In Part 1, we explained the structure, functions, and types of oil seals.
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Oil Seals (Part 1): The structure, functions, and types of oil seals
Oil seals come in various shapes to fit the machines and substances to be sealed.
For this reason, when designing a machine, it is important to select the oil seal that is right for that machine.
That's where this column comes in.
We will explain the key points for selecting the oil seal that is right for your machine.
Oil seals come in a wide range of types, and they also have various sizes.
When selecting the right oil seal for your machine from among these many varied types of oil seals, the following two criteria are very important.
If these criteria are met, damage of the machine can be reduced, the time needed to replace the oil seals when performing repairs can be shortened, and the machine can be used for a longer period of time.
In this way, selecting the appropriate oil seal will lead to machine design that is economically superior!
In general, oil seals should be selected in the order of priority indicated in Table 1.
However, when you actually select the oil seal to use, the most important factors are past success history and points of improvement, so it is not necessary to follow this order to the letter.
Select your oil seal type according to Table 2.
＜Seal selection example＞
Based on the above flowcharts, the oil seal type that meets the requirements shown in Table 3 would be the type code MHSA or HMSA shown in Table 4.
Shaft surface speed
(peripheral speed)
6 m/s 5 Air-side condition DustyFor a more detailed discussion of seal types and type codes, please see the following:
The rubber material used in the oil seal should be selected based on the operational temperature and substance to be sealed.
Table 5 lists the major rubber materials along with their operational temperature ranges.
Note that it is necessary to check the compatibility with fluids.
＜N.B.＞
Extreme pressure additives are compounds added to the lubricant. They are activated by heat and chemically react against rubber, which deteriorates rubber properties. For this reason, it is necessary to check for compatibility with rubber materials.
Nitrile rubber (NBR)
Standard typeWell-balanced in terms of resistance to abrasion and high and low temperatures
-30～100
Necessary to check compatibility with fluids
(See *2)
Fluids
• Fuel oil
• Lubricating oil
• Hydraulic fluid
• Grease
• Chemicals
• Water
110
Hydrogenated nitrile rubber (HNBR)
Standard typeCompared with nitrile rubber, superior in resistance to heat and abrasion
-30～140
Acrylic rubber (ACM)
Standard type High oil resistance and good abrasion resistance -20～150
High- and low-temperature-resistant type Improved low temperature resistance and same level of heat resistance as the standard type -30～150
Silicone rubber (VMQ)
Standard type Wide operational temperature range and good abrasion resistance -50～170
Fluoro rubber (FKM)
Standard type The most superior in resistance to heat, and good abrasion resistance -20～180
Notes
*1 ASTM: American Society for Testing and Materials
*2 For more details on fluid compatibility, please see the following:
Rubber materials, operational temperature ranges and their compatibility with fluids
The metal case and spring material used in the oil seal should be selected based on the substance to be sealed.
Table 6 shows how to select the metal case and spring materials.
Cold rolled carbon steel sheet
(JIS* SPCC)
Stainless steel sheet
(JIS* SUS304)
High carbon steel wire
(JIS* SWB)
Notes
* JIS: Japanese Industrial Standard
✓: Compatible
✗: Incompatible
―: Not applicable
Oil seals can show good sealing performance in combination with properly designed shafts and housings.
Table 7 shows the shaft design checklist.
Table 8 shows the housing design checklist.
Nominal seal width
b, mm
Nominal seal O.D.
D, mm
F
mm Over Up to ― 10 D - 4 10 18 D - 6 18 50 D - 8When the total eccentricity is excessive, the sealing edge of the seal lip cannot accommodate shaft motions and leakage may occur.
Total eccentricity is the sum of shaft runout and the housing-bore eccentricity.
Total eccentricity, shaft runout and housing-bore eccentricity are generally expressed in TIR (Total Indicator Reading).
The allowable total eccentricity is the maximum total eccentricity at which the sealing edge can accommodate shaft rotation and retain adequate sealing performance. The oil seal's allowable total eccentricity is affected by the design of the oil seal, the accuracy of the shaft, and the operating conditions.
For details on shaft and housing design, please see the following:
Examples of allowable total eccentricity for oil seals
Oil seal performance is affected by not only the type and material of the selected oil seal, but also a variety of other factors, such as operating conditions, total eccentricity, rotational speed, the substance to be sealed, and lubrication conditions.
Figure 9 shows items relating to oil seal characteristics.
