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Technical information

What is a spiral wound gasket(SWG)?

Introduction to Spiral Wound Gasket (SWG):

A Spiral Wound Gasket (SWG) is a type of industrial gasket that is widely used in high-temperature, high-pressure, and corrosive environments. It consists of a V-shaped metal strip and a softer filler material that is wound in a spiral fashion to create a resilient sealing surface. 

Construction of Spiral Wound Gaskets:

The construction of a Spiral Wound Gasket comprises four main parts: the outer ring, inner ring, winding strip, and filler material. The outer ring is made of carbon steel or stainless steel, and it acts as a compression stop to prevent over-compression and gasket blowout. The inner ring is made of the same material as the winding strip, and it provides additional support to the gasket. The winding strip is typically made of stainless steel or other alloys and is wound in a spiral fashion to create the gasket’s sealing surface. The filler material is placed between the winding strip to enhance the gasket’s sealing properties.

Types of Filler Materials Used in Spiral Wound Gaskets (SWG):

There are different types of filler materials used in Spiral Wound Gaskets. The most common types are:

Graphite: Graphite is a popular filler material due to its excellent thermal and chemical resistance. It is often used in high-temperature and high-pressure applications, such as in the oil and gas industry.

PTFE: PTFE (Polytetrafluoroethylene) is another popular filler material known for its chemical resistance and low coefficient of friction. It is often used in applications that require resistance to corrosive chemicals.

Ceramic: Ceramic filler material is ideal for applications that require high-temperature resistance and good electrical insulation. It is often used in the chemical and petrochemical industries.

Mica: Mica filler material is known for its excellent heat resistance and is often used in high-temperature applications.

Non-Asbestos: Non-asbestos filler materials are used in applications that require good chemical resistance without using asbestos.

Advantages of Spiral Wound Gaskets (SWG):

Excellent Sealing Performance: Spiral Wound Gaskets provide a tight seal and are suitable for high-pressure applications.

High Temperature and Pressure Resistance: Spiral Wound Gaskets can withstand high temperatures and pressures, making them suitable for use in demanding applications.

Resistant to Corrosion and Chemicals: Spiral Wound Gaskets are resistant to most chemicals and are suitable for use in corrosive environments.

Durable and Long-Lasting: Spiral Wound Gaskets are durable and long-lasting, reducing maintenance costs and downtime.

Applications of Spiral Wound Gaskets:

Spiral Wound Gaskets are used in various industries, including:

Oil and Gas Industry: Spiral Wound Gaskets are commonly used in the oil and gas industry for sealing pipelines, valves, and flanges.

Chemical Industry: Spiral Wound Gaskets are used in the chemical industry for sealing chemical reactors, heat exchangers, and distillation columns.

Petrochemical Industry: Spiral Wound Gaskets are used in the petrochemical industry for sealing flanges, heat exchangers, and reactors.

Power Generation Industry: Spiral Wound Gaskets are used in the power generation industry for sealing turbines, boilers, and heat exchangers.

Pharmaceutical Industry: Spiral Wound Gaskets are used in the pharmaceutical industry for sealing equipment that requires high levels of hygiene.

Working of Spiral Wound Gasket (SWG)

The working principle of a spiral wound gasket involves three main stages: initial sealing, creep relaxation, and resilience. During the initial sealing stage, the gasket is compressed between two surfaces, causing the V-shaped metal strip to bite into the filler material. This creates a seal between the two surfaces, preventing leakage.

During the creep relaxation stage, the gasket experiences a reduction in compressive load due to the relaxation of the material under constant pressure. This relaxation causes the gasket to creep, which leads to a reduction in sealing force.

Finally, during the resilience stage, the gasket recovers its sealing force due to the materials’ elasticity in its construction. This resilience allows the gasket to maintain its sealing capability even after multiple compression and relaxation cycles.

Factors to Consider When Choosing Spiral Wound Gaskets (SWG):

Temperature and Pressure Ratings: The temperature and pressure ratings of the gasket must be suitable for the application.

Chemical Compatibility: The gasket must be compatible with the chemicals used in the application.

Flange Surface Finish: The surface finish of the flange must be suitable for the gasket material.

Flange Load: The gasket must withstand the flange load without over-compression.

How do you install a Spiral Wound Gasket (SWG)?

The installation of Spiral Wound Gaskets involves the following steps:

Surface Preparation: The flange surfaces must be clean and free of debris.

Gasket Installation: The gasket must be installed correctly, with the inner ring facing the flange and the outer ring facing outwards.

Torqueing the Flange Bolts: The flange bolts must be tightened to the correct torque values in a crisscross pattern to ensure even compression.

Maximum pressure and temperature of Spiral Wound Gaskets (SWG)

The maximum pressure and temperature for a SWG depend on the material used for construction and the application in which it is being used. Table 1 below shows the maximum pressure and temperature limits for different types of SWGs based on the non-metallic material used:

Non-Metallic MaterialMaximum Pressure Limit (bar)Maximum Pressure Limit (PSI)Maximum Temperature Limit (°C)Maximum Temperature Limit (°F)
Graphite2503625550°C1022°F
PTFE1502175260°C500°F
Mica10014501000°C1832°F

Table 2 shows the maximum pressure and temperature limits for the metallic materials commonly used in SWGs:

Metallic MaterialMaximum Pressure Limit (bar)Maximum Pressure Limit (PSI)Maximum Temperature Limit (°C)Maximum Temperature Limit (°F)
Stainless Steel20029001000°C1832°F
Inconel25036251200°C2192°F
Monel1502175800°C1472°F

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