VacTran 3 Manual (779748), страница 16
Текст из файла (страница 16)
Change directoriesif necessary to find the gas file. Click on the name of the gas file, and click on Open. For a short cut, double clickon the name of the gas file. The new name will be displayed in the Environment dialog.Rate of rise start time: Specifies that starting value for calculating pressure rise in the vessel. The gas load valueswill be calculated based on this elapsed time. Most gas loads decrease with time, so a higher value for the starttime will result in a lower gas load in the calculation.Rate of rise stop time: Specifies the end point for the pressure rise calculation.Initial vessel pressure: Specifies the pressure from which the pressure rise calculation will start.© 2011 Professional Engineering ComputationsSystem models8.11System model right-click optionsUnits of Measure…:Graph controls…:Delete all conductances instation:Activate the Units of Measure dialogActivate the Graph controls dialogClears out the entire list of conductance elements in the currentlydisplayed pump station.Delete all pumps in station:Delete all gas loads:Clears out the entire list of pump models in the displayed pump station.Clears out the entire list of gas loads in the system model.
Note that thesystem model only has one gas load list.Adds the contents of a pump station from a pump station file.Replaces the current pump station with the contents of a pump stationfrom a pump station file.Add external pump station:Replace with external pumpstation :Save this pump station:System model help:Write pumps:Saves the current pump station to a new pump station model saved as aseparate file.Clicking on the right mouse button over a System model will activate amenu unique to System models. This menu contains a few usefulfunctions and shortcuts as explained below:Dump all of the pump speed data for each pump station to the Main TextWindow.Write conductances:Dump all of the conductance data for each pump station to the Main TextWindow.Write system report:Summarize all of the System model parameters, such as start andtarget pressures, pumps, conductances, gas loads, etc.
This data isdumped to the Main Text Window for the active System model.© 2011 Professional Engineering Computations1391408.12VacTran 3About pump stationsA pump station is the active element of a system model that removes gas and therefore affects a decrease in vesselpressure. A pump station is defined as a set of vacuum pumps connected by a series of conductance elements tothe vacuum vessel. These conductance elements can be pipes, elbows, bends, orifices, or constant values.
Theminimum configuration for an active pump station is one pump and one conductance element. There is no programlimit to the number of pumps or conductance elements in a pump station.VacTran allows the definition of up to 6 independent pump stations in each system model. The following are thecapabilities and restrictions on VacTran pump stations.1) Each pump station can have individual start and stop pressures. All of the pumps in a given pump station will beconsidered active for the stop/start range of the pump station.2) One pump station may be set to turn off as another is turned on. This is typical of staged pumping, wheredifferent types of pumps are used for different pressure ranges of pump down.3) Pump station start/stop can overlap partially or completely with other pump stations.4) Parallel pump paths can be modeled.
By setting two pump stations to the same start/stop values, they areeffectively running in parallel.5) No pressure gaps are allowed between start/stop of sequential pump stations. For example, if the first stationstarts at 760 torr and stops at 10-2 torr, the second station must start at no lower than 10-2 torr.6) Pumps included in a pump station must have valid pumping ranges for the operating pressures of the pumpstation. A station cannot be set to start at 760 torr if no pump in the station has data spanning that pressure.7) The start/stop pressure of a pump station can be a subset of the operating range of the included pumps.
Forexample, if the operating range of a single pump in the station is 760-10-2 torr, one could legally set the start/stopof the station to 700 torr and 10-1 torr.8) Each pump station can bypass its conductance list. A set of bypass valves is provided to allow the pump stationto behave as it has no conductance losses. One can calculate the best possible pump down in an ideal world.Knowing the upper limit of performance can be useful in evaluating conductance alternatives.9) Each pump station can be selectively deactivated.
Deactivating a pump station causes VacTran to ignore itduring all subsequent pump down calculations. This can be useful if you want to temporarily disable a pump station© 2011 Professional Engineering ComputationsSystem models141without deleting it in order to see the effect on calculations.10) Each pump station can have an associated multiplier. For example, a multiplier of two will simulate twoidentical pump stations working in parallel.
The multiplier value is applied to the calculated delivered speed of thepump station.See also:Pump station settingsPump Station Settings dialog8.12.1 Pump station settingsThe following figure shows elements of the system model dialog which pertain to pump station settings.Station tabs:At the top of the dialog, the tabs allows you to select one of the pump stations to be displayed for editing. Thepump list, conductance list, valves, and pressure settings will be updated to show the selected station.Station settings button:Click here to open the Pump station settings dialog, which allows you to change several characteristics of eachpump station.© 2011 Professional Engineering Computations142VacTran 3Station Active check box:Even if you have loaded pumps and conductances into a pump station, you may want to temporarily deactivate thatstation if you are doing trade studies, so that it is not included in the next calculation.
Click on the check box totoggle its state.Add cond volume:Adding the conductance volume to the model will include that volume in all pump down calculations. It is equivalentto placing a valve between the pump and the conductance path, so that when the pump is turned on, it is evacuatingboth the conductance path and the vacuum vessel from the same start pressure.If Add cond volume is unchecked, calculations will assume that the valve is at the interface between the vessel andthe conductance path. In this case, the pump down calculations will assume that the conductance path is at thebase pressure of the pump before the pump down starts.Total volume:This indicates the total volume of system model, including conductance volumes that have been added using theAdd cond volume check box.Selected Range start and stop:These are the start and stop pressure settings for the displayed pump station that can be changed using theStation settings button.
Be careful not to confuse these pressures with the System start and target pressures inthe system model. Although they can be the same as the station on and off pressures, Start and Target pressuresrepresent the total range of the model, and can encompass the total pump down calculations of all the pumpstations combined. It is possible, and probable, that you will set each pump station on and off pressures to somerange within the System start and target pressures.© 2011 Professional Engineering ComputationsSystem models1438.12.2 Pump Station Settings dialogActivated from a System Model, the Pump station settings dialog allows you to change several characteristics ofeach pump station.© 2011 Professional Engineering Computations144VacTran 3The pump station setting dialog shows the active and available ranges of all pump stations.
It graphs all pumpstations start and stop pressures against the system start and stop pressures for reference.Click to expand© 2011 Professional Engineering ComputationsSystem models145Renaming pump stationsEach pump station can be renamed by clicking on the station name buttons..Maximize range:Clicking on this button will change the start and stop pressures for the pump station so that they are at the limits ofpumps in the model.For example, if pump station 1 has two pumps,pump 1: range 760 torr to 10 torrpump 2: range 10 torr to 0.01 torrFor this example, maximize range will set the Start pressure to 760 torr, Stop pressure to 0.01 torrSystem model start and target pressure:Start and target pressure for the system model are displayed in the graph but cannot be changed here.
![](https://s.studizba.com/z.php?f=/templates/si/i/noavatar.png&w=100&h=100&t=1"){kind=avatar}
