Thermo-acoustic oscillations pose a significant challenge in the operation of cryogenic systems, where extreme temperature differentials in a pipe can lead to detrimental effects on both process efficiency and equipment integrity. At WEKA, we have developed innovative solutions aimed at mitigating these oscillations and ensuring optimal performance of cryogenic installations.

Understanding Thermo-Acoustic Oscillations

In cryogenic plants, thermo-acoustic oscillations can occur when one end of a pipe is exposed to the very cold process fluid while the other is in contact with ambient temperature. This temperature differential can induce fluid oscillations within the system, resulting in increased heat input and potential freezing of external surfaces—a scenario highly undesirable for cryogenic operations.

Factors Influencing Oscillation Risk

Several factors influence the likelihood of thermo-acoustic oscillations:

• Design and Process Parameters: The positioning of warm and cold ends within the system, fluid volumes, pipe geometries, and operational parameters of the process fluid all play critical roles.
• Type of Process Fluid: Systems using supercritical, liquid, or superfluid Helium are particularly susceptible due to fluid properties of Helium.

Technical Solutions Developed at WEKA

To combat thermo-acoustic oscillations, WEKA has engineered specific solutions tailored for cryogenic valves and plants:

1. Convection Brakes on Valve Inserts: Valve inserts featuring convection brakes utilize plastic rings fixed to the pipe of the insert. This design devides the volume between the valve insert and the valve body pipes into several smaller volumes, effectively preventing the mixing of warm and cold layers. This eliminates the risk of oscillations  Convection brakes can be retrofitted
2. Application of Check Valves: In cryogenic cold boxes, auxiliary pipelines often connect warm, uninsulated sections with vacuum-jacketed process piping. Installing check valves in these pipelines prevents backflow, thereby maintaining the integrity of temperature differentials and dampening oscillations.
3. Thermal Intercepts: Cryogenic extensions of valves or couplings can be equipped with customizable flanges connected to thermal shield circuits. This setup stabilizes temperatures along the pipe, reducing the temperature ratio between hot and cold ends and minimizing the risk of oscillations. Copper is chosen for its efficient heat exchange properties. These thermal intercepts, mounted at the correct positions, ensure effective thermal management and reduce the static heat load to the fluid.

Conclusion

While thermo-acoustic oscillations present a formidable challenge in cryogenic installations, proactive measures can effectively mitigate their occurrence. By implementing solutions such as convection brakes, check valves and thermal intercepts, operators can significantly improve system reliability and performance. At WEKA, we recognize the critical importance of tailored design and meticulous assessment of operational risks to deliver solutions that meet the specific needs of each cryogenic installation.

For more information on how WEKA addresses thermo-acoustic oscillations and other challenges in cryogenic systems, please contact us. Our experts in cryogenic applications are always at your service.