The AFT Fathom XTS module displays transient output in a number of places in the Output window.
Each of the summary tables in the General Output section has a companion transient summary tab which displays the summary data at each time step in the transient run. Each junction included in the summary is included in the transient summary. The transient summary data for each junction may be expanded or collapsed by clicking the + or – sign beside the junction data list. The entire list may be expanded or collapsed by clicking the button in the top left-hand corner of the transient summary window. Figure 6.8 shows the Pump Transient summary tab, with the data for Pump J3 collapsed, and Pump J5 expanded.
Transient progress displayed
Figure 6.7 The Solution Progress window shows the progress of the transient analysis.
Figure 6.8 The transient summary tables (such as Pump Transient above) can be expanded or collapsed to improve viewability.
The Quick Graph feature can be used to conveniently plot transient data for quick examination. To use the Quick Graph feature, place the mouse cursor over the column of transient data you wish to examine. Then, right click with the mouse, and select Quick Graph from the list of options.
Figure 6.9 illustrates how to do this for J1 Reservoir Liquid Height vs.
Time. Figure 6.10 shows the resulting graph. The graph illustrates how the liquid level in the Reservoir drops with time. Figure 6.11 shows a Quick Graph plot of the volumetric flow rate through pipe P8. The plot shows the change in flow rate as each of the flow demand transients takes place.
Figure 6.9 The Quick Graph feature can be accessed from any transient data column using the right mouse button.
Figure 6.10 The Quick Graph feature can be used to quickly plot transient data from the Output for review.
The Graph Results window may also be used to create a full range of graphs related to the XTS transient output. An additional graphing feature available for XTS is transient output animation. Profile plots for flow paths can be animated to dynamically view transient effects. Figure
6.11 shows how to animate the transient response of the Volumetric Flow Rate for the flow path from the pump J3 discharge to assigned pressure junction J11. Figure 6.12 shows the resulting animation plot at time = 90 seconds.
Select Animate to use the animation feature Select the profile path Select the parameter to animate
Figure 6.11 The transient results for flow paths profiles can be viewed dynamically using the animation feature.
Similar to the transient summary data, the transient tabs in the Pipe and Junctions sections of the Output window are used to display the transient data for each pipe and junction at every time step, as shown in Figure 6.13. This transient data can be expanded or collapsed in the same manner as in the General Output transient summaries.
The animation can be paused or stopped at any point
The current time step is displayed
The speed of the animation can be controlled
Figure 6.12 The animation feature dynamically displays transient parameter data.
Figure 6.13 The Transient tabs in the Pipe and Junction sections show results for all time steps. The first number in the left column is the pipe/junction number and the second (in parentheses) is the time (in minutes here).
Figure 6.14 shows the output data for the pipes and junctions, found on the Pipes and All Junctions tabs, at the initial time step, Time = 0 minutes. The output for all of the pipes and junctions can be displayed at any time step by using the slider bar located at the bottom of the Output window. Figure 6.14 also shows the pipe and junction data at Time = 1 minutes.
When junction event transients occur, these events are recorded and displayed in the General section of the Output window. The events are displayed on two different tabs. The first tab sorts the events by junction number, and the second tab sorts the events by time, in the order in which they occur. The tabs are shown in Figure 6.15.
Slider bar allows current time to be changed
Time is currently zero minutes
Time is currently 1 minute
Figure 6.14 The Pipe and Junction output can be displayed at any time step using the slider bar at the bottom of the Output window (Time = 0 minutes shown above and 1 minute below).
Figure 6.15 The occurrence of event transients are recorded in the General Output section.
The event messages show the demand flow transients ocurring at 30-second intervals, as expected. Figure 6.16 shows the affect of the demand transients on the volumetric flow rate through pipe P8. The plot shows how the change in flow rate corresponds to the times when the transient events occur.
Figure 6.16 Volumetric flowrate through Pipe 8 (inlet to J8 control valve) increases over time as each of the demand point transients occur.
The event messages also show the auxiliary pump starting at just over 1 minute into the transient analysis. Figure 6.17 shows a plot of the transient pump speed, and clearly shows the pump starting at this time.
The auxiliary pump startup event was based on the control valve exceeding a percent open value of 50%. Figure 6.18 shows the control valve percent open vs. time. The plot shows the valve percent open exceeded the initiation criteria at just over 1 minute. The plot also shows that the control valve percent open continues to increase, even after the last demand transient has occurred. The valve is very close to its fully open state at the end of the analysis. This is due to the fact that the supply tank continues to drain as the analysis progresses, reducing the amount of hydrostatic head available upstream of the pumps.
Figure 6.17 The auxiliary pump transient occurs at just over 1 minute into the transient analysis.
Figure 6.18 The control valve open percentage exceeds 50% at just over one minute into the analysis, which triggers the auxiliary pump startup transient.
Analysis summary
This example illustrates how XTS can be used to analyze dynamic system behavior. Time and event-based transients give the user the flexibility to define a large variety of dynamic responses that can occur in piping systems. The ability to use both text and graphical means to display the transient output allows the user to clearly understand, and communicate, the impact of transient behavior on system designs.
