MapleSim Hydraulics Library from Modelon
Counter Balance — Counterbalance valve
The Counter Balance component describes a counterbalance valve. The counterbalance valve is a pressure control device and allows (almost) free flow from port A (inlet) to port B (load). It blocks reverse flow unless a pilot pressure is sensed at port C (pilot) or load pressure exceeds relief setting. This valve ensures that the actuator always sees a positive load pressure, even under overrunning load situations.
Backpressure at port A does affect the valve setting unless an atmospherically vented counterbalance valve is used where the spring chamber is atmospherically referenced.
The behavior of the valve is modeled as an orifice whose diameter depends on the pressures at the three ports.
port_B.p<pPreload and port_A.p=0 and port_C.p=0
Leakage flow from B → A (given by GLeak). This is the load holding function.
pPreload<port_B.p < pFull and port_A.p=0 and port_C.p=0
Flow from B → A. Valve is partially open. This is the pressure relief function.
pFull<port_B.p and port_A.p=0 and port_C.p=0
Flow from B → A. Valve is completely open. Flow rate is determined by qnom and Δpnom.
port_C.p<pPreloadpressureRatio and port_B.p=0 and port_A.p=0
Leakage flow from B → A (given by GLeak).
pPreloadpressureRatio<port_C.p < pFullpressureRatio and port_B.p=0 and port_A.p=0
Flow from B to A. Valve is partially open.
pFullpressueRatio<port_C.p and port_B.p=0 and port_A.p=0
Flow from B → A. Valve is completely open. Flow rate is determined by qnom and Δpnom. This is the normal operation when the valve is opened by the pressure at the pilot.
port_A.p<pCheckValvePreload and port_B.p=0 and port_C.p=0
pCheckValvePreload<port_A.p and port_B.p=0 and port_C.p=0
Flow from A → B through the check valve, given by qnomCheckValve and Δpnom.
pPreload<port_B.p−port_A.p⁢backpressureRatio+port_C.p⁢pressureRatio and port_B.p−port_A.p⁢backpressureRatio+port_C.p⁢pressureRatio<pFull
Flow from B → A. Valve is partially open.
Load pressure to start opening valve. Some manufacturers call this value the thermal relief pressure which is approximately 60e5 Pa above their holding pressure of counterbalance setting.
Load pressure to open valve completely. Typically not specified; depends on the spring characteristics and is responsible for the opening characteristic.
Pressure ratio (that is, the multiplier for pilot pressure).
Pressure ratio (that is, the multiplier for back pressure at port 2). It is zero for atmospherically vented valves and around 1.0 for others.
Pressure to open check valve completely.
Nominal flow rate at dpnom of load holding valve (that is, the poppet).
Pressure drop at qnom.
Nominal flow rate of check valve at Δpnom.
Conductance of leakage. Very small value.
The mass and flow forces are not included. Use the modifier(s)
to set the initial condition(s) for the pressure of the lumped volume(s) Pa.
The flow rate at the pilot port 3 is equal to zero. This pressure at this port is not modeled as a state.
Other names for this valve include motion control valve and over center valve.
Check Valve Two
Spring-loaded check valve with laminar/turbulent flow; gives the characteristic of the flow from port 2 to 1. This model is also used to model the linearly pressure dependent leakage with GLeak.
Flow rate flowing into port_A
Limited gauge pressure
Upstream kinematic viscosity
Absolute pressure pA
Absolute pressure pB
Pressure at port A
Pressure at port B
Gas saturation pressure
Layout of port where oil flows into an element (0<mflow, pB<pA means 0<Δp)
Hydraulic port where oil leaves the component (mflow<0, pB<pA means 0<Δp)
Port where typically the control pressure for the pilot is connected
Temperature offset from system temperature
use volume A
If true, a volume is present at port_A
use volume B
If true, a volume is present at port_B
Geometric volume at port A
Geometric volume at port B
Load pressure to start opening valve
Load pressure to open valve completely
Pressure ratio, i.e. multiplier for pilot pressure to open valve
Pressure ratio, i.e. multiplier for back pressure at port 2 to open valve; 0 for atmospherically vented valve
Pressure to open check valve completely
Conductance of leakage
Nominal flow rate at dpnom of load holding valve
Pressure drop at qnom
Nominal flow rate at dpnom of check valve
Laminar part of orifice model
Turbulent part of orifice model, k2=1Cd2
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