Analysis and elimination of cavitation in hydraulic pump of IP-750 die casting machine

1 The force of the impact, the metal surface will be quickly eroded or even damaged.

From the point of view of the cavitation phenomenon, the conditions for forming cavitation must be that the absolute pressure in the oil is lower than the air separation pressure of the oil in the nine hydraulic systems. Under what circumstances, the absolute pressure of the oil will be lower than Air separation pressure, but this time is many times, such as the oil through the throttle or valve port, resulting in high-speed jet, the formation of local low pressure; or pump suction and force too much, so that the pump suction side pressure is lower than the oil The air separation pressure; then, the hydraulic cylinder abruptly closes its oil inlet during the movement. Due to the inertial load, the inlet side of the hydraulic cylinder may produce absolute pressure lower than the air separation pressure. , hydraulic pressure. System, more, 6 will produce. The damage of a system that is giving birth to one point is very important when designing hydraulic components and hydraulic systems and using hydraulic machinery, and cavitation must be avoided as much as possible.

The harm caused by the cavitation phenomenon of the 750 die casting machine hydraulic pump is introduced here to attract the attention of their counterparts and be avoided in future work. 175, The die casting machine is a 750 tons die casting machine produced in Italy.艮 is beautiful; 1 company double, 坫, used as a medium for water alcohol, which allows a viscosity of 3512, about 38, 榭鱿娄gt; in the evening of February 15, 2000, the die casting machine automatically shut down due to 1750 die casting There are many reasons for the machine to shut down automatically, such as the hydraulic liquid level is not knee-hydraulic pump suction vacuum motor overload ultra high pressure.

The on-duty personnel at the time forcibly eliminated the equipment alarm. This was the restart of the hydraulic pump allowed by the equipment. Only 233 hours later, the equipment was shut down. At this time, the oil level was checked and the oil level was found to be low, but it was not enough to report the shutdown to take into account the start of the hydraulic pump. In the hydraulic system, the filling of the accumulator will cause the liquid level to decline, so the tank will be refueled by about 20,1 and then the hydraulic pump will be started. The equipment will still stop after 238, indicating that the fault has not been eliminated when checking the hydraulic pump suction port. When the pressure relay was found to operate immediately after the hydraulic pump was started, the pressure relay was a negative pressure relay. Therefore, it was initially determined that the hydraulic resistance of the hydraulic pump was too high, causing the negative pressure relay to act, thereby stopping the hydraulic pump from absorbing too much oil. The reasons are as follows: 1 The filter is asked, including the flow capacity of the filter design + foot. The insufficient flow capacity caused by the cold filter and the over-steering system adjusting the pressure regulator screw 9 can change the mantle of the pilot valve spring 7 against the cone age and can adjust the torque of the system (1). When the power is full, the screw plug 12 can be detached, and the pressure fittings can be installed to adjust the pressure. When the engine speed is 1500, the pressure regulating screw is adjusted so that the pressure reading becomes 7.35%. Does not change with changes in engine speed; in straight travel, turning.艮 unloading me, energy loss, high efficiency; volume ratio, energy small, easy to install 4 Conclusion Zhang Delin. Hydraulic construction machinery structure use and maintenance. Beijing Jindun hydraulic steering system uses liquid as working medium to transmit force and transport press, 1994.

Dynamic, working pressure is much higher than the mechanical transmission and pneumatic transmission, the work of high sensitivity, hydraulic transmission can make power more directly and quickly to the required position. Hydraulic system has high pressure, compact structure, light weight, small size, can absorb external impact, and also plays a role in shock absorption, and has good adaptability to impact loads. Therefore, it has been widely used in construction machinery vehicles. 7 homes. Chemical 4 Water Institute. Gong Pin Machinery Beijing Electric Power Industry Press, 1980.

3 Southwest Jiaotong University. Construction Machinery Beijing China Railway Publishing House, Jilin University of Technology + Construction Machinery Hydraulics and Hydraulic Transmission + Beijing Mechanical Industry Press, 1979.