For a more detailed discussion of seal characteristics, please see the following:
Seal characteristics
When selecting the oil seal that is right for your machine, it is important that the oil seal be appropriate for the requirements of the usage environment and that it be easily acquired for replacement.
In this month's column, "How to select the right oil seal," we conveyed the following points:
1) Oil seal shape and material should be selected based on the housing, substance to be sealed, pressure, rotational speed, total eccentricity, and air-side conditions.
2) Oil seals can show good sealing performance in combination with properly designed shafts and housings.
3) Oil seal performance is affected by not only the type and material of the selected oil seal, but also a variety of other factors, such as operating conditions, total eccentricity, rotational speed, the substance to be sealed, and lubrication conditions. For this reason, diligent care is required in oil seal selection.
In order for the sealing property of the oil seal you selected to really shine, attention needs to be paid to how it is handled.
In the event of seal failure, it is necessary to take effective countermeasures.
We will cover these points in the next column, "Oil Seals (Part 3)".
If you have any technical questions regarding oil seals, or opinions/thoughts on these "Bearing Trivia" pages, please feel free to contact us using the following form:
All units of the car are interconnected. Thanks to this, the vehicle is a single mechanism in which every spare part is important. One of the very first problems that the first ICE developers faced was how to minimize the leakage of lubricant in places where the shaft exits the unit housing.
Let's take a closer look at one small detail that no car can do without. This is an oil seal. What is it, what is its feature, when is it needed to be replaced, and how to do this work using the example of crankshaft oil seals?
What are oil seals
An oil seal is a sealing element that is installed at the junction of various mechanisms with rotating shafts. Also, a similar part is installed on parts that perform a reciprocating movement in order to prevent oil leakage between the movable element and the body of the mechanism.
Regardless of the design and purpose, this device is in the form of a ring with a compression spring. The part can be of different sizes, as well as made from different materials.
Principle of operation and device
The oil seal is enclosed in a housing through which the mechanism spindle passes. There is a sealing material on the inside of the housing. It rests on all sides of the shaft, which will come out of the unit body, for example, a motor or gearbox. The diameter of the product should be such that, during pressing, its seal is tightly pressed against the spindle from the inside, and from the outside - against the fixed part of the mechanism.
In addition to its sealing function to prevent grease from leaking out, the oil seal is also used as a dust seal that traps dirt and prevents it from entering the mechanism.
In order for a part to remain effective under different operating conditions, it must meet the following characteristics:
Due to the vibrations that occur during the operation of the unit, the seal must be elastic, which will reduce the wear of both the element itself and the working part.
The stuffing box must prevent grease from flowing out of the device, therefore it comes into contact with chemically active substances. For this reason, the material should not deteriorate from exposure to grease.
Continuous contact with moving and rotating parts can cause the seal contact surface to become very hot. For this reason, it is important that the material of this element retains its characteristics, both in the cold (for example, in the winter the car is parked in the parking lot), and during prolonged driving in hot summer.
Where are?
The number and design of oil seals depends on the car model and its features. In any vehicle that has an internal combustion engine, two seals will certainly be present. They are installed on both sides of the crankshaft.
In addition to this part, the following car parts need seals:
The valve stem of the gas distribution mechanism (also called valve stem or valve gland);
Timing camshaft;
Oil pump;
Front wheel drive vehicle wheel hub;
Steering rack;
Rear axle reducer;
Differential;
Rear axle shaft;
Gear box.
What materials are oil seals made of
Since the contact surface of the product and the mechanism can be very hot, the gland must have heat-resistant properties. Also, an increase in the heating temperature is due to the fact that during the rotation of the shaft, the edge of the part is in constant friction. If the manufacturer uses ordinary rubber or other material that does not withstand high temperatures to create this element, accelerated destruction of the stuffing box is ensured.
Seals of the crankshaft and camshaft should have such properties, since while the engine is running, these parts are constantly subjected to thermal loads and are subject to friction.
The same can be said for the hub seals. They must use quality material. In addition to resistance to friction and high loads, these parts must have a high-quality and durable body, and the main part must be reinforced. There should be an additional elastic element on the edge to prevent dirt from entering the knot. Otherwise, the working life of the stuffing box will be significantly reduced, and the mechanism itself will not be able to serve for a long time.
The following materials can be used by manufacturers of these parts:
NBR - rubber from butadiene rubber. The material retains its properties in a wide range of temperatures: from 40 degrees below zero to +120 degrees. Oil seals made of such rubber are resistant to most lubricants and do not deteriorate when fuel hits their surface.
