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.
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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.
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Avoid using any Chinese bearings,they are of notoriously poor quality,seals no better. Go to your local dealer that sells bearings and seals. Give him an old seal and measure the crank diameter,seal hole size in crankcase and width of the seal. Then be sure to specify a double-lip seal or you will likely get a single lip seal. As for the bearings there will be a number on them(And in the parts book)such as , etc, Then specify for the the bearings that they come with the teflon(Or plastic) cage,this is crucial!!! Especially for Huskys and Jonsereds which were still fitted from factory with metal cage bearings,and these type have a much higher failure rate. The bearings with teflon cages can tolerate higher revs,and do NOT destroy the piston and cylinder in a cage failure,in fact I haven't seen any blow... Then make sure the bearings are a good known brand. Buying your bearings and seals this way is cheaper too!
In fact the best bearing set-ups,have no cage a all! Mercury marine engines use all needle bearings on the crank,and the big end and piston pin end of the con rod. No cages. But what a job to assemble,on a 4 cylinder motors I rebuilt there something like 600 needle bearing total to install!(All glued in place with grease and your hands can't tremble or you spill the needles all over) In most applications(Not main bearing-ball bearing assemblies we use on saws) the cage is there simlply for ease of installation.Without the cage you can fit almost twice as many needles,rollers,or balls into the application and this increases the load carrying ability accordingly. They even sell ball bearing assemblies with no cage,all balls inside. But I've checked and they don't make those bearings quite as small as the or bearings most commonly used in saws. But I have built some competition saws with full needle bearings and no cages,they will never fail...
I would NEVER put them in a saw! I encountered them in various machines and they were always destroyed.Risk your saw to save only a few dollars?
Why wouldn't a person just buy his bearings from your local bearings dealer,far less cost than original bearings and the same thing.
Also if your old bearings had a metal cage you can order bearings with the "teflon" cages,They can handle more revs and last longer. Also when a main bearing fails in a saw you will see the metal bearing cage all bent and piled up and usually it's pieces of the cage that get pumped up into the cylinder and cause piston/cylinder damage.It's the cage that causes most bearing failures.
Also another real secret about bearings- They are all also rated C1,C2,or C3,that refers to the clearance of the ball bearings,how "tight" the bearings are. Stihl told me that they use a tighter bearing than Husky/Jonsered does.
It used to show in the parts books for husky and Stihl, for the bearing you would see a C2 or C3 number.I don't know if the parts pages for them now do that.. It would be good to investigate that because if Stihl was using a tighter bearing I would be using that style in other saws too. When you get a new bearing it has the C number on the box and the bearing too I think. It's been many years now but i think Stihls used a C2 bearing and Huskys C3. C1 would be too tight for high speed and high heat apllications.
I do know that I saw far less bearing failures in Stihls than Huskies,only a few over very many years...
In fact the best bearing set-ups,have no cage a all! Mercury marine engines use all needle bearings on the crank,and the big end and piston pin end of the con rod. No cages. But what a job to assemble,on a 4 cylinder motors I rebuilt there something like 600 needle bearing total to install!(All glued in place with grease and your hands can't tremble or you spill the needles all over) In most applications(Not main bearing-ball bearing assemblies we use on saws) the cage is there simlply for ease of installation.Without the cage you can fit almost twice as many needles,rollers,or balls into the application and this increases the load carrying ability accordingly. They even sell ball bearing assemblies with no cage,all balls inside. But I've checked and they don't make those bearings quite as small as the or bearings most commonly used in saws. But I have built some competition saws with full needle bearings and no cages,they will never fail...