Search Clear Form

Search Clear Form

Search Clear Form

Search Clear Form

Your Labyrinth Seal Guide

This Non-Contact Labyrinth Seal Guide is designed to provide everything you need to know about labyrinth seals - what they are, what they do, and how they are used. We've dissected each of the nuanced functions, theories, and application types for labyrinth seals, creating the practical, all-in-one reference tool. 

This guide provides a general understanding of labyrinth seals. GMN Bearing USA in-house engineers are happy to answer any of your questions and support your design to optimize the sealing efficiency.

Download the full in-depth guide

What is a Labyrinth Seal?

A labyrinth seal is also known as a non-contact seal or a mini maze seal. It is primarily used in rotating equipment to protect bearings. It consists of two rings that do not contact and rely on a complex labyrinth gap to prevent contamination, splashing liquids, or other particulates from crossing the seal barrier.

As the system rotates, the centrifugal forces on the particulate cause them to want to go tangentia to the radius of the gap as they attempt to make their way through the seal. This results in a radial outward force as the particulates potentially move around the outer ring. However, the labyrinth path progresses inward radially, either in a sawtooth pattern for the type L seals, M seals, and S seals, or in a special winding path in the CF seals. This means that the particulates must fight the centrifugal forces pushing them back out as they attempt to traverse through the seal.

Additionally, the gap height is minimized to increase the difficulty in the particulate flow and remove any momentum it had when entering the seal, thus preventing it from maintaining the momentum to cross the seal.

These principles result in seal that are able to provide up to 100% sealing efficiency with many features compared with other seals on the market.

See Performance Differences between Labyrinth & Contact Seals below for more information.

Application Conditions

Labyrinth seals are designed to function extremely well protecting sensitive components like bearings from both liquid and airborne particulates. This includes dirty or dusty environments and applications with splashing liquids like machine tool cutting fluid or other coolants. The seals can also be used to keep grease or oil inside the system to protect sensitive equipment or environments outside. This includes gearboxes with oil splashing and greased bearings.

Because the seals are non-contact and rely on a labyrinth path with centrifugal forces for sealing, there are some applications for which these seals are not optimal. This includes applications where the seals would be required to maintain a pressure differential or prevent a standing level of liquid from egressing through the seal. The pressure created by the differential, or the standing level of liquid would overcome the seal characteristics and leakage would occur.

Applications with low RPMs can utilize a labyrinth seal. These situations would call for the use of GMN's CF seal that is designed with a complex labyrinth path to properly function at low speeds. 

Improve Food Manufacturing Processes with GMN Bearing USA

GMN Type S SealIt is worth noting that in the food production industry, there are specific requirements for cleanliness, hygiene, and resistance to contamination. In such applications, GMN bearings offer special features like a shielded/sealed design.

This application is where our labyrinth seals shine, especially our S & SA Type seals. These types are made from high quality - food grade - POM plastic which resists corrosion. These seals stand up to heavy splashing - perfect for when equipment is routinely washed down.

Learn more about the markets and applications we serve.

Performance Differences

Labyrinth and Contact Seals

For rotating equipment, GMN labyrinth seals offer many advantages over standard contact seals. These advantages grow as the rotational speeds of the system increase. In fact, contact seals can be a limiting factor for system speeds due to the friction and subsequent heat that they create.

GMN Labyrinth Seals

GMN Labyrinth Seals

Seal Wear: No Wear

Power Loss: No power loss

Speed Limit: Only limit due to high-speed lift off that can be adjusted for

Contamination: No contamination wear

Life: Unlimited life

Seal Lubrication: Not needed

Mating Component Requirement: No hardening & grinding required

Temperature Increase: No temperature increase

Temperature Range: High operating range

Space Requirements: CF seals go directly against bearings

Learn More

Contact Seals

Contact Seals

Seal Wear: Rubbing wear

Power Loss: Power loss due to friction

Speed Limit: Speeds decrease life & seals will have a  lower max RPM

Contamination: Wear due to contamination on seal lip

Life: Decreased life due to contact wear

Seal Lubrication: Often recommended

Mating Component Requirement: Tight tolerances with hardening & grinding required

Temperature Increase: Increased temperature due to friction wear

Temperature Range: Low operating range due to seal rubber material

Space Requirements: Contact seals require additional space for incorporation

GMN Seal Differences

CF Seals

GMN CF Seal 

CF seals are designed to protect against heavy amounts of contamination and splashing liquids. These seals feature the most complex labyrinth path to provide optimal sealing efficiencies, including protection when the system is not rotating. This unique design incorporates thin axial gaps that employ the capillary effect and radial gaps that use centrifugal forces to prevent contamination from pushing through the seal.

