In the realm of gaskets, when it comes to sealing in the most challenging environments, one type stands out above the rest: the spiral wound gasket.

Spiral wound gaskets are semi-metallic mechanical seals that can operate in various harsh environments where standard gaskets would fail. From high heat to freezing, from high pressure to extreme toxicity, spiral wound gaskets can handle it all. For this reason, they are very common in the oil and gas, petrochemical and process sectors, as well as in applications such as cryogenics and research laboratories. So what makes them so resistant to the harshest conditions?

Most gaskets are cut from sheet material and that means they seal on their flat surfaces. When flanges are out of parallel the gap between them varies, forcing the use of thicker material. Where the gap is smaller the material must compress more. Pretty quickly the material reaches the limits of what it can do.

What is a Spiral Wound Gasket?

In contrast, the spiral wound gasket, made up of layers of metal with filler materials, seals on its edges rather than a flat surface. To do this a long thin strip of gasket material is coiled up to create a ring. When placed between flanges, it’s the sides of the strip that make the seal.

The choice of the metal winding and filler material used in a spiral wound gasket is critical for specific applications. The most common metal winding material used in a spiral-wound gasket is stainless steel, though specialist metals such as monel, a nickel-copper alloy with high tensile strength and resistance to corrosion, are also common. The metal used is selected for the appropriate degree of compressibility and its recovery properties, combined with corrosion resistance and durability.

Filler materials also vary, with a flexible graphite filler material commonly used for applications involving high temperatures. This choice not only ensures resilience to extreme heat but also enhances the gasket's flexibility, making it more accommodating of flange distortion and joint misalignment. PTFE, mica paper and ceramic fillers are also used depending on the resistance requirements.

Specific outside rim colours serve as indicators for distinct winding materials:

Meanwhile, the rim stripe colour serves as an indicator of the gasket's filler material:

5 Key Advantages of Spiral Wound Gaskets

• Operating temperatures from -250C to 1,100C
• Ability to handle extreme pressures
• Robust build for easy installation without damage
• Highly customisable and can optimised for any application
• Vibration and movement won’t break the seal

Spiral-wound gaskets are the brainchild of Flexitallic, who invented them in 1912 in response to the increasingly demanding nature of applications in the oil refinery sector. The development of better engines in automobiles had led to a huge increase in demand for better quality fuel and that same year, a process known as thermal cracking was patented to refine crude oil and produce gasoline at twice the previous rate.

With the increase in temperatures, pressures and chemical levels involved in the new processes, a resistant, hard-working sealant was of the highest priority to be able to maintain seals in those extreme conditions, and thus the spiral wound gasket was born.

They are still widely used in the petrochemical industry today, often to be found in pumps, pipes, valves, heat exchangers, and systems that encounter high pressures, extreme temperatures and chemical attacks.

Applications where Spiral Wound Gaskets are Critical

• Oil and Gas: Used in pipelines, refineries, and petrochemical plants where they provide reliable sealing against high-pressure and high-temperature fluids.
• Chemical Processing: Found in chemical plants, where they seal flanges in equipment handling corrosive substances and extreme temperatures.
• Steam Generation: Used in power plants for sealing joints in steam systems, turbines, and boilers.
• Water Treatment: In facilities dealing with water purification, sewage treatment, and desalination, spiral-wound gaskets help prevent leaks in pipes and valves.
• Food and Beverage: Found in processing plants to seal pipes and vessels in the production of beverages, dairy products, and processed foods.
• Pharmaceutical: Used in pharmaceutical manufacturing facilities to seal equipment in processes involving sensitive and sterile materials.
• Marine and Shipbuilding: In shipyards and marine applications, spiral-wound gaskets are used for sealing pipes, valves, and flanges in vessels.
• Aerospace: In aircraft manufacturing and maintenance, these gaskets are employed for sealing hydraulic and fuel systems.

No matter the application, Dobson offers bespoke manufacturing of spiral wound gaskets to meet your exact specifications. Our team of experienced technicians will guide you on the best material composition for any given situation.