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ACM - rubber with an acrylate structure. The material belongs to the category of budget goods, but with good properties suitable for the manufacture of such products. Automotive acrylate rubber oil seal can be operated in the following temperature range: from -50 to + 150 degrees. Hub seals are made from this material.
VMQ, VWQ etc. - silicone. A problem often arises with this material - as a result of contact with certain types of mineral oils, accelerated destruction of the material can occur.
FPM (fluororubber) or FKM (fluoroplast) - the most common material today. It is neutral to the effects of chemically active fluids used in cars. Such seals withstand thermal loads well in the range of -40 to +180 degrees. Also, the material has good resistance to mechanical stress. Most often it is used for the manufacture of seals for power unit assemblies.
PTFE - teflon. Today this material is considered ideal for the manufacture of seals for vehicle components. It has the lowest coefficient of friction, and the range of permissible temperatures varies from -40 to +220 degrees Celsius. None of the technical fluids used in machines will destroy the oil seal. True, the cost of such parts is much higher compared to other analogues, and during the installation process it is necessary to follow the manufacturer's recommendations for replacement exactly. For example, before installing the seal, it is required to wipe the shaft and the contact surface of the installation site dry. The part comes with a mounting ring, which is removed after pressing.
How to choose oil seals for a car
The advantage of most of the oil seal modifications is their low cost. True, when a master carries out the work on replacing the seal, the price of such a procedure is several times more expensive than the price of the part itself.
In addition to the price of elements, a number of factors affect the choice:
For which node the product will be used. The most loaded glands must withstand constant heating above 100 degrees, have a minimum coefficient of friction, and be resistant to chemically active technical fluids.
The part must be specific to the environment. For example, if an old product was used to contain antifreeze, then a new seal must be created to contact such a substance.
Do not use analogs that are intended for installation on other units. It is best to purchase an oil seal for the mechanisms of a particular car brand. If you can't find the original, then you can pick up an analogue from another manufacturer. In this way, malfunctions due to the installation of inappropriate seals are excluded.
Brand. Some motorists mistakenly believe that the word "original" always means that the part is made by the manufacturer of the car itself. But more often than not, this is not the case. The fact is that most auto concerns either have a separate subdivision with a narrow profile under their subordination, or use the services of third-party companies, but put their own label on the ordered batch. On the auto parts market, you can find parts that are not inferior to the original in quality, and in some cases even better. On the other hand, some wonder if it's really worth paying for a brand if there is an opportunity to buy a cheaper equivalent. In short, there is a reason for such a purchase, since self-respecting companies try to maximize the quality of their products, and this leads to an increase in the price of the product.
What to look for when choosing
In addition to these factors, when buying new oil seals, a motorist should pay attention to the following nuances:
If an analogue is purchased instead of the original, it is important to make sure that its design fully matches the old part;
The width of the new gland may be less than that of the old element, but not wider, because this will complicate or make it impossible to install a new gasket. As for the diameter of the contact hole through which the shaft passes, it should ideally fit the dimensions of the spindle;
Is there a boot on the new part - a thread that prevents dust and dirt from entering the mechanism. Most often this part consists of two elements. The first is the boot itself, and the second is the oil scraper;
If a non-original part is purchased, then preference should be given to a well-known brand, and not dwell on the cheapest product;
On domestic cars, you can use analogues designed for foreign cars. The opposite is unacceptable, although recently the quality of some parts of domestic production has become noticeably better;
A notch can be made on the inside of the gland. In the direction of this element, all parts are divided into three categories: left-hand, right-hand, and universal (capable of removing oil, regardless of the direction of rotation of the shaft).
When choosing a new part, you should pay attention to its dimensions. To speed up the search and eliminate the possibility of buying an inappropriate oil seal, you need to pay attention to its marking. Most manufacturers put the following designations on the body: h - height or thickness, D - outside diameter, d - inside diameter.
Leading manufacturers
An original product can be distinguished from a fake by the presence of the name of the manufacturer of the machine, which needs to be replaced. It should be borne in mind that not all companies independently manufacture replaceable components for their models. Most firms use the services of third-party companies, so the "original" is not always the cheapest option, and a more budgetary analogue may be identical to the spare part sold with the manufacturer's label.
