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.
In this blog, we attempt to highlight what are Oil Seals and the various Rotary Shaft Seals including Mechanical Face Seals, Water Pump Seals, Gland Packings, and V-Seals that are readily available.
The basic principle of sealing is straightforward &#; the flexible lip is held against the rotating part (usually the shaft) whilst the casing (or O.D.) is pressed into the housing or bore and holds the seal in place. The sealing lip needs some form of lubrication to avoid overheating and is usually energized by means of a garter spring.
Many &#; too numerous to list, covering a vast range of designs, sizes, and materials suitable for a never-ending range of applications. Some designs conform to International Standards such as BS and DIN for metric sizes and seal types, but the majority have been manufactured to suit particular applications &#; hence the enormous selection available. This blog is intended to assist in this selection and will consider seal type, materials, and sizes.
The simplest way is to know either the preferred manufacturers part number, the overall sizes of shaft diameter, housing diameter and bore depth, or use our brochure to establish the M Barnwell Services ordering reference. Many of the old traditional names of seal manufacturers have either changed or disappeared in this age of &#;acquisitions&#;. If no longer available, we will advise you and offer a suitable alternative seal, from stock whenever possible. If your concern is getting the right seals for the job, you will need to know something about the application as well as the overall sizes. If you have any doubts &#; contact us, we will help in your seal selection.
Leather is probably the oldest of the lip materials still in common use, but the move towards mass production methods has seen a massive increase in the development of synthetic rubbers which lend themselves to accurate and repeatable injection and compression moulding. Nitrile (NBR) is still by far the most common elastomer for &#;normal&#; use, whilst Viton® (FKM/FPM) is rapidly replacing Polyacrylate (ACM) and Silicone (VMQ) for high-temperature applications. Viton® also has high resistance to abrasion and chemical attack making it a preferred elastomer. Recent developments in the use of PTFE for Rotary shaft seals has caused widespread interest particularly for high-speed shaft rotation or poor lubrication applications.
Once you have selected the most suitable seal available, considering the environment, temperature, shaft speed, pressure, lubrication availability, as well as the size, of course, the seal should be stored adequately and then fitted properly. Here are a few suggestions that could help:-
There is a British Standard laid down for the control of synthetic rubbers. BS () helps to determine shelf life &#; for instance, Nitrile (NBR) and Polyacrylic (ACM) are Group &#;B&#; rubbers and have a 7-year life, whilst Silicone (VMQ) and Fluoroelastomers (Viton®) are Group &#;C&#; rubbers and have a 10-year shelf life. PTFE and Leather do not come into this category but like the others should be kept in the original packing for as long as possible away from direct light, dust, and humidity. Ozone, which can also be produced by battery-driven forklift trucks has a very bad effect on synthetic rubbers. Finally, protect the sealing lip &#; DO NOT hang the seals on nails, wire etc.
If the seal is being fitted to original equipment you may have some influence over the shaft and housing bore finish, but if you are replacing a worn seal you still need to take into account the condition of these 2 essential parts. Check for sharp edges and burrs &#; particularly on the shaft and housing chamfers or you could ruin the seal before you start up. If the shaft is too worn consider using an M Barnwell Services Shaft Repair Kit.
Oil seals, also referred to as shaft seals, are widely used to prevent the leakage of medium (such as oils and grease) along a rotating shaft. This leak prevention is primarily achieved by the sealing element which can be made from a wide range of materials that are chosen according to each application. They are commonly used in gearboxes, hydraulic cylinders, and related components.
An oil seal is designed to perform three major functions: to prevent lubricants from leaking outside the seal even under high pressure, to act as a barrier to retain the lubricating oil, and to prevent dirt and other contaminants from entering the unit.
Shop for Oil Seals
Oil seals normally consist of three basic components: the sealing element, the metal case, and garter spring.