The filter inlet port switch is not fully opened; 2 The question of the suction pipe, including the design of the suction pipe is too small and the hydraulic system is in the process of work, the soft deformation of the suction pipe is over the hydraulic pressure installation position and the installation position of the hydraulic pump is removed. If the fluid level of the tank is too high, or the relative position of the tank is too large, the relative position becomes large. This is a mature product for this Taiwan 750 die casting machine, and it has been used for several years, so the failure due to design deficiencies caused The factors can be ruled out and stay high for the reason that the suction pipe used by the machine is a hard pipe. Suction pipe deformation, to rule out, while the hydraulic pump suction port below the liquid level, the liquid surface can also ask questions. Remove the filter and found that the filter 1 plug is serious, after the dip wash is installed, and then start the hydraulic pump, found that the negative pressure relay in the 48 or so action, equipment, machine v. 11 application of electrical appliances, such as the start is careful; operation, found Hydraulic pump running continuously, but noisy, was forced to stop the installation of a negative pressure relay, start the hydraulic pump, 48 after the operation stop According to the duty officer introduced, after removing the negative pressure relay, the hydraulic pump can work continuously, but the noise from the phenomenon Analysis, it is obvious that the hydraulic pump suction resistance caused by excessive cavitation phenomenon due to filter cleaning, so it is likely to ask the viscosity of the oil. There is no on-site timing without viscosity; people accurately determine the viscosity of the liquid. Check the crude oil liquid viscosity test data, the viscosity is 5,12840, has exceeded the allowable range of die casting machine. At the same time due to the lower temperature and lower temperature of the original prisoner to the children's toe 1 environment Wenmao low ambient temperature of 33 or so; 2 long downtime from the cleaning filter to 3 back to the oil survey, so that the source version of the spoon below Overflow 6 adjusts the low; pump pressure. After inspecting the high-pressure pump and opening the hydraulic pump, it was found that the coupling of the high and low pressure pump couplings had been broken. That is to say, after the hydraulic pump was started, only the low pressure pump was working, and the high pressure pump was progressively disassembled and the stator and pump were connected. The sub-fragment breaks down and is caught in the stator ring by two rotor blades and fractured rotors with two blades, forming a low-pressure closure, but due to the fracture of the rotor, the high- and low-pressure zones of the high-pressure vane pump 3 are flooded. The oil pumped by the low pressure pump 4 can flow back to the tank through the valve 7 and the pump 3 so that the pressure reflected by the 8 is lower than the set pressure of the pressure relief valve 6. After the high pressure pump and the spline shaft are replaced, the system pressure returns to normal. Normal operation due to filter clogging, resulting in hydraulic pump suction negative pressure, large, so that the negative pressure relay 2 action after shutdown due to a long downtime, the ambient temperature is low and the original water ethanol viscosity is too high, the hydraulic pump oil resistance still Very large, resulting in shutdown, and the removal of negative pressure relays and the frequent start of the hydraulic pump under high negative pressure, so that the hydraulic pump suction side cavitation phenomenon, resulting in the high pressure pump rotor fracture oil After the tank is filled with water, the hydraulic pump starts normally. After reaching the fixed speed, the broken rotor block and adjacent two blades are thrown out by the action of centrifugal force, and suddenly they are caught in the stator ring, and the rotor has a great impact on the stator ring. As a result, the stator registration pin is broken so that the stator is rotated by the spline shaft as the stator and the pump body is suddenly jammed. 1. The spline shaft is broken and reinstalled, approximately 2, at which time the tank cooling system Not closed, the cooling water temperature is very low; 3 add 20,1 new oil, the temperature is ambient temperature for the above situation, taking into account the Taiwan 750 die casting machine 1 for the liquid water ethanol, add 7,1 distilled water to the tank, so that The viscosity of the ice drop 1 alcohol liquid in the bowl, the use of water between the public vaporization 1 viscosity will be high to reduce its viscosity can be directly added to distilled water, and heat the oil, and then start the hydraulic pump, hydraulic pump continuous work, but the pressure is low, for The high pressure is 14 and the low pressure is 5 during normal operation of ih. It is estimated that water and water ethanol are not fully mixed. The low-pressure cycle was mixed but the force was still not checked by a 1-liter pavilion. The oil source of the 750 ash-casting machine was originally observed because the pressure of the helium source at this time was 313.

Valve action, oil pressure is still 3 rivers below the adjustment pressure of the low pressure pump overflow width 6 5 rivers, 1 and high pressure chestnut pressure relief valve adjustment force 5.51 so there is a drainage network. The overflow valve 9 should be high enough to fail If the overflow valve 9 fails, both the low pressure record 4 and the high pressure pump 3 can be drained from the overflow valve 9 and no high pressure can be reflected in the 8 Therefore, check the relief valve 9 but found normal. After the installation and start up, the pressure on the 8 is still not up from the 1 analysis, if the high pressure pump 3 is damaged, it may also cause the above from the above fault conditions and analysis. We can see that in the hydraulic system, the clogging of the filter and the excessive viscosity of the oil will increase the hydraulic resistance of the hydraulic pump and cause cavitation on the oil suction side, resulting in cavitation and even destruction of the hydraulic pump. Therefore, in the process of using the hydraulic system, we must pay close attention to the viscosity of the oil and the cleanliness of the oil and the filtering flow capacity of the filter to avoid cavitation, so that the hydraulic pump and hydraulic system can be more reliable for a long time. M