C H A P T E R 7
Working With Cost Databases
Cost databases provide the information needed to perform cost calculations in the CST module. Users can build their own cost databases using tools in AFT Fathom. This chapter discusses how to build cost databases.
Sources of cost data supported
At present, the AFT Fathom CST module supports cost data in AFT Cost Database format.
Types of databases supported
AFT Fathom uses four types of databases:
• Engineering databases – Maintains equipment performance and size data
• Cost databases – Maintains cost data for the equipment
• Energy Cost Databases – Maintains detailed cost of energy for pump calculations
Engineering and cost databases
The first part of this chapter focuses on the first two database types:
Engineering Databases and Cost Databases. Energy Cost Databases are discussed in the AFT Fathom 7.0 User’s Guide.
There can be multiple cost databases for each engineering database. This allows cost data sets to be maintained separately from the engineering data. This can be useful for maintaining costs in different currencies or differences based on geographical location or times of the year.
AFT Fathom engineering and cost databases can be set up on local or wide area networks (see AFT Fathom 7.0 User’s Guide Chapter 7). AFT Fathom’s engineering databases are nearly identical to the traditional AFT Fathom database used in versions 5.0 and before. Figure 7.1 shows how engineering and cost databases fit into AFT Fathom.
Cost Database window
The Cost Database window is opened from the Database menu. This window allows you to create a cost database for items that are in a specific engineering database. Cost can be entered for pipes, junctions, and pipe fittings & losses. The costs can be of several types:
1. Material 2. Installation 3. Maintenance
Connected Databases
Figure 7.1 Relationship between engineering and cost databases in AFT Fathom.
One time vs. recurring costs
AFT Fathom can include costs that occur once up front (i.e., first cost or capital cost) and recurring costs such as maintenance.
The Cost Settings window allows you to input the Cost Time Period.
This affects all recurring costs. Typically this will not affect non-recurring costs, except when non-non-recurring costs occur at some future
time. An example would be a phased project where later phases incur non-recurring costs, but these do not occur until some later time.
Creating cost databases
Before a cost database can be setup, an engineering database must exist.
The engineering database can be an AFT Fathom internal database, which means that it was created by AFT and included with the AFT Fathom software. An example of an internal database item is the steel pipe materials available in the Pipe Specifications window.
Figure 7.2 When creating a cost database, you must first associate it with an engineering database.
Other databases controlled by the end user are the local user database and external databases that are connected in the Database Manager.
To create a cost database, open the Cost Database window from the
the New button. The Open Available button allows you to open a cost database that is currently available in the Database Manager. Finally, you can open any cost database by clicking the Open Any button and browsing to the database file.
When you click on the New button, you are prompted to choose the engineering database with which the cost database will be associated (Figure 7.2).
Important: Make this choice carefully, because once you have made the association you cannot change it.
After you have made changes to a new or exiting cost database, click the Save button to save those changes, or Close button to exit with saving the changes.
Once the database is created, you should enter a meaningful description and select the cost units (see Figure 7.3).
Figure 7.3 General information for new cost database.
Pipe material costs
The Pipe Materials tab shows all the pipes in the engineering database (Figure 7.4). Costs can be entered at several levels. You can enter costs at the material level, the nominal size level, and finally at the type (i.e., schedule) level. Costs entered at the material level apply to all nominal sizes and types in that material type. Costs entered at the nominal size level apply to all schedules within that nominal size. Costs entered at the type (schedule) level apply only to that type.
To enter a new cost, navigate to the material, nominal size and type combination for which you want to enter a cost. Click the New Cost button, and a new cost item is created in the table below. The new cost item will appear as a new column.
Figure 7.4 Example of pipe material cost data
Some cells are displayed in black, which means they are not relevant to the type of entry selected.
Non-recurring costs
Pipe non-recurring costs can be entered as cost per length (e.g., dollars per foot) or cost per mass (e.g., dollars per pound). Enter the cost in the Cost field, and select whether the cost is per length or per mass in the
“Cost Per” field. Finally, select the units of length or mass in the Cost Per Units field.
Recurring costs
Recurring costs are entered as cost per time per length or cost per time per mass. Because recurring costs can change over time for various reasons, a scaling table can be specified. This is done in the Time Scaling Table field. If no scaling table is selected, the costs will be assumed to be constant over time. On the other had, selection of a scaling table will cause the costs to change over time, perhaps increasing or decreasing. Scaling tables are created on the Tables tab, and will be discussed later in this chapter.
Junction costs
Costs can be entered for all junction types except for Volume Balance junctions. To enter cost for a junction, it must first be in an engineering database. Cost data is entered in a cost database associated with that engineering database.
Figure 7.5a shows an example of entering cost data for a bend junction.
Here the bend is a standard elbow made of steel.
Deleting costs
To delete a cost item, select the column in the cost table and click the Delete button.
