How many types of flange faces
The process of flange facing (or flange refacing) involves the machining of flange mating surfaces so that they they produce a tight, leak-proof seal when assembled.
The frequently used term “flange face” refers to the shape of the flange surface area (i.e., the area where the gaskets are positioned and the two mating flanges are tightened). When making a flanged connection, operators should use two flanges with the same type of face, and never mate flanges with different surface areas, such as a flat face with a raised face or a ring joint with a male and female (in this case, the joint would not seal properly and leak).
Industry standards for flange facing
The American Society of Mechanical Engineers (ASME) are the go-to organisation for many standards for mechanical engineering around the world. They have the set the standards to which many engineers work to for flange facing surface finishes.
ASME set the standards for flange face surface finish types through the ANSI accredited ASME Standard B 16.5 ensuring all gasket and flange fittings are consistent and fit for purpose allowing a high quality seal.
Different types of flange faces are used as the contact surfaces to seat the sealing gasket material. ASME B16.5 and B16.47 define various types of flange facings, including the raised face, the large male and female facings which have identical dimensions to provide a relatively large contact area. The ASME B16.5 and ASME B16.47 norms mention a few different types of flange face types:
- Flat face (“FF”)
- Raised face (“RF”)
- Ring joint (“RTJ”)
- Lap joint
- Male and female (“M&F”)
- Large and small tongue-and-groove (“T&G”)
FLAT FACE FLANGE (FF)
RAISED FACE FLANGE (RF)
RING JOINT FLANGES (RTJ)
TONGUE AND GROOVE FLANGES (T AND G)
MALE AND FEMALE FLANGES (M AND F)
Better sealing properties, more precise location and exact compression af sealing material, utilization of other, more suitable sealing and spezialized sealing material (O-rings).
Commercial availabillity and cost. Normal raised faced is far more common and ready available both regarding Valves, flanges and sealing material. Another complexity is that some rigid rules must be applied to the piping design. Do you order Valves to be female end both sides, or on one side maybe, in which case do you point all male ends in the flow direction, or what. Same applies to any flanged joint / vessel connection of course.
Flange facing vs milling
Milling is the process of machining a surface using a multi-point cutting tool. While a milling machine is capable of getting a smooth surface finishes and cutting in a circular stroke (such as our range of orbital milling machines), they are not capable of getting the required surface finish needed to meet the ASME B 16.5 standard.
In order to reach some of the finishes required to meet ASME B 16.5, the flange should be machined using a single point cutting tool. The single point tool enables on-site machinists to achieve the grooves required to created surface finishes suitable of creating a strong leak-proof seal for gasket flanges, such as the serrated surface (see image). As such, single point cutting tools will be used with a flange facing machine.
For users that are happy simply to produce a flat finish on the flange (with no defined machine profile), machines can be supplied with milling heads rather than single-point cutters. This dramatically reduces the machining time which has made flange facing machines an ideal tool for use in wind turbine production.
Source: China Flanges Manufacturer – Yaang Pipe Industry (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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