Thompson, CT USA - Numa, a leading designer and manufacturer of down hole hammers and bits, has recently announced some surprising results of vibration monitoring tests conducted on one of its largest DTH hammers.
The tests were conducted by Frankipile Australia in the city centre of Melbourne, Australia on a Numa Champion 240 DTH hammer during their foundation drilling project for the Mirvac Group's Quay West Apartments. Conventional wisdom regarding vibration emitted from a DTH hammer weighing 5605 lbs (2545 kg) and producing 925 blows per minute at 200 psi (13.6 bar) would be similar to a small earthquake. In fact, many cities have strict requirements that will not allow vibration from construction projects to be any higher than 6.0 mm/sec ppv (peak particle velocity).
The Champion 240 with a 34" (864 mm) bit was tested while it drilled in a basalt formation amongst existing downtown buildings. Measurements were taken by three (3) geophones located at various places near the drill site including on a concrete slab 10 feet (3 m) away from the hammer, the ground floor of an adjacent building and in a service corridor located on the first floor of a neighboring building. At each of these locations, the ppv in mm/sec was recorded in three (3) orthogonal directions with channel 1 oriented in the vertical direction, channel 2 oriented horizontally and normal to the source and channel 3 oriented horizontally and parallel to the source.
Results of the monitoring tests were very surprising. The vibration output of the Champion 240 in these conditions was as low as 0.1 mm/sec to a high of 3.6 mm/sec ppv making it well within the limits of the authorities' requirements. Thus proving that although the DTH hammer is a big hitter, it doesn't mean it sends tremors rumbling throughout the land.
Numa is a major manufacturer of down hole hammers and bits for the international drilling industry. The company designs and builds down hole hammers and bits for drilling vertical and horizontal holes 3-1/2 to 43 inches (89 - 1092 mm) in diameter.