Principles and precautions for selecting load sensitive multi way valves

2024-07-13 14:18
65

Selection of reversing coupling:
1. Non differential pressure reducing valve, used for equipment without composite action. Constant pressure difference at the valve port is achieved through the flow control valve on the load sensitive variable pump. Because the pressure difference of the flow control valve on the load sensitive variable (about 14 bar) is greater than the pressure difference of the differential pressure reducing valve on the load sensitive multi way valve (about 6 bar), the flow capacity of the load sensitive valve will slightly increase.

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2. Pre select switch valve, used to switch between boarding and alighting, so that the multi way valves for boarding and alighting cannot operate simultaneously, improving safety. The B-position is connected to the gate valve, with a rated flow rate of 40L/min, while the A-position is connected to a load sensitive multi way valve, with a rated flow rate that can be selected as needed.

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3. The directional coupling is equipped with a fixed differential pressure reducing valve, which controls the pressure difference to approximately 6 bar. LS overflow valve and flow cut-off valve can be installed. Usually used for devices that require composite actions.

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4. The directional coupling with an enhanced two-way differential pressure reducing valve will have an   increased rated flow rate due to the increased pressure difference of the differential pressure reducing valve.

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Switching online can be selected
L. M, F, and H machines have low oil return back pressure, with approximately 10 bar throughout the entire stroke. J. B, R, and O machines have high oil return back pressure, approximately 20 bar throughout the entire stroke. Therefore, it is recommended that J, B, R, and O functions be used in situations where shaking is prone to occur, such as telescopic arm extension and amplitude change. Especially when using a combination of multi way valves and balance valves, it is recommended to choose J, B, R, and O functions.

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Selection of rated flow rate for reversing A/B ports
The rated flow rate of the selected A/B ports cannot be much higher than the actual flow rate. Because limiting the maximum stroke of the spool through the spool stroke limit screw will reduce the linear space and decrease the proportional control performance of the multi way valve. Therefore, it is recommended that the rated flow rate of A/B ports be 1.2 times the actual flow rate, which not only ensures the linear control space of the multi way valve, but also leaves a certain margin for the installation and commissioning of the multi way valve.
Pre pressure and damping valves for pressure balance
4a one-way valve. The 4b back pressure valve opens at a pressure of approximately 25 bar. When the LS   oil circuit of the quantitative pump system exceeds 25 bar, the LS oil circuit will quickly release pressure through the 4b back pressure valve; When the LS oil circuit is less than 25 bar, slowly release pressure through thread damping 4c. 4d is used to limit the flow at the LS interface, making the LS oil pressure fluctuation smaller, and has a certain effect on reducing or eliminating the oscillation of the quantitative pump/variable pump system.
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Double ended electromagnetic vibration frequency and amplitude

In order to improve the proportional characteristics and resolution of the valve, if conditions permit, vibration signals are added to the proportional solenoid control model. The parameter settings are as follows:
PWM frequency: 1K
Flutter frequency: 40-70Hz, preferably 55Hz

Flutter amplitude: 20% ≤ Ad ≤ 35%

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When there is no flutter signal, the effect of adding flutter signal can be achieved by adjusting the PWM frequency. The parameter settings are as follows:
PWM frequency 60-100Hz, 75Hz is optimal



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