Spiral Wound Gaskets
A Spiral Wound Gasket is the most common semi metallic gasket used in industrial plants. A properly selected and installed spiral wound gasket can withstand high temperatures and pressures, preventing leaks throughout their intended lifespan.
A spiral wound gasket consists of three elements:
1. Outer ring
- Made of SS304, SS316, Carbon Steel, this outer ring is sometimes called the centering ring or guide ring.
- It’s used to center the gasket when you insert it into a bolted flange joint.
2. Inner ring.
- The inner ring is pivotal for the gasket because it prevents windings from buckling inside the pipe. When a gasket buckles, parts of it get sucked into the pipe.
- From there, pieces of the gasket will typically flow through the pipeline until they get caught on something.
- Often, they’ll get wrapped around rotating equipment like a pump. The mess that results is known as a “bird’s nest.”
- Inner rings help you avoid this problem.
3. Sealing element.
- As you might guess from the name, the sealing element creates the seal that prevents leaks.
- A sealing element encompasses both windings and filler material. Most spiral wound gaskets in oil and gas refineries will use a flexible graphite filler material rated for high temperatures.
- A flexible graphite filler also allows the gasket to be more tolerant of flange distortion and joint misalignment.
- Polytetrafluoroethylene (PTFE) is another common filler material. PTFE is not rated for high-temperature applications, however. Meanwhile, most winding materials in refineries will be stainless steel and monel.
Spiral Wound Gasket Markings
Spiral Wound Gaskets have several different markings on them. Each tells you something specific and important about the gasket itself. Starting from the top
ASME B16.20
At the top of a spiral wound gasket, you ought to see a marking that states “ASME B16.20.” this indicates the gasket is made to the ASME B16.20 standard, which is the standard governing metallic gaskets for pipe flanges (which includes spiral wound gaskets).
Manufacturer
First, the manufacturer’s name is usually positioned on the right-hand side of the gasket. This tells you who made the gasket.
Winding Material and Filler Material
Indicates what the gasket is made of. Gasket color also tells you a lot about these materials — more on that in a moment.
Diameter and Pressure class
These markings tell you the size of the gasket, along with the load the gasket can handle.
There are different pressure classes: 150, 300, 400, 600, 900, 1500 and 2500. Higher numbers indicate the ability to tolerate greater pressures.
Spiral Wound Gasket Color Codes
