St Marys Carbon Knowledge Base

Why a Carbon Graphite Seal Could Fail

In the intricate world of industrial machinery and equipment, mechanical seals play a pivotal role in maintaining a delicate balance between efficiency and reliability. Among the diverse materials used for crafting these seals, carbon graphite is a popular choice due to its exceptional qualities.

However, like any mechanism, a carbon graphite seal can falter under certain conditions. In this blog, we delve into the factors that can contribute to mechanical seal failure.


What Is a Carbon Graphite Seal?

A mechanical seal is a device used to create a tight and reliable sealing mechanism between two components, typically rotating and stationary parts in machinery such as pumps, compressors, and mixers. Its primary purpose is to prevent leakage of a liquid or gas.

Carbon graphite is a popular choice for mechanical seals in a variety of industrial applications where preventing leakage is critical. Some of the key advantages of carbon graphite mechanical seals is that they are dry-running, offer high temperature stability, have a high thermal conductivity, and have low friction to reduce wear.


Factors that Can Cause Carbon Graphite Seal Failure

When a mechanical seal fails, it’s typically due to one of two reasons: either the seal face opens, or the seal was damaged via heat, corrosion, or physical contact.

Wrong Material

1. The Wrong Material for the Application

No two carbon graphite grades are exactly the same. St. Marys Carbon has hundreds of proprietary carbon graphite grades, and a custom grade is always an option. If the mechanical seal fails, it could indicate that you’re using the incorrect material for the application.

The carbon graphite grade may just not be compatible with the environment, due to any number of reasons. It may not be able to handle atmosphere, the operating temperature may be too low or high, it isn’t in line with regulator requirements, or something else entirely.


Incorrect Dimensions

2. Incorrect Dimensions

If the part is not manufactured to the necessary dimensions, or the customer provides the wrong dimensions, seal failure is likely. It’s essential for customers to provide the correct dimensions, and parts should always be tested to make sure they’re within tolerance before being put to use.


Improper Installation

3. Improper Installation or Handling

It’s also common for the mechanical seal to be machined correctly, but fail due to installation or handling errors. For example, seal faces may be damaged if couplings are hammered onto the shaft. As durable as carbon graphite is, mishandling has been known to chip seal faces, which will lead to failures.



4. Vibration

Vibration can be caused by a variety of factors, such as warped shafts, loose bearings, or pump and drive misalignment. When excessive or prolonged vibration occurs, the mechanical seal face may chip, and the seal could open. If the seal face does open, contaminants could cause premature wear.


What Can Happen if a Carbon Graphite Seal Does Fail?

When a carbon graphite mechanical seal fails, a variety of things may occur:

  • Fluid or gas leak
  • Equipment downtime
  • Reduced efficiency
  • Product contamination
  • Damage to other parts or the whole component


How to Prevent Carbon Graphite Seal Failure

Improved quality control processes should take care of improper installation, but how else can mechanical seal failure be prevented? It’s all about quality materials and great service.

Identify the Proper Material

1. Identify the Proper Material

Carbon graphite can be impregnated with other materials, making it incredibly versatile. Take advantage of this versatility and work with your manufacturer to ensure that your carbon graphite grade is a perfect match for the seal’s environment and application.


Measure Twice

2. Measure Twice, Manufacture Once

The proper material can only get you so far. Take extra care to ensure you’re providing your manufacturer with the correct dimensions. If the manufacturer receives inaccurate data, the seals won’t be properly installed and failure will occur.


Understanding Carbon Graphite Seal Failure

Mechanical seals create a reliable barrier in machines like pumps and compressors, preventing leaks. Carbon graphite's role in these crucial applications hinges on attributes such as dry-running capability, temperature resistance, thermal conductivity, and friction reduction.

Seal failures often trace back to two issues: seal face separation or damage from heat, corrosion, or mishandling. Our focus has been on a common blunder: selecting the wrong material. Carbon graphite grades vary, and choosing an incompatible one can lead to issues. Contact St. Marys Carbon today to select the perfect carbon graphite grade for your mechanical seal.

For more information about our services, call us at 814.781.7333