Hydrolock, in the context of trenchless construction, is a phenomenon that occurs when circulation is lost in a hydraulic cylinder (pipe) in front of a reamer during a drilling process due to its holding greater pressure than the pullback capacity of the drill rig. When this hydraulic cylinder exerts more pressure than a rig’s available thrust, drilling or boring operations come to a sudden halt.
Trenchlesspedia Explains Hydrolock
When hydrolock occurs during the drilling process, pipe ramming is often used in conjunction with the drilling process to free the stuck product pipe.
Common causes of hydrolock include:
- Loss of flow through the annular relief space;
- Pumping too little drilling fluid, which creates a slurry with too thick a consistency to effectively provide sufficient flow;
- Too great a backreaming speed;
- The backreamer isn’t mixing the slurry properly;
- When a compactor encounters soils that don’t readily compact, such as sand or heavy, wet clay, slurried spoils cannot pass by a compactor and creates an ideal situation for hydrolock to occur.