Ring-Joint Facings Dimensions - Class 150 to Class 2500

Ring-Joint Facings is a common kind of flange sealing surface. Ring-joint facings flange, also a narrow flange, has a ring trapezoid cut out on the protruding surface of the flange as the flange sealing surface. This flange must be separated axially during installation and removal. The ring-joint facings is specially designed to fit with metal gaskets with octagonal or circular shape processed by metal materials. It also has low installation requirements and is suitable for high temperature and pressure situations. However, the machining precision of sealing surface is high. Ring-joint facing is mainly used on butt-welded flange with neck and integral flange, and the applicable pressure range is 6.3MPa-25.0MPa.

The Flange Sealing Surface 

• Raised Face(RF)

• Flat Face(FF)

• Male/Female Face(M/FM)

• Tongue-Groove Face(TG)

• Ring-Joint Face(RJ)

The type selected varies depending on the working condition, medium, pressure, specification, temperature, and other conditions.

Technical Drawings of Ring-Joint Facings

Requirements for Ring-Joint Facings in ASME B16.5 Standard

1. Class 150 and 300 pipe flanges and companion flanges of fittings are regularly fur nished with 2 mm (0.06 in.) raised face, which is in ASME B16.5-2009 addition to the minimum flange thickness, tf. Classes 400, 600, 900, 1500, and 2500 pipe flanges and companion flanges of fittings are regularly furnished with 7 mm(0.25 in.) raised face, which is in addition to the minimum flange thickness, tf.

2. For flanges that have a ring joint, groove, or female face, the minimum flange thickness shall first be provided and then sufficient thickness added thereto so that the bottom of the ring joint groove, or the contact face of the groove or female face, is in the same plane as the flange edge of a full thickness flange.

3. The thickness of the lap remaining after machining the ring groove shall be no less than the nominal wall thickness of pipe used.

4. A distance of at least four times the maximum radial projection shall separate adjacent imperfections. A radial projection shall be measured by the difference between an outer radius and inner radius encompassing the imperfection where the radii are struck from the centerline of the bore. Imperfections less than half the depth of the serrations shall not be considered cause for rejection. Protrusions above the serrations are not permitted.

Common Factors Affecting Flange Seals

• Effects of operating conditions. The operating conditions are pressure, temperature and the physicochemical properties of the medium. In petrochemical plants, there are many low pressure flanges, and the influence of pure pressure or medium factors on flange leakage is not main. The problem only becomes serious when combined with temperature. Seals are more likely to fail when the temperature changes repeatedly.

• The influence of gasket coefficient and compression ratio in design parameters. Gasket coefficient and compression ratio, even for the same material, are also related to factors such as gasket width, preload, media properties, flange sealing surface width and roughness.

• Effect of bolt pretension. Increasing bolt pretension can increase gasket sealing performance, but excessive bolts and elves can cause gasket to lose elasticity, even crush gasket or foundation, which can not guarantee sufficient elasticity in operation.

• Effect of gasket performance. Gasket deformation includes elastic and plastic deformation. Gasket material is the main factor affecting gasket performance, so the quality of gasket will affect the seal of flange.

• Effect of flange stiffness. Insufficient flange stiffness can cause excessive warpage deformation, which is often one of the reasons for seal failure.

• Effects of sealing surfaces. The shape and roughness of the flange sealing surface shall be compatible with the gasket. Flatness of sealing surface and perpendicularity of sealing surface to flange axis are prerequisites for uniform gasket compression, so reasoning or eccentric force caused by thermal expansion of pipeline must be considered in design and installation.

Dimensions of Ring-Joint Facings - Class 150 to Class 2500