Non-recurring costs, non-pumps and control valves
For non-recurring cost types for junctions that are not pumps or control valves, there are three ways to enter junction cost data that captures the diameter dependence of the junction. The diameter used for dependence is that of the upstream pipe of the specific junction. These are the three ways:
1. Specify the Use Size Table as “none”, enter the cost in the Cost field, and in the Cost Per field specify the cost as per Diameter as
shown as Cost #2 in Figure 7.5a. When the Cost is per Diameter, the Cost Per Units field will allow you to specify if the cost is per inch, per foot or otherwise. This cost will then vary linearly with diameter.
This method offers the least cost precision.
2. Specify the Use Size Table as Table of Costs, enter the cost in a table of cost vs. diameter as a size scale table (on the Tables tab), and then select the table in the Size Scaling Table field. Cost #3 in Figure 7.5a uses the scaling table called “90 deg. Steel Acq.”.
3. Specify the Use Size Table as Table of Multipliers, enter the cost in the Cost field, enter a table of cost multipliers vs. diameter as a size scale table (on the Tables tab), and then select the table in the Size Scaling Table field. This is shown as Cost #4 in Figure 7.5a.
Figure 7.5a Examples of junction non-recurring costs
Recurring costs, non-pumps
Non-pump junction recurring cost types have available the same three options to account for recurring costs that vary with diameter as the preceding discussion for non-recurring costs. In addition, how the costs vary over time is specified.
The cost over time variation is specified in the Time Scaling Table. If the table is specified as none, the cost over time is assumed to be constant. If you want to vary the cost over time, you can specify a Time Scaling Table to vary the cost. Scaling tables are created on the Tables tab, and will be discussed later in this chapter. Cost #5 and #6 in Figure 7.5b show examples.
Figure 7.5b More examples of junction non-recurring and recurring costs
Pump and control valve costs
The cost data for pump and control valves function differently than for other junctions. Rather than cost data that depends on diameter, pump cost data is entered as it depends on power. Control valve cost data is entered as it depends on the Cv value. This applies to both recurring and non-recurring costs.
Pump junctions are also the only junction type that includes
operation/energy costs. These are setup in a separate type of database called an Energy Cost Database.
Costs for tees and branches
Cost data for tees and branches can be entered as a function of diameter.
But with multiple connecting pipes, which diameter should be used as the cost basis?
AFT Fathom always obtains the cost for tees and branches based on the largest diameter of any connecting pipe.
Pipe fitting & loss costs
Pipe fittings & losses cost specification functions the same as non-pump junctions, with the exception that costs can be associated with a
particular pipe material and size. Costs for Pipe Fittings & Losses from the AFT Fathom internal database can be entered when the cost database is associated with the internal engineering database. Costs for user specified Pipe Fittings & Losses would be associated with the Local User Database or other external database in which the engineering information has been saved.
Figure 7.6 Scale table example of a table of costs.
Figure 7.7 Scale table example of a table of multipliers.
Scale tables
Scale tables are used to vary a cost with time, diameter (i.e., size), power, or Cv. The same scale table can be applied to multiple cost items, whether pipe materials, junctions, or pipe fittings & losses.
Time scale tables are always based on a multiplier. This is the format of the table (see Figure 7.6). The diameter and power type tables can have the format of a multiplier, or the format of actual cost. When the format is a multiplier, the multiplier is obtained from the table and multiplies a base cost value of a cost item. When the format is a cost table, the actual cost is obtained from the table and then multiplied by a scalar multiplier for an item. By default, the item’s multiplier value is 1. Figure 7.6 shows an example of a table of costs, and its usage is shown in Figure 7.5a, Cost #3. Note in Figure 7.6 in the table at the right that the parameters are Diameter (in inches) vs. Cost (in U.S. Dollars here).
Figure 7.7 shows an example of a table of multipliers, and its usage is shown in Figure 7.5a, Cost #4. Note in Figure 7.7 that the table shows a Diameter (in inches) vs. Multiplier (with no units).
Figure 7.8 Cost multipliers can be entered on the General tab that multiply all items in the cost database.
Global multipliers in cost database
To account for cost fluctuations perhaps due to geographic or seasonal causes, global cost multipliers for all items in the cost database can be entered in a table on the General tab. Figure 7.8 shows an example.
These multipliers are built in to the database.
Global multipliers in Database Manager
Multipliers on cost data can also be applied in the Database Manager (Figure 7.9). While Cost Database multipliers (discussed in previous section) are built into the database, and may be beyond control of the user, the Database Manager multipliers are more flexible and under complete control of the user.
General use of Database Manager is discussed in the next section.
Figure 7.9 Global multipliers for cost databases in Database Manager.
Using cost databases
To be used in an AFT Fathom model, cost databases must be connected.
To connect a cost database, open the Database Manager from the Database menu (see Figure 7.10). Since each cost database depends on an engineering database, the engineering database must also be
connected.
To connect an engineering or cost database, first make it available using the Add Engineering Database or Add Cost Database menu selections on the Edit Available list button. This adds the database to the list of Available Databases at the top.
Once available, click the Add to Connections button to add it to the list of Connected Databases below. Note how the cost databases in both the
Once available, click the Add to Connections button to add it to the list of Connected Databases below. Note how the cost databases in both the