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Percussion drilling By Batch -2 Percussion drilling • Cable Tool Drilling • Percussion drills have been used to drill thousands of feet, though they are generally used for wells from 30 to 250 feet deep. • This drilling method has been used in China for over 3000 years. Hand powered percussion drill Method: -The lifting and dropping of a heavy (50kg+) cutting tool will chip and excavate material from a hole. - The tool can be fixed to rigid drill-rods, or to a rope or cable. - With a mechanical winch, depths of hundreds of metres can be reached. Working of percussion drill • The drill involves a heavy steel bit attached to a rope which is lifted, either by hand or by machine, and then dropped to cut the earth. • As the bit chops the earth, water is added to the well hole so that the bit makes mud out of the earth it has cut. • After the hole is filled with several feet of mud, the heavy bit is withdrawn and a tool called a bailer is attached to the rope and lowered into the hole. • The bailer is a hollow tube with a door at the bottom. • The door, called a flap valve, opens when it hits the mud to allow the mud to fill the bailer, and then closes to trap the mud inside the tube so that the mud can be lifted to the surface. • The tube is emptied at the surface and the procedure is repeated until the hole is clear. Cont ……. • The bit is then re-attached to the rope and the above process begins again. • If the earth being drilled will not cave in, then the drilling continues until water is reached. • But if the earth is made of loose material like sand, a large heavy steel pipe is driven into the hole to keep the walls from falling in. • The large pipe is called casing and it holds the hole open until the drilling is done. • It is removed after the permanent casing (usually smaller) is installed • When the water level has been reached the drilling stops and the permanent casing, which is smaller than the well hole, is installed. • hen the rest of the hole around the casing is filled and sealed. Materials • • • • Percussion gouges Electrical percussion hammer Connections Extraction systems Percussion gouges • Used to take undisturbed samples from depth to about 10 meters. • Higher drilling speed. • The design enables easy emptying and cleaning. • Depending on the soil type, drilling depth and desired quantity of sample one of various gouge types is chosen. • Available in various diameters 40, 50, 60, 75 and 100 mm and with a length of 50, 100 and 200 cm. • All percussion gouges have a hardened steel cutting head Percussion gouges in various diameters Electrical percussion hammer, Light model: - Beating power of 31.7 Joule at 1200 beats per minute, a net weight of 17 kg and an overall length of 613 mm. Heavy model : - Beating power of 55.3 Joule at 1000 beats per minute, a net weight of 29.1 kg and an overall length of 825 mm. • RD32-connection • Extension rods and percussion gouges are screwed together using a coupling sleeve. • Takes very little time to attach and take off. • The RD32-rods connect together by means of a coupling sleeve • Wedge-connection • The gouges and the extension rods are connected using so called wedge connections • Easy and quick coupling and un-coupling is possible. RD32-connection Wedge connection Pulling devices (rod pullers) Rod puller extension for the first gouge Extraction system • Pulling device (Rod pullers) • Rod puller extension • Hydraulic extrator: Pulling force of 80 kN, is supplied with extracting cylinder (diameter 65 mm) and a hydraulic aggregate with electric hydraulic extractor tube set. Hydraulic extraction system Hydraulic extractor Percussion drilling applied, • If drilling has to be executed in hard soils, possible containing layers of rubble and/or stones usually percussion drilling is applied. • Percussion drilling for instance is applied for research on soil pollution, grain size distribution, general soil classification, profile descriptions, etc. Advantages of percussion drilling: • Simple to operate and maintain. • Suitable for a wide variety of rocks. • Operation is possible above and below the water-table. • It is possible to drill to considerable depths. Disadvantages of percussion drilling: • Slow, compared with other methods. • Equipment can be heavy. • Problems can occur with unstable rock formations. • Water is needed for dry holes to help remove cuttings. References *http://www.albertasource.ca/petroleum/technology/innovations_profiles_percussi on_drilling.html *www.wellspringafrica.org/drildesc.htm *www.ekotechnika.cz/pdf/P1-21e.pdf *www.lboro.ac.uk/well/resources/technical-briefs/43-simple-drilling-methods.pdf Questions ??