Study on Glass Fiber Reinforced Plastic Flange Connections

Abstract The new release of the Technical Instructions on Air Quality Control (TA Luft), which was published on August 18, 2021 as the first general administrative regulation to the Federal Immission Control Act, presents new challenges for operators of industrial plants in Germany, particularly regarding the control of diffuse emissions at flange connections. To address these expanded regulations, experts from several German companies have joined forces to form an interdisciplinary working group. The administrative regulation, TA Luft, requires compliance with a maximum leakage rate of 0.01 mg/(s·m) (L0.01). In order to demonstrate compliance with these requirements for glass fiber reinforced plastic flange connections (GRP), a corresponding investigation was initiated; the verification methods used were type-based component tests and computational verification in accordance with EN 1591-1. The originally planned scope of the project was the proof of leak tightness according to the requirements of the TA Luft by means of component tests based on VDI 2290 or the type-based component test described by the VCI (Association of the Chemical Industry). After failed component tests with PTFE gaskets, calculations were carried out according to EN 1591-1. The calculation method of EN 1591-1 can be applied to flange connections with circular flanges, bolts, and gaskets; consideration of non-metallic materials is not explicitly excluded. With the minimum requirements for the strength of GRP components described in DIN 16965 and EN 13121-6, strength parameters are now available for the first time that can also be used in the calculation method of EN 1591-1. For this purpose, the safety factors defined in EN 13121-3 for the GRP bundles were used in the calculation routine. The behavior of the lining materials is not considered in the calculations, but consideration of the different creep/relaxation properties would be conceivable. This paper reports on the experimental and computational investigations in this project. Although not all GRP flange systems defined in the regulations were included in the study, the results of the investigation provide important insights for the development and design of GRP flange systems that meet the stricter emission requirements of the revised TA Luft.