Bearing Seal Types-Your Essential Guide To Bearing Seal.

Overview of bearing seal types gives you a comprehensive analysis of all that you need to know about the types of bearing seals. Although not all types of bearings have seals, the ones with seals have superior advantages compared with the ones with no steel. Learn more by reading further.

Contents hide

1 Meaning Of Bearing Seal

2 Type Of Bearing Seals

2.1 Contact Seals

2.2 Non-Contact Seals

2.3 Labyrinth Seals

3 Functions And Importance Of Bearing Seal Types

4 Designation Of Bearing Seals Types

4.1 Bearings Closed On One Side

4.2 Comparison Table Of Bearing Seals

5 Factors To Consider Before Choosing Bearing Seal Types

6 FAQ

6.1 What Type Of Bearing Seal Is The Best?

6.2 Are Sealed Bearings Greased?

7 Conclusion

Meaning Of Bearing Seal

A bearing seal is also known as a grease seal. It’s an important part of the bearing that prevents the lubricant inside the bearing from leakage and it protects the bearings from contacting dirt, moisture, dust, and other foreign objects.

Type Of Bearing Seals

Contact Seals

Another name for a contact seal is a lip seal. It’s a rubber component, usually made of nitrile/Buna-N. It’s bonded to a steel and inserted to form a contact seal. The seal’s name refers to the contact that’s created when constant pressure is applied to a bearing’s inner ring. In addition, contact seals make it very difficult for impurities like dust, dirt, and moisture to enter the inner components of your bearing by establishing direct contact with the inner ring.

Furthermore, Contact seals are quite good at keeping lubricants inside your sealed bearing. The washer is a product of SPCC cold rolled steel for chrome steel bearings or 304 stainless steel for stainless steel bearings. In conclusion, some sizes come with high-temperature PTFE (Teflon) seals or Viton seals.

Features:

Reduce maximum speed by approximately 40%
Excellent protection against contaminations.
Greatly reduces lubricant leakage.
Increase bearing torque.
Temperature ranges from –100°C/+260°C.
Resilience to the harsh environment.
Versatile.
Minimal wear.
Temperature ranges from –40°C/+230°C for Viton.

Non-Contact Seals

Just like contact seals, non-contact seals also consist of Nitrile/Buna-N rubber components connected to a steel insert. The primary distinction between these types of contact seals is that non-contact seals do not pressurize your bearing’s inner ring; instead, they are affixed to the outer ring. Non-contact seal bearings come with a small lip that lies next to the inner ring, but they are not in contact with it.

Additionally, non-contact seals protect against contaminants and leaks too, but not up to the protection contact seals offer. On the other hand, there’s less friction when there’s no contact with the inner bearing, which can help minimize overheating and other possible problems.

Features:

Excellent protection against contaminations.
Temperature range –40°C/+110°C for nitrile rubber.
Temperature ranges from –90°C/+220°C for PTFE.
Maximum reduction in lubricant leakage.
No torque increase.
Do not affect maximum speed.
Temperature ranges from –40°C/+80°C for PE.
Temperature ranges from –70°C/+250°C for PEEK.

Labyrinth Seals

A labyrinth seal is a type of bearing isolator that incorporates aspects of both contact and non-contact seals into one unit. The primary purpose of this type of bearing seal is to prevent contaminations and leakage by making it difficult for them to penetrate the bearing. Labyrinth seals consist of up to two parts; a rotating and a stationary piece that moves with the system. The two halves fit together to form an intricate, lengthy, and narrow channel that makes it difficult for substances to pass through or penetrate the bearing.

In addition, labyrinth seals give excellent sealing capabilities due to their complexity. This bearing seal can prevent leakage and contaminants without having contact with the inner ring. Therefore, labyrinth seals perform the same sealing capabilities as contact seals while reducing added friction like a noncontact seal.

Functions And Importance Of Bearing Seal Types

Contamination Prevention: One paramount of bearing seals is to prevent the bearing from premature wear, reduced performance, and corrosion by digressing dirt, water, dust, and other foreign particles.

Retaining Lubrication: They ensure proper lubrication for optimized and smooth operation as well as reducing friction. In addition, seals keep the lubricants intact inside the bearing.

Environmental Protection: Bearing seals help bearings operate in high temperatures and high humidity to maintain reliability and functionality.

Designation Of Bearing Seals Types

Z and ZZ are the types of bearing designations The metal case is a shield plate fixed to the outer ring. The following are the popular seal designations you’ll find in many catalogs LLU, LLB, 2RS, LU, RS, and LB. As for sealed bearing, the inner ring is incorporated with a labyrinth and v-groove clearance.

