How should the thickness and outer diameter of the PTFE gasket be selected for flanges of different sizes? Are there any standards?

Tetrafluoro gaskets (usually made of polytetrafluoroethylene PTFE) are commonly used corrosion-resistant and high-temperature resistant sealing gaskets, suitable for connections such as pipes and valves. The selection of tetrafluoro gaskets is usually determined by factors such as the type and size of the flange, as well as the operating conditions. The selection of the outer diameter and thickness of PTFE gaskets generally follows these principles: 1. Outer diameter: The outer diameter of the gasket should be slightly larger than that of the flange’s sealing surface, to ensure that the sealing surface is fully covered. 2. Inner diameter: The inner diameter of the gasket should be slightly smaller than that of the flange to ensure a good seal without hindering the flow of the medium. 3. Thickness: The choice of thickness is primarily determined by factors such as the roughness of the sealing surface, the material of the gasket, and the operating pressure. Generally speaking, when the flange sealing surfaces are relatively flat and smooth, a thinner gasket can be chosen ； Conversely, if the sealing surface is rougher, a thicker gasket may be required to fill in the uneven areas. Regarding standards, the selection of dimensions for PTFE gaskets can be based on the following standards: – International standards: such as ISO (International Organization for Standardization) or ASTM (American Society for Testing and Materials) standards. - **Standards: Such as China’s GB standards (GB/T 9126), the US’s ASME standards, etc. In practical applications, it is recommended to refer to specific flange standards and the manufacturer’s recommendations. Due to the diversity of working conditions, it is sometimes necessary to conduct experiments based on specific operational conditions or consult with specialized manufacturers in order to determine the most suitable gasket specifications. When selecting gaskets, other factors to consider include the type of medium, temperature, pressure, etc., to ensure that the gasket meets the requirements of the actual working environment. .

Reference standard: GB/T 9126.1-2023 Non-metallic flat gaskets for pipe flanges – Part 1: PN series