Bolted joints are one of the most common elements in piping design and serve as critical components in piping systems. When bolted flanged joints are used, bolted connections keep flanges together and avoid flange leakage problems. To ensure this important bolted connection, ASME PCC-1-2022: Guidelines For Pressure Boundary Bolted Flange Joint Assembly provides the procedure for bolted flange joint assembly.
What Is a Bolted Flange Joint (BFJ)?
A bolted flange joint (BFJ) is a joining mechanism to maintain a clamping force between two pipes or pipe to equipment. Materials in a BFJ include flange joints, lubricants, threaded fasteners (bolts/studs, nuts, and washers), and gaskets. The goal of a BFJ is to create a tight-leak sealing load on the gasket material. Typically BFJs are used for aboveground service for water, wastewater, air, oil, and other liquids where rigid, restrained joints are needed in pressure containing equipment like pressure vessels and pipes.
What is ASME PCC-1-2022?
ASME PCC-1-2022 covers the assembly elements that are essential in ensuring a high level of leak-tightness integrity of properly designed and constructed bolted flange joint assemblies (BFJAs). Specifically, the standard defines BFJAs as those applied to pressure-boundary flange joints with ring-type gaskets that are entirely within the circle enclosed by the bolt holes and have no contact outside this circle.
Users of ASME PCC-1-2022 should develop written assembly procedures based on the requirements of the owner—the entity responsible for the leak tightness of BFJAs on their pressure equipment. Moreover, the standard applies to the owner, owner’s representative, manufacturer, fabricator, erector, or other contract personnel.
How Does a Bolted Flange Joint (BFJ) Work?
The main function of the bolts in a BFJ is to transfer the energy of the loading mechanics into a clamping force that ensures the BFJ reliably operates. Both the bolt load and clamping load are important in ensuring a BFJ works:
- Bolt load: the load in the bolt, which must be able to overcome resistances, such as hydraulic load and friction, changes in bolt and gasket characteristics, and uncertainties during the tightening process.
- Clamping load: the compressive load on the gasket material.
The bolted flange joint (BFJ) works by inducing a primary clamping force (preload) on the joint. The preload ensures that the clamped parts remain in compression, and it is done by either threading the fastener into a nut or into threads. The nut factor is dependent on lubrication, bolt material, bolt diameter, bolt and nut coating, and assembly temperature.
ASME PCC-1-2022: Guidelines For Pressure Boundary Bolted Flange Joint Assembly is available on the ANSI Webstore.