Non return valve

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Navigation: Main Page -> Models -> Pressure Changing Models

General Description

The valve model will add pressure drop to the stream or operates at a specified pressure.


Valve image001.gif

The diagram shows the default drawing of the Valve, with the required connecting streams. The unit will not operate unless all of the above streams are connected.

The physical location of the connections is not important; the user may connect the streams to any position on the drawing.

Inputs and Outputs

Label Required
Number of Connections Description
Min Max.
Input Required In 1 1 Input stream to valve.
Output Required Out 1 1 Output stream from valve.

Model Theory

The valve is a constant enthalpy process.

Step 1) Enthalpy can be calculated from the inlet conditions.

Step 2) Outlet temperature can be calculated from enthalpy and outlet pressure.

Data Sections

The default access window consists of a number of sections,

  1. Valve_NR-1 tab - Contains general information relating to the unit.
  2. VLE - Optional tab, only visible if the VLEquilibrium is enabled in the Evaluation Block.
  3. Info tab - Contains general settings for the unit and allows the user to include documentation about the unit and create Hyperlinks to external documents.
  4. Links tab, contains a summary table for all the input and output streams.
  5. Audit tab - Contains summary information required for Mass and Energy balance. See Model Examples for enthalpy calculation Examples.

Non Return Valve Page

Unit Type: Valve_NR-1 - The first tab page in the access window will have this name.

Tag (Long/Short) Input / Calc Description/Calculated Variables / Options
Tag Display This name tag may be modified with the change tag option.
Condition Display OK if no errors/warnings, otherwise lists errors/warnings.
ConditionCount Display The current number of errors/warnings. If condition is OK, returns 0.
GeneralDescription / GenDesc Display This is an automatically generated description for the unit. If the user has entered text in the 'EqpDesc' field on the Info tab (see below), this will be displayed here. If this field is blank, then:
  • For pipes, SysCAD will use the text in the 'ConnectDesc' field - this displays the Source and Destination tags of the pipe;
  • For Feeders/Cross Page Connectors, SysCAD will display the state of the unit, i.e. if it is a Feeder or a Sink, etc.;
  • For other units SysCAD will display the unit class ID.


PressMethod None No pressure change across the unit.
Drop The user specifies a pressure drop. Therefore, Pout = Pin - Pdrop
Fixed The user specifies a fixed outlet pressure from the unit.
Atmos The outlet pressure from the unit is set to atmospheric pressure.
PressDropRqd / PDrop Input The required pressure drop. Visible if the Drop method is selected.
OutletPressRqd / PRqd Input The required outlet pressure. Visible if the Fixed method is selected.
VLEquilibrium Off Vapour Liquid Equilibrium is off.
On Vapour Liquid Equilibrium (VLE) is enabled. The associated section, VLE becomes visible and may be configured.
Note: This option may automatically adjust the species make-up in Qo.


MassFlow / Qm Calc The mass flow rate.
TemperatureIn / Ti Calc The inlet temperature.
TemperatureOut / To Calc The outlet temperature.
PressIn / Pi Calc The inlet pressure.
Press_Change / dP Calc The pressure change.
PressOut / Po Calc The outlet pressure.
DensityIn / Rhoi Calc The inlet Density.
DensityOut / Rhoo Calc The outlet Density, after pressure change.
VapourFracIn / Vfi Calc The inlet vapour fraction.
VapourFracOut / Vfo Calc The outlet vapour fraction.

Adding this Model to a Project

Insert into Configuration file

Sort either by DLL or Group.





Piping: Valve - Non Return(1)



Mass Transfer


Piping: Valve - Non Return(1)

See Project Configuration for more information on adding models to the configuration file.

Insert into Project


Insert Unit


Valve - Non Return(1)

See Insert Unit for general information on inserting units.