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Mechanical face seals:
robust sealing systems for demanding applications

Mechanical face seals are used to protect moving machine components from aggressive media such as sand, stones, mud, dust and soil. These include axles, brake discs and wheel hubs. The seals provide effective protection against the ingress of harmful substances. They are also used in gearboxes, pumps, axles and bearings.

Particularly in areas such as forestry, agriculture, mining, tunnelling, pellet production, material handling, construction and tracked vehicles, high demands must be met in terms of resistance to wear. The mechanical face seals also prove themselves under extreme conditions where effective protection against excessive wear is required.

Mechanical face seals offer protection under extreme conditions

Mechanical face seals keep even abrasive media such as sand, mud, dirt, dust and soil away from moving parts. This provides improved protection compared to radial shaft seals or cassette seals. These seals have a long service life and are easy to install. Typically, mechanical face seals are used to seal rotating shafts from stationary housings in applications such as axles, gearboxes and wheel hubs. Their main function is to retain the lubricant and prevent leakage.

Structure and function of the seals

The mechanical face seals consist of two identical metal rings that seal against each other on a precisely machined sliding surface. The metal sliding rings distribute the axial pressure and ensure the static seal between the housing and the sliding ring.

While one half of the seal is fixed, the other half rotates on the mating surface with the housing. O-rings or special moulded rings made of nitrile butadiene rubber (NBR) or fluorocarbon rubber (FPM/FKM) are generally used for additional sealing. These elastic rings fix and position the metal glide rings in the housing.

The areas of application for mechanical face seals

Mechanical face seals are used in a wide range of applications, including
  • construction machinery
  • agricultural equipment
  • tunnelling machines
  • wind turbines
  • agitators
  • concrete mixers
  • military technology
  • Tracked vehicles of various types

Mechanical face seals designs

Here you will find some important information on the different designs and their installation:

Standard-Type L-Type X, Y-Type

Standard type of mechanical face seals

The standard type of mechanical face seals consists of two identical metal sliding rings and two elastomer O-rings. These O-rings are fitted to the profile of the metal seal. At ttv, these seals are available in two material versions: alloyed cast iron and alloyed forged steel. The choice of O-ring material depends on the specific requirements of your application.

When installing the seal, the O-rings are pressed together between the conical contact surfaces of the sealing ring and the housing. The O-rings are subjected to a compression that is calculated according to ttv's standards and is around 25 per cent of the volumetric compression. This is crucial for the proper functioning of the sealing system.


L-Type mechanical face seals

The MRTZ type mechanical face seals, also known as L-type, consists of two metal rectangular sealing rings with identical geometric profiles. These sealing rings are mounted in the corresponding housing bores using trapezoidal rubber profiles. The geometry of the housing profile is comparatively easy to manufacture, and the installation of the seal requires only a simple assembly tool. Compared to mechanical seals of the ANTN type, the trapezoidal rubber ring is generally stiffer, which limits the permissible axial movement and tolerance.

Numerous mechanical face seals designs have been developed in the past to meet the diverse requirements. At ttv, we have some unique designs that are well suited for particularly demanding applications under difficult operating conditions.


Customised X, Y-type mechanical face seals

In addition to our standard designs, we also offer the opportunity to work with your engineers to develop customised mechanical face seals. It doesn't matter if it's a new seal size, a new seal type or the use of new metal or elastomer materials. ttv's Engineering Solution Team has the necessary expertise to develop, produce, test and implement these concepts through to series production. We are ready to fulfil your individual requirements and develop customised solutions for your applications.

More about the function of the mechanical face seals

ttv's mechanical face seals are specially designed to open from the sealing surfaces towards the centre axis and form a conical gap. This design offers several advantages: - The lubricant easily reaches the sealing surfaces through capillary action and centrifugal force. This ensures sufficient lubrication and cooling at all times.
  • The continuous lubrication prevents cold welding of the sealing surfaces.
  • This sealing system maintains a continuous oil film on the sealing surfaces at all times.

The alloyed cast iron sealing rings are preloaded with trapezoidal rings or O-rings. This achieves the good sealing function.

The relative movement in the circumferential direction only takes place between the sealing surfaces.

The importance of elastomer O-rings in the sealing unit

  • The pressure of the O-rings or trapezoidal rings ensures the axial load on the sealing surfaces.
  • The frictional torque is transmitted via the O-rings and housing parts.

The static seal between each seal and the housing is ensured by an O-ring.

The sealing surfaces of the metal rings are hardened and precisely lapped. The elastomers are selected according to the application conditions.

Lubrication of the mechanical face seals

Here are some tips on lubrication. Various types of lubrication are taken into account:

Oil lubrication

The use of oil lubrication significantly increases the service life of the seal as it ensures better cooling. The selection is made taking into account the area of application, the available oil circuit arrangement in the system and the circumferential speed. As a rule, applications with higher speeds are suitable for oil lubrication. SAE 80 and SAE 90 gear oils are suitable for the typical operation of mechanical seals. After filling, the oil level should be approximately 2/3 of the available oil volume of the oil housing and above the seal axis. If filled correctly, the sliding surfaces are generally maintenance-free.

