Also known as grease seals, rotary shaft seals, or fluid seals, oil seals play a pivotal role in mechanical equipment. They are often overlooked because they are a small part of the machine, but when these oil seals fail, the consequences can be huge, like seal leakages that are costly to fix.

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From assembly machines to car engines, oil seals prevent any harmful damage from occurring, which is why you must choose the right oil seal with the highest quality. There are many kinds of oil seals, all of which have several uses.

This article will guide you through the most common factors you should look for when buying oil seals to help you choose the right one for the machinery you’re working on.

11 Factors to Consider When Buying Oil Seals

Improper installation and poor-quality oil seals are some of the reasons that pieces of machinery get damaged. When choosing an oil seal, consider the following factors.

1. Temperature

The temperature range of the seal elastomer should match the temperature range of where you’ll install the seal. For example, high-temperature and high-pressure environments need more durable rubber, like Viton. If the oil seal is exposed to extreme temperatures outside of the elastomer’s range, the sealing lip may harden, break, and crack.

2. Material

The oil seal’s material matters, as it can determine how well it performs depending on its use. Sealing elements can come in leather, silicone, synthetic rubber, Viton, nitrile, and polyacrylate. Nitrile is good for general purposes, as it’s flexible and resistant against oils, hot water, and gasoline. However, it doesn’t do well in extremely high temperatures. Meanwhile, silicone oil seals lessen wear and tear by absorbing lubricants. They have a wide temperature range and high thermal resistance, too.

3. Pressure

Understanding the compression requirements of your components is important. Most ordinary oil seals are designed for very low-pressure applications (about 8 psi or less). If the intended application has high pressure, you should consider choosing an oil seal ideal for high pressure or changing to a pressure-free structure.

4. Shaft speed

The oil seal shouldn’t suffer from spiraling or abrasions. As such, you should consider the maximum allowable shaft speed, runout, type of oil seal material, type of fluid being sealed, and housing bore and shaft concentricity before buying an oil seal.

5. Shaft and bore tolerances

Close shaft and bore tolerances should be present if you want the best seal performance. It would be best to consider the shaft’s vibration, eccentricity, and end play.

6. Concentricity

You must align bore and shaft centers because misalignment can shorten the oil seal’s life cycle due to the excessive wear concentrated on only one side of the sealing lip.

7. Runout

It would be best if you kept runout to a minimum. When the center of rotation moves, it’s usually caused by a shaft whip or bearing wobble. When you add misalignment, then you’ll face a greater problem. Contrary to common practice, installing flexible couplings won’t correct misalignment, which is why you need the right oil seal to prevent all these issues from arising.

8. Quality

The quality of the oil seal affects its service life. The higher the quality, the longer the lifespan, reducing wear and tear and increasing your ROI through lower maintenance costs. While wear and tear issues are inevitable, you should mitigate them by using materials that last long. Here, the first step to ensuring quality oil seals is purchasing from a reputable oil seal supplier.

9. Shaft hardness

When shafts have a Rockwell (RC) hardness of 30 or more, you can expect the oil seal to have a longer seal life. For shafts exposed to more abrasive contamination, your oil seal should handle RC 60.

10. Shaft surface finish

You can tell that you have effective sealing if the shaft surface finish is in excellent condition. Sealing performance is greatly influenced by the spiral lead and the direction of the finish tool marks.

You’ll get the best sealing results when the shafts are ground or polished with concentric (no spiral lead) finish marks. If the shaft can’t help but have spiral finish leads, they should lead toward the fluid when the shaft rotates.

11. Lubricant

Oil or lubricants play a significant role in improving the oil seal’s performance. You should choose a lubricant compatible with the seal lip elastomer material and the right viscosity for the application. Incompatible lubrication can result in the wearing out of the oil seal.

An example of a lubricant you can use is Permatex Anti-Seize Lubricant, a highly refined blend of graphite, aluminum, and copper lubricants.

