I. Introduction Sequence valve is the use of imported oil pressure to control the hydraulic system in which two or more executive agencies have a sequence of pressure control valve. When the inlet pressure can not reach the pre-set sequence valve pressure is good, the sequence valve is closed; when the sequence valve reaches or exceeds the predetermined pressure, the valve opens, the oil from the outlet into the secondary pressure circuit, so that The next actuator action, play a switch role. If the outlet pressure oil back to the tank, then constitute the unloading valve. Sequence valve according to the structure and working principle can be divided into direct acting and pilot; according to the control oil is divided into internal control and external control. The structure of the sequence valve is basically the same as that of the relief valve and the relief valve. However, since the ports P1 and P2 are both pressurized oil, the drain port L of the sequence valve should be individually connected to the fuel tank from the outside of the valve. Sequence valve and check valve combination into a one-way sequence valve. Second, the failure analysis and troubleshooting (A) set value instability, can not make the order of action of the actuator, or the order of action disorder Order valve is the hydraulic system in the use of system pressure to control the other hydraulic components (such as fuel tank) the order of action , When the system reaches the set value (set value), the sequence valve opens, in order to achieve automatic control. In a control circuit that operates sequentially with multiple cylinders controlled by a sequence valve (two or more cylinders), normal sequence operation can not be achieved if the sequence valve setting is not stable. (B) when the system does not meet the sequence valve set working pressure, the pressure of the oil flow from the second port ①the main valve and valve hole with the gap is too large, or due to the use of wear and tear caused by too much time to make a gap P1 side of the pressure oil discharge to the secondary side, so that the pressure on the secondary side, coupled with the spring force, it will be possible to open the sequence valve, at this time although the P1 cavity pressure does not meet the regulatory pressure regulating valve, two The secondary side also has oil outflow. At this point, the main spool can be repaired or replaced, and a reasonable assembly clearance is ensured. ② other causes of internal leakage. (C) exceeds the set value, the sequence valve does not open ①main valve spring misloaded into a hard spring. ② control piston stuck. ③ dismantling reload, the control piston leakage, the results of the control of the pressure oil from the valve orifice through the drain hole relief, the main spool in the spring force closed, the spool can not open. (D) large pressure fluctuations, large pressure swing According to JB2146-77 standard, X-B low-pressure sequence valve pressure swing allowed error of ± 0.2Mpa, X-type medium pressure sequence valve is ± 0.3Mpa, XF medium and high pressure Sequence valve is ± 0.5Mpa, more than this standard pressure swing large. Pressure vibration is too large, the same will appear misoperation or non-sequential action.
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