Check Valve (G)

Check valve in the gas network.

blockType: EngeeFluids.Gas.Valves.DirectionalControl.Check

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Description

Block Check Valve (G) It is an opening with a unidirectional opening mechanism that prevents unwanted backflow. The opening mechanism reacts to pressure and opens the hole when the pressure drop decreases from the entrance to the hole A to the exit to the hole B. Check valves protect upstream components from pressure surges, temperature surges, and chemical contamination occurring downstream.

The valve starts to open when the pressure reaches the actuation pressure and continues to open until the end of the pressure control range. The actuation pressure is the initial resistance due to friction or spring force that the valve must overcome in order to open. Below this threshold, the valve is closed and can only allow leakage flow. Beyond the pressure control range, the valve is fully open, and the maximum flow rate is determined by the instantaneous pressure conditions.

The flow can be laminar or turbulent and can reach sonic velocities. The maximum speed is reached in the valve seat, where the flow is narrowest and fastest. The flow reaches a critical mode and maximum speed when a pressure drop downstream can no longer increase the speed. The flow becomes critical when the ratio of outlet pressure to inlet pressure reaches a critical value characteristic of the valve. The unit does not calculate supersonic flow.

Control and other pressures

The pressure that the valve responds to is the control pressure. By default, the control pressure is the pressure difference from the inlet to the outlet. This setting ensures that the valve closes if the flow direction is reversed.

You can also set the control pressure as the excess inlet pressure. Use this setting if you know that the inlet pressure will always be higher than the outlet pressure. For example, if the inlet is connected to a pressure source such as a pump.

You can select the control pressure by setting the parameter Opening pressure specification meaning Pressure difference of port A relative to port B or Gauge pressure at port A.

_ Pressure difference from port A to port B_

If for the parameter Opening pressure specification the value is set Pressure difference of port A relative to port B Then:

Control pressure:

where and — absolute pressures at ports A and B respectively.
Actuation pressure — parameter value Cracking pressure differential.
Maximum valve pressure , at which the valve is fully open , is the value of the parameter Maximum opening pressure differential.

_ Excessive pressure on port A_

If for the parameter Opening pressure specification meaning Gauge pressure at port A Then:

Control pressure:

where — the atmospheric pressure specified in the block Gas Properties (G).
Actuation pressure — parameter value Cracking pressure (gauge).
Maximum valve pressure , at which the valve is fully open , is the value of the parameter Maximum opening pressure (gauge).

Degree of valve opening

The degree to which the control pressure exceeds the actuation pressure determines how much the valve opens. The normalized control pressure is:

where

– control pressure;
– actuation pressure;
– the maximum valve pressure at which the valve is fully open.

The degree of opening is normalized so that when the valve is fully closed, it is equal to 0, and when fully open – 1. If the calculation returns a value that goes beyond these limits, the block equates it to the nearest of the two limits.

Degree of valve opening:

where – parameter value Leakage flow fraction.

calculated smoothing

If the parameter Smoothing factor If it has a non-zero value, then the unit applies numerical smoothing to the normalized control pressure., . Enabling anti-aliasing helps maintain the numerical stability of the simulation.

Parameterization of the valve

The block behavior depends on the parameter Valve parameterization:

Cv flow coefficient – expense ratio determines the dependence of the throughput on the pressure drop.
Kv flow coefficient – expense ratio determines the dependence of throughput on pressure drop, .
Sonic conductance – steady-state acoustic conductivity determines the throughput at critical flow, a condition in which the flow velocity is equal to the local speed of sound. The flow becomes critical when the ratio of outlet pressure to inlet pressure reaches a value called the critical pressure ratio.
Orifice area – the area of the hole determines the throughput.

The unit scales the set flow rate according to the degree of valve opening. When increasing the degree of valve opening from 0 before 1 The throughput indicator increases from a set minimum to a set maximum.

