Non-metallic expansion joints (also known as non-metallic compensators) are commonly used to absorb thermal expansion, contraction, vibration, or displacement in piping systems, particularly in applications such as chemical, petrochemical, power, and exhaust gas treatment. They are made from flexible materials such as rubber, fluoroplastics, silicone, or fabric composites to accommodate high temperatures, corrosive media, and high pressure environments. Flanges are critical components for connecting non-metallic expansion joints to piping systems.
When designing flanges for non-metallic expansion joints, the following factors need to be considered:
Standards and Specifications：
The design of flanges shall comply with relevant international standards, such as ASME B16.5, DIN 2533/2536 or ISO 7005-1, etc., to ensure compatibility and safety with the pipeline system.
The nominal diameter (DN), pressure Class (PN or Class) and material specifications of the flange need to be confirmed.
Material selection：
The flange material should be matched to the environment in which the expansion joint is used, including temperature, pressure, and media characteristics. Commonly used materials are carbon steel, stainless steel, alloy steel, etc.
Considering the nature of the non-metallic expansion joint, the flange material should have good corrosion resistance and sufficient strength.
Type of sealing surface：
According to the requirements of the pipeline system, the sealing surface of the flange can be RF (convex surface), FF (flat surface), FM/MF (concave and convex surface), TG (tongue and groove surface) or RJ (ring connection surface), etc.
Bolt hole distribution：
The number and distribution of bolt holes shall be determined according to the size and pressure class of the flange, ensuring even force distribution and tightening.
Gasket fit：
Choose suitable gasket materials, such as graphite, PTFE, metal wound pads, etc., to guarantee good sealing performance.
Installation and operating conditions：
The design should take into account the installation space, weight, maintenance requirements, and the displacement range of the expansion joint during operation.
Manufacturing and Inspection：
The flanges shall be manufactured in accordance with quality control standards, with necessary non-destructive testing (NDT) such as magnetic particle testing, penetration testing or ultrasonic testing, and pressure testing.
Marking and Identification：
Each flange shall be clearly marked including size, material, pressure class, lot number and manufacturer information for easy traceability and identification.
Designing the flange of a non-metallic expansion joint is a complex process, which requires comprehensive consideration of many factors to ensure that the expansion joint can operate safely and reliably in the intended application environment.