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What Is a Vacuum Flange?

By Karize Uy
Updated May 17, 2024
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A vacuum flange is a small device used in vacuum systems that uses many pipes and tubing. Its main purpose is to link and interconnect the pipes with each other, or connect the tubes to the chambers. The flange usually appears as a rim that has a larger circumference than the actual pipe it is connected to. It also has little holes running in its edges that help attach the vacuum flange with the pipes and the chamber openings.

Generally, a vacuum flange can either be a fixed or a rotatable type. The fixed flange usually has four to five holes that fit right into the holes of a pipe or a chamber opening. The rotatable one, however, typically has more holes, so even if the plumber rotates the flange in either direction, the holes can still align to the holes in the pipes. The holes are then filled with bolts that are screwed tight to bond the flange and the pipe. Vacuum flanges can also be welded to the plumbing system to ensure no pressure escapes the vacuum system through little holes.

Steel is one of the most commonly used materials in making a vacuum flange, as the alloy is long known to be very durable. Variants of the steel may be stainless or carbon, making the flange more resistant to rusting and high heat. Copper, bronze, brass, and aluminum are also used as manufacturing materials. Vacuum flanges can also be made from non-metal materials, such as glass, ceramic, or from PVC. All these materials are durable and can weather through water, heat, cold, and even pressure.

Vacuum flanges come in many varieties and standard measurements. One of these is the Quick Flange (QF), sometimes known as the Klein Flange (KF). The QF is usually fastened to pipe clamps that are attached to the pipe itself. An O-ring, a plastic-like disc, is then placed to seal any openings, before the flange is finally bolted in. The QF is available in four measurements, ranging from a diameter of .629 inches (16mm) to 1.968 inches (50mm).

For larger flanges, the International Organization for Standardization (ISO) issued the LF or the “large flange.” The LF variety has eight different sizes, the smallest of which is 2.5 inches (63.5 mm). The medium-sized vacuum flange has a diameter of 7.87 inches (200 mm), while the largest of the LF is 19.68 inches (500mm). Just like the QF, the LF also comes with an O-ring and is also attached to pipe clamps.

Another type of vacuum flange is the “ConFlat,” or the CF, which looks like a gasket that binds the two pipes together. When the pipes are in place, the CF is bolted around the pipes, leaving no room for any leakage. The CG vacuum flange is typically used in “ultrahigh” vacuum systems.

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