Conservation of momentum

Parameter Valve parameterization determines which equations will be used to calculate the flow rate. If for the parameter Valve parameterization the value is set Cv flow coefficient, then the mass consumption will be defined as:

where

— expense ratio;
— a constant equal to 27.3 for mass flow rate in kg/hour, pressure in bar and density in kg/m3³;
— expansion coefficient;
— inlet pressure;
— outlet pressure;
— density at the entrance.

The expansion coefficient is defined as:

where

— the ratio of the adiabatic index to 1.4;
— parameter value xT pressure differential ratio factor at choked flow.

When is the pressure ratio exceeds the value of the parameter Laminar flow pressure ratio, , there is a smooth transition to using the linearized equation:

where

When is the pressure ratio falls lower , the flow becomes critical, and the equation is used:

If for the parameter Valve parameterization the value is set Kv flow coefficient, then the block uses the same equations, but replaces on using a relationship . More detailed information about the mass flow equations when for the parameter Valve parameterization the value is set Kv flow coefficient or Cv flow coefficient, is given in [2] and [3].

If for the parameter Valve parameterization the value is set Sonic conductance, then the mass consumption defined as:

where

— acoustic conductivity;
— critical pressure ratio;
— parameter value Subsonic index;
— parameter value ISO reference temperature;
— parameter value ISO reference density;
— temperature at the entrance.

When is the pressure ratio exceeds the value of the parameter Laminar flow pressure ratio, , there is a smooth transition to using the linearized equation:

When is the pressure ratio falls below the critical pressure ratio , the flow becomes critical, and the equation is used:

Meaning Sonic conductance the parameter Valve parameterization designed for pneumatic systems. If you use this value for gases other than air, you may need to adjust the acoustic conductivity value by the square root of the specific gravity.

More detailed information about the mass flow equations when for the parameter Valve parameterization the value is set Sonic conductance, is given in [1].

If for the parameter Valve parameterization the value is set Orifice area, then the mass consumption defined as:

where

— the area of the hole or valve;
— parameter value Cross-sectional area at ports A and B;
— parameter value Discharge coefficient;
— the adiabatic index.

When is the pressure ratio exceeds the value of the parameter Laminar flow pressure ratio, , there is a smooth transition to using the linearized equation:

When is the pressure ratio falls lower , the flow becomes critical, and the equation is used:

More detailed information about the mass flow equations when for the parameter Valve parameterization the value is set Orifice area, is given in [4].

Conservation of mass

It is assumed that the volume and mass of gas inside the component are very small, and these values are not taken into account, so gas cannot accumulate in the valve. According to the principle of conservation of mass, the mass flow rate of gas entering through one port is equal to the flow rate of gas exiting through another port.:

where and — the mass flow rate at ports A and B respectively.

Energy conservation

The valve is an adiabatic component. There is no heat exchange between the gas and the valve wall. When the gas passes through the valve, no work is performed on it. Under these assumptions, energy can enter and exit the valve only through convection through ports A and B. According to the principle of energy conservation, the sum of energy flows through ports is always zero:

where and — the flow of energy entering the valve through ports A and B, respectively.

Assumptions and limitations

The equation for parameterization Orifice area it has lower accuracy for gases that are far from ideal.
This block does not simulate supersonic flow.

Ports

Conserving

# A — valve inlet
gas

Details

Gas port associated with the valve inlet.

Program usage name

inlet

# B — valve outlet
gas

Details

Gas port associated with the valve outlet.

Program usage name

outlet

Parameters

# Opening pressure specification — the pressure drop used to control the valve
Pressure difference of port A relative to port B | Gauge pressure at port A

Details

Determines the control valve opening pressure.

Meaning Pressure difference of port A relative to port B defines the control pressure as the pressure difference between ports A and B.

Meaning Gauge pressure at port A defines the control pressure as the excess inlet pressure.

Values	`Pressure difference of port A relative to port B` \| `Gauge pressure at port A`
Default value	`Pressure difference of port A relative to port B`
Program usage name	`opening_pressure_type`
Evaluatable	No

# Cracking pressure differential — pressure drop required to open the valve
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The minimum pressure difference between the inlet and outlet required to open the valve. This value indicates the beginning of the differential pressure range of the valve, in which it gradually opens, providing an increase in flow.

