| 摘要 |
PROBLEM TO BE SOLVED: To prevent cavitation caused by a negative suction pressure of a mud removing pump due to blocking of a mud removing pipe. SOLUTION: The cavitation preventing device for the slurry shielding device has a first bypass pipe 27A connecting mud transmitting piping 23 and mud removing piping 34, and the first bypass pipe 27A is provided with a first bypass valve 27 operating on and off. The second bypass pipe 27B bypassing the first bypass valve 27 is provided in the first bypass pipe 27A, a control valve 28 controlling a flow rate by opening is provided in the second bypass pipe 27B, and a control means is provided for holding a negative suction pressure at a positive pressure by adjusting the opening of the control valve 28 in response to the negative suction pressure of a second variable speed pump 31 provided in the mud removing piping 34. COPYRIGHT: (C)2004,JPO |
