Leakage-cause analysis of a flange joint designed according to standards

Abstract

Flange joints and their sealing play an important role in many industries. The gasket performance and its behaviour are influenced by a number of factors, such as non-linear material properties with permanent deformations, assembly procedures and the preparation of sealing surfaces. Additionally, a proper seal function is also affected by the design and strength design of the flanges. Determination of the respective tightening torque needed to achieve a suitable contact pressure between the seal and the flange face is equally important. This paper deals with finite element method (FEM) analyses of a flange joint designed in accordance with the modern standard EN 13445-3 Annex G and examines the influence of operating conditions on the gasket contact pressure. The article also discusses the effects of assembly on the tightness of the joint and the reason for the leakage of the operating medium that took place. The analyses show the effects of operating states on the contact pressures of gaskets and the pre-stressing of bolts. They demonstrate the contact pressure after the application of the pre-stressing of the bolts and its reduction after the temperature-field stabilization due to the start-up of the device. The results of the analyses show that only a relatively small surface of the seal achieves the compression required by the manufacturer to maintain the seal integrity during the application of the tightening forces determined in accordance with EN 13445-3 Annex G. The force of the pre-stressing of the bolts is reduced by approximately 6 % when the normal operation condition is reached. The analyses were performed due to a suspicion of a significant influence of the temperature distribution on flange joints. The main cause of the flange leakage was subsequently revealed by a physical inspection that demonstrated assembly failures when installing gasket 2. The description of these deficiencies is not a subject of this article. Keywords: flange joint, sealing, gasket, FEM, contact pressure Spoji prirobnic in njihovo tesnenje igrajo pomembno vlogo v mnogih industrijskih vejah. Lastnosti tesnila in njegovo vedenje je odvisno od mnogih faktorjev, kot so: nelinearne materialne lastnosti s stalno deformacijo, kakor tudi postopek namestitve in tesnilna povr{ina. Dodatno je pravilno tesnenje odvisno tudi od oblike in trdnosti prirobnice. Prav tako je pomembna dolo~itev tesnilnega navora za doseganje primernega kontaktnega tlaka med tesnilom in povr{ino prirobnice. V~lanku avtorji opisujejo analizo spoja prirobnice s pomo~jo metode kon~nih elementov (FEM; angl.: Finite Element Method), ki je oblikovana v skladu z modernim standardom EN 13445-3 Annex G in preiskuje vpliv delovnih pogojev na kontaktni tlak tesnila. V~lanku avtorji prav tako razpravljajo o vplivih monta`e na tesnost spoja ter podajajo mo`ne razloge za pu{~anje delovnega medija. V analizi so pokazali, kak{en je vpliv obratovalnih pogojev na kontaktni tlak tesnila in prednapetost pritrdilnih vijakov. Analiza je pokazala, kak{en je kontaktni tlak po predob...

Identification of the piston machine combustion chamber tightness

“…Flange joint sealings have been examined by various authors (e.g. Lošák et al , 2018; Jaszak, 2019).…”