Types Of Gaskets For Flanges || An Overview

What is a Gasket?

A gasket is a mechanical seal that is used to fill the space between two or more mating surfaces, typically to prevent leakage from or into the joined objects.

Gaskets are commonly made from a variety of materials, including rubber, metal, and non-metallic materials like graphite and PTFE. The choice of material depends on the specific application and environmental factors that will be present.

Types of Gaskets:

Generally, gaskets are classified into three different types these are,

Metallic gaskets
Non-metallic gaskets
Composite gaskets

1). Non-Metallic Gaskets:

Non-metallic gaskets are a common choice for a wide range of flange applications. These gaskets are typically made from materials such as rubber, cork, fiber, and various polymers.

One of the primary advantages of non-metallic gaskets is their ability to conform to irregularities in flange surfaces, providing a tight seal. They are also generally lightweight, inexpensive, and easy to install.

However, the choice of gasket material depends on the specific application and the requirements of the flange. For example:

Gasket Material	Temperature Range	Pressure Range	Application
Cork	-40°F to 225°F (-40°C to 107°C)	Up to 400 psi (27.6 bar)	Low-pressure steam, oil, and water
Aramid Fiber	-100°F to 750°F (-73°C to 399°C)	Up to 2500 psi (172.4 bar)	Chemical processing, oil refining, and steam service
PTFE (Teflon)	-450°F to 600°F (-268°C to 315°C)	Up to 1500 psi (103.4 bar)	Chemical and food processing, pharmaceuticals, and high-purity applications

Different Types of Non-Metallic Gaskets:

There are various types of non-metallic gaskets, each with its unique characteristics and applications. Some of the commonly used types of non-metallic gaskets include:

A). Compressed Non-Asbestos Fabre Gasket:

These gaskets are made by compressing a mixture of aramid fibers, mineral fibers, and fillers, which results in a material that is strong, flexible, and resistant to high temperatures and pressures. Compressed non-asbestos Fabre gaskets can be used in a wide range of applications, including chemical, oil and gas, and power generation industries.

Some of the advantages of compressed non-asbestos Fabre gaskets include:

Excellent sealing capabilities.
Resistant to high temperatures and pressures.
Chemical resistant.
Good flexibility and strength.
Suitable for a variety of flange applications.

Applications:

Compressed non-asbestos Fabre gaskets are commonly used in the following applications:

Industry	Application
Chemical	Acid, alkali, and solvent service
Oil and gas	Pipeline flanges, heat exchangers, and valves
Power generation	Steam and gas turbines, boilers, and compressors

B). PTFE Gasket:

PTFE (polytetrafluoroethylene) is a popular choice due to its exceptional sealing capabilities and chemical resistance.

Advantages of PTFE Gaskets:

PTFE gaskets offer several advantages that make them a popular choice in various industries. Here are some of the benefits of using PTFE gaskets:

Chemical resistance: PTFE gaskets have excellent resistance to chemicals, making them suitable for use in corrosive environments.
Temperature resistance: PTFE gaskets can withstand a wide range of temperatures, from -250°F to 550°F.
Low friction coefficient: PTFE has a low friction coefficient, which makes it easy to install and remove the gasket.
Non-stick properties: PTFE is non-stick, which means it does not adhere to the flange surface, making it easy to remove even after prolonged use.

Applications of PTFE Gaskets:

Due to its unique properties, PTFE gaskets are used in various flange applications, such as:

Application	Industry
Chemical processing	Chemical industry
Food processing	Food industry
Pharmaceuticals	Pharmaceutical industry
Cryogenic applications	Oil and gas industry

C). Rubber Gasket:

Rubber gaskets are made from various types of rubber and are used to seal flanged connections. They are designed to create a tight seal between two surfaces, preventing leakage of fluids or gases.

Types of Rubber Gaskets:

There are different types of rubber gaskets, each with its own unique properties and applications. Some common types of rubber gaskets include:

Neoprene gaskets: known for their resistance to oil and chemicals, often used in oil and gas industry applications.
Nitrile rubber gaskets: resistant to heat, oil, and solvents, usually used in automotive and mechanical applications.
Silicone rubber gaskets: offer excellent resistance to temperature extremes, often used in food and medical applications.
EPDM rubber gaskets: provide excellent resistance to weathering and aging, usually used in outdoor applications.

Applications of Rubber Gaskets:

Rubber gaskets are used in a wide variety of industries and applications, including:

Automotive and mechanical applications
Oil and gas industry
Food and medical applications
Plumbing and HVAC
Aerospace and aviation

2). Metallic Gaskets:

Metallic gaskets are a popular choice for flange connections that require high-pressure and high-temperature sealing. These gaskets are made of different types of metals, including stainless steel, copper, and nickel alloys.

