True Triaxial Stress Cell

True Triaxial Stress Cell

CDMS were commissioned to design a True Triaxial Stress Cell (TTSC) from concept right through to detailed design for fabrication.

The design parameters required CDMS to design a triaxial test rig capable of simulating geosequestration, or Carbon Capture and Storage (CCS), on large interchangeable rock samples at pressures up to 70MPa.

CDMS started with a collaborative design process between the CDMS engineering team, NAR Engineering and the end user (CSIRO), to discuss a range of different triaxial stress cell concepts suitable for strict laboratory simulations. CDMS was solely responsible for the design of the pressure envelope used to contain the triaxial stress cell during very high pressure operation. After selecting the most suitable design, a 3D model was developed of the concept to visualise the design and troubleshoot any conflicts. With the conceptual design approved by the client, CDMS then commenced the detailed design phase.

The mechanical design of the internal triaxial stress cell components comprised the major portion of the engineering and drafting work. The complex simulation and laboratory requirements of the triaxial stress cell required intelligent use of standard mechanical components/fittings as well as complex custom piston housings, platens and rams to maximise compressive stress in a very compact and efficient design package.

For further details on Product Development services provided please contact the CDMS team on (+61 8) 9421 9060 or email us at info@cdmsengineering.com.


Project Brief

Outcome

  • Design of external pressure envelope
  • Design of internal triaxial stress cell
  • Detailed fabrication and machine shop drawings of mechanical components

Background

The TTSC represents an innovative advancement in carbon capture research technology. This new vessel will give laboratory-based researchers at CSIRO an advanced test instrument to demonstrate the feasibility and safety of large-scale geosequestration. The TTSC is a highly specialised, targeted research vessel that will minimise risk and uncertainty regarding long-term underground storage of carbon dioxide. The geological storage of carbon dioxide emissions underground is a key technology that can help reduce greenhouse gas emissions from the atmosphere.

The client required CDMS to design the TTSC to be built for laboratory-based CCS studies. This one of a kind design comprises both an external pressure envelope as well as an internal triaxial stress cell. Both mechanisms work in unison to mechanically and hydrostatically stress large interchangeable rock samples up to 70MPa.

Project Objectives

CDMS was to design a triaxial test rig capable of simulating geosequestration, or carbon capture and storage (CCS), on large interchangeable rock samples at pressures up to 70MPa.

Challenges

The biggest challenge CDMS faced during the design of the TTSC was safely simulating the geological conditions experienced deep within the earth’s crust over 300mm square sided rock samples. Operating within strict laboratory conditions, at very high pressures up to 70MPa and temperatures at approximately 100°C, risk minimisation and operator safety were paramount during each aspect of the detailed design.

The design of the pressure envelope surrounding the TTSC, conforming to AS1210-2010, proved an interesting challenge for the CDMS design team. The combination of an operational pressure of 70MPa and internal diameter of 1300mm meant that the wall thicknesses stretched to reach the welding limits and high peak stresses required rigorous fatigue analysis. Special high strength, low alloy, chrome-molybdenum steel was selected to suit such high pressure, while minimising the pressure vessel design to only a single circumferential weld seam.

CDMS leveraged its extensive pressure vessel expertise when designing a specialised quick opening closure (QOC) for the top head. This required the utilisation of specialist Finite Element Analysis (FEA) software to perform linear and non-linear static analysis under all possible operational pressure and temperature cycles.

Our Approach

CDMS started with a collaborative design process between the CDMS engineering team, NAR Engineering and the end user (CSIRO), to discuss a range of different triaxial stress cell concepts suitable for strict laboratory simulations. CDMS was solely responsible for the design of the pressure envelope used to contain the triaxial stress cell during very high pressure operation.

After selecting the most suitable design, a 3D model was developed of the concept to visualise the design and troubleshoot any conflicts. With the conceptual design approved by the client, CDMS then commenced the detailed design phase. The mechanical design of the internal triaxial stress cell components comprised the major portion of the engineering and drafting work. The complex simulation and laboratory requirements of the triaxial stress cell required intelligent use of standard mechanical components/fittings as well as complex custom piston housings, platens and rams to maximise compressive stress in a very compact and efficient design package.