Mechanical seals for pumps: description, uses and types

In mechanisms or systems such as pumps, a mechanical seal is a component that helps to join a fixed part with a rotating part under pressure to hermetically seal. This prevents leaks or drips that would imply a deterioration in the seals and, consequently, continuous stoppages in the pumping system.

The most important parts of the seals are the mechanical faces: a rotating or swivel face that is attached to a shaft and a stationary face that is fixed to the system cover.

It is important to mention that the materials used to manufacture mechanical seals will depend entirely on the liquids that will be pumped. In the most common case, which is potable water, the ideal material composition is graphite with ceramic.

If the liquids to be pumped are abrasive, graphite is used with silicon carbide, a material that resists and prevents wear. Carbon prevents overheating during dry start-up.

Finally, both seal faces made of silicon carbide offer greater resistance to abrasives that may be found in liquids.

Because graphite is self-lubricating, mechanical pump seals can be pressed into the shaft of a pump, which will rotate smoothly and the oil from the equipment will remain inside.

Types of mechanical seals

Although there is currently a wide variety of types of mechanical seals for pumps and each one is used according to its functionality, we can divide them taking into account their characteristics into three main groups.

Thrust and non-thrust seals

Thrust seals work from a spring to impart a fixed sealing force, while non-thrust seals use springs with a sealed bellows.

Conventional

These parts are primarily used for compressor and pump modifications or upgrades.

Balanced and unbalanced

Balanced are capable of withstanding higher pressures and are ideal for liquids that have low lubrication. Unbalanced are better for jobs with misalignment and vibration.

In the industrial area, mechanical seals are used in mixers, compressors, industrial centrifugal pumps and other machines that need a rotating shaft.

In the automotive field, these components are installed in engine cooling systems and air conditioning compressors. In more domestic applications, mechanical seals are found in water pumping systems and household appliances such as washing machines.

To learn about other applications of graphite in industry, click on this link. If you need guidance in choosing a carbon or graphite-based solution, contact us here for more information.

Limitations to consider

Performance depends on graphite grade, grain orientation, temperature, load, pressure, speed, and operating environment. Material selection should be confirmed for your actual process conditions.

Information needed for a quote

To guide selection or prepare a quote, ESGRAF typically needs:

• Application and operating conditions (temperature, atmosphere, load).
• Dimensions, technical drawing, or CAD file when applicable.
• Required quantity.
• Requested grade or material currently in use.
• Observed issue with the previous part or lubricant, if any.

Request a quote

Share these details with our team at ESGRAF or request information. A specialist will review your application before recommending a grade or geometry.