There are various types of metallic gaskets, each with its unique characteristics and applications. These Are:

A). Oval Ring And Octagonal Gasket:

In pipe flanges, ring gaskets are commonly used to create a seal between the two flanges. Two types of ring gaskets are the oval ring gasket and the octagonal ring gasket. These gaskets are made from soft iron or low carbon steel and are designed to withstand high pressure and temperature.

The oval ring gasket has an oval cross-section and is used in sealing flanges with flat and raised faces. In contrast, the octagonal ring gasket has an octagonal cross-section and is used in sealing flanges with groove faces.

The oval ring gasket is easier to install and remove due to its flexible nature. It also provides a more effective seal on damaged flange faces. However, it is less suitable for use in high-pressure applications than the octagonal ring gasket.

The octagonal ring gasket is more difficult to install and remove due to its rigid shape, but it provides a better seal under high pressure and is more resistant to movement. It is commonly used in the oil and gas industry for sealing pipe flanges in high-pressure applications.

Gasket Type	Cross-Sectional Shape	Flange Face Type	Advantages
Oval Ring Gasket	Oval	Flat and Raised Faces	Flexible, better seal on damaged flange faces
Octagonal Ring Gasket	Octagonal	Groove Faces	Better seal under high pressure, more resistant to movement

3). Composite Gaskets:

Composite gaskets offer excellent sealing performance by combining the best properties of both non-metallic and metallic gaskets. These gaskets are constructed from various layers of different materials, such as graphite, PTFE, and metal, laminated together under high pressure and temperature to form a single gasket.

Construction and Characteristics:

Composite gaskets typically consist of three main layers:

The sealing layer, which is usually made of flexible and compressible materials such as graphite or PTFE;
The support layer, which provides rigidity and stability to the gasket and may be made of stainless steel or other metals; and
The cover layer, which protects the sealing layer from damage and may also be made of metal.

Types of composite gaskets:

There are thee general types of composite gaskets are available these are,

A). Spiral Wound Gasket:

Spiral wound gaskets are composed of a metal winding strip and a soft filler material such as graphite or PTFE. The winding strip is formed into a spiral, with the filler material located between the windings. The outer edge of the gasket is reinforced with a metal ring to provide additional strength and prevent buckling.

Spiral wound gaskets are commonly used in high-pressure and high-temperature applications, as they can withstand extreme conditions and provide excellent sealing capabilities. They are particularly useful in flange connections where thermal cycling is a concern.

Gasket Material	Temperature Range	Pressure Range	Chemical Resistance	Sealability
Spiral Wound Gaskets	-250°F to 2000°F	Up to 2500 psi	Excellent	Excellent
Compressed Non-Asbestos Fibre Gasket	-150°F to 550°F	Up to 1500 psi	Good	Excellent
PTFE Gasket	-350°F to 550°F	Up to 1500 psi	Excellent	Excellent

B). Cam profile Gasket:

Cam profile gaskets are made of a metal core with raised concentric sealing rings on each side, covered with a soft filler material, typically PTFE. The sealing rings provide improved sealing performance by concentrating contact pressure on the gasket's sealing surfaces.

Cam profile gaskets are commonly used in flange connections requiring high-pressure sealing capabilities. They are particularly useful in applications where extreme temperatures and pressures, as well as thermal cycling, are concerns.

Gasket Material	Temperature Range	Pressure Range	Chemical Resistance	Sealability
Camprofile Gaskets	-300°F to 1200°F	Up to 6000 psi	Excellent	Excellent
Metallic Gaskets	-450°F to 1500°F	Up to 20,000 psi	Good	Excellent
Composite Gaskets	-400°F to 950°F	Up to 2500 psi	Excellent	Good

C). Metal Jacketed Gasket:

Metal jacketed gaskets consist of a metallic outer shell and a soft filler material, which is typically a non-asbestos material or graphite. The outer shell provides strength, while the soft filler material ensures a tight seal. Metal jacketed gaskets are ideal for applications where high pressure and temperature conditions are present.

The metallic outer shell of a metal jacketed gasket can be made of a variety of materials, including stainless steel, carbon steel, and monel. The choice of material depends on the specific application requirements, such as the operating temperature and pressure, the corrosiveness of the fluid being sealed, and the flange surface finish.

The soft filler material used in metal jacketed gaskets can also vary based on the application requirements. Non-asbestos materials, such as compressed fiber, are commonly used as filler materials. Graphite is also a popular choice due to its excellent high-temperature and chemical resistance properties.