Choose the Correct Oil Seal for Your Needs

Types of Oil Seal Materials / Material Selection Guide for Oil Seals

Material Chart for Oil Seals

Oil Seals are also known as a Rotary Shaft Seal, shaft seal, lip seal, elastomeric lip seal or any variation of these. It is a simple device for excluding dust, dirt, water or any other contaminant whilst retaining lubricant in rotary shaft equipment. Generally, it has been developed as a means of protecting the bearings of rotating shafts.

Below is the chart for oil seal Materials selection:

Temperature range: between -10°C and +205°C (intermittent/compound specific between -20°C and +250°C)

Applications: Aflas® are created from an exceptional Fluoroelastomer (FKM), which is resistant to steam, petroleum oils, amine corrosion inhibitors, and hydrogen sulphide.

Resistant to: Steam, Petroleum Oils, H2S

Temperature range: between -55°C and +135°C

Applications: Carboxylated Nitrile (XNBR) oil seals are created from a low-temperature tolerant compound, also has an excellent abrasion resistance.

Resistant to: Water, Petroleum Oils

Temperature range: between -20°C and +205°C or between -45°C and +230°C (intermittent/compound-specific)

Applications: FKM Fluorocarbon oil seals distinguish a great resistance to solvents and petroleum oils. They are, therefore, great for high-temperature installations and have present low compression set attributes. Additionally, they are adapted for use with large chemical exposure and hard vacuum applications.

Resistant to: Transmission Fluids, Gasoline, Petroleum Oils

Temperature range: between -55°C and +205°C (dependant on core material)

Applications: FEP oil seals are an excellent option for static and slow intermittent dynamic applications. FEP is interfered by a poor memory at low temperatures. FEP is, however, very tough, a chemically inert polymer that has a spectacular working scope.

Resistant to: Majority of chemicals

Temperature range: between -60°C and +180°C (intermittent/compound specific up to +200°C)

Applications: Fluorosilicone (FVMQ) oil seals incorporate a good low and high-temperature persistence of Silicone (VMQ) and Fluorocarbon’s resistance to solvents, oil, and fuel. It also presents great resistance to gasoline and petroleum oils.

Resistant to: Gasoline, Petroleum Oils

Temperature range: between -30°C and +170°C (intermittent/compound specific up to +190°C)

Applications: Oil seals produced from Hydrogenated Nitrile (HNBR) present superior sour gas and petroleum oils resistance. Due to an extensive temperature range of Highly Saturated Nitrile, it happens to be most preferable material in Oil Industries.

Resistant to: H2S, CO2, Petroleum Oils

Temperature range: Buna-N between -40°C and +135°C (intermittent up to +150°C); Low-Temp between -65°C and +120°C

Applications: Nitrile (NBR) is currently the most extensively used elastomer in the Fluid Seal Industry. Furthermore, Nitrile oil seals incorporate exquisite reluctance to hydraulic oils, water, silicone greases, petroleum-based oils and fluids, and alcohols. Nitrile presents great stability of working attributes such as high tensile strength, high abrasion resistance, and low compression set combined with low cost.

Resistant to: Water, Petroleum Oils & Fluids, Hydraulic Oils

Temperature range: between -20°C and +150°C

Want more information on rubber oil seal? Feel free to contact us.

Applications: Polyacrylate oil seals have superior high-temperature resistance than that of Nitrile. Therefore, they are ideal for high surface speed oil applications.

Resistant to: Freon, Petroleum Oils

Temperature range: between -15°C and +85°C (intermittent/compound specific between -50°C and +100°C)

Applications: Polyurethane oil seals are used in high-stress hydraulic applications, in which highly pressured compounds are exposed to wear. Polyurethane, however,  presents a great high abrasion resistance qualities and high tensile strength.

Resistant to: Hydraulic Oils, Petroleum Oils

Temperature range: between -60°C and 250°C (special grades up to +300°C)

Applications: Silicone (VMQ) oil seals present a high lubricant absorbency. It minimizes wear and friction in certain applications.