The sealing element makes up the interior of the oil seal, and the materials commonly used are:
a. Nitrile Rubber (NBR) &#; this is the most commonly used material. It has good heat resistance properties and has good resistance to salt solutions, oils, hydraulic oils, and gasoline. Operating temperatures are recommended from -40 to 248&#; F (-40 to 120 deg.C). Nitrile also functions well in a dry environment, but only for intermittent periods. The disadvantage of this material is poor chemical resistance.
b. Polyacrylate Rubber (PA) &#; also known as acrylic rubber, this material has better heat resistance than nitrile. PA is also recommended for a high surface speed environment. Operation temperatures are recommended from -4 to 302&#; F (-20 to 150&#; C). Polyacrylate rubber should not be used with water or in temperature below -4&#; F (20&#; C).
c. Silicone Rubber (SI) &#; these compounds operate effectively in a broad temperature range of -58&#; F to 356&#; F (-50 to 180&#; C). Silicone rubber is a leading choice for its resistance to both low temperatures and heat. The high lubricant absorbency of the material minimizes friction and wear. These oil seals are usually used as crankshaft seals. Silicone has poor resistance to hydrolysis and should not be used in oxidized or hypoid oils.
d. Fluorocarbon Rubber (FKM) &#; is widely known under the Chemours (formerly Dupont&#;) trade name of Viton® and offers the best resistance to chemicals and superior performance to high temperatures.
The metal case is the exterior (or frame) of the oil seal, the principal function of which is to give rigidity and strength to the seal. The material of the case must be selected depending on the environment where the seals are to be used. Often the metal case is covered by the same rubber material used in the sealing element, which also helps seal the exterior of the oil seal in the housing bore. Common case material types are:
a. Carbon Steel &#; the most common material used in oil seals.
b. Stainless Steel &#; for applications that require resistance to water, chemicals, or corrosion. (Stainless steel metal cases are also recommended for many FDA applications.)
The garter spring is located at the end of the primary sealing lip and used to apply pressure to the sealing lip against the shaft. Common garter spring material types are:
a. Carbon Steel &#; which is used in conjunction with regular lubricants.
b. Stainless Steel &#; which is used when resistance to water, seawater, and chemicals are involved.
PRESIDENT/OWNER:
Bill has served in the sealing industry for more than 25 years, and founded Global O-Ring and Seal nearly 10 years ago.
Oil seals are widely used as sealing devices for machines.
JTEKT's oil seals are described in our catalog, Oil Seals & O-Rings.
However, the catalog uses a large number of technical terms and is very long, so many people seem to have trouble handling it.
Therefore, this series of columns will summarize the following in order:
&#; The structure, functions, and types of oil seals
&#; How to select the right oil seal
&#; Handling of seals, and causes and countermeasures for oil seal failure
A wide range of sealing devices are used in various machines.
Sealing devices serve the following functions:
Prevent leakage of sealed lubricant from inside
Prevent entry of dust and foreign matter (dirt, water, metal powder, etc.) from outside
As shown in Figure 1, sealing devices come in two types: contact and non-contact.
Oil seals are among the major contact type sealing devices.
Figure 1: Types of sealing devices
Please see the following for the types of sealing devices for bearings.
How to Select the Right Bearing (Part 7): Components surrounding the bearing
Oil seals come in various shapes to fit the machines and substances to be sealed.
Figure 2 shows the structure and the names of the various components of the most typical oil seal.
The functions of the various components are also indicated in Table 1.
Figure 2: Typically shaped oil seal and component nomenclature
* "KOYO" is a registered trademark of JTEKT.
Table 1: The functions of the various components
No.
Name
Functions
&#;
Main lip The main lip is the most critical component of the seal.
Its sealing edge comes in full contact with the shaft surface in order to provide excellent sealing performance.
(See Figure 3.)
&#;
Minor lip The minor lip prevents the entry of dust and contaminants from outside.
Lubricant can be retained in the space between the main lip and the minor lip.
&#;
Sealing edge This refers to the component of the oil seal that makes contact with the shaft.
It is wedge-shaped to be pressed against the shaft surface and makes contact with the shaft to ensure sufficient sealing performance and suitability for operation at high peripheral speed.
&#;
Spring The spring supplements the tightening force (i.e., the lip radial load) to ensure enhanced sealing performance and tight contact between the shaft and the sealing edge.The spring also prevents the deterioration of main lip sealing performance caused by high heat or other such factors.
&#;
Metal case The metal case provides rigidity to the seal, helping it settle on the housing securely. It also ensures easy seal handling and mounting.
&#;
O.D. (outside diameter) surface The O.D. surface affixes the oil seal to the housing and prevents leakage , through the fitting area, of substances to be sealed, while excluding contaminants.