Grease lubrication

For applications with lower sliding speeds of up to approx. 1 m/s, grease lubrication is suitable as permanent lubrication of the sealing system. The gap in the sealing surface is an important design feature here. When filling with grease, it should be noted that increased grease pressure can cause the elastomer round cord rings to loosen from their position. Adequate lubrication of the sealing surfaces is crucial for the proper functioning of mechanical seals.

Application parameters for mechanical face seals

What should be considered when using mechanical mechanical face seals:
  • The mechanical face seals must be able to withstand circumferential speeds of up to 10 m/s.
  • To prevent cold welding due to frictional heat, the sealing surfaces must be continuously lubricated.
  • Continuous contact between the sealing surfaces and the elastomer within the sealing system is necessary to prevent leakage.
  • These seals must ensure effective tightness in both static and dynamic applications.
  •  The heat generated by friction must be dissipated by sufficient oil flow in the sealing system.

Friction management of the mechanical face seals

ttv's sealing solutions are characterised by outstanding friction management. This is already taken into account in the development of our own materials, the implementation of innovative process engineering technologies and the understanding of the tribology (investigation of friction, lubrication and wear in machine elements) of wear parts.

Our seals are suitable for harsh working environments and have been specially developed to withstand extreme conditions. Various technological developments are taken into account:

  • Seal design for a wide range of applications
  • Lifetime prediction of contact surface wear
  • FKM analysis of the deformation of the O-rings used
  • Special surface treatments for demanding applications
  • Conformity of metallurgical properties of chilled cast alloys and sealing surface unevenness in abrasive environments

Our seals feature the most advanced and innovative corrosion-resistant surface treatments, including TSB (thermal protective coating), which effectively insulates high temperatures and improves heat dissipation.

Materials for metal sealing rings of mechanical face seals

To minimise the risk of failure of the sealing system, the wear and corrosion resistance of the metal surfaces is crucial. ttv uses alloyed steel of various grades for its cast designs. These steel grades are optimised for the requirements of metal seals.

For applications in extreme environments such as mining, dredging and rice cultivation, ttv has developed its own special cast iron materials that offer high abrasion and corrosion resistance and improve heat dissipation. Depending on customer requirements and applications, ttv offers various coating options to meet the demands of the harshest environmental conditions.

Elastomeric materials for mechanical face seals

ttv uses a variety of elastomeric materials, including NBR, FKM/FPM, silicone and HNBR, to meet the different requirements of various applications. These materials offer different degrees of hardness and are highly versatile.

Frequently asked questions

What is an undercarriage seal and what is it used for in various machines and vehicles?

An undercarriage seal is used in machinery and vehicles to prevent the ingress of dirt, dust, water and other foreign bodies. It is used in a wide range of applications, including construction machinery, agricultural vehicles, mining machinery, conveyor systems, wind turbines and more. Mechanical face seals protect high-value components such as axles, gears, bearings and shafts from wear and damage caused by abrasive media.

What types of mechanical face seals are there and how do they differ in terms of their areas of application?

There are different types of mechanical face seals, including standard types, L-types and special designs such as X- and Y-types. These seals differ in their design and function, which makes them suitable for different areas of application. The standard seal types are suitable for many applications, while L-types offer easier installation. Customised designs are developed individually. The choice depends on the specific requirements of the application, including speed, environment and load.

What materials are typically used for mechanical face seals?

Typical materials for mechanical face seals include alloyed cast iron and alloyed forged steel for the metal parts and elastomers such as NBR, FKM/FPM, silicone and HNBR for the sealing rings. The choice of material depends on the requirements of the application, wear and corrosion resistance and temperature resistance.

How does a mechanical face seals work to prevent dirt, dust, water or other foreign bodies from entering a system?

The mechanical face seals are designed to create a secure barrier between the moving parts of a machine and the environment. They utilise special sealing profiles and elastomers to ensure an effective seal at all times. This prevents the ingress of foreign bodies and protects the critical components. Proper lubrication and cooling also minimise the risk of cold welding. Even under extreme working conditions.

Are there special monitoring methods or technologies to monitor the condition of mechanical face seals and prevent premature failure?

Yes, there are various methods for monitoring mechanical face seals, including temperature sensors, pressure sensors and condition monitoring systems. These technologies can help to monitor the condition of the seals, detect leaks at an early stage and initiate maintenance measures in good time to prevent failures of the machines and their components.

How do environmental factors such as temperature, pressure and contamination affect the service life and performance of mechanical face seals?

Environmental factors such as temperature, pressure and contamination can have a significant impact on the service life and performance of mechanical face seals. High temperatures can damage elastomers, high pressure can stress the seal and contamination can lead to premature wear. Therefore, choosing the right seal and considering the environmental conditions is crucial to optimise performance and service life.

What role do mechanical face seals play in the automotive industry, the aviation industry and other sectors?

Mechanical face seals play a crucial role in various industries. In the automotive industry, they are used in gearboxes, axles and wheel bearings. In the aviation industry, they are indispensable in aircraft landing gear and engines. They are also used in construction machinery, mining equipment, wind turbines, agricultural machinery and many other areas where they protect high-value components from wear and damage.


Whether agricultural machinery, construction machinery, forestry technology, drive technology, mechanical engineering, automotive or aerospace, we are ready for your challenges. With our engineering solutions, we manage to offer added value in all decisive product parameters through solutions developed specifically for customers and applications. Get to know our competence and best examples in the most diverse markets.