Process Steam System - Cost (English Units)

Summary

This example demonstrates the fundamental concepts of the cost calculation features of AFT Arrow. The example illustrates how the cost calculation features can be used to calculate costs for a given system design.

Topics Covered

• Creating cost libraries

• Entering pipe, junction and fitting cost data into libraries

• Connecting cost libraries

• Using Cost Settings

• Using the Cost Report

Required Knowledge

This example assumes the user has already worked through the Beginner: Air Heating System example, or has a level of knowledge consistent with that topic.  You can also watch the AFT Arrow Quick Start Video (Metric Units) on the AFT website, as it covers the majority of the topics discussed in the Beginner: Air Heating System example.

In addition, it is assumed that the user has worked through the Beginner: Compressed Air System - Cost example and is familiar with the basics of  cost analysis.

Model Files

This example uses the following files, which are installed in the Examples folder as part of the AFT Arrow installation:

• Metric - Process Steam System.aro

• Metric - Process Steam System Costs.aro

• Process Steam System.dat - engineering library

• Process Steam System Costs.cst - completed cost library for Process Steam System.dat

• Metric - Process Steam System Pipe Costs.cst - completed cost library for Steel - ANSI

Problem Statement

After designing a process steam plant, it is necessary to calculate the system cost to determine the feasibility of the design. Use the cost calculation features to determine the initial cost of the system. Include material and installation costs for pipes and fittings.

Step 1. Start AFT Arrow

From the Start Menu choose the AFT Arrow 9 folder and select AFT Arrow 9.

To ensure that your results are the same as those presented in this documentation, this example should be run using all default AFT Arrow settings, unless you are specifically instructed to do otherwise.

Important: The GSC module and cost calculations can be used in the same run, but we are not going to do this here. Before proceeding, make sure to disable GSC by selecting the radio button for Ignore in the Modules panel in Analysis Setup.

Step 2. Define the Pipes and Junctions Group

Open the Metric - Process Steam System.aro example file listed above, which is located in the Examples folder in the AFT Arrow application folder. Save the file to a different folder.

Once the model is opened and saved to a new location, load the Base Scenario. This is the only scenario needed for this example, so right-click the Base Scenario and select Delete All Children. The workspace should look like Figure 1

Step 3. Define the Cost Settings Group

Open Analysis Setup and go to the Cost Settings panel. Turn on Cost Calculation by selecting the Calculate option at the top.

This example does not have any components for which energy costs can be calculated, so operational/energy costs will not be included in the Cost Report. For this example, leave the energy cost blank.

In the Cost Definitions section, select Material and Installation costs. Additionally, because we are only accounting for material and installation costs, there is no need to enter a system life period for costing purposes.

The Cost Settings panel should now resemble Figure 2

Step 4. Connect the Engineering Library

For detailed information on using the Library Manager, consult the AFT Arrow Help System.

Select Library Manager from the Library menu. Add the Process Steam System.dat engineering library file to the list of available libraries by clicking Add Existing Library at the bottom. Browse to the engineering library file in the AFT Arrow Examples folder. The engineering library should now appear in the list of available libraries.

Make sure the library is connected to the model - indicated by the check mark next to its name.

The Library Manager should appear as shown in Figure 3.

Any pipes and junctions for which costs are to be generated must be associated with an engineering library.

The engineering libraries associated with the junctions in this example are the AFT INTERNAL LIBRARY, and an external library called Process Steam System. The junctions in the model must be associated with one of these two engineering libraries to be able to access the cost data in the cost libraries we will be creating.

The pipes for this example are already using data from the Steel - ANSI pipe material library, so no modifications need to be made for the pipes.

The Bend and Tee junctions must be modified to use the component data contained in the external engineering library. Do this by opening the Properties window for each junction, and selecting the component name displayed in the Library Jct list. Make this change for all of the Bend and Tee junctions.

Step 5. Create the Cost Libraries

Refer to the AFT Arrow Help System for detailed information regarding creating and using cost libraries.

In order to calculate the material and installation cost for the pipes and fittings, these costs must be included. This will be accomplished by creating two new cost libraries. The first library will be associated with the engineering library that contains the pipe material data, and the second library will be associated with the engineering library that contains the fitting data.

Create a new cost library for the pipe costs

Create a new cost library for the pipe costs by opening the Cost Library window from the Library menu. Create a new cost library by clicking on the New button. When you click on the New button, you are prompted to choose the engineering library with which the cost library will be associated.

The piping material data used in the model comes from the default Steel - ANSI library, so the pipe cost library will be connected to this library. Select Steel - ANSI from the library list shown in the Select Library window, then click the Select button.

Note: Make this choice carefully, because once you have made the association you cannot change it.

Once the library is created, you must enter a meaningful description and select the cost units. Enter the following data on the General tab:

1. Cost Type = Monetary

2. Monetary Unit = U.S. Dollars

3. Description = Metric - Process Steam System Pipe Costs

4. Notes = This library is for the Process Steam System Cost Example File

Save the cost library to a file by clicking the Save button. Name the library Metric - Process Steam System Pipe Costs.cst. When prompted, choose to add the new library to the list of available and connected libraries. The information on the General tab should appear as shown in Figure 4. The selected library file information, cost type and monetary units, a description of the cost library, and any notes you have added will be displayed.

Note: The library file pathnames may be different than those shown in Figure 4.

For this example, you will enter Pipe Material costs for the pipes.

Enter the pipe material costs

After the pipe cost library has been created, select the Pipe Materials tab in the Cost Library window. This is where you will enter the material and installation costs for the piping.

The Pipe Materials tab shows all the pipes in the engineering library (Steel - ANSI pipe material library). 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. For this example, all of the pipe material costs will be entered at the type (schedule) level.