&#;
Fluid side face The front-end face of the seal is called the nose. The nose is made of rubber and forms a gasket seal when compressed on the housing shoulder.
&#;
Air side face The oil seal surface vertical to the center line of the shaft on the side that does not come in contact with substances to be sealed is called the back face.
Figure 3: Sealing function of main lip radial load
* "KOYO" is a registered trademark of JTEKT.
Figure 4 shows the features of a JTEKT oil seal.
Figure 4: JTEKT oil seal features
For more detailed information, please see the following:
Names and functions of seal components&#;
Seals are classified by O.D. wall material, lip type, and whether they have a spring or not.
Major oil seals are specified in ISO -1 and JIS B -1.
Table 2 shows the common types of oil seals, while Table 3 shows the features of each type of oil seal.
Table 4 lists the JTEKT oil seal type codes and corresponding ISO and JIS standards.
Table 2 a): Common types of oil seals (with spring)
With spring Rubber O.D. wall Metal O.D. wall
Metal O.D. wall
(with a reinforcing inner metal case)
Without minor lip
Type code
With minor lip
Type code
Table 2 b): Common types of oil seals (without spring)
Without spring Rubber O.D. wall Metal O.D. wall
CDI contains other products and information you need, so please check it out.
Without minor lip
Type code
With minor lip
Type code
Table 3: Features of each seal type
No.
Type
Features
1
With spring type Secures stable sealing performance.
2
Rubber O.D. wall type Provides stable sealing performance around the seal O.D. surface.
3
Metal O.D. wall type Ensures improved fitting retention between the seal O.D. and the housing bore.
4
Metal O.D. wall type (with a reinforcing inner metal case) Protects the main lip.
5
With minor lip type Used for applications where there are contaminants, such as dust and foreign matter, on the air side face of the oil seal.
Table 4: JTEKT oil seal type codes and corresponding ISO and JIS standards
JTEKT
ISO -1 1)
JIS B -1 2) MHS Type 1 HMS Type 2 HMSH Type 3 MH &#; HM &#; MHSA Type 4 HMSA Type 5 HMSAH Type 6 MHA &#; HMA &#;
Notes
1) ISO: International Organization for Standardization
2) 2) JIS: Japanese Industrial Standard
JTEKT provides special seals for use in a wide variety of machines and applications.
Table 5 lists the major special seals, their shapes, and their features.
Table 5: The major special seals, their shapes, and their features
Name Type
(type code) Shape Features
Helix Seal
The hydrodynamic ribsa) provided in one direction on the air side face of the lip ensure higher sealing performance. Perfect Seal The hydrodynamic ribsa) provided in two directions on the air side face of the lip ensure higher sealing performance (higher sealing performance in both rotational directions of the shaft).
Super Helix Seal
The hydrodynamic ribsa) have a two-stepped rib configuration provided in one direction on the air face of the lip. Even if the first rib is worn out, the second rib comes into contact with the shaft surface, meaning that this type of oil seal ensures higher sealing performance. Seal with Side Lip A large side lip ensures prevention of entry of dust/water.
&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;a)
Function of hydrodynamic ribs
For more detailed information, please see the following:
Special seal types and their features
Figure 5 explains the JTEKT seal numbering system.
Seal numbers consist of
&#;(1) the seal type code,
&#;(2) the spring code,
&#;(3) the lip type code,
&#;(4) the dimensional numbers, and
&#;(5) the special type code,
and Table 6 shows examples of each of these codes/numbers.
Figure 5: JTEKT seal numbering system
Table 6: Codes and numbers used in seal numbers
No. Code and number Example &#; Seal type code (*)
MH: O.D. wall is a rubber material
HM: O.D. wall is a metal case
MH(S)H: O.D. wall is metal with a reinforced inner metal case
&#; Spring code
No code: without minor lip
A: with minor lip
&#; Lip type code
No code: without minor lip
A: with minor lip
&#; Dimensional numbers Shaft number 45: The seal suits the shaft diameter of ϕ45 mm. Housing bore number 70: The seal suits the housing bore diameter of ϕ70 mm. Width number 8: The seal width is 8 mm. &#; Special shape code
J: Additional code is added here as an identifier when two or more seals have exactly the same type codes and dimensional numbers.