Dependencies

To use this parameter, set for the parameter Opening pressure specification meaning Pressure difference of port A relative to port B.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.01 MPa`
Program usage name	`delta_p_crack`
Evaluatable	Yes

# Maximum opening pressure differential — the pressure drop at which the valve is fully open
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The pressure difference between the inlet and outlet at which the valve is fully open. This value indicates the end of the differential pressure range of the valve, in which it gradually opens, providing an increase in flow.

Dependencies

To use this parameter, set for the parameter Opening pressure specification meaning Pressure difference of port A relative to port B.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.1 MPa`
Program usage name	`delta_p_max`
Evaluatable	Yes

# Cracking pressure (gauge) — minimum excess inlet pressure required to open the valve
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The minimum excess inlet pressure (port A) required to open the valve. This value indicates the beginning of the differential pressure range of the valve, in which it gradually opens, providing an increase in flow.

Dependencies

To use this parameter, set for the parameter Opening pressure specification meaning Gauge pressure at port A.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.1 MPa`
Program usage name	`p_crack_gauge`
Evaluatable	Yes

# Maximum opening pressure (gauge) — maximum excess inlet pressure
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The maximum excess inlet pressure (port A) at which the valve is fully open. This value indicates the end of the differential pressure range of the valve, in which it gradually opens, providing an increase in flow. If the valve in your model does not fully open as expected, you can try to reduce the value of this parameter.

Dependencies

To use this parameter, set for the parameter Opening pressure specification meaning Gauge pressure at port A.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.2 MPa`
Program usage name	`p_gauge_max`
Evaluatable	Yes

# Valve parameterization — the method of defining the characteristics of the flow through the hole
Cv flow coefficient | Kv flow coefficient | Sonic conductance | Orifice area

Details

The method of calculating the mass flow is based on:

Cv flow coefficient — the expense ratio .
Kv flow coefficient — the expense ratio , which is defined as .
Sonic conductance — acoustic conductivity in steady-state mode.
Orifice area — the area of the hole.

Values	`Cv flow coefficient` \| `Kv flow coefficient` \| `Sonic conductance` \| `Orifice area`
Default value	`Cv flow coefficient`
Program usage name	`valve_parameterization`
Evaluatable	No

# Maximum Cv flow coefficient — the flow rate corresponding to the maximum opening area

Details

The value of the flow coefficient , when the cross-sectional area of the hole is maximal. The flow coefficient determines the dependence of the throughput on the pressure drop.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Cv flow coefficient.

Default value	`4.0`
Program usage name	`C_v_max`
Evaluatable	Yes

# xT pressure differential ratio factor at choked flow — critical pressure drop ratio

Details

The ratio between inlet pressure and the outlet pressure , defined as at which point the flow becomes critical. If this value is not known, it can be found in Table 2 in ISA-75.01.01. [3]. Default value 0.7 suitable for many valves.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Cv flow coefficient.

Default value	`0.7`
Program usage name	`delta_p_ratio_C_v`
Evaluatable	Yes

# Maximum Kv flow coefficient — the flow rate corresponding to the maximum opening area

Details

The value of the flow coefficient, , when the cross-sectional area of the hole is maximal. The flow coefficient determines the dependence of the throughput on the pressure drop.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Kv flow coefficient.

Default value	`3.6`
Program usage name	`K_v_max`
Evaluatable	Yes

# xT pressure differential ratio factor at choked flow — critical pressure drop ratio

Details

The ratio between inlet pressure and the outlet pressure , defined as at which point the flow becomes critical. If this value is not known, it can be found in table 2 in ISA-75.01.01 [3]. Default value 0.7 suitable for many valves.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Kv flow coefficient.

Default value	`0.7`
Program usage name	`delta_p_ratio_K_v`
Evaluatable	Yes

# Maximum sonic conductance — acoustic conductivity corresponding to the maximum hole area
l/(bar*s) | gal/(min*psi) | m^3/(Pa*s)

Details

The value of acoustic conductivity, when the cross-sectional area of the hole is maximum.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Sonic conductance.

