall operational reliability of industrial equipment. For equipment manufacturers, it is necessary to first clarify their own operating requirements, match materials with corresponding compliance levels and performance parameters, and then select appropriate molding processes based on batch requirements, and control risks through standardized quality verification processes. With the development of industrial equipment towards high reliability and long maintenance cycles, silicone sealing gaskets for industrial equipment will move towards low compression permanent deformation, customized modification, and high-precision molding in the future. The adaptability of materials and processes will become the core direction to improve sealing reliability, and manufacturing manufacturers also need more refined technical control to match downstream demand upgrades.