Présentation
RÉSUMÉ
Les assemblages à brides boulonnées sont largement utilisés dans les installations industrielles mettant en œuvre des fluides sous pression, notamment dans les secteurs du nucléaire, de la pétrochimie, du forage offshore ou encore de l’industrie navale. Leur rôle est d’assurer simultanément la continuité structurelle du circuit et l’étanchéité de la barrière de pression. La maîtrise de ces assemblages repose sur l’interaction entre trois composants principaux : les brides, le joint d’étanchéité et la boulonnerie. Cet article présente les caractéristiques essentielles de ces composants, leurs fonctions respectives et les principes permettant d’assurer leur compatibilité dans la conception des liaisons étanches. Il introduit également la logique de maîtrise du serrage et la méthode TBSS (Tight Between Seal and Strength). Il constitue le premier volet d’une série consacrée aux assemblages à brides boulonnées.
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Lire l’articleAuteur(s)
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Simon PLANCHE : Head of the Inspection and Regulatory Affairs Department (SIR) - EDF SA, Golfech Nuclear Power Plant, Golfech, France
INTRODUCTION
Bolted flange assemblies are widely used in many demanding industrial sectors, including nuclear facilities, petrochemicals, offshore drilling, and the shipbuilding industry. They are frequently integrated into systems that handle pressurized, high-temperature, cryogenic, or potentially hazardous fluids.
In these environments, a loss of seal integrity in a joint can have significant consequences. Failures can manifest in various forms, ranging from a simple leak to more severe phenomena, such as gasket extrusion, bolt ejection, or flange rupture. Mastering these assemblies is therefore a major industrial challenge, both to ensure the safety of people and the protection of the environment and property, and to guarantee the availability and performance of the facilities.
The operation of a bolted flange joint relies on applying the proper tightening torque to the bolts, which generates sufficient contact pressure on the gasket to ensure the joint is leak-tight. However, such a joint cannot be considered a simple juxtaposition of independent components. The flanges, gasket, and bolts constitute a mechanical system in which the components interact closely. The overall performance of the joint therefore depends on their combined behavior.
With this in mind, this article presents the main components of a bolted flange assembly and describes their essential characteristics. The objective is to provide designers with the necessary information to guide the selection of flanges, gaskets, and fasteners based on operating conditions and the characteristics of the fluid to be contained.
This overview serves as a first step toward understanding the fundamental principles of bolted flange assemblies. Subsequent articles in this series will address the mechanical modeling of these assemblies as well as methods for determining clamping force, particularly using the TBSS (Tight Between Seal and Strength) method.
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4. Bolts
Bolts are the essential component through which preload is applied in a bolted flange assembly. They maintain the contact pressure of the gasket, which is essential for ensuring a leak-tight seal during operation. The bolting system consists of various components, each of which plays a specific role.
4.1 Overall Role of Bolts
Bolts and fasteners are the set of components through which clamping force is applied and controlled (screws, studs, nuts, and washers). They are what generate the preload necessary for the seal and the mechanical integrity of the assembly.
From an operational standpoint, it is the element on which the operator acts: it is through these components that preload is generated in the assembly, an essential condition for ensuring sealing and mechanical strength. From a functional standpoint, the role of the bolted joint is to develop sufficient tensile stress and maintain it over time despite the effects of creep, thermal expansion, or vibrations, thereby ensuring the reliability of the assembly. Finally, from a mechanical standpoint, threaded rods (see §4.2.1) behave like a spring: they store the energy from tightening and release the force in response to load variations caused by internal pressure, thermohydraulic cycles, or dynamic stresses. Through these various functions, fasteners serve as the active interface between the assembled parts and determine the desired balance between sealing performance, mechanical strength, and the durability of the assembly.
HAUT DE PAGE4.2 Bolt Assembly Components
The selection of fastener components can be based on standards EN 1092-1, EN 1759-1 and EN 1515-1.
HAUT DE PAGE4.2.1 Threaded rods
There are several types of threaded rods: screws, studs, and tie rods.
A screw consists of a threaded shank and a head. The head allows the tightening torque to be transmitted by the tool, while the shank transmits the tensile force. The use of screws offers the advantage of minimizing space requirements and simplifying the design, particularly...
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Bolts
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BIBLIOGRAPHIE
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(1) - LAMONS® - Gasket & fastener handbook, a technical guide to gasketing & bolted flanges - . – (2016).
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(2) - LEFRANÇOIS (M.) - Metal-to-metal seals : the innovative route in static sealing - . – (2004).
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(3) - PLANCHE (S.) - Assemblages à brides boulonnées – Modèle et calcul mécanique. - [BM 5 572] (2026).
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(4) - PLANCHE (S.) - Assemblages à brides boulonnées – Méthode TBSS (Tight Between Seal and Strength). - [BM 5 573] (2026).
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(5) - LEJEUNE (H.), OMNES (B.) - Étanchéité en mécanique – Étanchéité aux liaisons statiques. - [BM 5 418] (2023).
NORMES
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Flanges and Their Assemblies – Circular flanges for pipes, valves, fittings, and accessories designated PN – Part 1: Steel flanges. - NF EN 1092-1 - 2018
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Flanges and their assemblies – Circular flanges for pipes, valves, fittings, and accessories, designated Class – Part 1: Steel flanges, NPS ½″ to 24″. - NF EN 1759-1 - 2005
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Metal products – Types of inspection documents. - NF EN 10204 - 2005
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Flanges and Their Assemblies – Gasket specifications and test procedures related to design rules for circular flange assemblies with gaskets. - NF EN 13555 - 2014
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Flanges and Their Assemblies – Bolting – Part 1: Selection of bolting. - NF EN 1515-1 - 2000
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Flanges and Their Joints – Bolts – Part 2: Classification of bolting materials for steel flanges, designated PN. - NF EN 1515-2 - 2002
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