Three Basic Choices for Pipe Flanges
A pipe flange is a type of bridge used to establish a connection between two pipes which can be used for dismantling ductwork, temporary or mobile installations, transitions between dissimilar materials, and joining in environments not conducive to cementation.
Flanges are relatively simple mechanical connectors that are particularly common in high-pressure pipeline applications. Recognized in the industry for reliability and being extremely cost-effective, the flange’s torque carrying capacity is very high compared to other mechanical connectors. This is an important function in systems that experience pipeline flow due to temperature and pressure changes (such as deepwater pipelines). Flanges can be designed to meet various application requirements such as high temperature and corrosion resistance.
Mode of Operation
Pipe flanges are flush with the pipe to which they are connected. Apertures in the surface are mechanically connected by bolts, collars, adhesives, or welds.
Welding joins materials by melting the workpiece and adding filler material. For strong, high-pressure connections of materials, welding is often the most effective method of flange joining. Most pipe flanges are designed to be welded to the pipe.
Brazing is used to melt a material by melting a filler metal, which solidifies to act as a connecting meson. This method does not melt the workpiece and causes thermal deformation, resulting in tight tolerances and clean seams.
Many connection methods have distinctive characteristics, and there are other more important considerations when selecting pipe flanges. Factors consumers should consider are the flange’s physical specifications, type, material, and performance characteristics that are best suited for the application.
Physical Specifications
First, the flange must fit the pipe for which it is designed. Physical specifications for pipe flanges include size and design shape.
Flange Size
Physical dimensions should be specified so that flange dimensions can be appropriately sized.
The outside diameter (OD) is the distance between two opposing edges of the flange face. Thickness refers to the thickness of the outer edge of the connection, excluding the flange portion that secures the pipe.
The bolt circle diameter is the length from the center of the bolt hole to the center of the opposite hole.
Pipe size is the corresponding pipe size for the pipe flange, usually made to recognized standards. It’s designated by two unsized numbers–the nominal pipe size (NPS) and the schedule (SCH).
The nominal diameter is the inner diameter of the flange connector. When manufacturing and ordering pipe connectors, match the bore diameter of the fitting to the bore diameter of the mating pipe.
