For the majority of geotechnical applications except when drilling through clay, a maximum pressure of 7 – 20 bar is normally sufficient to ensure full placement of grout when using simultaneous drilling and grouting. Where pressures do not exceed these pressure, standard grout pumps with direct mixing and screw pumps (e.g. Metis MAI grout pump M400 NT) are sufficient.
For larger pressures of 20 bar (300 psi), as sometimes needed in clay or larger circulation of grout volumes for dill bit diameter larger then 100 mm, or where grouting is performed as a subsequent operation following drilling, e.g. mining and tunneling, higher pressures are also required. Typically pressures ranging up to 28 bar (400 psi) are sufficient, although pressures upt to 60 bar (860 psi) have been used in some underground applications. For these applications a double action piston pump with volume control should be selected .
As a general rule all grouting equipment, components and hoses must meet hydraulic specifications.