Resistant to: Number of Acids, Petroleum Oils

Temperature range: between -50°C and +327°C (intermittent up to +350°C; compound specific)

Applications: Simriz® oil seals are created of an elastomer, which has the widest chemical resistance our of all elastomer materials. They incorporate all the elasticity and sealing strength of an elastomer and chemical resistance similar to that of FEP (Fluorinated Ethylene Propylene).

Resistant to: Majority of chemicals

The above information had been derived from numerous sources and the ratings are therefore intended as a guide only. Users must test under their own operating conditions to determine the suitability of any compound in a particular application and temperature.

M Barnwell Services is the UK’s largest independent stockist, manufacturer, and distributor of fluid sealing products and services. For more information about Barnwell O Rings click here, or to download a brochure click here.
For more information on our range of products click here.

E & OE. M Barnwell Services endeavours to make sure all the content is correct. Information has been gained from manufacturing partners.

A Guide to Select Oil Seals for Your Industrial Application

A Guide to Select Oil Seals for Your Industrial Application

An oil seal is a type of seal used in various industrial equipment to close the gap between its moving and non-moving components. These oil seals help prevent lubricant leakage at high pressures and block foreign components from entering the machinery. With such an important role to play, these oil seals must be chosen carefully. This post discusses the types of oil seals and also guides you through the important factors to choose an appropriate oil seal for your industry.

Types of Oil Seals – Based on Materials 

There is a wide range of seals to select according to the type of material. Some of the types of oil seals are as follows:

• Rubber Oil Seals:

Rubber seals are the most common types of sealing solutions preferred for tight sealing. Rubber seals are corrosion resistant and are used in both high and low-pressure applications. Nitrile, polyacrylate, Viton®, silicone, and polytetrafluoroethylene are a few common types of rubber materials used for this purpose. Each material possesses the typical capability, so, you must choose the rubber material carefully for your application.

Rubber seals are the most common types of sealing solutions preferred for tight sealing. Rubber seals are corrosion resistant and are used in both high and low-pressure applications. Nitrile, polyacrylate, Viton®, silicone, and polytetrafluoroethylene are a few common types of rubber materials used for this purpose. Each material possesses the typical capability, so, you must choose the rubber material carefully for your application.

• Metal Cased Oil Seals:

These seals feature stamped metal cases with an elastomer bonded sealing lip. Carbon steel is the metal used for making the case. The case protects the lip seal during installation. Metal encased seals are generally used for high-pressure or high-temperature applications.  

These seals feature stamped metal cases with an elastomer bonded sealing lip. Carbon steel is the metal used for making the case. The case protects the lip seal during installation. Metal encased seals are generally used for high-pressure or high-temperature applications.

• Leather Oil Seals:

These seals possess good running properties and are generally preferred for abrasive applications. The seals are usually used for shafts that possess surface roughness higher than rubber seals.

These seals possess good running properties and are generally preferred for abrasive applications. The seals are usually used for shafts that possess surface roughness higher than rubber seals.

7 Important Factors to Consider When Choosing Oil Seals

With varieties of seals available, choosing the right seal for application can be a daunting task. The following factors will help make the right selection. 

1. Lubricant: If choosing lubricated seals ensure they are continuously lubricated with oil that possesses appropriate viscosity required for the application and the lubricant is compatible with the elastomer material of seals.
2. Shaft Finishing: A good surface finishing of shafts gives a very effective oil sealing. The ground or polished shafts with concentric finish marks provide the best sealing that prevents leakage even during the shaft rotations. Hence, it is important to make sure that the shaft finishing is well maintained.
3. Shaft and Bore Tolerance: The seals must be strong enough to tolerate the pressure and vibrations caused by shaft and bores. The authenticity of metal and elastomer material is something that makes the shaft and bore tolerance possible. Therefore, check if the material meets these requirements before buying the seal.
4. Shaft Hardness: The life expectancy of a seal is measured on the basis of the hardness of its shaft. A shaft must possess a Rockwell hardness of 30 or above. When a seal is exposed to abrasive contaminants or high pressure, this RC hardness protects the seal from getting damaged. Hence, it is an essential factor.
5. Temperature: The temperature of the process should not exceed the temperature of the seal elastomer. Any increase or decrease in temperature may affect the sealing capability of the seal. Hence, it is an important point to be considered.
6. Pressure: Most seals are designed for applications where they may be subjected to pressures as low as 8 psi. However, if they are subjected to even low pressures then pressure relief must be ensured.
7. Shaft Speed: Shaft speed depends on many factors including shaft finish, its concentricity, the type of liquid being transferred, and the type of oil seal material. So each of these factors must be considered to achieve a maximum shaft speed. 

