Grigg’s Apparatus

The Grigg’s Apparatus is a hydraulic press machine for studying, for example, rock deformation processes mirroring the conditions up to ca. 100 km deep underneath earth’s surface. It has separate pressure systems for the confinement pressure, end-load, and differential stress, which makes it a kind of triaxial piston cylinder press.

The STRECON type Grigg’s Apparatus includes a unique tooling system that differs from similar available machinery: Sigma-1 and Sigma-3 piston are acting from opposing sides, so that each tool’s position can be measured close to the tool itself and controlled precisely. Furthermore, the press frame is stripwound using STRECON’s own signature technology, which enables a compact and very robust mechanical construction at a small footprint. The press is safe to operate and has a CE marking.

The following press specifications describe the standard STRECON type Grigg’s Apparatus but can also be adapted according to customer specifications. The Grigg’s Apparatus has a total press force of 420t. Up to 140t of these are allocated for the confinement pressure, and up to 20t for the Sigma-1 piston. With this press force, 2 GPa of confinement pressure are achievable in a 1’’ system, and 3.5 GPa in a ¾’’ system. The apparatus supports test temperatures of up to 1800°C. The overall press dimensions are W2090 x D690 x H2010 mm with a weight of ca. 1800 kg.

The speed of the Sigma-1 piston can be adjusted between 10^-1 and 10^-7 mm/s using a stepper motor and a three-speed gearbox. The power transmission to the Sigma-1 piston is done using a wedge with linear guides so that the system has both a high axial stiffness and low friction. Sigma-3 and end-load pressure are controlled using a 600-bar hydraulic system.

The hydraulic press is fully automated with a control system based on NI-LabView. Test sequences can be preprogrammed, adapted in-process, and analyzed via the user-friendly 15'' touch screen panel.