How to select between a tandem and back - to - back double seal pump?

When it comes to the selection between a tandem and back-to-back double seal pump, there are several crucial factors that need to be carefully considered. As a double seal pump supplier, I have witnessed firsthand the diverse requirements of our customers and the importance of making the right choice in pump sealing solutions. In this blog post, I will delve into the key aspects that can guide you in deciding whether a tandem or back-to-back double seal pump is the most suitable option for your specific application.

Understanding the Basics of Double Seal Pumps

Before we dive into the comparison between tandem and back-to-back double seal pumps, let's first understand the concept of double seal pumps. Double seal pumps are designed to provide an extra layer of protection against leakage, which is especially critical when handling hazardous, toxic, or valuable fluids. They consist of two mechanical seals arranged in a specific configuration, with a barrier or buffer fluid circulating between them. This setup not only enhances the sealing performance but also helps to extend the service life of the seals by reducing wear and tear.

Tandem Double Seal Pumps

Tandem double seal pumps feature two mechanical seals arranged in series, with the primary seal closest to the pumped fluid and the secondary seal acting as a backup. The barrier or buffer fluid is introduced between the two seals, creating a pressure differential that helps to prevent the leakage of the pumped fluid. One of the main advantages of tandem double seal pumps is their ability to handle high-pressure applications effectively. The secondary seal provides an additional level of protection in case the primary seal fails, ensuring that the pumped fluid is contained within the pump.

Another benefit of tandem double seal pumps is their flexibility in terms of seal materials and configurations. You can choose from a wide range of seal materials, such as Carbon Mechanical Seal and Ceramic Mechanical Seal, depending on the properties of the pumped fluid and the operating conditions. Additionally, tandem double seal pumps can be easily customized to meet specific requirements, such as temperature, pressure, and chemical compatibility.

However, tandem double seal pumps also have some limitations. They tend to be more complex and expensive than single seal pumps, requiring additional components and a more sophisticated control system. The installation and maintenance of tandem double seal pumps can also be more challenging, as they require precise alignment and proper monitoring of the barrier or buffer fluid.

Back-to-Back Double Seal Pumps

Back-to-back double seal pumps, on the other hand, have two mechanical seals arranged in a back-to-back configuration, with the primary seal facing the pumped fluid and the secondary seal facing away from it. The barrier or buffer fluid is introduced between the two seals, creating a pressure differential that helps to prevent the leakage of the pumped fluid. One of the main advantages of back-to-back double seal pumps is their simplicity and reliability. They are less complex than tandem double seal pumps, with fewer components and a simpler control system.

Back-to-back double seal pumps are also more suitable for applications where the pressure of the pumped fluid is relatively low. The back-to-back configuration provides a more stable sealing performance, reducing the risk of leakage and improving the overall efficiency of the pump. Additionally, back-to-back double seal pumps are easier to install and maintain, requiring less specialized knowledge and equipment.

However, back-to-back double seal pumps may not be as effective in handling high-pressure applications as tandem double seal pumps. The secondary seal may not provide as much protection in case the primary seal fails, and the pressure differential between the two seals may be more difficult to maintain.

Factors to Consider When Selecting Between Tandem and Back-to-Back Double Seal Pumps

Now that we have a better understanding of the characteristics of tandem and back-to-back double seal pumps, let's discuss the key factors that you should consider when making a selection.

Pressure

The pressure of the pumped fluid is one of the most important factors to consider when choosing between a tandem and back-to-back double seal pump. If the pressure of the pumped fluid is high, a tandem double seal pump may be the better option, as it can provide a higher level of protection against leakage. On the other hand, if the pressure of the pumped fluid is relatively low, a back-to-back double seal pump may be sufficient.

Chemical Compatibility

The chemical compatibility of the seal materials with the pumped fluid is another crucial factor to consider. Different seal materials have different chemical resistance properties, and it is important to choose a seal material that is compatible with the pumped fluid to ensure long-term reliability. For example, if the pumped fluid is corrosive, you may need to choose a seal material such as Ceramic Mechanical Seal, which has excellent chemical resistance.

Temperature

The temperature of the pumped fluid and the operating environment can also affect the performance of the double seal pump. High temperatures can cause the seal materials to expand and contract, which can lead to leakage. Therefore, it is important to choose a seal material that can withstand the temperature range of the application. Additionally, you may need to consider using a cooling system to maintain the temperature of the barrier or buffer fluid within a safe range.

Cost

Cost is always a consideration when selecting a double seal pump. Tandem double seal pumps tend to be more expensive than back-to-back double seal pumps, due to their complexity and the additional components required. However, the cost of the pump should be weighed against the potential benefits, such as improved reliability and reduced maintenance costs.

Maintenance

The maintenance requirements of the double seal pump are also an important factor to consider. Tandem double seal pumps may require more frequent maintenance and monitoring, due to their complexity and the need to maintain the pressure differential between the two seals. Back-to-back double seal pumps, on the other hand, are generally easier to maintain and require less specialized knowledge and equipment.

Conclusion

In conclusion, the selection between a tandem and back-to-back double seal pump depends on several factors, including pressure, chemical compatibility, temperature, cost, and maintenance requirements. As a double seal pump supplier, I recommend that you consult with our experts to determine the most suitable option for your specific application. We have a wide range of double seal pumps available, including those equipped with Burgmann Mg12 and other high-quality seal materials, and we can provide you with customized solutions to meet your unique needs.

If you are interested in learning more about our double seal pumps or would like to discuss your specific requirements, please feel free to contact us. Our team of experienced professionals is ready to assist you in making the right choice and ensuring the reliable operation of your pumping system.

References

• ASME B73.1 - 2015, Specification for Horizontal End Suction Centrifugal Pumps for Chemical Process.
• API 682 - 4th Edition, Pumps - Shaft Sealing Systems for Centrifugal and Rotary Pumps.
• ISO 21049 - 2008, Mechanical Seals and Accessories - Terminology.