Percussion drilling is a manual drilling technique in which a heavy cutting or hammering bit attached to a rope or cable is lowered in the open hole or inside a temporary casing. The technique is often also referred to as 'Cable tool'. Usually a tripod is used to support the tools. By moving the rope or cable up and down, the cutting or hammering bit loosens the soil or consolidated rock in the borehole, which is then extracted later by using a bailer. Just as with hand augering, a temporary casing of steel or plastic may be used to prevent the hole from collapsing. When the permanent well screen and casing are installed, this temporary casing has to be removed.
Percussion drilling is suitable for unconsolidated and consolidated formations: Sand, silt, stiff clays, sandstone, laterite and gravel layers.
Manual percussion drilling is generally used up to depths of 25 meters.
Before drilling starts, it is good to analyse where the water might be. There are lots of clues to look for in WellSpringAfrica.org's Selecting a Site.
| - Unlike any other drilling method, percussion can remove boulders and break harder formations, effectively and quickly through most types of earth.
- Percussion drilling can in principle deal with most ground conditions.
| - The equipment can be very heavy and relatively expensive. |
- Especially in harder rock the method is slow (weeks, rather than days).
Construction, operations and maintenance
Equipment is commercially produced in western countries. Local production is possible. Percussion drilling is hard work. Use of a small engine may be appropriate.
The percussion drill can be powered by hand, with several men pulling on a rope to lift and drop the bit, or it can harness the power of an engine. It can take the form of a few pieces that can be transported in the trunk of a car and carried into remote villages, or it can be mounted on the bed of a truck and driven to the drill site. The drill parts can be bought from the numerous world-wide companies that make drilling tools or they can be made from readily available scrap steel and local materials.
- Eijkelkamp Agrisearch Equipment - Drilling equipment and manuals on hand auger and percussion gouges.
- Van Reekum Materials - Drilling equipment, hand auger and percussion drilling.
For cost comparisons between hand drilling and percussion drilling: Wellspring Africa's Hand Powered Percussion Drill illustrates costs for materials, tools, and labour.
Percussion drilling is mainly used in Niger, Nigeria, Chad, Liberia, Ghana, Central America and western countries.
- Robert Vuik, Don de Koning and Arjen van der Wal. Percussion: Manual Drilling Series. Technical Training Handbook on Affordable Manual Well Drilling. Practica Foundation, June 2010. French version: FORAGE À LA PERCUSSION: Série forage manuel.
- Percussion Drilling. Different kinds of drills and connectors.
- Drilling Wells by Hand, Cliff Missen, Wellspring Africa, draft 4 - Manual on Percussion drilling, well construction, manufacturing tools. Website of WellspringAfrica
- KOEGEL, R. (1985) Self Help Wells, FAO Irrigation and Drainage Paper, FAO, Rome.ISBN 92-5-100398-X html version.
- CARTER, R. C. (2005) Human-Powered Drilling Technologies. an overview of human-powered drilling technologies for shallow small diameter well construction, for domestic and agricultural water supply , Silsoe College , Cranfield University , Bedfordshire, UK Download
- Drilling Boreholes for Hand pumps, Peter Wurzel, Skat, Switzerland, 2001 - A book on hydrogeology, well construction, drilling techniques, well development - Download. Website of SKAT
- Low-cost shallow tube well construction in West Africa, M. Sonau, FAO - An overview of shallow tube well drilling techniques - website. Website of FAO documents.
- Technical note 43. Simple drilling methods, Bob Elson and Rod Shaw, WEDC - An overview of simple drilling methods Download. Website of Loughborough University Technical Briefs section. Website of Loughborough University WELLS.
- A Water Handbook, Technical Guidelines Series, UNICEF, 1999 - Programming and implementation. Download.
- Technology notes, section 7; Tube wells and boreholes, WaterAid - An overview of human-powered drilling technologies. Download. Website of Wateraid.org.
- Water for the World, Technical note series rws 2, USAID 1982 - Technical notes on methods of developing of groundwater, manual drilling techniques. Website Lifewater International. Under 'Cable Tool Wells'.
- Multi-service procedures for well-drilling operations, field manual chapter 9, US Military Chapter 9, alternative well construction, manual drilling techniques - Download.