Emissions Control
must be considered to ensure effective control of fugitive emissions and maintain long-term system integrity : Chemical compatibility : The solvent Power of sCO2 can dissolve various substances , potentially degrading lubrication packages not designed for such conditions . Permeation and phase transitions : The permeation of sCO2 into the packing set and subsequent phase transitions between supercritical , liquid , and gas states can induce physical stress on materials . This can lead to mechanical failure , increased wear , and the formation of additional leakage paths . External leakage and cooling effects : External leakage can cause rapid cooling around the packing interface , potentially freezing the external part of the system through the Joule-Thomson effect . This can result in mechanical changes within the system , leading to excessive leakage or premature failure . Selecting a proven & validated fugitive emissions control packing can support longterm system integrity by mitigating the risk of an initial leak path forming .
Retention of low frictional load
The correlation between fugitive emissions and frictional behaviour is significant . Controlling frictional behaviour involves managing the impact of the sCO2 medium , which can degrade lubrication packages due to chemical incompatibility and subject the packing to mechanical stresses through media phase transitions caused by
Fig 2 : Supagraf ® 100FXI CS has been developed , tested and validated by James Walker for valve stem sealing in sCO2 service .
temperature and pressure changes . Rapid cooling effects through leakage can induce additional mechanical and thermal stresses in the system , causing premature material degradation and frictional performance losses . To manage these effects and maximise long-term system performance , careful specification of base materials , lubrication packages , control of fitting procedures and technical assessment of the original equipment design is essential .
Packing integrity and robustness in high-pressure duties
In high-pressure applications , ensuring the integrity and robustness of packing systems is paramount to maintaining operational efficiency and safety .
Mechanical stability : Maintaining mechanical stability is essential , especially with supercritical CO2 ( sCO2 ) under high pressures , which can increase sealing leakage and wear due to elevated hydrostatic unloading effects . Material selection and housing design : High-pressure sealing challenges require advanced materials that withstand hydrostatic forces , thermal transients , and creep relaxation . Precision manufacturing can ensure seals fit correctly and perform under sCO2 conditions , meeting diverse customer housing design needs . Phase transitions and material stress : Transitions between supercritical , liquid , and gas states can stress materials , leading to mechanical failure or wear . Cooling during pressure reduction , especially to a gaseous phase , can cause thermal stress and material degradation . Utilising proven materials : Using tested materials ensures resilience against creep relaxation and thermal expansion variations , maximising product performance and lifecycle under challenging conditions . The selection of appropriate materials and precise manufacturing processes are critical to developing sealing solutions that can withstand the rigorous demands of highpressure environments . By focusing on mechanical stability , material resilience , and the ability to handle phase transitions , we can ensure the longevity and reliability of sealing products in supercritical CO2 applications .
Fig 3 : Illustrates the fugitive emissions performance of James Walker ’ s product under supercritical CO2 media with both pressure and dynamic cycling .
Validation of a packing solution
To tackle these challenges , highquality , high-purity graphite , fugitive emissions rated combination packing ring sets can present an effective
54 Valve World December 2024 www . valve-world . net