Fastener seal basics

January 10, 2024
By Freudenberg-NOK Industrial Service, for the Blue Print

What is a fastener seal?

Fastener seals consist of an inner rubber component used in conjunction with an outer metal washer that supports the sealing functionality of applications such as screws or bolts. The rubber and metal combination creates an ideal fit to eliminate any clearance gaps between the housing components and protects against potential leaks in many static applications. Fastener seals cover a wide variety of applications in bolts, screws, and tube fittings to provide a reliable solution to seal from simple to complex applications.
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How does a fastener seal work?

Thread, fastener, and bonded seals are used to seal off potential leak paths on threaded fasters such as bolts, screws, washers, or thread rods. They are designed so that after tightening down the fastener in the assembly, the rubber of the seal will be compressed to the predetermined amount closing the clearance gap between the fastener and the mating components. The built-in metal ring allows the seal to be efficient and easy to use because it regulates the amount of compression on the elastomer.

​Applications

Fastener seals are intended to take the place of an O-ring in certain assemblies. By utilizing a fastener seal there is no longer a need to have an O-ring groove machined into the component that the faster will pass through. Fastener seals are typically used in situations where equipment needs protection from possible exposures to water, dust, dirt, chemicals, oils, gases, or other liquids or if there is a need to prevent leaks of pollutants leaking into the surrounding environment. The specialized seals are also ideal for situations with extreme conditions such as weather, temperatures, or pressures.
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Benefits of using fastener seals

Using fastener seals is incredibly effective for applications that are going to be in highly adverse conditions or need a seal that cannot fail because any liquids or contaminants could cause serious damage. This could range from anything such as being outdoors where it is exposed to dust, dirt, mud, or water, or equipment that has electrical components that could be damaged if liquids get in. Replacing an O-ring with a fastener seal around screws, bolts, washers, or other items allows you to confidently know that nothing can get in or out of that seal.
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Common industries

Fastener seals can be used in a wide variety but below are some of the most common uses:

• Electrical components, like circuit boards, sensors, cameras…etc.
• Manufacturing Equipment
• Medical Equipment
• Hydraulics equipment
• Conveyor belts
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Common material varieties

Our 2 most common materials for Dichtomatik branded fastener seals are NBR 70 or FKM 70 and include a metal ring.

• NBR 70 temp:-22°F to +212°F (-30°C to +100°C): good resistance to mineral oils and greases, hydraulic oils, Flame retardant hydraulic fluids (max. +122°F or +50°C)
• FKM 70 temps: +5°F to +392°F (-15°C to +200°C): good resistance to mineral/synthetic oils and greases, ATF oils (max. +302°F or +150°C), flame-retardant hydraulic fluids HFD, aliphatic, aromatic, and chlorinated hydrocarbons, weather, ozone, and aging. Pressures of up to 25 MPA are possible for installation without a counterbore.
• Metal ring: made of standard steel with a zinc-chromate surface, rust, and acid-resistant steel

 
Fastener seals are incredibly effective seals in highly demanding applications because of their ability to keep fluids and contaminants from leaking into or out of the equipment.
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Content originally from Freudenberg-NOK Industrial Service​​. Reused here with permission.

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