What is pipe flanges?
Flanges General
Flanges are used to connect pipes, valves, pumps, and other equipment to construct a pipeline system. Additionally, it facilitates cleaning, inspection, and customization. Typically, flanges are welded or screwed. Two flanges are bolted together with a sealant between them to create a flanged junction.
The most used flange types in Petro and chemical industry are.
All types except the Lap Joint flange are provided with a raised flange face.
Components for Flanges
Pipe flanges are created from a variety of materials, including stainless steel, cast iron, aluminum, brass, bronze, and plastic, but the most common material is carbon steel that has been forged and machined.
In addition, for specialized applications, flanges, like fittings and pipes, are frequently internally lined with layers of materials of an entirely different quality than the flanges themselves.
In most circumstances, the material of a flange is determined during the selection of the pipe; flanges are typically made of the same material as the pipe.
Unless otherwise stated, all flanges covered on this website adhere to the ASME and ASTM standards. ASME B16.5 discusses dimensions, dimension tolerances, etc., whereas ASTM describes the various material characteristics.
Measurements for Flanges
Each ASME B16.5 flange has a set of prescribed dimensions. If a draftsman in Japan, a work preparer in Canada, or a pipefitter in Australia is referring to a Welding Neck flange NPS 6, Class 150, Schedule 40 ASME B16.5, then it refers to the flange pictured below.
If the flange is ordered, the supplier desires to know the quality of the material. ASTM A105 is a carbon steel forged flange, while A182 is a stainless steel forged flange.
Therefore, a correct order to a supplier must specify two standards.
Welding Neck flange NPS 6, Class 150, Schedule 40, ASME B16.5 / ASTM A105
A - Ø192.1 | OD - Ø168.3 | L - Ø22.4 | ID - Ø154.1 | G - Ø215.9 | K - Ø241.3 | D - Ø279.4 | B - 25.4 | H - 88.9 | RF Height - 1.6
The flange above has 8 bolt holes, and a welding bevel of 37.5 degrees (red circle). All given dimensions are in millimeters. The raised face (RF) does not need to be specified, because ASME B16.5, each flange is standard delivered with a raised face. Only a different design (Ring Type Joint (RTJ), Flat Face (FF) etc., should be specified.
Flanged bolted connections
A bolted flange connection is a mix of numerous complex elements (Flange, Bolts, Gaskets, Process, Temperature, Pressure, Medium). All of these factors are interconnected and dependent on one another for a good outcome.
Critical to the reliability of the flanged joint is competent control of the joint-making procedure.
Typical bolted flange connection
Since a number of years ago, the industry has realized the importance of installation and assembly.
In Europe, the emphasis has been on ensuring that joint making is performed by trained and validated experts, and this has resulted in the production of TS EN 1591 Part 4, a European Technical standard. This standard applies to bolting technicians and their supervisors, the responsible engineers, who remove, assemble, and tighten the bolted connections of vital service pressurized systems of any configuration.
The standard provides a methodology for the training and evaluation of technicians engaged in the fabrication and disassembly of flange joints, and can be compared to the training requirements for welders performing pressure vessel work. Its publishing highlights the significance of competent supervision of the joint-making process in ensuring that the flange will work without leaking.
A bolted flange joint connection can leak for several causes, including the gasket.
Even when all the complex interdependent components of a bolted joint flange connection work in perfect harmony, the single most important factor determining the success or failure of that bolted joint flange connection will be the installer's attention to proper installation and assembly procedures. If performed correctly, the assembly will stay leak-free for its intended lifespan.
There are still a number of special flanges such as..
What Is a Flanged Fitting?
Flanged fittings are used to connect two or more pipes. Each pipe must have a flange, which is a raised ridge that goes around the pipe's exterior circumference. Utilizing bolts, clamps, or other fasteners, installers join the two flanges by compression. In place of conventional threaded connectors, welding, or soldering, a flanged fitting may be utilized. Certain types of flanges are combined with welding or soldering to make a stronger pipe joint.
By their function or appearance, various types of flanged fittings can be identified from one another. Fittings used on extremely big pipes or gas lines have a flange with a smooth face and a succession of pre-drilled holes. When two of these flanged fittings are linked together, bolts are put into the flanges' holes to establish a robust, long-lasting connection. High pressure applications may utilize a flanged fitting with a tapered neck. This form of connection typically requires both welding and bolting in order to resist the tremendous pressure exerted by the pipe's contents.
Installers who must add a flanged fitting in the field might choose for a threaded fitting, which has internal threads similar to those found at the extremities of most pipes. This enables the installer to simply screw the fitting onto the pipe in order to secure it. A threaded fitting makes it simple for workers to cut pipes to whatever size required for rapid repairs, then manufacture threads on the end using a pipe threader to accommodate the flange.
Depending on its intended purpose, flanged fittings may have a number of profiles. To link two pipes at an angle, elbow fittings have a curved shape with flanges on either end for a more stable connection. A tee-shaped flanged fitting connects two pipes in a single run with a perpendicular pipe, whereas a Y-shaped fitting connects three pipes running at three angles. Some flanged fittings may have a four-way or cross-shaped configuration to allow four independent pipes.
Numerous flanged fittings are utilized in conjunction with specific gaskets to avoid leaks at the union of two pipes. These gaskets are sometimes referred to as "o-rings" and are constructed of rubber or synthetic materials. When flanged fittings are manufactured to extremely precise tolerances and the face of the flange is very smooth, leak prevention may not require the use of a gasket. In certain circumstances, grease or lubricant can be used instead of an o-ring to assist seal any gaps between the flanges.
