Troubleshooting of proportional control failure of horizontal hydraulic cylinder of walking beam furnace
Troubleshooting of proportional control failure of horizontal hydraulic cylinder of walking beam furnace
1. Proportional control of horizontal hydraulic cylinder of walking beam furnace
The load driven by the horizontal hydraulic cylinder of the walking beam furnace is large and has great inertia. In order to prevent impact, slowly accelerate the horizontal hydraulic cylinder of the walking beam furnace when it is just started, and implement two-stage deceleration before walking. The ideal movement speed curve is shown in Figure 20.
In order to meet the requirements of the moving speed of the horizontal cylinder, the constant pressure variable swashplate piston pump A4VSO is used as the pump source, and the two-way plug-in electro-hydraulic proportional throttle valve fe25c10 with displacement electric feedback is used as the valve console (with the advantages of controlling large flow, high-power hydraulic system and high steady-state accuracy). The electro-hydraulic proportional system diagram is shown in Figure 21, and the control block diagram of the electro-hydraulic proportional system of the speed of the plug-in horizontal cylinder is shown in Figure 22.
The control principle is: the liquid flow at the valve port of the two-way cartridge valve is equivalent to the flow form of the small hole outflow, and its flow rate is related to the flow coefficient at the valve port (generally constant), the pressure difference at the valve port, and the flow area at the valve port, while the flow area at the valve port is related to the gradient of the valve port area and the displacement of the valve core. Its flow formula is q=cdwxv √ (2 Δ p/ ρ）； The displacement of valve core XV is linear with the current of proportional electromagnet. Therefore, as long as the pressure difference between the inlet and outlet of the valve is constant (using the constant differential pressure reducing valve system with pressure compensation function), and the flow rate at the valve port is linear with the given current of the proportional electromagnet, giving a certain electric control signal to the proportional amplifier can obtain an ideal horizontal cylinder movement speed curve.
2. Typical symptoms and causes of control failure
In case of failure, the movement deceleration is not obvious, but the movement speed is low, or even does not act. This kind of fault either comes from the electronic control system, including amplifier, proportional electromagnet, displacement sensor, etc; Or from the hydraulic system, including proportional throttle system and differential pressure reducing valve system.
3. Troubleshooting procedures
(1) Detect the current of the given proportion electromagnet and the electrical signal of the main valve core displacement sensor to ensure its normal operation.
(2) Check and disassemble the differential pressure reducing valve, check whether the valve core of the pressure reducing valve is within the normal wear range, and whether the rigidity of the return spring is good; The pressure reducing valve controls whether the wear of the cone valve core of the cover plate is within the normal range, whether the rigidity of the return spring is good, and whether the damping plug in the cover plate is unblocked.
(3) Clean the two-way cartridge proportional throttle valve block to ensure that its control oil passage and damping plug are unblocked, and properly adjust the differential pressure of the differential pressure reducing valve.
After taking the above measures, the proportional valve can restore the speed control function, and the movement speed of the horizontal cylinder can be ideally controlled.
