Abstract: Four bypass pipes were installed with the regulatory valves on each pipe in the ultra fast cooling(UFC)supply system of the hot strip rolling process. The series and parallel water pressure control methods were designed in order to improve water pressure control precision. A suitable control method that was used in UFC water pressure control was obtained by the comparison analysis. A research on the water pressure stability when the bypass valve broken down had been done in the design of the control system. The theoretical analysis and practical application results indicated that both the series and parallel control methods manage the water pressure within the ideal range when the set water pressure is 035MPa.When the set water pressure is 085MPa， the effect of the practical application of the parallel control method is good， because the parallel control method has significant effects on decreasing of the water flow impact on the plates of regulatory valves during the reduce procedure of the open degree and the water hammer phenomenon is also avoided.

Key words: bypass pipes, ultrafast cooling(UFC), water pressure, series control method, parallel control method