CF seals come standard with either hardened and ground steel (CF 619XX and CF 60XX series) or aluminum (CF 62XX) rings and are designed to be installed directly against the bearings they are protecting using the shaft and housing dimensions specified for the bearings. The steel version is also designed to allow bearing preloading to pass through the seal.

Read more about CF seals.

L & M Seals

GMN Type L Seal GMN Type M Seal

L & M seals are designed to protect against moderate amounts of contamination and splashing liquids and are made of a steel inner ring and an aluminum outer ring. These seals use a sawtooth-like labyrinth profile to force the airborne contaminants and liquids to fight centrifugal forces to cross the seal boundary. The M series incorporates drain grooves along the outer diameter of the outer ring to encourage contaminates to be expelled through the grooves by the centrifugal forces.

Read more about L seals and M seals.

S & SA Seals

GMN Type S Seal GMN Type SA Seal

The S & SA seals are designed to protect against moderate amounts of contamination and splashing liquids in corrosive or washdown environments and are made of high-performance plastic rings. The labyrinth profile is a similar sawtooth pattern to the L & M seals, differing in the conical nature of the labyrinth gap. With the larger gap diameter facing the contamination, there is added resistance with the centrifugal forces as the contaminates must fight the decreasing gap diameter moving across the seal. The SA seals incorporate a drain grove on the outer ring that encourages drainage back through the face of the seal.

Read more about non-contact gap seals.

Design Considerations

Designing an application for GMN's labyrinth seals can raise numerous questions about best practices or specific design considerations that must be examined. Let's talk about a few key points.

Seal Location

CF Seals

GMN's CF seals are designed to be located directly against  angular contact or radial ball bearings using the same shaft and housing tolerances as the bearings. The CF 619XX S10 and CF 60XX S10 versions will have a slip fit against both the shaft and housing and will require some form of axial clamping to prevent rotation. The CF 62XX A0 will have a press fit against the shaft and housing, so no additional restraint is necessary.

L, M, S & SA Seals

The L, M, S, and SA seals are all designed to be installed offset from the bearings, typically on the nose or close to the front of the rotating system and would use their own recommended tolerances. These tolerances result in a press fit against both the shaft and the housing.

Non-Contact Seal (metal) Type CF...A0 Non-Contact Seal (metal) Type L Non-Contact Seal (plastic) Type S

CF Seal (metal)                                                   Type L Seal (metal)                                        Type S Seal (plastic)

RPM Limits

All GMN seals (except for the CF 619XX S10 and CF 60XX S10 series) have maximum RPM limits. However, these limits are only due to the possibilities of the centrifugal forces causing the inner rings to lift off the shaft and lose the press fit, which would result in inner ring rotation relative to the shaft. This can cause micro-fretting and premature failure. It is possible to adjust the recommended shaft tolerances to increase the RPM limit, but care must be taken to gauge the effect on the reduction of radial clearance. Adding axial clamping to the system can also greatly increase RPM capability.

Bearing Preload

One additional feature of the CF 619XX S10 and CF 60XX S10 versions is their ability to transfer bearing preload. They are made with hardened and ground bearing steel, resulting in no deformity under axial loading. This means that the seals can go between the bearing and the shoulder or lock nut.

Non-Contact Seal (metal) Type CF...A0

CF Seal (metal)

Splash Disc

While all GMN seals have a proven track record of excellent performance, steps can be taken to add additional layers of protection to the system to help prevent contaminants from getting where they are not supposed to go. One option is to include a splash disc on the shaft to cover the seal. This forces all the contaminants to go around the disc before contacting the seal face which greatly reduces the contaminant’s momentum and helps prevent it from going far into the seal.

Note: Don’t incorporate a cover on the housing that extends down over the seal or that could cause contamination to build up over the gap. If a housing cover is the only option, then a drain port should be included in front of the seal to prevent contamination build up.

Non-Contact Seal (metal) Type CF...A0 with disc Non-Contact Seal (metal) Type L with disc Non-Contact Seal (plastic) Type S with disc

CF Seal (metal) with disc                             Type L Seal (metal) with disc                     Type S Seal (plastic) with disc

Drain Ports

The M style seal comes with drain holes in the middle of the seal. There should be corresponding drainage in the system to make sure any contamination that makes it to the drain ports is removed from the system.

