Different Types of Oil Seals
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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.
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.
Contact us to discuss your requirements of high speed rotary shaft seals. Our experienced sales team can help you identify the options that best suit your needs.
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.
Mechanical seals are used mainly in pumping applications (although the principles are the same for mixers, blowers and compressors). In essence, the pump has two main elements; the first being a rotating shaft and the second being the pump casing. Without a seal, the pumped medium (water, waste, oil, etc) would leak and the pump would be ineffective. The mechanical pump therefore creates the seal between the moving part (dynamic) and the stationary part (static). Because of this Mechanical seals are often called many things including shaft seals, pump seals, rotary shaft seals, water pump seal and combinations of these. Whatever you call it, the product is essentially the same.
Mechanical seals or more technically “end face mechanical seals” were designed in the early s but really came to prominence during the post-war boom (late s) in both industrial and domestic equipment sales.
The elements of a mechanical seal are what make it unique. They are:
- Stationary component (commonly referred to as the seat).
- Stationary component sealing member.
- Rotating component.
- Rotating component sealing member.
- Spring.
- Gland plate.
- Clamp ring
The seal between the stationary component and the rotating component is called the ‘Primary Seal’ and is the most important. However there is a ‘Secondary Seal’, which is typically an O Ring and sits between the rotating component sealing member and the shaft of the pump.
The spring is used to create just the right pressure in the primary seal between the stationary and rotating surfaces.
The primary seal surface in various mechanical seal types come in a vast array of materials, such as Carbon-graphite, Silicon carbide, Tungsten carbide and Alumina ceramic. The choice of material is dependent on the medium (the liquid to be sealed), the pressures the seal must withstand and the temperatures of the medium. Speak with your mechanical seals supplier to determine the best materials for your application.
Before the invention of mechanical seals, mechanical packings or gland packings were used. These worked well in principle, but had a higher leakage rate (not ideal for some applications) and can handle higher temperatures and pressures (thanks to the sprint component).
Additionally, the use of packing in earlier designs caused shaft and sleeve wear that reduced the life of the pump and increased costs. Mechanical seals therefore improve equipment lifespan.
The other benefit is that they are self-lubricating in that their design specifically allows a very small amount of leakage onto the sealing surface, which lubricates and keeps the primary seal from eroding. Finally, mechanical seals require virtually zero maintenance as they do not require periodic tightening as Gland packing would.
Ultimately therefore, mechanical seals are a simple, elegant and cost effective solution to creating a long-life seal in dynamic applications.
For more Oil Seal Kitinformation, please contact us. We will provide professional answers.
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