Importance of Gasket and Bolt in Flange Connection
What is a flange gasket?
It is a sealing device. This device nests in the centre of two sections of pipes while offering a higher surface area in flared piping systems. There are parameters which require consideration before selecting this device. For instance, - Fugitive Emissions, Compatibility with the fluid, Temperature, as well as Internal Pressure. Apart from the fore mentioned parameters, some special conditions have to be taken into consideration as well, i.e. erosive media, vibration, risk of the device contaminating the media, integrity, corrosion resistance, not to forget its economic value. While there may be many standards for gasket flanges, they could be divided majorly into four different sections:
- Sheet gaskets - Known to be simple, cut to size with or without bolt holes. These gaskets are manufactured in different widths and material, depending upon the suitability to the application, the media flowing through a system, temperature and pressure settings of a pipeline.
- Corrugated metal gaskets -Used on sealing surfaces that are asymmetrical or distorted, these components are seen in applications where more elastic materials with better sealing performance are required.
- Ring gaskets - Shortened as RTJ, they are used mostly in offshore equipment, especially the oil and gas industry, where the work conditions are extreme. In the sense that the pressure is high. These gaskets are solid rings which are made of different metals and produced in different cross-sections such as oval-shaped. Or they could be round or octagonal etc. And on occasion, they are constructed with a hole in the centre for pressure.
- Spiral wound gaskets - Used in high-pressure applications, outer and inner ring are made of stainless steel.
Importance of gasket and bolts in flange connections
Gaskets permit a less than perfect mating surface on machine parts. They are regularly used to fill in irregularities along with preventing leakage from or into the joined flanges, especially under compressed conditions. On the other hand, a bolt aids to clamp either two Flanges together or to a piping system. Selecting appropriate Bolts to make these connections will depend on the type of flange used, diameter as well as the length of bolts in addition to the Pressure Class. These bolts often have a circular flange under their head, which acts as a washer that in turn distributes the load. Achieving a leak-free connection is possible if Bolts get used in conjunction with a proper gasket. During the installation of a gasket, the bolt assigned to it must have the right amount of tension, and strength. The load must be divided evenly over the whole flange area.
Full face gasket vs Ring gasket
The position of an RTJ or ring gasket is on the inside of bolts. Thus, surrounding the pipe bore. In a raised face design, a ring gasket sits on the raised surface. This design of a ring gasket would require less material. And ultimately less cutting to be performed. Although installation can be without completely disassembling the joint, they prove to be harder to clamp in position. While providing specifications for a ring gasket, three dimensions are required 1. ID that corresponds to the pipe bore, 2.OD that is the same as the OD of the raised face, 3. gasket thickness.
On the other hand, a full face gasket specifies the ID. The ID is the same as the pipe bore, whereas the OD that is the same as the OD of the flange bolt circle diameter. That is the diameter on which the bolt hole centre exists, number of bolt holes and spacing if they are not regular in addition to the gasket thickness.
Similar to a ring-type, a full face Gasket seals raised flange faces. The only exception is that a full face type would have an OD, which is the same as the flange. Hence, these gaskets would require holes to secure the bolts that pass through, thus, aiding its location with a much simpler alignment. Moreover, since they extend out to the OD of a flange results in filling the gap between bolting surfaces, thereby proving to be advantageous as dirt stops getting in. However, these joints are to be dis-assembled fully before being installed.