Sealing gaskets, also commonly referred to as sealing washers or seals, help prevent leakage at a pipe or component joint. To achieve a successful seal, the gasket must be flexible enough to conform to both mating surfaces while resisting extrusion, creep, and blowout. Clamping forces act on the gasket surface, squeezing the gasket and forcing it to conform to the flange flaws, resulting in a seal.
Sealing gaskets are made from a variety of materials that enable them to retain their functional integrity in specific environments. Operational environments may include extreme temperature fluctuations, continuous exposure to corrosive materials, or exposure to abrasive materials. Whatever the use case, there are specific sealing gaskets for each unique application.
To choose the right gasket for an application, the elimination of materials is the first step. The more extreme the use case, the more specific the choice will be. Below is an overview of the materials used in sealing gaskets and their unique properties.
Figure 1: Rubber sealing washers
PVC is a cost-effective and durable material that has excellent shock absorption and vibration properties. Due to a pressure range of -0.95 to 16 bar (-13.77 to 232 PSI) this softer, malleable material has extensive potential including vacuum applications. Below are the key characteristics of the PVC sealing gasket:
Polytetrafluoroethylene (PTFE), also referred to as Teflon, is mainly known for its resistance to heat and non-stick properties. When using PTFE as your material of choice for a gasket it must be noted that once tightened, the joint should be retightened after 24-hours. A characteristic of PTFE is that it flows under pressure.
Polyamide, more commonly referred to as Nylon, stands out for its resistance to wear, excellent damping capacity, and a low creep tendency. Besides this, Nylon has high compressive/tensile strength, good shock-absorbing properties, and impact resistance is a good electrical insulator and can be used in vacuum applications.
Copper is commonly used for electrical conductivity and heat-absorbing properties. Copper seal gaskets are widely used in high performance motorsports industries due to their high heat tolerance while being malleable under pressure offering increased sealing qualities.
Aluminum has unique properties that make it one of the world''s most widely used metals. This material has a ductile property, which means it can be formed into intricate shapes without damaging or deteriorating. In the right forms, aluminum can withstand tremendous forces and is incredibly durable. Aluminum naturally forms a thin surface layer of aluminum oxide on contact with oxygen through oxidation, creating a physical barrier against corrosion or further oxidation in many environments, including contact with other metals.
Vulcanized fibers are natural fibers that have been heat-treated to form a hard rubber. It is among the oldest plastics ever developed and is used in a wide variety of applications, including washers and gaskets. There are very few downsides to using vulcanized fibers, they have an incredible range of resistance for pressure, chemicals, penetration by solvents and oils, and have high integrity.
The size of the gasket, as well as its ability to endure degradation and damage, all play a role in how well it can prevent gasses or fluids from escaping. Because the two surfaces aren''t precisely flush or straight, there will be gaps through which gas or water can escape. Gaskets fill in the spaces by compressing between the two surfaces, effectively blocking any leakage path.
Selecting a size is not an exercise of visual guessing. Rather, it’s the discipline of considering both the union surfaces, the flow aperture, and the joint type. Consider using a caliper to measure the exact requirements.
A good suggestion is to seek the advice of a fluid flow specialist. For each of the material types listed above there are variations in compounds and production methods, each designed for specific applications. Speaking to a specialist exponentially reduces the risk of failure. At Tameson we have continuous access to the latest developments and evolving solutions and can provide you with the best advice to address your needs.