COUNTERBALANCE VALVE REXROTH PDF

Load Holding: P. Checks vs. Counterbalance Valves Counterbalance valve or pilot-operated P. Here are some guidelines for when it is most appropriate to use a P. Pilot-operated check valves, or pilot-to-open check valves, are non-modulating valves and in operation should be considered either fully open or fully closed. They are not capable of metering the oil flow through them.

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Basic Parameters Tab Valve pressure setting The parameter specifies the pressure at port L necessary to start opening the valve. The setting is controlled with the valve spring. The default value is 50e5 Pa. Valve spring stiffness The valve spring pressure stiffness cp.

Pilot ratio The ratio between the effective areas of the control member face in the pilot chamber and in the load chamber. This is one of the fundamental valve characteristics in a catalog or data sheet. The default value is 3. Backpressure ratio The ratio between the effective area of the control member, onto which the backpressure acts, and the load chamber valve area.

There is a wide variety of counterbalance valves with compensated or partially-compensated backpressure. The parameter can take zero value if the valve is completely compensated. The default value is 4. Time constant The valve dynamics are approximated with the first order lag.

This parameter is the time constant of the lag. The default value is 0. Leakage area The total area of possible leaks in the completely closed orifice and check valve. The main purpose of the parameter is to maintain numerical integrity of the circuit by preventing a portion of the system from getting isolated after the orifice or check valve is completely closed.

The parameter value must be greater than 0. Variable Orifice Tab Variable orifice parameterization Select one of the following methods for specifying the orifice: By maximum area and opening — Provide values for the maximum orifice area and the maximum orifice opening. The passage area is linearly dependent on the control member displacement, that is, the orifice is closed at the initial position of the control member zero displacement , and the maximum opening takes place at the maximum displacement.

This is the default method. By area vs. The passage area is determined by one-dimensional table lookup. You have a choice of two interpolation methods and two extrapolation methods.

Orifice maximum area Specify the area of a fully opened orifice. The parameter value must be greater than zero. This parameter is used if Variable orifice parameterization is set to By maximum area and opening. Orifice maximum opening Specify the maximum displacement of the control member.

The default value is 5e-4 m. Orifice flow discharge coefficient Semi-empirical parameter for orifice capacity characterization. Its value depends on the geometrical properties of the orifice, and usually is provided in textbooks or manufacturer data sheets. Orifice laminar transition specification Select how the block transitions between the laminar and turbulent regimes: Pressure ratio — The transition from laminar to turbulent regime is smooth and depends on the value of the Orifice laminar flow pressure ratio parameter.

This method provides better simulation robustness. Reynolds number — The transition from laminar to turbulent regime is assumed to take place when the Reynolds number reaches the value specified by the Orifice critical Reynolds number parameter.

Orifice laminar flow pressure ratio Pressure ratio at which the flow transitions between laminar and turbulent regimes. This parameter is visible only if the Orifice laminar transition specification parameter is set to Pressure ratio.

Orifice critical Reynolds number The maximum Reynolds number for laminar flow. The value of the parameter depends on the orifice geometrical profile. You can find recommendations on the parameter value in hydraulics textbooks. The default value is This parameter is visible only if the Orifice laminar transition specification parameter is set to Reynolds number. Tabulated orifice openings Specify the vector of input values for orifice openings as a one-dimensional array.

The input values vector must be strictly increasing. The values can be nonuniformly spaced. The minimum number of values depends on the interpolation method: you must provide at least two values for linear interpolation, at least three values for smooth interpolation. The default values, in meters, are [-2e-3,0,5e-3,15e-3].

This parameter is used if Variable orifice parameterization is set to By area vs. Tabulated orifice openings values will be used together with Tabulated orifice area values for one-dimensional table lookup. Tabulated orifice area Specify the vector of orifice areas as a one-dimensional array. The vector must be of the same size as the orifice openings vector. All the values must be positive.

Interpolation method This parameter is used if Variable orifice parameterization is set to By area vs. Select one of the following interpolation methods for approximating the output value when the input value is between two consecutive grid points: Linear — Select this option to get the best performance. Smooth — Select this option to produce a continuous curve with continuous first-order derivatives.

Extrapolation method This parameter is used if Variable orifice parameterization is set to By area vs. Select one of the following extrapolation methods for determining the output value when the input value is outside the range specified in the argument list: Linear — Select this option to produce a curve with continuous first-order derivatives in the extrapolation region and at the boundary with the interpolation region.

Nearest — Select this option to produce an extrapolation that does not go above the highest point in the data or below the lowest point in the data.

Check Valve Tab Check valve maximum passage area Valve passage maximum cross-sectional area. Check valve cracking pressure Pressure level at which the orifice of the valve starts to open. The default value is 3e4 Pa. Check valve maximum opening pressure Pressure differential across the valve needed to fully open the valve. Its value must be higher than the cracking pressure. The default value is 1. Check valve flow discharge coefficient Semi-empirical parameter for valve capacity characterization.

Check valve laminar transition specification Select how the block transitions between the laminar and turbulent regimes: Pressure ratio — The transition from laminar to turbulent regime is smooth and depends on the value of the Check valve laminar flow pressure ratio parameter.

Reynolds number — The transition from laminar to turbulent regime is assumed to take place when the Reynolds number reaches the value specified by the Check valve critical Reynolds number parameter. Check valve laminar flow pressure ratio Pressure ratio at which the flow transitions between laminar and turbulent regimes. This parameter is visible only if the Check valve laminar transition specification parameter is set to Pressure ratio.

Check valve critical Reynolds number The maximum Reynolds number for laminar flow. The transition from laminar to turbulent regime is assumed to take place when the Reynolds number reaches this value. This parameter is visible only if the Check valve laminar transition specification parameter is set to Reynolds number.

When your model is in Restricted editing mode, you cannot modify the following parameters: Variable orifice parameterization Interpolation method Extrapolation method All other block parameters are available for modification. The actual set of modifiable block parameters depends on the value of the Variable orifice parameterization parameter at the time the model entered Restricted mode.

Global Parameters Parameters determined by the type of working fluid: Fluid density Fluid kinematic viscosity Use the Hydraulic Fluid block or the Custom Hydraulic Fluid block to specify the fluid properties. Ports The block has the following ports: P Hydraulic conserving port associated with the valve pilot port.

L Hydraulic conserving port associated with the valve load port. B Hydraulic conserving port associated with the valve backpressure port. Examples The Hydraulic Actuator with Counterbalance Valve example illustrates the use of counterbalance valve to balance the load of a double-acting cylinder controlled by an open-center 4-way directional valve.

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Rexroth - Counterbalance valve

Basic Parameters Tab Valve pressure setting The parameter specifies the pressure at port L necessary to start opening the valve. The setting is controlled with the valve spring. The default value is 50e5 Pa. Valve spring stiffness The valve spring pressure stiffness cp. Pilot ratio The ratio between the effective areas of the control member face in the pilot chamber and in the load chamber. This is one of the fundamental valve characteristics in a catalog or data sheet.

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Counterbalance valves - Bosch Rexroth Oil Control (2)

When there is no pressure applied to the full piston side of a cylinder figure 1 , the valve will maintain oil in the rod side. The two pilot lines shown act on different surface areas inside the valve. The ratio of these areas is usually or For explanation we will use the ratio. To overcome a spring tension of 1, lbs, the pressure would have to build to PSI. Since the load in the example is exerting a force of only PSI, the valve will remain closed. When necessary to lower the load, the full piston side of the cylinder is pressurized.

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