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 to create a new cost item in the table below. The new cost item will appear as a new column.

Each pipe size in this example has two non-recurring costs associated with it. The costs to be entered are the material and installation costs. Figure 5 shows the costs entered for 8-inch STD (schedule 40) Steel. Enter the non-recurring pipe costs for the pipe in this example, as shown below.

All pipes are STD (schedule 40) Steel - ANSI:

Cost Type	Material (NR)	Installation (NR)
Size (inches)	Cost (U.S. Dollars)	Cost (U.S. Dollars)
6	28.00	65.50
8	34.50	78.75
12	67.25	169.00
Cost Per	Length	Length
Cost Per Units	meters	meters

Create a new cost library for the piping components

To enter cost for a pump, or any other junction type, the junction must first be added to an engineering library. Cost data is then entered in a cost library associated with that engineering library. The piping components (bends and tees) used in this example have been added to an engineering library. Create a new cost library associated with the Process Steam System.dat engineering library with the following general information:

1. Cost Type = Monetary

2. Monetary Unit = U.S. Dollars

3. Description = Process Steam System Costs

Save the cost library to a file by clicking the Save button. Name the library Process Steam System Costs.cst. When prompted, choose to add the new library to the list of available and connected libraries.

Create cost scale tables for the bends

The model contains several 90-degree bend junctions. The cost of these bend fittings can be included in the cost calculation. The costs for these items will be accounted for in scale tables. Scale tables can be used to vary a cost with a parameter such as diameter (i.e., size). Once created, this scale table can be applied to the bend items.

The first table you will create is the scale table for the 90-degree bend installation costs. Select the Tables tab, and click the New Table button.

Enter the following data for the scale table on the New Scale Table window:

1. Name = Installation Table

2. Table Type = Diameter

3. Table Format = Cost

The window should appear as shown in Figure 6. After entering the data, click OK.

After the table has been created, enter the cost data for the table. Do this by selecting the table name in the Table list, then entering the cost values in the table provided. Enter the following installation cost data into the scale table:

Diameter (inches)	Cost (U.S. Dollars)
4	85
6	125
8	185.5
12	298
18	446

You do not need to enter data in the scale tables for every diameter in the model. If a diameter falls between two data points in the table, AFT Arrow will use the points on either side to linearly interpolate for a value. If the cost function is non-linear, you may need to add additional data points to achieve a more accurate cost value.

Create another scale table for the material costs using the following data:

Name = Material Table

Table Type = Diameter

Table Format = Cost

After the scale tables have been created, and the cost data entered, the Tables tab should appear as shown in Figure 7.

Add the costs for the bends

With the cost scale tables for the bends defined, the costs for the bends can be added. Select the Junctions tab. A list of all of the available junctions is displayed in Junction Components list.

The bends in the model are called Bend for Process Steam System Cost Example. Select this junction and add the material cost by clicking the New Cost button, and entering the following data:

1. Description = Material

2. Cost Type = Material (NR)

3. Use Size Table = Table of Costs

4. Multiplier = 1

5. Size Scaling Table = Material Table

Now add the installation cost by clicking the New Cost button, and entering the following data:

1. Description = Installation

2. Cost Type = Installation (NR)

3. Use Size Table = Table of Costs

4. Multiplier = 1

5. Size Scaling Table = Installation Table

The actual cost values used for the fittings are the values that were entered in the scale tables on the Tables tab. The scale table to use for each cost is specified when the cost is defined. After the cost data is entered, the Junctions tab should appear as shown in Figure 8.

Add the costs for the tees

Add the material cost for the tees by clicking the New Cost button, and entering the following data:

1. Description = Material

2. Cost Type = Material (NR)

3. Use Size Table = (None)

4. Cost (U.S. Dollars) = 150

5. Cost Per = Item

Now add the installation cost for the tees by clicking the New Cost button, and entering the following data:

1. Description = Installation

2. Cost Type = Installation (NR)

3. Use Size Table = (None)

4. Cost (U.S. Dollars) = 225

5. Cost Per = Item

Save the cost library and click the Close button.

Connecting the cost libraries

The cost libraries should have been added to the list of available libraries, and been connected to the example model. If they were not, you can use the Library Manager to connect the cost libraries now (see Figure 9). Refer to the AFT Arrow Help system for information on how to connect libraries using the Library Manager.

Step 6. Including Items in the Cost Report

The final step before performing a cost analysis is to specify which pipes and junctions you want to be included in the final cost report. This is done by choosing Include in Cost Report on the Cost tab in the Properties window for each pipe and junction to be included, as shown for Pipe 1 in Figure 10.

The Global Edit feature may be used to update this information for all of the pipes and junctions.

For this example, we want to include the costs for all pipes, bends and tees.

Step 7. Run the Model

Click Run Model on the toolbar or from the Analysis menu. This will open the Solution Progress window. This window allows you to watch as the AFT Arrow solver converges on the answer. Once the solver has converged, view the results by clicking the Output button at the bottom of the Solution Progress window.

Step 8. Examine the Output

The Cost Report is displayed in the General section of the Output window. View the cost report by selecting the Cost Report tab. The content of the Cost Report can be controlled from the Output Control window. Figure 11 shows the Cost Report for this example with the Material, Installation, and Total costs displayed.

The Cost Report shows the total system cost, as well as the individual totals for the material and installation costs. In addition, the Cost Report displays the detailed cost for each pipe, junction, and fitting that was included in the report. The items are grouped together by type, and a subtotal for each category is listed.

Cost analysis summary

The Cost analysis for the Process Steam System shows that the total initial system cost for the process steam system is $172,504. Of that cost, $52,203 was for Material costs and $120,301 was for Installation costs