Ammonia is already a commodity product in various sectors but with 185 Mt produced in 2020, the sector was responsible for around 1 % of global GHG emissions. Bloomberg NEF( Source: Scaling Up Hydrogen: The Case for Low-Carbon Ammonia, November 28, 2023) has identified 185 low-carbon ammonia projects totalling 28.7 Mtpa that will be π www. valve-world. net Valve World May 2025 19
Sealing co 2
Absorption / Decompression
Diffusion
Elastomer Swelling Blistering
Figure 1: Schematic showing the events leading to blistering of polymers when depressurised after being exposed to a high-pressure CO2( Source: TWI,“ Selection of materials for high pressure CO2 transport”, paper presented at Third International Forum on the Transportation of CO2 by Pipeline, Newcastle, June 2012)
Certification of thermoplastics
To ensure safe transport and storage as well as prevent leakage from various components in the value chain, e. g., valves, wellheads, compressors, pumps and loading systems, soft sealing materials and their durability are often scrutinised. Sealing and material companies, such as Omniseal Solutions, are often asked about assessing the behaviour of these sealing materials and their integrity in challenging environments. NORSOK M-710 provides materials and functional testing for critical non-metallic( polymeric) sealing, seat and back-up ring materials and components. The intent of NORSOK M-710 is to ensure that non-metallic sealing material manufacturer and end user have sufficient understanding and experience with the applicable materials to be reassured that they will give acceptable performance in the specified environment.
Catching CO2 with certified thermoplastic materials
The compatibility of soft sealing materials for exposure to CO2 and impurities in dense phase CO2 service needs to be considered and various failure modes have been identified. Soft sealing materials can be split into two sub-categories: elastomers and thermoplastics, with each exhibiting different behaviours because of their intrinsic properties. According to published technical papers, elastomeric seals can undergo severe degradation, i. e., chemical ageing, swelling and blistering with“ impure CO2” blends containing SOx, NOx, O2, H2S and Brine. CO2 at high pressure can diffuse and dissolve in elastomeric materials. The initial sorption of CO2 into elastomers results in swelling, which changes their mechanical and physical properties. The most important effect during the sorption is the reduction in Tg, often called plasticisation. Furthermore, blistering of elastomeric seals is caused by absorption / diffusion of CO2 at high pressure often creating catastrophic failure when depressurised, called Rapid Gas Depressurisation( RGD).( see Figure 1).
With elastomer seals, it is not always possible to provide a straightforward summary of what makes an elastomer RGD resistant or high performance in CO2 applications. Rather, it is more practical to rank the elastomeric seals by their relative resistance to RGD. For thermoplastic polymer materials, evaluation is more straightforward, in which one considers their higher modulus and their higher resistance to fracturing or blistering from RGD. This methodology is done to an extent that RGD testing of thermoplastics are not required by the oil & gas industry standards such as NORSOK M-710 and ISO 23936-1. It is also well known and proven that thermoplastics can withstand CO2 impurities such as H2S, oxygen, steam, benzene, xylene, toluene and carbonic acid( if H2O and CO2 react to form it). In partnership with an energy major, Omniseal Solutions’ technical team collaborated on a 100 % CO2 certification campaign of several proprietary thermoplastic materials that consisted of a bespoke immersion testing in compliance with the pass / fail criteria of NORSOK M-710, Edition 3. The following are the test conditions( the selected pressure / temperature conditions ensure testing in liquid and supercritical CO2):
Soak Media
Soak Pressure
Soak Temperature
Soak Durations
Omniseal Solutions’ polymer & metal seals within CCS value chain
100 % Carbon Dioxide
34.5 MPa [ 345 bar / 5000 psi ]
-46 ° C / RT / 97 ° C / 127 ° C
7, 14, 28, 42, and 56 days
According to these test results, every selected material successfully passed the acceptance criteria for tensile properties, mass and volume change, proving these materials are a better option compared to standard elastomers for sealing applications when exposed to CO2. All third-party certificates are available upon request.
Safe low-carbon ammonia transfer with certified thermoplastic materials
Ammonia is already a commodity product in various sectors but with 185 Mt produced in 2020, the sector was responsible for around 1 % of global GHG emissions. Bloomberg NEF( Source: Scaling Up Hydrogen: The Case for Low-Carbon Ammonia, November 28, 2023) has identified 185 low-carbon ammonia projects totalling 28.7 Mtpa that will be π www. valve-world. net Valve World May 2025 19