Oil seals are essential for keeping lubricant and other necessary substances inside rotary shaft equipment and preventing debris from getting inside. These invaluable devices, also called rotary shaft seals, shaft seals, lips seals or elastomeric seals, protect the bearings of rotating shafts. In simple terms, oil seals form a protective barrier that separates the inside from the outside.
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Oil seals work by forming a secure plug on shafts. All oil seals consist of three basic components:
When choosing an oil seal for a shaft, many factors must be considered. These include temperature, size, shaft speed, pressure, lubrication availability and environment. Each setting is unique, and the correct fit is essential to ensure that oil seals will remain in place and effectively protect the bearings. Custom-molded oil seals are usually required to provide a superior fit and increased durability.
Although choosing quality, custom-molded oil seals can greatly prolong the device's life span, many other factors affect the longevity of parts. These include:
Due to the complexity of the factors involved, there is no accurate way to predict how long oil seals last.
Oil seals have a flexible inner lip that presses firmly against the shaft. The garter spring maintains pressure, and the sturdy metal casing holds the unit firmly in place. When optimally fitted and in good condition, oil seals create a protective seal around the shaft that protects the inside components.
The Global Elastomeric Products, Inc. team has been providing high-quality, custom oil seals for more than fifty years. Our in-house design engineer will work with you to choose the best oil seals for your equipment.
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.
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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.
For more information on the characteristics of Oil Seals click on some of the links below:
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