HP and HPHT treatments were performed in a horizontal WAVE
6000/55 HT (Hiperbaric, Burgos, Spain). This industrial scale
equipment of 55 L capacity has a thermostatized vessel that
enables maintenance of the target temperature with a variation
below 0.7 C. Dimensions of the cylindrical pressure vessel were
200 mm internal diameter, 680 mm external diameter and
2000 mm length. Water was used as transmission fluid. The vessel
was filled by a low pressure circuit independent of the high pressure
circuit. Once it was full, high pressure water was pumped with
an intensifier until working pressure was reached. Pressure buildup
(from 0.1 to 625 MPa) takes place at a rate of 3 MPa/s with the
consequent rise of temperature (from 87 to 117 C) at 0.14 C/s.
Depressurisation and cooling of the samples to initial temperature
is instantaneous (1–2 s). The temperature was measured by several
thermocouples in the external diameter of the vessel and 2 thermocouples
in each flank in contact with water. Temperature and
pressure of the treatment were recorded by the Supervisory Control
And Data Acquisition (SCADA, Hiperbaric, Burgos, Spain) software.
Samples were located in cylindrical recipients and always
in the same place.