Drainage groove (metal - design M)

Drainage groove (metal - design M)

For heavy contamination applications, two seals can be incorporated into the system with a drain port in between them. If any contamination makes it past the first seal, the gap between the seals with the drain port would encourage it to drain out rather than go through the second seal.

Drainage - Metal Seal (Type L) Drainage - Plastics Seal (Type S)

Metal Seal (Type L)                                          Plastic Seal (Type S)

Greased Labyrinth

All the GMN labyrinth seals can also be delivered with the labyrinth profile filled with grease. The grease would act as an additional barrier for the contaminants. However, life and temperature as well as other application conditions would need to be considered for this option. Speak with a GMN Bearing USA technical specialist or engineer to learn if this is the best option for your application.

Air Pressure

If an air supply is readily available for the system, the bearing compartment could be supplied with clean and dry air slightly above atmospheric pressure to help push contaminants back out of the labyrinth gap. This adds an additional boundary that the contaminants must fight against.

Axial clearance within a seal

Radial and Axial Clearance

Because all GMN seals have a labyrinth gap between the inner and outer rings, a set axial and radial movement is allowable before the rings will rub against each other. This is known as the radial and axial clearance or “play.”

The axial clearance value is specified on the seal datasheets and represents the total amount of axial movement possible from one extreme of ring contact to the other. Thus, the allowable distance from having the rings be aligned to touching would be half the axial play. This value is important when designing a system to consider possible axial movement from application conditions like thermal expansion. In situations where thermal expansion or other forces cause larger axial movement than the standard seals can accommodate, the L & M seals can be ordered with increased axial clearance

The radial clearance is either specified on the datasheet (or a formula can be provided for calculation) and represents the maximum possible radial movement from contact on one side to contact on the other (i.e. going from contact at the 12 o’clock position to contact at the 6 o’clock position). This value is important in system design because numerous factors can cause the seal to either grow or move radially. This includes thermal expansion, press fit effects, or misalignment.

light bulb iconAny type of contact from the seal rings will result in decreased life and performance. It is imperative that the system be designed to prevent the two rings from touching each other.

Installation Considerations

To ensure optimal performance and life of GMN labyrinth seals, care must be taken with proper installation. Let's look at several installation options and design considerations. 

Proper Seal Orientation

The L and M seals have a symmetric labyrinth path, therefore they can be installed facing either direction. However, the CF, S, and SA seals all have a larger gap diameter on one side. The side with the larger gap diameter is intended to face toward the contamination so that the centrifugal forces work as intended. Additionally, the CF and SA seals are designed to allow contamination to drain back out the face with the larger gap diameter.

Proper Seal Orientation diagram

Shaft & Housing Chamfers

Adding a chamfer to the shaft and housing will help the seals align properly when being pressed onto the shaft and in the housing. GMN recommends a chamfer length of 0.1xW at a 15° angle where W represents the width of the seal.

Shaft and Housing Chamfers diagram

Installation Sleeve

It is critical that the two seals remain aligned after installation. One of the best ways to achieve this is to use an installation sleeve that contacts both rings. This sleeve can be used to press the seal onto the shaft and in the housing simultaneously. Additionally, it can be used to support the seal after installation on the shaft as the shaft assembly is being inserted into the housing.

Installation Sleeve diagram

Installation Shim

Sometimes it is not possible to support the seal already installed on the shaft as the assembly is inserted into the housing. One way to get round this is to use a shim with a width of half the axial clearance of the sea and temporarily install it between the seal housing and the rest of the housing. The shim can be removed after the seal is installed resulting in proper seal alignment.

Seal installation assembly diagram

1. The GMN seal is pre-assembled onto the shaft. A thin metal sheet mounting aid (Thickness Sax/2, half the amount of the seal's axial clearance) should be inserted between the housing and an additional ring. 

Seal installation assembly diagram


2. Shaft (with the seal) and housing (with the bearing) are fitted into each other carefully. Now the outerring stands in the right end position of the seal. 

Seal installation assembly diagram

3. Finally, the mounting aid is removed, and the screws are tightened. With this process the seal's outer ring moves to the left by Sax/2 and finds itself in the final, correct non-contact position.

Desktop Tablet Mobile