Sealing 101: Everything You Need to Know to Pick the Right Seal

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.

Different Types of Oil Seals

If you are looking for more details, kindly visit NNK.

Are you looking to keep your machinery free from any unwanted leakages but aren’t sure which rotary shaft seal is right for your needs? This guide will provide you with everything you need to know in order to select the right one for your application.

Oil seals, which are also known as rotary shaft seals, fluid seals or grease seals, play an important role in closing down the gaps between moving and stationary elements of mechanical equipment.

By preventing lubricants from escaping, they protect key components of machinery from being damaged by leaks of various fluids. Everything from car engines to assembly machines use these oil seals to remain free from any harmful interactions that can cause serious and expensive damage to any of their critical parts.

There are a wide range of oil seals to select from for any number of uses, so this guide will break down the most common seals to help you choose the right one for whatever piece of machinery you are working on.

What are rotary shaft seals?

Rotary shaft or oil seals are placed between moving and stationary pieces of machinery to ensure that contaminants, moisture, corrosive materials and abrasives do not damage the various components. They can also prevent unwanted mixing of fluids, including water and oil combining within a machine.

How are Oil Seals made?

First, an elastomer, most often nitrile, is vulcanised to a metal ring. This creates a stiffening effect that includes a specialised metal tension spring directly behind the sealing lip, keeping the oil seal firmly in place against the moving part.

Oil Seal Materials

There are many different materials used to manufacture oil seals.

Leather Oil Seals - Leather Seals, also known as Type L Oil Seals, are most common in components that are subject to dirt and poor lubrication. Since they come pre-lubricated and are able to absorb fluids, leather oil seals are able to provide sealing properties in conditions that synthetic rubber is unable to.

Synthetic Rubber Oil Seals - Styrene Butadiene Rubber oil seals, or just SBR oil seals, offer strong resistance to abrasions and lesions, making them an ideal seal for fast-moving machinery. With the ability to withstand extreme temperatures with its heat-aging qualities, they can be used in outdoor components. They are also seen as more cost-effective oil seals than natural rubber.

Nitrile Oil Seals - Nitrile oil seals, which is the commonly used term for acrylonitrile-butadiene rubber seals, is a very good general-purpose option due to the flexibility of use across a variety of components. The resistance is strong against fats, hot water, gasoline, mineral oils, grease and animal oils, making them the most often-used oil seals. They do not have a wide temperature range, making them a poor choice for machinery that can see extreme changes in temperature.

Viton Oil Seals - A synthetic rubber and fluoropolymer elastomer, Viton is used to make oil seals that provide resistance in both high temperature, up to 250°C and low compression set components. They also offer a high resistance to chemicals and abrasions, so they can be used in elements that regularly interact with petroleum and solvents.

For more information, please visit rubber oil seal.

Polyacrylate Oil Seals - Mostly selected for automotive and transmission uses, polyacrylate seals are able to withstand fuel, oil, ozone, sunlight and weather when used. With cars exposed to all these different fluids and elements, they are the perfect choice. However, they should not be used in low temperatures, as their flexibility weakens when cold.

Silicone Oil Seals - Designed to absorb lubricants in order to lessen wear and friction, silicone rotary shafts also offer high thermal resistance and a large temperature range. But, they do not handle abrasions well or interact with oxidized oils.

PTFE Oil Seals - A relatively new and exciting oil seal, the use of polytetrafluoroethylene means that they can withstand dry or unlubricated operations. With a massive thermal range of  -130ºC to +200ºC and a strong resistance to chemicals, they are considered to be the future of rotary shaft seals.

How to Choose the Right Oil Seal

There are several key factors to consider when you are selecting the oil seals for your next project to ensure that you protect your machinery from immediate and long-term damage.

Pressure - Many oil seals can only withstand low-pressure applications, so understanding the compression set of your components is key.

Temperature - Just like pressure, the temperature that your oil seal will be operating in must be known so that you can choose one that can withstand the heat or cold. PTFE have the widest range of temperature, making them useful for machines who can see usage in extreme weather or elements.

Shaft Speed - Considering the speed that the shaft will be moving, the runout, the housing bore and the type of oil being sealed is vital to making sure you select an oil seal that will not suffer from abrasions or spiralling.

Fluid Types - Various oil seals are able to withstand interactions with oils, fuels, grease, water and more. Knowing what type of fluid the rotary shaft seal will be in constant contact with will ensure the longevity of the seal and surrounding components.

Lubricant Amount - Seals will always perform best when lubricated, however in some machines there are more likely to be dry spells. For these cases, selecting a leather or PTFE seal will be beneficial, as both can operate with less lubrication than others.

If you require any assistance in discovering the factors that lead to the right oil seal choices, the Simply Seals Team is happy to assist you!

Find the right Oil Seal for your needs with Simply Seals!

With dozens of specifically-designed oil seals made from a variety of materials, it can be very difficult to understand the best choice for their machinery.

That is why the Totally Seals team is always available to assist you with choosing the correct style, material, and size of oil seal for everything from commercial machinery to hobby car building.