The high pressure facility consists of:
Housing:
The housing serves both as the framework for the complete machine and as its protective shielding. It accomodates the high-pressure components, which are accessable through sliding doors at the back and top of the instrument, as well as the instrumentation. Special attention has been paid to safety through the provision of adequate shielding and door locks, the use of multiwall contruction for ear protection, and the minimisation of the volume of gas at high pressure. The doors are automatically locked when pressure is raised above 30MPa or when the power fails.
Pumping system:
A Haskel AGT-62/152H gas booster pump is used for the first pumping stage from bottle pressure, followed by a 10:1 intensifier of 0.35 litre stroke driven by a Haskel AW-100 oil pump. The pressure transducer is provided with signal conditioning, digital display and control facilities, enabling the pressure to be maintained automatically by pumping or bleeding as required. Rupture disks are fitted to prevent accidental over-pressuring of the different stages of the pumping system and door interlocks prevent pumping above 30MPa when the safety doors are open.
Main pressure vessel:
The steel cylinder, with axis vertical, has a working volume of 65mm diameter, 360mm length and is provided with blank plugs for both ends. It is test to 750MPa and is intended for routine usage upto 500MPa. A 700MPa rupture disk is fitted. The vessel also has a soft steel safety sleeve incorporating the water cooling coils. With the solid-zirconia-insulated furnace and internal load cell fitted, the free volume is about 0.2 litres, from which the maximum available energy in adiabatic expansion of the gas from 500MPa is not more than about 125kJ.
Leak detectors:
A bubbler system is provided for quick location of any leaks from the 'O'-ring seals in the high-pressure system.
Instrumentation:
All the basic wiring is included, covering the confining pressure and furnace facilities, and allowing for the connection of the modules for the mechanical testing systems (both axial and torsion) and for the pore fluid system, as required. No additional wiring is required for retrofitting.
High temperature facility
An internal furnace is supplied for high temperature studies. This permits relatively rapid heating and cooling while maintaining the pressure vessel walls close to ambient temperatures.
Top Closure plug:
The plug is fitted with six insulated feed-throughs, six earth pins, and a steel piston on which a specimen can be mounted. The piston has a small bore for direct access to the specimen for thermocouples or pore fluid connections. With the specimen mounted, the piston can be inserted or removed through the main plug without disturbing the furnace.
Furnace:
The standard internal furnace has three molybdenum windings to provide a uniform (±1K) high temperature zone of 21mm diameter and 50mm length. A control thermocouple is situated opposite each winding. An alternative furnace of 27mm internal diameter, but otherwise the same is also available.