Description

Flange gaskets are designed to seal the space between two sections of pipe. Most pipes, of course, are joined at a flanged surface. The surface where two pipes join isn’t smooth or otherwise flat. Rather, it’s flanged, meaning it flares out. For flanged surfaces such as this, flange gaskets are used.

They are considered much more superior than the conventional ring or full-face gaskets. Although pipe flange gaskets are usually used for all normal water and sewer service, they are especially useful in demanding services like in very large diameter flanged piping.

For specially designed long-span installations, involving 2 or 3 or more lengths of pipe or with any underground flanges, flange gaskets are of great help because they could be subjected to undesirable beam loading.

These gaskets are available in numerous standard materials in various thickness and hardness options for various flange sizes. Flange gaskets are also available with adhesive on one or both sides or without adhesive. Most materials are available starting at 1/32” thick and can be supplied up to 1” thick. Some manufacturers supply flange gaskets in wide rolls from which you can cut your flange gaskets to size. Flange gaskets are also available to your exact requirements. Pipe flange gaskets are being very frequently used for flanged joints which are subjected to extreme chemical attacks.

Flange gaskets come in a variety of sizes and are categorized by their inside diameter and their outside diameter.
There are many standards in gasket for flanges of pipes. The gaskets for flanges can be divided in major 4 different categories:

Sheet gaskets
Corrugated metal gaskets
Ring gaskets
spiral wound gaskets

Sheet gaskets are simple, they are cut to size either with bolt holes or without holes for standard sizes with various thickness and material suitable to media and temperature pressure of pipeline.
Ring gaskets also known as RTJ. They are mostly used in offshore oil- and gas pipelines and are designed to work under extremely high pressure. They are solid rings of metal in different cross sections like oval, round, octagonal etc. Sometimes they come with hole in center for pressure equalization.
Spiral wound gaskets are also used in high pressure pipelines and are made with stainless steel outer and inner rings and a center filled with spirally wound stainless steel tape wound together with graphite and PTFE, formed in V shape. Internal pressure acts upon the faces of the V, forcing the gasket to seal against the flange faces.

Bolted Flange connections

A bolted flange connection is a complex combination of many factors (Flange, Bolts, Gaskets, Process, Temperature, Pressure, Medium). All these various elements are interrelated and depend upon one another to achieve a successful result.

The reliability of the flanged joint depends critically upon competent control of the joint making process.

Some other disadvantages of flange connections:

Each flange connection can leak (some people claim that a flange connection is never 100 percent leak proof).
Flanged pipe systems need much more space (just think of a pipe rack).
Insulation of flanged pipe systems is more expensive (special flange caps).

How flange gaskets work

Flange gaskets work in the same way as most other gaskets. When installed, they create a sealed mating surface so that water or other liquids won’t leak out. Pipes typically have water or liquids flowing through them. If two pipes are joined together, the water or liquids may leak out through this mating surface. Flange gaskets prevent this from happening by sealing the surface.

Pipes generally don’t offer a sealed mating surface when used alone. This is especially true in the case of pipes with a flanged surface. Since flanged surfaces are flared, water and liquids can easily escape through the cracks. A simple solution to prevent leaks is to install a flanged gasket. The flanked gasket will contour to the shape of the pipes’ flanged surface so that water or liquids stay within the pipes.

Types of flange gaskets

There are several types of flanged gaskets. Sheet flange gaskets are those comprised of a single sheet of metal that’s cut and shaped. There are also corrugated flange gaskets. A flange gasket is considered corrugated if it’s made of galvanized iron or steel in a corrugated pattern. Like sheet flange gaskets, they are cup and shaped to fit the flanged surface of a pipe. But only corrugated flange gaskets feature a corrugated pattern.

A third type of flange gasket is ring. Ring flange gaskets are intended for high-pressure applications. They consist of solid metal rings in a variety of shapes, including round, oval and octagonal. Ring flange gaskets aren’t as common as sheet or corrugated flange gaskets.

Lastly, there are spiral wound flange gaskets. Spiral wound flange gaskets live up to their namesake by featuring a spiral pattern. When inspecting the inner rings, you’ll notice spiral ridges. These ridges are what distinguish spiral wound flange gaskets from other types of flange gaskets.

