Differenct effect of shaker screen with different vibration modes2013-08-16
The requirement for shale shaker by the drilling technical is to recover the drilling fluid as much as possible, and clean the harmful solid phase as much as possible. Therefore, it requires:
a. In order to increase the processing quality, recover the drilling fluid, the solid phase on the screen should be discharged ASAP.
b. To decrease the wear degree of screen, it is better that the solid particles do not do sliding motion.
c. The stuck critical particles should be easy to pass the mesh or jump out of screen.
The vibration mode of shaker screen
A. Traditional elliptical vibration mode
Because there is a vibration exciter on the right above of barycenter of screen box, and all the trajectory of each points of the inlet and outlet is ellipse, but the long shaft extension cords intersect on the shaker screen. Because the transverse amplitude is larger than normal amplitude and the specific value of these two amplitude is larger than the circular vibration mode’s, the average transport speed is higher than circular shale shaker. The sand grains’ transportation at the entrance of this shaker is good, but, because the long axis of ellipse trajectory at the outlet hole inclines into the shaker, the moving speed of drilling particles become lower and it is difficult for the particles to jump out of screen, even accumulation of drilling particles appears. The accumulation of drilling particles increases the chance of passing the mesh and quantity of solid phase in drilling fluid. If screen extended, backflow would appear, and would affect the disposing of drilling fluid. Therefore, it requires a inclination angle of the shaker screen to discharge the sand via gravity to avoid chucking backward. Though the inclination of screen box has improved the moving performance of the sand particles, but the thruput of drilling fluid also decreased, this is the main disadvantage of non translational elliptical vibrating shale shaker.
B.Circular vibration mode
The vibration is installed on the barycenter of screen box, the resultant force of vibration force and spring reaction will pass the barycenter, the vibration mode of each point on the screen box is approximate circle. The transverse amplitude is equal to normal amplitude. The shaker screen can be installed horizontally, and there will be no accumulation of drilling particles, the disposing thruput will be larger. But the chucks angle is the function of acceleration of screen type. When the normal velocity is 3-6times of gravity velocity, the chucks angle of solid phase will be 70-80 degree. The chucks angle makes a large whereabouts inertia, smashing easily and high speed of sand transportation, the through sieve rate is be increased accordingly, which is disadvantageous for the cleaning of drillign fluid.