Definition - What does Percussion Cycle mean?
Percussion cycle refers to the action of the operation of the reverse circulation (RC) hammer as it activates the piston from up to down. The piston rests on the percussion bit and the hammer during a drilling operation.
When high-pressure air is directed into the bottom of the hammer, the piston rises to commence the cycle. The RC hammer system works by feeding high-pressure air through an intake system that controls a piston which delivers the energy to the percussion bit.
Trenchlesspedia explains Percussion Cycle
During the drilling operation when the piston rises it forms a chamber at the top by forming a seal with the inner tube and the inner diameter of the piston. As it rises further, the movement seals the port that feeds air into the bottom of the hammer while simultaneously releasing the seal allowing the air to exhaust and expand down the spline of the percussion bit.
At the same time, the port at the top chamber is opened feeding high-pressure air into the previously formed chamber at the top increasing the pressure over the piston and forcing it back down. As the piston comes down it stops the exhaust air creating a chamber of high-pressure below the piston that forces the piston back up.
The percussion cycle is activated by the reverse circulation (RC) hammer into which air from the compressor is blown through the swivel inlet located between the outer and inner tubes.
When the percussion cycle ends, the cuttings are picked up by the same airflow and passed from the bit face through the inner tube to the surface where the RC cyclone collects it.