Here are the most famous companies that sell not only worthy oil seals, but also other products:
Among the German manufacturers of automotive components and repair kits, the following stand out: AE, the products of the VAG concern, Elring, Goetze, Corteco, SM and Victor Reinz;
In France, Payen is engaged in the manufacture of quality seals;
Among Italian manufacturers, products such as Emmetec, Glaser and MSG are popular;
In Japan, good quality oil seals are made by NNK and Koyo;
South Korean company KOS;
Swedish - SRF;
In Taiwan - NAK and TCS.
Most of the listed companies are official suppliers of replacement parts for car assembly concerns. Many leading brands use products from some of these companies, which clearly demonstrates the reliability of spare parts sold in the market.
How to replace crankshaft oil seals
The very first thing you should pay attention to before choosing a new oil seal is wear that may be present at the contact point of the old part. This wear should be taken into account when choosing an analog. If the diameter of the seal does not match the size of the shaft, the part will not cope with its task, and the technical fluid will still leak out.
If it is not possible to purchase a repair analog among the products (which is extremely rare, except that you can search among options for other cars), you can buy a new oil seal, just install it so that the edge does not fall into the place of wear. When the bearings are worn out in the mechanism, but they can still not be changed, then the new oil seal on the inside should have special oil-bearing notches.
Before changing the seal to a new one, a little analysis should be done: for what reason the old part is out of order. This may be natural wear and tear, but in some cases the oil seal begins to leak oil due to breakdowns in the mechanism. In the second case, installing a new oil seal will not save the day.
An example of such a situation would be a breakdown that causes the shaft to move freely in the horizontal direction. In this case, one cannot be content with just replacing the seal. It is required first to repair the unit, and then change the consumable, otherwise even a new element will still pass fluid.
As for the procedure for replacing the crankshaft oil seals, then first you need to do some preparatory work. First, disconnect the battery. For information on how to do this correctly, read separate review... Secondly, we must drain the oil from the motor. To do this, warm up the engine, unscrew the drain plug in the pan, and drain the grease into a prepared container.
Replacing the front and rear oil seals has its own specifics, so we will consider these procedures separately.
Replacing the front crankshaft oil seal
To get to the front crankshaft seal, you will need to do some dismantling work:
A cover is removed from the drive belt (or chain) to prevent foreign objects from entering the timing drive;
The timing belt or chain is removed (some of the subtleties of the procedure for removing and installing the timing belt are described here).
The pulley attached to the crankshaft is disconnected;
The old oil seal is pressed out, and a new one is installed instead;
The structure is assembled in reverse order. The only thing is that for the engine to work adequately, it is required to correctly set the labels of the gas distribution mechanism. Some engines fail in valve timing can damage the valves. If you do not have experience in performing such a setting, it is better to entrust it to a master.
When installing a new front crankshaft seal, there are several nuances to consider:
The seating area must be perfectly clean. The presence of foreign particles is not allowed, as they will contribute to accelerated wear of the consumable.
A small amount of oil should be applied to the shaft contact (seating edge). This will facilitate installation on the shaft, prevent tearing of the elastic part of the part, and the oil seal will not wrap (the same applies to replacing other oil seals).
The seal of the unit body must be treated with a special heat-resistant sealant.
Replacing the rear crankshaft oil seal
As for replacing the rear seal, then in this case it will be necessary to put the car on an overpass or take it to the inspection pit. This is the safest way to work. All other options (using a jack or props) are unsafe.
Here is the sequence in which this work is performed:
First you need to dismantle the gearbox;
The clutch basket is removed from the flywheel (at the same time, you can check the condition of this unit);
The flywheel itself is dismantled;
The old seal is removed, and a new one is installed instead;
The flywheel, clutch and gearbox are installed back.
It is worth considering that each car model has its own engine device, which means that the process of dismantling and installing oil seals will be different. Before starting to disassemble the mechanism, you should make sure that not a single part of the unit is damaged, and that its settings are not lost.
The most important thing when replacing seals is to prevent bending of their edges. For this, a sealant or engine oil is used.
Gland sizes
Most manufacturers of auto parts make standard oil seals for specific units and mechanisms of different car brands. This means that the crankshaft oil seal for the VAZ , regardless of the manufacturer, will have standard dimensions. The same applies to other car models.
Using car manufacturer standards makes it easier to find the part you want. At the same time, the motorist only needs to determine for which unit he is choosing a spare part, choose the highest quality material, and also decide on a brand.
