What Is the Difference Between Cartridge and Mechanical Seals

By Published On: November 24, 2023

When it comes to industrial pumps and machinery, the right choice of sealing solutions is crucial for ensuring efficiency, longevity, and safety. Among the various types of seals available, cartridge seals and mechanical seals stand out as popular options. But what is the difference between cartridge and mechanical seals? What sets these two apart?

what is the difference between cartridge seals and mechanical seals

Let’s look into the differences, how each type works, their lifespans, common types, and more.

How Does a Cartridge Seal Work?

A cartridge seal is a self-contained unit that includes all the components of a seal assembly. Its design simplifies installation and maintenance, making it a go-to choice for many applications.

Here’s how it works:

Pre-assembled unit

Unlike traditional seals, a cartridge seal comes as a pre-assembled, ready-to-install unit. This design minimizes the risk of incorrect installation, which is crucial in maintaining seal integrity.

Installation

To install the cartridge seal is slid onto the pump shaft in a single movement. It’s then secured in place with set screws or a locking collar. This ease of installation reduces downtime and the possibility of human error.

Sealing mechanism

Inside the cartridge, a stationary seal face is pressed against a rotating face, typically attached to the pump shaft. This creates a tight seal that prevents fluid leakage.

Materials used for seal faces:

  • Silicon Carbide: Offers excellent thermal conductivity and hardness, ideal for abrasive fluids and high temperatures.
  • Tungsten Carbide: Known for its toughness and wear resistance, it is suitable for heavy-duty and high-pressure environments.

Spring Mechanism

Most cartridge seals have a spring mechanism that maintains constant pressure between the seal faces, ensuring effective sealing even under varying operating conditions.

spring mechanism of a mechanical sealTypes of spring mechanisms and their adaptability:

  • Conical Springs: Known for their robust design, they provide consistent pressure, making them ideal for high-speed applications.
  • Wave springs: Preferred in space-limited applications, they offer the necessary sealing force in a compact design and adjust well to pressure and temperature changes.

Self-Alignment

One of the critical advantages of cartridge seals is their self-aligning capability. This feature compensates for misalignment or movement in the pump shaft, maintaining seal effectiveness.

Typical Applications of Cartridge Seals

Cartridge seals are used across various industries due to their robustness and versatility. Here are some key applications:

  • High-speed pumps: Cartridge seals minimize vibration and maintain operational stability in high-speed pump applications. Essential in water treatment, chemical processing, and energy generation, their robust design ensures the reliability and efficiency of the pumps.
  • Corrosive environments: Ideal for chemical manufacturing and mining, cartridge seals excel in corrosive environments. Their resistance to chemical degradation reduces maintenance costs and prevents seal failure, making them crucial for handling acidic or basic fluids.
  • Pharmaceuticals and food processing: In industries where hygiene is paramount, like pharmaceuticals and food processing, the easy-to-clean nature of cartridge seals is vital. They prevent contamination, ensuring product safety and purity in environments where sterility is a top priority.

These applications demonstrate cartridge seals’ adaptability and essential role in maintaining operational efficiency and meeting industry-specific requirements.

How Long Do Mechanical Seals Last?

The lifespan of mechanical seals can vary significantly based on factors such as material quality, operating conditions, and maintenance practices. However, here’s a general comparison:

Cartridge seals

Typically, high-quality cartridge seals can last anywhere from 3 to 5 years and, in some cases, even longer, especially when maintained properly and used under optimal conditions. Their pre-assembled design and ease of installation contribute to this extended lifespan. 

Traditional mechanical seals

These seals generally have a lifespan ranging from 1 to 3 years. The variance is larger due to the precision needed in installation and the sensitivity to operational conditions. With meticulous maintenance and ideal operating circumstances, they can reach the higher end of this range.

Factors affecting lifespan:

  1. Material quality: High-grade materials resist wear and corrosion better, extending seal life.
  2. Operating conditions: Temperature, pressure, and the nature ocartridge versus mechanical sealsf the fluid being sealed all impact seal longevity.
  3. Maintenance: Regular inspection and maintenance can significantly extend the life of both cartridges and traditional mechanical seals.
  4. Installation 
  5. precision: Proper installation, especially for traditional mechanical seals, is crucial to ensure maximum lifespan.

What is the Most Common Type of Mechanical Seal?

Mechanical seals are utilized in a myriad of applications, and their types vary widely. However, some types are more prevalent due to their versatility and efficiency. Let’s explore the most commonly used mechanical seals:

  1. Single-spring mechanical seals: These are widely used for their simplicity and effectiveness. They consist of a single spring coil that maintains pressure on the seal faces, suitable for various applications, particularly in water and low-pressure duties.mechanical seal with spring mechanism
  2. Balanced mechanical seals: Designed for high-pressure applications, balanced mechanical seals are engineered to reduce the hydraulic load on the seal face. This balancing extends the seal’s life and allows it to operate under higher pressures.
  3. Cartridge mechanical seals: As previously mentioned, these have become more popular thanks to their ease of installation and maintenance. They are used in various chemical, pharmaceutical, and food processing industries.
  4. Double mechanical seals: These are ideal for handling hazardous, toxic, or volatile fluids. They provide a higher level of safety by ensuring that if the primary seal fails, the secondary seal contains the fluid.
  5. Bellows mechanical seals: Employing a bellows design instead of a spring, these seals are adept at handling high temperature and corrosive materials. The bellows design accommodates a range of movement and compensates for shaft misalignment.

Additional Considerations for Seal Selection

When choosing between cartridge and mechanical seals, consider these additional aspects:

  1. Application specifics: The nature of the fluid, pressure, temperature, and pump type all play crucial roles in seal selection.
  2. Cost implications: While cartridge seals may be more expensive upfront, their ease of installation and longer lifespan can lead to cost savings in the long run.
  3. Maintenance and replacement: Consider the ease of maintenance and availability of replacement parts. Cartridge seals are generally easier to maintain and replace.
  4. Environmental and safety concerns: In industries where leakage can have serious safety or environmental consequences, the reliability of cartridge seals often makes them a preferable choice.

Final Thoughts

Understanding the difference between cartridges and mechanical seals is crucial for informed decision-making in pump and machinery applications. Each type of seal has unique advantages and appropriate applications, and the selection largely depends on specific operational needs and constraints.

When considering “what is the difference between cartridge and mechanical seals,” it’s important to remember that the longevity and effectiveness of any seal greatly depend on proper installation, regular maintenance, and selecting the right seal for the specific application. 

Choosing a cartridge seal for its convenience and durability or opting for a mechanical seal for its adaptability and cost-effectiveness requires a thorough understanding of your operational requirements. Ensuring the right fit for your application is paramount in achieving optimal performance and longevity.