The most common types of gaskets are:

Gaskets used in piping (flange gaskets)
Gaskets used in vehicles (cars, boats, planes, trains)
Gaskets with certain material properties (cork, rubber paper etc.)
Gaskets used for a particular function (for pressure, temperature, or chemical resistance)
Bespoke or custom made gaskets

Materials

A flange gasket is a type of gasket made to fit between two sections of pipe that are flared to provide higher surface area. Flange gaskets come in a variety of sizes and are categorized by their inside diameter and their outside diameter.

Flange gaskets are made of various materials like:

Rubber:Neoprene, EPDM, Nitrile, EVA, Silicone, Cork and Cork Rubber
Closed Cell Foam:Cross-linked Polyethylene, PVC
Plant Fiber
Cellulose Fiber

What is the difference between a RTJ, FF, and RF flange on seals and thermowells?

Pipe gaskets (otherwise known as flange gaskets) are made from wide range of materials such as rubber, non-asbestos and graphite. The gaskets can be bought as either Full Faced (with bolt holes) or Inner Bolt Circle (IBC, ring type or raised face).

There are many standards in gasket for flanges of pipes.

The raised face, RF, is the standard process connection on our third party seals and thermowells. Both have options for a RTJ and FF type flange connections. The Raised Face (RF) is the most common type used in process plant applications.

The gasket surface of the flange is raised above the bolting circle face. A Ring-type Joint (RTJ) can also have a raised gasket face with the difference being the ring groove machined in this face. This groove will accommodate a steel ring gasket for flange mating. The Flat Face, FF, flange has a gasket surface that is in the same plane as the bolting circle face. None of these three flange types are interchangeable between types, i.e. RTJ flange cannot be mated to a RF flange.

Sub-threaded flange connection (wiretapping) flange and welding flange. Low-pressure small-diameter wire access flange, high pressure and low pressure are the use of large-diameter welded flange, different pressure, flange thickness and bolt diameter and the number of connections are different.

Within the family, pipe diameter, and are low-voltage, see flange connection. If produced in a boiler room or scene is full of flanged pipes and fittings.

As iron welded flange, a lot of customers have doubts is the quality is better than the forging of iron welding flange welding flange. Actually iron welding flange of quality and forged of welding flange of quality is as of, but iron welding flange what place cannot has guarantees does, is iron welding flange of material most no guarantees has, because General of process among, iron welding flange of density is no problem of, but in for production of process among, iron welding flange of rough rarely for detection, so for, by production out yahoo, not after detection of iron welding flange of material cannot guarantee.

The different grades based on the pressure, flange pad also has a variety of materials, from the low-pressure asbestos pad, high-pressure pads to the metal pads are asbestos.

Within the family, pipe diameter is small, but also ow-voltage, see flange connection. If a boiler room or a production site, full of flanged pipes and equipment. Flange connection is to two pipes, fittings or equipment before each fixed at a flange on the flange between the two, together with flange pad, fastened together with bolts to complete the connection. Some of pipe fittings and equipment have been built-flange, also falls within the flange connection.

How to select the gasket for flange connections?

One of the best all-around seals, the spiral wound gasket offers a low-cost solution that has the ability to handle temperature and pressure fluctuations. Multiple plies of metal and filler in the spiral create a barrier that reduces the possibility of leaks.

Temperature and Chemical Considerations

Be certain that the gasket you order is as resistant as possible to the media and temperature involved. Check the chemical compatibility of the metal as well as the filler material for the media to be sealed. As a general rule, the metal used in either the spiral winding or double-jacketed gasket should be similar to the flange material.

The compressibility of flexible graphite makes it an excellent filler material for metallic gaskets. Flexible graphite may be used in services with temperatures up to 950ºF (485ºC), though it should not be used with strong oxidizers such as nitric or sulfuric acid.

PTFE filler material provides excellent chemical resistance at temperatures below 500ºF (260ºC). In accordance with ASME B16.20, an inner ring is required when using conventional PTFE filler materials, in order to protect the winding from radial buckling.