11 Factors to Consider When Buying Oil Seals

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.

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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

Mechanical seals are used mainly in pumping applications (although the principles are the same for mixers, blowers and compressors). In essence, the pump has two main elements; the first being a rotating shaft and the second being the pump casing. Without a seal, the pumped medium (water, waste, oil, etc) would leak and the pump would be ineffective. The mechanical pump therefore creates the seal between the moving part (dynamic) and the stationary part (static). Because of this Mechanical seals are often called many things including shaft seals, pump seals, rotary shaft seals, water pump seal and combinations of these. Whatever you call it, the product is essentially the same.

Mechanical seals or more technically &#;end face mechanical seals&#; were designed in the early s but really came to prominence during the post-war boom (late s) in both industrial and domestic equipment sales.

The elements of a mechanical seal are what make it unique. They are:

1. Stationary component (commonly referred to as the seat).
2. Stationary component sealing member.
3. Rotating component.
4. Rotating component sealing member.
5. Spring.
6. Gland plate.
7. Clamp ring

The seal between the stationary component and the rotating component is called the &#;Primary Seal&#; and is the most important. However there is a &#;Secondary Seal&#;, which is typically an O Ring and sits between the rotating component sealing member and the shaft of the pump.

The spring is used to create just the right pressure in the primary seal between the stationary and rotating surfaces.

The primary seal surface in various mechanical seal types come in a vast array of materials, such as Carbon-graphite, Silicon carbide, Tungsten carbide and Alumina ceramic. The choice of material is dependent on the medium (the liquid to be sealed), the pressures the seal must withstand and the temperatures of the medium. Speak with your mechanical seals supplier to determine the best materials for your application.

Before the invention of mechanical seals, mechanical packings or gland packings were used. These worked well in principle, but had a higher leakage rate (not ideal for some applications) and can handle higher temperatures and pressures (thanks to the sprint component).

Additionally, the use of packing in earlier designs caused shaft and sleeve wear that reduced the life of the pump and increased costs. Mechanical seals therefore improve equipment lifespan.

The other benefit is that they are self-lubricating in that their design specifically allows a very small amount of leakage onto the sealing surface, which lubricates and keeps the primary seal from eroding. Finally, mechanical seals require virtually zero maintenance as they do not require periodic tightening as Gland packing would.

Ultimately therefore, mechanical seals are a simple, elegant and cost effective solution to creating a long-life seal in dynamic applications.

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