John Crane joined forces with Pumps and Systems Media to host the webinar “Sealing Solutions for Ammonia and Liquid CO2 in the Hydrogen and Carbon Capture Utilization and Storage Value Chain.” Together, we explored the most effective sealing solutions for ammonia and liquid CO2 and how to enhance efficiency and safety across these value chains. Amy Hyde, editor of Pumps and Systems Media, joined two of John Crane's subject matter experts (SMEs), Engineering Manager Milosz Zielinski and Wet Seals Engineer Ian Gaffing, for this immersive webinar.
To help you navigate these sealing solutions, we're sharing a transcript of the webinar's Q&A session — an interactive end cap to a mission-critical discussion. Want to dig deeper into the dynamics of ammonia and liquid CO2? Explore the full on-demand webinar, our latest article on ammonia sealing solutions and our approach to CCUS innovation.
Which barrier fluids can be used for CO2 applications?
Our barrier fluid suggestions vary based on the specific application and situational requirements; it comes down to the conversation between our team and the end user. Typical options include alcohols (mainly propanol) and oils, but it depends on the situation. Barrier fluid will always leak a controlled amount into the process fluid, so if the solutions are incompatible, adverse reactions could compromise process integrity and delay operations. Ultimately, the end user needs to ensure the suitability of barrier fluids with their process as they understand the exact composition and likely contamination.
Can O-rings be used in mechanical seals for pumping ammonia?
We recommend using neoprene — or, in some cases, EPDM elastomers — for ammonia applications. Elastomers do have a risk of explosive decompression, so we need to consider materials for ammonia that are inherently decompression-resistant. It's critical to exercise extreme caution when using them with barrier oil fluids.
Are there any special seal face and elastomer material requirements for ammonia and CO2?
Yes, there are specific seal face and elastomer requirements for both ammonia and CO2 applications. For ammonia, the primary and mating rings should be made from materials that can handle ammonia's challenging properties, such as its tendency to harden elastomers and crystallize. Neoprene is recommended for elastomers due to its resistance to these issues. For CO2, we can typically utilize standard seal face materials; however, as previously discussed, elastomers carry a high risk of explosion. Depending on the temperature and pressure of the application, harder elastomeric materials could be preferred to withstand rapid gas decompression when CO2 transitions between phases. Due to a potentially low operating temperature, specialist elastomers are often required to cope with operating conditions beyond the capability of the most commonly available.
What is the preferred barrier fluid for API Plan 52 on ammonia applications?
Again, our barrier fluid recommendation depends upon the application's specific requirements and operating conditions. The most common options include oils like Royal Purple 22 or water and water-glycol mixtures, but we would need to understand more about the exact system before suggesting moving forward with one barrier fluid over another. That being said, oils are often preferred for their lubricating properties, while water-glycol mixtures can be used in certain situations to provide the necessary cooling and lubrication.
Is there a flush option for ammonia crystals?
Flushing helps manage ammonia crystals, improve the operational life of mechanical seals and enhance the efficiency of your operation. John Crane offers several plans with flush options. API Plan 11, API Plan 13 and API Plan 32 are available for ammonia applications and can enhance seal performance by preventing crystallization and ensuring proper lubrication. Flushing can dissolve formed crystals and maintain the integrity of the seal faces. Explore which plan is right for you.
CO2 pumps are often seen encased in ice when operating. Is this typical of a well-operating CO2 pumping application?
Typically, ice formation on the outside of a CO2 pump is simply water vapor in the air freezing due to pump temperature. Ice formation occurs because the CO2 pump operates at temperatures well below the freezing point of water, leading to condensation and freezing of atmospheric moisture. This is not a sign of poor operation and should not be seen as a cause for concern.
How do seals account for nitrogen's two-phase effect?
When using nitrogen as a buffer gas in a seal arrangement such as API Plan 72, the nitrogen purge is only slightly above atmospheric pressure and exists in gaseous form across all liquid CO2 operating conditions.
What are the best practices to increase the mean time between repair (MTBR) for CO2 mechanical seals?
A lot of this comes down to ensuring we are doing everything we can to give the mechanical seal as good a life as possible. This includes seal design, seal maintenance, appropriate commissioning and consistent operational practices. It is critical to ensure conditions are correct and that all functions are running properly. Monitoring of the seal is recommended so if transient conditions occur— for example, if a nitrogen source cuts out — the operator is notified immediately and can take corrective action to mitigate any potential damage or downtime.
John Crane recommends following these best practices:
- Using nitrogen purge consistently to prevent ice formation within the seal cavity
- Maintaining a seal temperature below 87.8°F (31°C) to keep CO2 in the liquid phase
- Ensuring that all operational conditions are within the specified parameters to prevent rapid phase changes and maintain seal integrity
Are there any special considerations for explosive decompression in CO2 applications?
Yes. For CO2 applications, it's crucial to mitigate the risk of explosive decompression or rapid gas decompression. This can be achieved by:
- Using elastomers inherently resistant to explosive decompression, this is typically harder elastomeric materials
- Following proper material design and operating procedures to ensure seal integrity during depressurization
- Avoiding rapid depressurization, especially during shutdowns or changes in operating conditions
Careful material selection and adherence to operational protocols can also significantly reduce or eliminate the risk of explosive decompression, ensuring safe and efficient operation. It's impossible to underestimate the role of consultation when making these kinds of decisions.
At John Crane, we're committed to supporting customers as they navigate the energy transition's many challenges — including the sealing dynamics of ammonia and liquid CO2. Let's discuss your initiative and how our market-ready sealing solutions can help you power reliability and sustainability.