Six large-volume autoclaves commissioned at TWI are expanding the company's existing capability for exposure testing of polymeric, composite and metallic test specimens together with larger components. Early tests, carried out during a recent joint industry project, have demonstrated the new facility’s potential for extended research of materials’ behaviour in supercritical environments.
The long-term performance of polymeric, composite, cementitious and metallic materials in oilfield, construction and automotive applications is of interest to many of TWI’s Industrial Member organisations. Until now, it has been difficult to test large components in a maintained constant test environment. Recently, TWI and a subcontractor designed a new series of autoclaves to exacting specifications. This new facility was installed in the harsh environment (H2S sour service and corrosive produced fluids) testing laboratory in Cambridge and expands the exposure testing opportunities.
The autoclaves have already been used in a joint industry project on materials selection for transport of supercritical carbon dioxide (MASCO2T), investigating the conditioning of large polymeric tensile specimens at elevated temperatures and pressures. Also included in the test programme for the project was a metre-long section of composite tube, which could be aged for the customer for extended periods while keeping the ratio of fluid reservoir volume to surface area at 25 cm (as specified by oilfield standards including ISO 23936).
New large-volume autoclaves commissioned at TWI
Five of the autoclaves have an internal depth of 600mm and two of these are lined with C276. A resulting 19.4L volume allows application of testing standards where the ratio of the fluid volume to the sample surface area is specified as 25cm. The sixth C276-lined autoclave has an internal depth of 1000mm making it ideal for conditioning tubular components made from thermoplastics, fibre-reinforced composite or coated metal parts. The autoclaves can be run under conditions up to 190bar and 180°C.
All six autoclaves can be compartmentalised to allow for testing different materials under similar conditions, using specially welded leak-proof inserts to prevent cross-contamination of fluids within the vessels.
A dual-stage 2L syringe-pump enables materials conditioning operations with starting feed pressures as low as 20 bar and, thanks to a specially designed single thermocouple holder, operators can routinely check internal temperatures throughout the vertical depth while the autoclave is still under pressure.
At the end of an extended period of conditioning, pressure in the autoclave can be reduced under operator control to reproduce a rapid gas decompression (RGD) event. Note this can be applied even in the largest autoclave, significantly enhancing our current RGD capabilities to larger components, whilst maintaining high safety and environmental standards. As pressure reduces, the released gas is sampled to TWI’s extensive suite of gas chromatographs, ready for analysis.
For further information please visit the Material Properties section of our website or contact us.