What Is a Gasket?

A gasket is a common term for any seal that holds two things together. Although rarely discussed, gaskets such as vehicles, pumps, and phones are used in everyday applications. A gasket seals the gap between two mating surfaces that otherwise fail to meet. These items are typically made of rubber, plastic, metal, or other materials and are often available in different shapes and sizes, depending on their application. An O-ring gasket consists of numerous metal rings with an inner diameter smaller than the outer diameter of the sealed object. The ring then expands outward until it contacts both sides of the gap. Once contact occurs, the force causes the opposing surface to form inward, creating a seal. These are perfect for maintenance and industrial uses, intending to prevent leakage.

Gaskets vs. Seals:

Gaskets and seals both form barriers between two objects to prevent leakage. However, seals protect at least two moving parts, whether one or both moves, and are typically composed of flat and round washers.

On the other hand, a single gasket consists of two static seals that lock two non-moving parts together. Gaskets are often molded to fit a specific application and may be shapeable enough to fit into a given position and remain in place if they don't move against each other. 

Strength is the most crucial feature of any application because gaskets and seals must be strong enough to withstand pressure without deforming under normal conditions, allowing them to create a tight seal over a long period. Additionally, the gasket will seal, protect against corrosion, and resist abrasion, vibration, impact, and possibly extreme temperature. The ideal gasket material has good flexibility, low density, and high tensile strength. Many materials that match this description are chemically resistant and possess internal pressure and durability.

Types of Gaskets

To create structure, we organize materials into three categories based on their compressibility: Soft, Medium, and Firm. The soft category includes cellular elastomers such as sponges and foam. Examples of medium materials include solid rubber elastomers like sheets and extruded or molded rubber with no bubbles or fillers. Materials in the firm category include metal and reinforced rubber elastomers, which usually have fillers added to strengthen the rubber. Within these categories, specific materials are used to create gaskets.

Foam comprises two layers of closed-cell urethane foam bonded with adhesive tape. It is generally more expensive than rubber but less expensive than silicone. Foam offers thermal insulation and sound absorption qualities and reduces the heat that passes through an object. 

The synthetic rubber gasket, developed around 1844, is one of the oldest forms of sealing technology. It is commonly used in industrial applications because it can remain sealed while withstanding harsh chemicals and temperatures. Developed in 1953, silicone gaskets have many desirable properties that make them useful in industrial applications. These include resisting high temperatures, low compression sets, and good electrical insulation. Another material is ethylene propylene diene monomers (EPDM), which, like silicone, contains additional ingredients like fillers, stabilizers, antioxidants, and flame retardants. Because of these properties, this material is highly resistant to heat and chemicals and has good flexibility, making it perfect for industrial applications.

EMI shielding is made from metal alloys and other flexible dampening materials. They fit inside or outside electronic devices to prevent outside signal interference from damaging the inner mechanisms.

When are gaskets used?

Gaskets are widely used in various scenarios to serve different purposes based on the specific application. Some places you can find gaskets include at-home use, medical, food service, and plumbing.

In household settings, gaskets are found in water faucets, around windows, and in refrigerators to maintain cold air. They are also used in various workplaces, such as machinery, pipes, valves, and pumps. In the medical field, gaskets are crucial for maintaining a tight seal in devices like catheters, tubing, and IV bags to prevent contamination and infection. Hospital dehumidifiers rely on airtight seals to keep an indoor environment clean and dry. Gaskets are essential for ensuring proper sanitation and safety in the food industry. Food processors use them to prevent cross-contamination, and beverage bottlers to avoid leaks while filling bottles.

Planning a Gasket System

Before selecting gasket material, it's best to plan the sealing system. The compression of the gasket material depends on other factors of the assembly, which work together to be cost-effective.

The compression of a gasket comes from the clamping force applied by fasteners and the design of the flange. The flange is a protruded rim that attaches, guides, or strengthens an object. The surface area of the flange plays a crucial role in how pressure spreads across the gasket. Factors such as the fasteners' size, spacing, and retained force determine the pressure required to compress and effectively seal the gasket. The quality of the flange's surface finish and any irregularities can impact the contact pressure, potentially leading to leaks. For optimal performance, the gasket must be resilient and resistant to creep to maintain adequate sealing pressure across its surface. It should also possess sufficient strength to withstand static and dynamic conditions without being crushed under load.

Gasket Material Selection

Thousands of specialized gasket materials are available worldwide, but no one suits all applications. Although there are over 2,500 engineered gasket options, rubber is the core technology for most due to its barrier properties and flexibility. All sealing solutions depend on flexible rubber for effective sealing, but the key is how rubber is modified to meet specific performance requirements. Despite its advantages, rubber has failure modes, and ASTM provides standardized tests for its aging, chemical, and temperature compatibility. 

Engineered composites, often based on rubber, enhance sealing and durability. Material developers blend rubber with fiber fillers in proprietary recipes to create leak-resistant gaskets and maintain their shape under load. Without these fillers, rubber alone fails under pressure, leading to leaks and loss of fastener load/torque.

At PGC, our knowledgeable application engineers assist customers in finding the appropriate gasket for their specific applications. This involves examining the entire assembly and determining how the gasket will function within it. Our various gasket technologies help maintain tolerances, protect sensitive equipment, and prevent moisture and dirt buildup. Although gaskets are small components within a larger assembly, selecting the right one for the application can compensate for less precise machining and reduce the overall project cost.