Comparison between hydraulic and pneumatic drilling systems
The reference project chosen for this study is located in Stockholm. Twenty nine borehols with a designed depth of 220 to 250 meters for supplying two adjacent terraced houses have been drilled using either the conventional pneumatic down-the hole-hammer or the hydraulic GeoJetting system.
The results show that due to the smaller borehole drift the hydraulic system is better suited for narrower borehole distances and for small properties of existing buildings. Furthermore this system needs less diesel fuel resulting in lower operational costs. For flat boreholes without groundwater impact the pneumatic system has advantages due to a higher drilling progress.
Read the full article (German)
Source: Bracke, Rolf (2011): Beachtenswerte Unterschiede - Ein Vergleich hydraulischer und pneumatischer Bohrsysteme für Erdwärmesonden. Deutsches IngenieurBlatt, Ausgabe 11/2011 - November