In addition to the above-given factors, sourcing high-quality seals from a trusted manufacturer are quite important.  SSP Seals provides high-quality

In addition to the above-given factors, sourcing high-quality seals from a trusted manufacturer are quite important. SSP Seals provides high-quality oil seals for industrial applications in automotive, oil and energy, and other sectors. The company can provide seals made of a wide range of materials including PTFE, Viton, Silicone, Nitrile, and so on.

Oil Seal Material Design Guide

Oil Seal Material Design Guide

Lip Materials

Nitrile Buna-N 70 durometer compound is the standard material for our seals and is recommended for a majority of common applications. Nitrile lip seals work well within the temperature range of -65°F to 250°F and provide compatibility with water and most common mineral oil and greases.

Polyacrylate compounds are recommended for higher temperature applications, ranging from -30°F to 300°F. They also work well with mineral oils, EP additives and greases. However, they offer poor sealing in dry running conditions and cost more than Nitrile.

Silicone compounds offer the widest range of normal operating temperatures ranging from -90°F to 340°F. However, they do not perform well in dry running conditions, and should not be used with EP compounds and oxidized oils.

Viton® compounds are premium lip materials offering the widest temperature range and chemical resistance. Viton® will handle temperatures from -40°F to over 400°F (-40°C to over 240°C).

Viton® will resist most special lubricants and chemicals that can destroy Nitrile, Polyacrylates and Silicones. Viton® is extremely resistant to abrasion and provides superior wear performance. Viton® works in dry running applications, but only for intermittent periods.

Graphite is available as an additive to any compound. Normally graphite is added at a 3% factor to aid in lubricity.

Case and Spring Materials

The cases and springs for our seal products are produced from carbon steel. In applications where corrosion resistance is important, either case or spring or both can be produced from stainless steel. In addition, rubber coated seals can provide the best resistance to corrosive environments in the most economical design. HYPALON® coating is an O.D. sealant which is available on any metal case design by customer request.

Lip, Case and Spring Tables

The following tables identify the most common lip and case designs. Additional, more complex designs are available for special applications; however, the lip and case designs below represent those which will fill the needs of most seal requirements.

Lip Design

The following designations indicate the configuration of the sealing members:

V = Single Lip  U = Triple Lip  K = Double Lip  D = Double Lip, Double Spring Loaded  S = Single Lip, Spring Loaded  WP = Wiper Lip Design  OB = Oil Bath (Prefix) O = External Seal Type WS = Wiper w/Bronze Scraper

Case and Spring Design

The following designations indicate the case type or any special features of the basic case designs. The designations for lip designs, attachment configuration and case style are then put together to indicate the specific seal type desired.

A = Double Case  N = Short Flex High Pressure Design  B = Lip Attached to End of Case Only  P = Flanged Case  C = Fully Rubberized Casing  Q = All Rubber Split Seal Design  E = Metal Reinforced Sealing Lip  SP = Other Special Feature  F = Special Fully Encased Design  X = Special Fitting Condition Design  G = Ridged Rubber Coated O.D.  Y = Indented Back Case  H = Reverse Case Style  Z = Rubber Covered Chamber J = Special Flanged Indented Case NOTE: Basic single case design has no designation M = Fully Rubberized Inner Case