Units	`l/(bars)` \| `gal/(minpsi)` \| `m^3/(Pa*s)`
Default value	`12.0 l/(bar*s)`
Program usage name	`C_max`
Evaluatable	Yes

# Critical pressure ratio — critical pressure ratio

Details

The pressure ratio at which the flow becomes critical and the flow velocity reaches a maximum determined by the local speed of sound. The ratio between the outlet pressure and inlet pressure : .

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Sonic conductance.

Default value	`0.3`
Program usage name	`B_critical_linear`
Evaluatable	Yes

# Subsonic index — the value of the degree used to calculate the mass flow rate in subsonic flow mode

Details

An empirical value used for more accurate calculation of mass flow rate in subsonic flow mode.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Sonic conductance.

Default value	`0.5`
Program usage name	`m`
Evaluatable	Yes

Details

The temperature in the standard reference atmosphere in the ISO 8778 standard.

The ISO reference parameter values need to be adjusted only if acoustic conductivity values obtained with excellent reference values are used.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Sonic conductance.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`293.15 K`
Program usage name	`T_reference`
Evaluatable	Yes

# ISO reference density — reference density according to ISO 8778
kg/m^3 | g/m^3 | g/cm^3 | g/mm^3 | lbm/ft^3 | lbm/gal | lbm/in^3

Details

The density in the standard reference atmosphere in the ISO 8778 standard.

The ISO reference parameter values need to be adjusted only if acoustic conductivity values obtained with excellent reference values are used.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Sonic conductance.

Units	`kg/m^3` \| `g/m^3` \| `g/cm^3` \| `g/mm^3` \| `lbm/ft^3` \| `lbm/gal` \| `lbm/in^3`
Default value	`1.185 kg/m^3`
Program usage name	`rho_reference`
Evaluatable	Yes

# Maximum orifice area — the area of the flow passage section corresponding to the maximum opening area
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The maximum cross-sectional area of the flow is when the cross-sectional area of the opening is maximum.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Orifice area.

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
Default value	`1e-4 m^2`
Program usage name	`max_restriction_area`
Evaluatable	Yes

# Discharge coefficient — expense ratio

Details

The correction factor is the ratio of the actual mass flow to the theoretical mass flow.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Orifice area.

Default value	`0.64`
Program usage name	`C_d`
Evaluatable	Yes

# Leakage flow fraction — cost ratio

Details

The ratio of flow through a closed and through an open hole.

Default value	`1e-6`
Program usage name	`leakage_fraction`
Evaluatable	Yes

# Smoothing factor — numerical smoothing factor

Details

The continuous smoothing coefficient, which ensures smooth opening by correcting the characteristic of the hole in the almost open and almost closed positions.

Default value	`0.01`
Program usage name	`smoothing_factor`
Evaluatable	Yes

# Laminar flow pressure ratio — the pressure ratio at which the flow transitions between laminar and turbulent modes

Details

The ratio of outlet pressure to inlet pressure at which the flow transitions between laminar and turbulent flow modes.

Typical values range from 0.995 before 0.999.

Default value	`0.999`
Program usage name	`B_laminar`
Evaluatable	Yes

# Cross-sectional area at ports A and B — the area at the inlet or outlet of the valve
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

This area is used when calculating the mass flow through ports.

The ports have the same size. The value of this parameter must correspond to the area of the inlet of the component to which the unit is connected.

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
Default value	`0.01 m^2`
Program usage name	`port_area`
Evaluatable	Yes

Literature

ISO 6358-3. "Pneumatic fluid power – Determination of flow-rate characteristics of components using compressible fluids – Part 3: Method for calculating steady-state flow rate characteristics of systems". 2014.
IEC 60534-2-3. "Industrial-process control valves – Part 2-3: Flow capacity – Test procedures". 2015.
ANSI/ISA-75.01.01. "Industrial-Process Control Valves – Part 2-1: Flow capacity – Sizing equations for fluid flow underinstalled conditions". 2012.
P. Beater. "Pneumatic Drives." Springer-Verlag Berlin Heidelberg. 2007.