Everything from the size of the gasket to its ability to withstand degradation and damage plays a role in how well it can stop the escape of air, gas, water, or other fluids. Gaskets are placed between two flush surfaces that have a channel for fluid movement. Because the two surfaces might not be perfectly flush or straight, they’re going to have gaps that fluid can move through. Gaskets correct those gaps by being compressed between the two surfaces to effectively eliminate any leakage pathway.
Key Gasket Selection Factors — Gasket Materials, Types, and Uses
Some factors that buyers should consider as they purchase gaskets include:
- The amount of force the two surfaces will exude on the gasket
- The degree of surface unevenness (which dictates how thick the gasket should be)
- The fluids and any ambient contaminants
- The compressibility of the gasket material
If you know all the details of the application environment, you can choose gasket materials that withstand exposure to water, acidic or alkaline chemicals, oxidation, and more factors as needed. You can also pick gaskets with the right thickness, longevity, and malleability.
Selecting the right characteristics prevents gasket failure. These parts can fail if they’re exposed to chemicals that degrade the material or if the forces acting on the gasket are too great. This guide will focus on the six most important tips for choosing the perfect gasket for your needs:
- 1. Selecting the Right Gasket Material
- 2. Evaluating Fluid Temperature, Corrosive Properties, and Pressure
- 3. Choosing the Best Types of Gaskets
- 4. Talking to a Gasket Design Engineer
- 5. Testing for Gasket Performance
- 6. Choosing the Right Gasket Manufacturer
Metal gaskets work best in extremely high-pressure applications. They create an initial line contact or contain the fluid through wedging once the two flush connection surfaces touch. Metal gaskets are also known as ring gaskets, and have either an ovular or octagonal cross-section. Octagonal cross sections provide a great deal of strength in the face of high pressure, such as the BX type that can handle 20,000 psi. Metal gaskets are commonly used in oil and gas industrial systems and secured with high-tension bolting.
Popular materials for metallic gaskets include:
- Low carbon steel
- Stainless steel
Non-metallic, or soft, gaskets, compress between two surfaces with little tension or pressure. This makes them ideal for applications where the fluid contents have low pressure levels and can’t force a leak pathway through the gasket. Soft gaskets are affordable, easy to find in different materials and specifications, and able to be used in low-temperature applications.
One common non-metallic material option, graphite, can also be used in high-temperature applications up to 500°C. These gaskets come in full face varieties, which cover the entire face of a connecting surface, and inside bolt circle gaskets, which cover a smaller ring of surface area on the face; one common application for full face gaskets is temporarily connecting utility lines.
Popular materials for non-metal gaskets include:
- Compressed Non-Asbestos Fiber (CNAF)
- Polytetrafluoroethylene (PTFE)
Composite gaskets use both metal and non-metal materials, giving them the ability to provide a reliable seal in a variety of environments with different pressure and temperature factors. They are commonly used in male-female, raised face, and tongue-and-groove flanges. Because they contain less metal, they are often more affordable.
Three popular types of composite gaskets are:
- Elastomeric: Elastomers are polymers with similar stretch and flexibility to rubber. Elastomeric gaskets are commonly used in utility applications alongside non-metallic gaskets. While these gaskets are elastic and can be deformed, they’re incompressible and can’t reduce in volume.
- Fibrous: Fibrous gaskets are another specialized type of non-metallic gasket. This category includes materials such as aramid, carbon, and glass fibers, cork, mica, and more. Each material offers very distinct properties.
When gaskets aren’t properly aligned to the application environment’s temperature, materials, or pressure, they are at an increased risk of failure. Each gasket’s material is best suited for a specific range of fluid or ambient temperature; silicone, for example, has a much wider temperature range (-30°F to 350°F) than neoprene, which is only viable at temperatures between 30°F and 180°F. One of the first considerations when choosing a gasket material is to know the minimum and maximum operating temperatures of the fluid.
The chemical makeup of the contained fluids should also determine which material your gasket has. Factors such as pH level, oil or water content, oxidation qualities, and more can corrode or destroy different materials through regular or irregular exposure.
Gaskets also perform differently depending on the pressure levels. Non-metallic gaskets, which can provide a compressed seal at relatively low pressures, cannot provide adequate resistance if the contained fluid is too pressurized; the fluid can force a path through the gasket’s seal. Synthetic rubbers, for example, often have a cap of 60 psi for reliable performance. Metallic gaskets, on the other hand, are well matched to the extremely high pressures in oil and gas processing plants.
Once you know which material is best for the end application, you can select the right type, or structure, of the gasket. Some popular varieties include:
- Jacketed Gaskets: These have a soft non-metallic interior and a metallic coating. Jacketed gaskets are available in many varieties, such as single- or double-jackets (which have a coating on one or both sides), corrugated jackets, and more. The metallic coating gives non-metallic gaskets better resistance to damage.
- Solid Gaskets: These solid metal gaskets are extremely durable, but they require a lot of compression force to create a seal.
- Spiral Wound Gaskets: This gasket style has windings of metallic materials in soft, non-metallic gaskets, which combines both resistance to damage and flexibility. Piping and pumping systems often use spiral wound gaskets because of the reliable seal.
- Kammprofile Gaskets: These have a metal core surrounded by non-metal material on the top and bottom. It can create a tight seal along the gasket’s edge with extra reinforcement. They’re also easier to repair than comparable composite gaskets.
Working with a gasket design engineer is an excellent choice for creating a custom gasket for unique applications or for expert assistance in selecting the features your system needs. If you choose the wrong materials, design style, and type, you may degrade the life span of the surrounding system. Further, mass manufacturing a flawed gasket type can result in a failed project or excessive expenses. Talk to a gasket design engineer about your design specifications and environmental factors that should shape the final product.
There are multiple factors to test on a new gasket design to ensure the materials, specifications, and style create an adequate and cost-effective seal. Regulatory or standardizing organizations like Underwriters Laboratories set objective standards that industrial and commercial parts must meet to be safe for sale or use. The same organizations often establish what sort of tests or testing conditions are necessary to certify that a product is safe. These tests assess a gasket’s ability to withstand temperature, chemicals, pressure, and compression to retain a seal.
The right manufacturer is essential for ensuring the material success of your project. Look for manufacturers that have experience creating gaskets for the industries or markets you serve. It’s also important to choose a manufacturer with established design, testing, and inspection capabilities, so the final product is high quality and reliable.
Why Mercer Gasket & Shim?
At Mercer Gasket, we specialize in creating custom gaskets that meet our clients’ needs. Our team of technical specialists, design engineers, and industrial experts has created custom gaskets for the refining and power generation industries. We’re an ISO 9001:2015 certified company, and our standard is 100% on-time and 100% defect-free products.