Seal From Both Sides Of Bearing
Brand Suffixes	FAG	NACHI	NKE	NSK	NTN	SKF	SNR	ZEN
2x Sheet Metal Shields	2Z	ZZ(E)	2Z	ZZ	ZZ	2Z	ZZ	ZZ
2x Rubber Seals	2RSR/2HRS	2NSL / 2NSE(9)	2RSR / 2RS2	DDU	LLU	2RS1 / 2RSH	EE	2RS
2x Low-friction Contact Rubber Seals	–	–	–	–	LLH	2RSL	–	–
2x Non-Contact Rubber Seals	2BRS	2NKE(9)	–	VV	LLB	–	–	2DU

Warning

Bearings that are serially sealed often consist of grease that lasts a lifetime. Therefore, you do not need to lubricate them again during their lifetime.

You must open the bearing to allow oil to enter it without interruption if the bearing is exposed to oil lubrication (without seals). If not, there’s the possibility that the oil will wash away the grease from the sealed bearing gradually, which will then lead to failure due to insufficient lubrication.

Bearings Closed On One Side

You’ll find one-sided bearings in the market, they are used in cases of oil lubrication. Here, the bearing is provided with a seal on one side of the bearing to protect against the ingress of dust, dust, moisture, and other contaminants while the second end is open for uninterrupted oil lubrication. That is why the manufacturers use the below designation.

Seal From One Side Of Bearing
Brand Suffixes	FAG	NACHI	NKE	NSK	NTN	SKF	SNR	ZEN
1x Shield	Z	Z(E)	Z	Z	Z	Z	Z	Z
1x Rubber Seal	RSR / HRS	NSL / NSE(9)	RSR / RS2	DU	LU	RS1 / RSH	E	RS
1x Low-Friction Contact Rubber Seal	–	–	–	–	LH	RSL	–	–
1x Non-Contact Rubber Seal	BRS	NKE(9)	–	V	LB	RZ	–	DU

Comparison Table Of Bearing Seals

Type, code no.		Shield Type	Rubber Seal Type
Type, code no.		Non-Contact Type	Contact Type	Non-Contact Type	Low-Friction Contact Type
Designation by brand	FAG	2Z	2RSR / 2HRS	2BRS	–
	NACHI	ZZ(E)	2NSL / 2NSE(9)	2NKE(9)	–
	NKE	2Z	2RSR / 2RS2	–	–
	NSK	ZZ	DDU	VV	–
	NTN	ZZ	LLU	LLB	LLH
	SKF	2Z	2RS1 / 2RSH	2RZ	2RSL
	SNR	ZZ	EE	–	–
	ZEN	ZZ	2RS	2DU	–
Construction
Construction		Fixed sheet steel to the outside ring. Clearance on inner ring.	Synthetic rubber molded to a steel plate and fixed on the outside ring. Seal edge contact on inner ring.	Molded synthetic rubber molded to a steel plate and fixed on the outside ring. Inner ring aligns with the seal edge with very small clearance.	2RS type is the same as basic construction. Low friction construction. Designed specifically on the lip edge of the seal.
Performance Comparison	Friction	Very Low	Medium	Very Low	Low
	Dust Protection	Good	Best	Very Good	Excellent
	Water Protection	Poor	Very Good	Poor	Good
	High Speed Capacity	Same as open type	Limited by contact seals	Same as open type	Better than 2RS- type
	Temp range	-20 ℃～120 ℃	-20 ℃～100 ℃	-20 ℃～100 ℃	-20 ℃～100 ℃

Factors To Consider Before Choosing Bearing Seal Types

When you want to select the right bearing seal, considering your type of bearing is one important thing. This is because some bearings can only work under certain conditions due to their unique features. In this case, there will be seals that are specifically made to suit them. However, the list below will show you crucial factors to consider before you select a bearing seal:

Application: Know the bearing load, temperature, lifespan, and access speed of your vehicle.
Environment: Be sure that your seal will work in either a dry/wet, clean/contaminated environment. Determining the working conditions matters.
Contaminants: Be sure of the type of contaminant you want the grease to work against.
Lubrication: Make sure you consider the retention of grease or oil, and the ability for you to replace the bearing lubricant which are the lubrication needs.
Seal Type: If your application is operating on higher friction in a low-speed setting, go for a contact seal. Or non-contact seals for minimal heat at high speeds.
Application-Seal Matching: Make sure the seal aligns with your machinery needs

While it’s important for you to consider the list above, some other factors you can consider include an arrangement of the shaft or possible misalignment, the physical available space, the amount of friction in the seal or maximum temperature, as well as cost.

FAQ

What Type Of Bearing Seal Is The Best?

Rubber is considered the best seal type due to their effectiveness in providing a reliable seal that gives bearings the ability to be free from contaminants and retain lubrication.

Are Sealed Bearings Greased?

Yes, sealed bearings are greased to give extra protection to the bearing.

Conclusion

You cannot underestimate the importance of a seal in bearings due to the tons of advantages it renders. Therefore, knowing the type of bearing seal that works for your application is important to optimize your engine performance, reduce cost, etc.

Overview Of Bearing Seal Types