Introduction To Agitator Seals – A Definitive Guide
April 6, 2023
Different Types Of Mechanical Seals For Centrifugal Pumps - A Detailed Overview
Mechanical seals are central to all industrial processes, and centrifugal pumps are the one that is extensively used in municipal and complex industrial applications.
Centrifugal pump systems require proper sealing arrangements to prevent fluid leakage and pump protection against various conditions.
Here comes the role of Mechanical Seals.
Mechanical Seals are the popular choice for sealing the pump. With minimum maintenance and maximum durability, they detect leaks, control the sealing environment, and lubricate secondary seals.
But what types of Mechanical Seals are out there, and what to keep in mind when choosing them?
Selecting the appropriate type of Mechanical Seal is essential for pump success. There exist wide types based on design, functions, and others. So how do you choose the right one? Keep reading to find the answer.
In this detailed guide, we’ll introduce you to the different types of Mechanical Seals and their advantages with key considerations to choosing the right mechanical seals.
What is a Mechanical Seal?
A mechanical seal is a device utilized on a rotating shaft to keep liquids in and contaminants out. It prevents the liquid traveling through the centrifugal pump from leaking or spilling.
These mechanical seals are situated in the centrifugal pump’s stuffing box or seal chamber, the area of the pump where the pump shaft interfaces with the drive, for instance, an electric motor.
Most mechanical seal types consist of two flat faces installed perpendicular to the shaft. One of these faces is mounted fixed to the seal chamber housing, and the other face rotates with the shaft to deliver immediate sealing.
The contact caused between the seal face materials prevents leakages in the pump. The contact is maintained by axial mechanical force and fluid pressure.
What are the different types of Mechanical Seals for Centrifugal Pumps?
Mechanical seal types come in different designs and arrangements and with different abilities to disperse the hydraulic forces’ action at mechanical seal faces.
Below are some of the common types of mechanical seals used in centrifugal pump processes.
Balanced Seals –
A balanced mechanical seal arrangement is a system where the forces acting on the seal faces are evenly distributed, resulting in lower face loading, better lubrication, and longer seal life.
This type of seal is particularly suitable for high-pressure operations above 200 PSIG and handling low lubricity and highly volatile liquids.
Balanced seals are well-designed to maintain a stable position and provide effective sealing even under high pressure and extreme operating conditions.
This type of mechanical seal is widely used in pumps, mixers, compressors, and other industrial equipment due to its excellent ability to handle aggressive fluids and compatibility with various materials.
Unbalanced Seals –
An unbalanced mechanical seal is an economical alternative to the complex balanced seal and is commonly used in low/medium pressure applications.
They are highly stable and can still function effectively in conditions where there are vibrations, shaft misalignments, or fluid cavitations. Due to tighter control of the face film they exhibit less product leakage.
However, unbalanced seals have a much lower mean time between failures; hence, they are not recommended for high-pressure or most hydrocarbon applications.
Pusher Seals –
Pusher seals are mechanical seals that utilize one or more springs to maintain the seal closing force. The springs can be located in either the rotating or stationary element of the seal.
These seals rotate along the shaft or sleeve to maintain contact with the faces of the seal to reduce any wearing and wobbling caused by misalignment.
They come in different sizes and designs and are less expensive compared to other types of mechanical seals.
One of the primary advantages of pusher seals is their ability to provide sealing at very high pressures.
However, their main drawback is the elastomer under the primary seal face, which can be subjected to wear as the face moves along the shaft/sleeve during operation.
Despite this disadvantage, pusher seals are a reliable and cost-effective solution for high-pressure applications.
Non-Pusher Seals –
Non-pusher seals rely on metal or elastomeric bellows to maintain the sealing force. It supports the contact between the faces without rotating axially.
These seals are well-suited for high-temperature and dirty applications. However, they are limited to medium or low-pressure applications. Non-pusher seals are especially useful in environments where corrosion is a concern. However, the bellows used in these seals must be often replaced in corrosive conditions.
Conventional Seals –
Conventional seals are a cost-effective option and are commonly installed on general service equipment. These seals are made up of separate components and require a higher level of operator skill to service.
It is crucial that operators have the necessary skills and knowledge to perform repairs and replacements when necessary.
Cartridge Seals –
Cartridge-type mechanical seals are a highly efficient and convenient option for sealing applications.
Designed as a one-piece unit, they incorporate all of the seal components, including the primary sealing element, stationary and rotating faces, and gland, into a single assembly. This reduces the potential for assembly errors and saves installation time.
Cartridge seals provide easy maintenance. They can be easily removed and replaced without disassembling the equipment, reducing downtime and maintenance costs.
Additionally, they provide consistent and reliable sealing performance, ensuring long-lasting and leak-free operation, making them a preferred choice for a wide range of industrial applications.
Advantages of using Mechanical Seal
Using mechanical seals in centrifugal pumps provide several benefits, including:
- Reduced friction and loss of power
The faces of mechanical seals are lubricated with a film of fluid, which reduces friction and power loss compared to traditional packing seals.
- Zero product leakage
Mechanical seals provide a tight seal that eliminates product leakage, ensuring a safer and cleaner environment.
- Elimination of excessive wear
The design of mechanical seals reduces wear and tear on the equipment, resulting in longer-lasting and more reliable performance.
- Low maintenance
Mechanical seals require less maintenance than packing seals, as they do not need frequent adjustment or replacement.
Key Considerations When Choosing Different Types Of Mechanical Seals For Centrifugal Pumps
When choosing the seal system for a centrifugal pump, operators must select according to their unique application requirements.
Improper selection of mechanical seals can lead to loss of pump integrity, breakdowns, and heavy costs of repairs.
To avoid all these undesirable results,read our comprehensive guide on choosing the Right Mechanical Seal. From what factors and materials to consider, the guide will help with proper mechanical seal selection.
Concluding Thoughts
Choosing the right mechanical seal for your centrifugal pumps is important to ensure it performs well.
Above were all the details you need to understand the different types of mechanical seals available, their unique features, and their advantages. Hope this information helps you make a better and more informed decision that meets the specific needs of your application.
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