Note: For seal type codes, see Table 2.
Oil seals are used in a great many machines.
Oil seals are used in many areas around the car.
Figure 6 shows the places where each seal type is used.
Figure 6: Oil seals for cars
For more detailed information, please see the following:
Oil seals for cars
Oil seals are used in a great many devices for steel production equipment.
Figure 7 shows the places where each seal type is used in a rolling mill.
Figure 7: Oil seals for steel production equipment (rolling mill)
For more detailed information, please see the following:
Oil seals for steel production equipment
Oil seals are one of the major contact type sealing devices.
&#; They prevent leakage of the lubricant or other sealed substance, and
&#; prevent entry of dust and foreign matter (dirt, water, metal powder, etc.) from outside.
Oil seals come in various shapes to fit the machine or substance for sealing.
For this reason, when designing a machine, it is important to select the oil seal that is right for that machine.
Next time, we will explain the key points to consider when selecting your oil seal.
Oil seals, also known as rotary shaft seals or grease seals, are vital components used in various machinery and industrial applications. These seals play a crucial role in preventing the leakage of lubricants, such as oil or grease, and protecting vital components from contaminants and debris. This article delves into the significance of oil seals, their types, materials, and their widespread usage across industries.
Oil seals are specialized devices designed to retain lubricants within a system while excluding external contaminants. They are commonly used in rotating or reciprocating shafts, ensuring efficient operation and reduced friction. By maintaining the lubrication levels, these seals extend the lifespan of mechanical components and prevent premature wear and tear.
a) Metal Case: The outer metal casing provides structural support and protects the seal's internal components from external pressures and environmental conditions.
b) Elastomer (Rubber) Seal: The elastomer or rubber lip is the primary sealing element of the oil seal. It forms a tight seal around the shaft to prevent lubricant leakage and the entry of contaminants.
c) Spring: Positioned behind the rubber lip, the spring exerts constant pressure, ensuring the seal remains in contact with the shaft, maintaining an effective seal.
a) Radial Oil Seals: These are the most widely used oil seals, primarily employed in rotary shaft applications. Radial seals can be further categorized into single lip, double lip, and multiple lip seals, depending on the level of sealing needed.
b) Axial Oil Seals: Unlike radial seals, axial seals are designed to seal along the axis of a rotating shaft, preventing axial leakage of lubricants.
c) V-Rings (V-Seals): V-rings are specialized oil seals with a V-shaped cross-section. They are suitable for sealing applications where conventional radial seals might not be effective.
d) Cassette Seals: Cassette seals are pre-assembled units that include multiple sealing lips and protection against contaminants, making them ideal for challenging environments.
a) Nitrile (NBR): Nitrile rubber is a versatile material known for its excellent resistance to oil, water, and many other fluids. It is a popular choice for general-purpose oil seals.
b) Fluoroelastomer (FKM/Viton): FKM offers superior resistance to high temperatures, chemicals, and various fuels, making it suitable for applications in demanding environments.
c) Polyacrylate (ACM): ACM exhibits excellent resistance to mineral oils, making it suitable for automotive and industrial applications.
d) Silicone (VMQ): Silicone rubber is ideal for extreme temperature applications, maintaining flexibility at both low and high temperatures.
a) Automotive: In engines, transmissions, axles, and other critical automotive components, oil seals prevent lubricant leakage and the entry of contaminants, contributing to the efficiency and longevity of the vehicle.
b) Industrial Machinery: Oil seals are used in pumps, gearboxes, motors, and other rotating equipment to ensure smooth operation and prevent costly breakdowns.
c) Aerospace: In aircraft engines and various aviation systems, oil seals play a crucial role in maintaining optimal performance and safety.
d) Marine: Oil seals are utilized in ship propulsion systems, ensuring smooth operations in harsh marine environments.
Oil seals are indispensable components in a wide array of machinery and industrial applications. By providing effective sealing, they help prevent lubricant leakage, reduce friction, and protect critical components from contaminants. Proper selection of oil seal types and materials ensures optimal performance and extends the lifespan of the equipment, making them a fundamental element in modern engineering practices. As technology continues to evolve, oil seal designs and materials will likely improve, further enhancing their role in various industries.
For more information, please visit Oil Seal for Agricultural Equipment.