MTS Model 286-31 Transient Permeability Pore Pressure Intensifier - Manual (Page 39)

Purging and Filling the Fluid Lines
286.31 Transient Permeability Pore Pressure Intensifier Operation 39
2. Purge the reservoir return line of air and fill it with fluid.
Turn the Reservoir Return valve to the Open position.
As soon as bubbles stop coming out at the Fluid Reservoir, go on to step 3.