Sealing 101: Everything you need to know to pick the right seal

July 11, 2023
By Freudenberg-NOK Industrial Services for the Blue Print

Are you asking yourself what is a seal, and where do I find them? Today we're hopefully going to bring more clarity than Google when you search for "seal" which brings up cute animals and a British singer. Many people have heard of O-rings but many never realize that there are so many other important seals beyond a simple O-ring.
 
Seals are one of the most critical components that most people wouldn’t even think twice about. You can find seals in almost any application where you need to prevent leakage of liquids, or gases escaping or prevent outside contaminants such as dirt getting into the equipment.
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Where do I find seals?

So when I go visit my customers do they have seals in their equipment? In most cases, it will be yes because seals are one of the most critical components in equipment to prevent leaks, contamination, and damage from exposure to the environment.

​Some common examples of where you find seals would be in a shaft of hydraulics or pneumatics, pumps, engines, rollers at a steel mill, compressors, or preventing leaks at a chemical plant. The places where you find a seal are truly almost limitless, the easiest way to think of it is anywhere a liquid, gas, or solid could escape or get into the equipment there will be a seal ensuring safe and reliable operation.
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Types of seals

Okay so I can find these seals almost everywhere but what types of seals are in that equipment? Well, seals can be broken down into two main categories, static seals and dynamic seals. Static seals are found in mating glands where there is no motion on the sealing surface. Dynamic applications are used to create a barrier between a static and a moving surface. These seals are used to retain fluids, pressure and remove contaminants most commonly used in linear, oscillating, and rotating applications.
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Static seals

• O-rings: These are one of the most common seals that you can find anywhere because of the diversity of applications where they are utilized. O-rings are the most simple seal you can find on the market because it is a simple circle designed to seal around mechanical components or fill spaces along groves to prevent leaks. Due to the huge range of applications, you may find an O-ring in a massive range of sizes, materials, and hardness.
• Clamp Seals: Clamp seals are most commonly used to maintain hygienic standards during the manufacturing process in applications such as dairies, distilleries, bakeries, breweries, or other food and beverage production facilities.
• Gaskets: Gaskets are used to fill the space between mating components and prevent leakage between the two objects while under compression. These are extremely common seals to find in applications that don’t come into contact with movement such as a pipe fitting.

Dynamic seals

• Oil seals: Also called radial shaft seals are used in dynamic applications to keep oil, grease, and other harsh chemicals leaking out of moving applications. An oil seal consists of a metal case and rubber sealing lift that fits closely around the shaft. The rubber lip creates a barrier that prevents oil and other fluids from leaking and causing damage.
  Fluid power seals: are most commonly used in hydraulic and pneumatic applications and are designed to prevent fluids or gases from leaking into or out of the system. The most common fluid power seals are piston and rod seals.
• Other dynamic seals:
  • Rotary seals
  • U-cups
  • V-rings
  • Wipers
  • Guide rings

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Common sealing materials

There are truly a massive amount of different sealing materials and compounds but below are some of the most common you will see utilized.

• NBR (Nitrile Butadiene Rubber)
• FKM (Fluoroelastomer) 
• PTFE (Polytetrafluoroethylene)
• FFKM (Perfluoroelastomer)
• HNBR (Hydrogenated Nitrile Butadiene Rubber)
• Silicone

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Selecting the right seal

Selecting the right seal is critical to ensuring the efficient operation of equipment. When selecting what material to use in your application seal there are a few key aspects to consider.
 
The first thing to consider when selecting what seal is right for you is to know what the temperature range will be for the application. Every sealing material has a unique range of temperatures it performs best, and extreme heat, cold, or fluctuations affect the materials differently. It is critical to ensure the seal can perform in the temperatures you will be subjecting it to avoid a sealing failure and ensure it operates efficiently.
 
Next, you need to consider the environment that the seal will be in because this could greatly affect the lifespan or even cause a seal failure if the wrong material is utilized. You need to consider the pressures, chemicals, and outside environment such as exposure to sun, dirt, or water. Just like temperature certain materials perform excellently in certain chemicals but can begin to break down when subjected to the wrong contaminants.
 
You also want to consider what unique needs your industry requires. For example, if you are manufacturing pharmaceuticals or food and beverages you can’t just use any seal off the shelf. You need to take extra care in ensuring you are utilizing hygienic FDA seals to ensure you comply with the regulation.
 
We know that selecting the right seal is an incredibly important decision that isn't always easy without specialized knowledge. As a company that specializes in seals and sealing technology our experts at Freudenberg-NOK are here to support our partners at Fastenal, and your customers find the ideal seal for their unique needs.

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​Content originally from Freudenberg-NOK Industrial Services. Reused here with permission.

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