Vibration fault of hydraulic system of coiler auxiliary roll
Vibration fault of hydraulic system of coiler auxiliary roll
(1) Coiler fault
The coiler of a 1500mm hot strip rolling line is full hydraulic horizontal cored coiler, equipped with hydraulic coiler and AJC step control, which can effectively reduce the impact load and noise and improve the surface quality of strip steel. At the initial stage of production, the hydraulic system of No.1 coiling aid roll, as the core of coiling quality control, had problems, that is, the hydraulic system vibrated and impacted heavily at the initial stage of automatic engagement of coiling aid roll, resulting in frequent welding and oil injection of hydraulic oil pipe.
(2) Hydraulic system of coiler auxiliary roll
① The action of the hydraulic cylinder of the coiling aid roll controls the strip steel to enter between the No.1-3 coiling aid roll and the drum in order to start coiling. When the whole coil is finished, the auxiliary roll begins to implement step control. When coiling 2-3 turns, the drum is expanded for the second time to make the steel coil and the drum more closely. When the coil reaches a proper number of turns (generally 5-7 turns), the auxiliary roll will be opened and the coil will be reeled by the drum. At this time, the coiling speed should be equal to the strip running speed. A certain coiling tension is formed between the drum and F6 frame. When the tail of strip steel is rolled out from F6 rolling mill, the output roller table and the inlet roller table of No. 1 coiler speed down, and the tension between the drum and No. 1 pinch roll is formed to continue coiling. When only the last few laps are left, No. 1-3 auxiliary coiler presses the steel coil with the set pressure to complete coiling. There are two working states of the coiling aid cylinder: one is that when the coiling aid roll retreats, the hydraulic cylinder has oil in the rod cavity, and the piston rod retracts to the process setting position; when the coiling aid roll advances, there is no oil in the rod cavity, and the piston rod extends to the process setting position; It is a typical displacement closed-loop control; The other is that when the coiler is close to the strip, the oil will continue to feed into the non rod cavity, the piston rod will extend, and the coiler will press the strip tightly. It is required to control the pressure, which is a typical pressure closed-loop control. In an action cycle, the two closed loops need to be switched, which determines the complexity of the control system.
② The principle of the hydraulic system of the wrapper roll is shown in Figure R. when the hydraulic cylinder of the wrapper roll is adjusted forward and fast backward, the servo coil c1h8.3ys1 of servo valve 12.1 inputs the control signal. The electromagnet c1h8. 3yhs1 of 14.1 is powered on and turns on 13.1. The adjustment of the direction and speed of the tension and retraction of the hydraulic cylinder is controlled by the control signal of the input servo valve. When the hydraulic cylinder of the wrapper roll retracts, the left side of the electromagnet c1h8.3yhd1 of the electromagnetic directional valve 8.1 is powered on, the electromagnet c1h8.3yhs1 of the electromagnetic directional valve 14.1 is powered off, and the hydraulic control check valve 13.1 is closed. When the hydraulic cylinder of the wrapper roll moves forward, the right side of the electromagnet c1h8.3yhd1 of the electromagnetic directional valve 8.1 is powered on, the electromagnet c1h8.3yhs1 of the electromagnetic directional valve 14.1 is powered off, and the hydraulic control check valve 13.1 is closed. All electromagnetic coils shall not be electrified when it stops working. Filter 4.1 can provide high precision control oil to servo valve; Accumulator 22 is used to supply oil under the pressure of supplement and stable operation, and its nitrogen charging pressure is 18.5mpa; The position sensor c1h8. 3sh1 built in the servo cylinder is used to detect the position of the hydraulic cylinder of the wrapper roll and realize stepless position control; The pressure sensors c1h8.3sp1 and c1h8.3sp2 are used for the pressure detection and computer control of the piston side and piston rod side of the hydraulic cylinder of the coiler; Relief valve 16.1 is used to absorb the impact of hydraulic cylinder of coiler; The check valve 15.1 is used to replenish the oil on the piston rod side of the hydraulic cylinder of the roll aid during impact.
(3) Cause analysis of vibration of coiler
① The mechanical transmission system requires to eliminate the gap of each link as far as possible and reduce the hinge point as far as possible, so the hydraulic cylinder must be used to directly drive the roll frame of the wrapper roll, and the taper sleeve shall be used for the pin shaft of the hydraulic cylinder to eliminate the gap. On site inspection found that the mechanical gap is small, with good cooperation, manual closing of the wrapper roll, no vibration phenomenon, thus eliminating the cause of large mechanical gap.
② According to the analysis of hydraulic servo system, the causes of this phenomenon are the delay of one-way valve opening, poor response characteristics of servo valve and slow response of servo cylinder. Replace the servo valve, and manually press and hold the solenoid valve 14.1 which controls the opening of the hydraulic control check valve to automatically close the coiler, and the hydraulic cylinder of the coiler still vibrates, thus eliminating the faults of the servo valve and the hydraulic control check valve. The response of servo cylinder can only be adjusted by program.
③ The information of automatic monitoring of the automatic control system shows that the response of the hydraulic cylinder action lags behind the control enable signal more and cannot keep up with the rhythm. From the fact that the program and parameters of No.1 coiler are the same as those of No.2 coiler, the fault of the program and detection elements can be eliminated, and then it can be concluded that it is caused by the mismatch between the response characteristics of servo cylinder and the set parameters. Adjust the slope of the program, increase it to 3 times of the original, and eliminate the fault.