Many shops make it even easier to find a new part. Tables are created in online catalogs where it is enough to enter the name of the machine: its make and model, as well as the unit for which you want to select an oil seal. According to the results of the request, the buyer can be offered an original spare part from the manufacturer (or its official distributor) or a similar, but different brand.
At first glance, replacing seals in a car might seem like an easy procedure. In fact, in each individual case, the procedure contains many subtleties, due to which sometimes the machine starts to work even worse after repair. For this reason, such a complex procedure is best carried out in auto repair shops, especially if it is a foreign car of the latest generations.
In conclusion, we offer a detailed video about the difference between externally identical oil seals:
EVERY AUTOMOTIVE SHOULD KNOW THIS! ALL ABOUT OIL SEALS
Watch this video on YouTube
Questions and answers:
What is an engine oil seal? It is a rubber sealing element that is designed to seal the gap between the motor housing and the rotating shaft. The engine oil seal prevents engine oil leakage.
Where is the oil seal in the car? In addition to the motor (there are two of them - on both sides of the crankshaft), oil seals are used wherever it is necessary to prevent oil leakage between the body and the moving parts of the mechanism.
Additives & Oil Seals
Today’s cars are becoming increasingly powerful but are still retaining the convenient size which fits with the chaotic world we live in. With cars becoming more demanding, the engines have to do more while trying to meet efficiency targets, this is helped by the engine oil that we put in to keep the car ticking over.
Today’s cars are becoming increasingly powerful but are still retaining the convenient size which fits with the chaotic world we live in. With cars becoming more demanding, the engines have to do more while trying to meet efficiency targets, this is helped by the engine oil that we put in to keep the car ticking over. However, although this oil is beneficial for many parts within the engine it also causes a lot of harm to components such as oil seals.
Oil additives are chemical components that improve the lubricating performance of the base oil. These additives are vital for the proper lubrication and prolonged use of engine oil in modern combustion engines. Without many of these the oil would become contaminated, breakdown, leak out or not properly protect the engine parts at all operating temperatures. Some of the most important additives include those used for viscosity and lubricity, contaminant control, for the control of chemical breakdown and for seal conditioning. The viscosity of oil also changes with temperature, becoming more viscous when cold and less viscous when hot. So the viscosity of the oil can be affected both by the weather and how hot your engine is.
Although the additives in the oil are extremely beneficial for most engine components, the additives being used today have an adverse effect on oil seals, often causing them to wear or leak causing early repairs being done to fix the problem. One way a seal can fail from oil additives is due to chemical compatibility, this is an issue that arises when changes are made to the formula of lubricants. Sometimes even though the base fluid remains the same an additive causes the seal to fail. However, the effect is not always predictable as the seal may wear out faster than expected or simply not perform as it should.
Alternatively the seal material can break down when it encounters a corrosive fluid. This will occur when the improper seal material is chosen for an application. The use of non-compatible materials can lead to chemical attack by oil additives, hydrolysis, and/or oxidation of seal elements. This will result in the loss of the seal lip interface, softening of the seal durometer, swelling, and/or shrinkage of the seal. Discolouration of the seal is an indicator of chemical erosion.
To avoid the seal from wearing early or not performing as expected then certain things need to be looked at. The fluid pressure range needs to be checked, this includes not just the operating range of the fluid system pressure, but also the severity and frequency of the system pressure peaks.
Another crucial factor is the temperature range as this will be effected by the additives within engine oil and can also be effected by the engine temperature and even the weather. The resting and operating temperature range of the fluid and the cylinder assembly are important with seal selection.
The fluid type due to the fluid media and viscosity are important for seal efficiency and effectiveness. Getting this right will ensure the long life of an oil seal as well as reduce the need for early repairs.
The size of the seal will determine the size of the cylinder. This includes the rod and bore dimension, seal groove dimensions, gaps, cylinders overall length, surface finish specifications and the stroke length. How the cylinder is used will impact how long it can last under certain operating conditions. This includes cylinder installation, environmental factors, and exposure to harsh conditions.
With oil additives being added to engine oil it is becoming ever more crucial to ensure the right seal is chosen not just for the application but for operating conditions and to work well alongside the additives.
Corteco offers a range of more than 7,000 gaskets and over 6,500 different shaft seals Simmering® and valve stem seals in OEM quality for a wide range of vehicle applications to ensure you can get the right seal for the job.
For more information on Corteco’s range of products head to www.corteco.com/en/products/sealing alternatives head over to Facebook, Twitter or LinkedIn and follow Corteco to get all the latest new, technical information and promotions.
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