LIQTHERM - Liquid Pipeline Thermal Simulation      
LIQTHERM simulates the steady state hydraulics of a heated liquid pipeline with several pump and heater stations, considering heat transfer with the surrounding medium. The pipeline may be buried or portions may be above-ground. Various liquid products may be injected or stripped at locations along the pipeline. The resultant blended liquid properties (specific gravity and viscosity) are calculated for each pipe segment at the flowing liquid temperature. Batching of different liquids can also be simulated by specifying the batch size, specific gravity and viscosity of each liquid batch. Pressure drop for each pipe segment is calculated using one of the various equations, such as Colebrook-White, Moody, Miller, MIT or Hazen-Williams. 

Multiple pump stations along the pipeline may be modeled, considering pump curve data. The pump performance data (flow rate, head and efficiency) may be specified for each pump station along with the pump configuration (series or parallel). If pump curve data is not available, each pump station may be assigned an average pump efficiency for calculating the horsepower required. Calculations can be performed such that maximum allowable operating pressure (MAOP) of each pipe segment is not exceeded. Optionally, the MAOP check may be turned off to determine the maximum pumping capability for a given pipeline and pump station configuration. Branch piping and parallel piping (pipe loops) off the main pipeline can also be modeled.           

The liquid temperature, specific gravity, viscosity and the pressure profile along the pipeline at the flow rates are calculated considering heat transfer with the surroundings. Using the input values of pipe, insulation and soil thermal conductivities, heat transfer and pressure drop calculations proceed along the length of the pipeline. The heat generated due to friction is included in the temperature calculations. For high viscosity liquids, the API method for calculating the effect of high viscosity on pressure can be included, as an option. If heaters are present, the heater duty at each heater station site is calculated based on the specified heater outlet temperature, heater efficiency and the calculated liquid temperature at the heater inlet. The total pump horsepower required at each pump station is calculated, by considering the combined pump performance based on the pump configuration. 

           

The input data consists of pipeline profile (distance, elevation, pipe diameter and wall thickness, pipe roughness, MAOP), thermal conductivity data (for pipe, insulation and soil), soil temperature, burial depth of pipe (cover), liquid flow rates, specific gravity, specific heat and viscosity of each liquid at two distinct temperatures, heater station data (inlet temperature, heater outlet temperature, heater efficiency) and delivery pressure required at the end of the pipeline. All of the above properties are considered variable along the length of the pipeline. Thus the pipe roughness may be varied at specific points along the pipeline to simulate different internal conditions of pipe such as internally coated pipe versus un-coated pipe. Similarly, the pipeline may be buried for a portion of its length and the rest may be above ground. Pipe may be insulated with a certain thickness and type of insulation for a specified length, while the remaining pipe may be bare or un-insulated. The properties of the liquid, such as specific gravity, viscosity are specified at two known temperatures for determining the property versus temperature correlation. In addition, the locations of pumps and heater stations are input along with the minimum suction pressure and maximum discharge pressure at each pump station. If pump curves are not available, an average pump efficiency for each station is input. If pump curve data is available, efficiencies will be automatically calculated by the program.

Most data are entered in Microsoft Excel compatible spreadsheets that results in easy editing and cut and paste operations via the Windows clipboard. The spreadsheets are saved in a proprietary file format compared to the familiar .XLS file extension for Microsoft Excel. For the sample problem, pipeline profile data (distance, elevation, pipe diameter and wall thickness, pipe roughness, MAOP)  is saved in a file designated as MyPipe001.DAT.  All other data for the specific pipeline such as thermal conductivity data,  pump and heater station data, liquid flow rate data etc. are saved in a text file named MyPipe001.TOT. Auxilliary data files such as pump curves, liquid data that may be used with other pipelines will be saved separately from the specific pipeline data. For example in the MyPipe001.TOT file they may be references to pump curves such as PUMP1.PMP, PUMP2.PMP etc. All liquid properties are stored in common Liquid Properties Database files.

If the input pipeline flow rate is too high for the pumps or require pipeline pressure exceeding MAOP, the program iteratively calculates the maximum pipe inlet flow possible. This feature can be turned off, if desired, as indicated above. The amount of pump impeller trim required to minimize energy lost due to throttling can also be calculated. LIQTHERM can be used for the design of a new pipeline or checking capabilities of existing pipelines. The hydraulic gradient showing the pipeline pressures superimposed on the pipeline elevation profile along the pipeline can be plotted. The flowing liquid temperature profile along the pipeline may also be plotted, if desired. 

The program output consists of the flowing liquid temperature, specific gravity, viscosity, and the pressures along the pipeline, along with the heater duty and horsepower required at each heater station and pump station. 

In each data entry screen, default data is provided in most cases. Help is available on each screen and on the status bar at the bottom of each data entry screen. 

The calculated results are displayed on the screen, as well as saved in a disk file for later viewing or printing. A printed hard copy of the calculated results can be created simultaneously with screen output.

For quick economic analyses, the capital cost and  operating cost   for a pipeline system can be calculated. The annual cost of service and transportation tariff can also be determined for various project financing scenarios.


Features

Use LIQTHERM to calculate the pipeline hydraulics, temperature and pressure profile, pump station HP required, heater duty and pump performance. Despite the complexity of the program it is very user friendly. Online HELP is available for all data entry screens and the program has extensive error checking features.  In addition, the How do I? screen provides further help on specific topics, such as creating a pipe data file, pump curve, etc.

Pipe diameter, wall thickness, roughness, burial depth, insulation thickness, insulation conductivity and the ambient soil temperature can all be varied along the pipeline. An Microsoft Excel compatible spreadsheet for data entry makes it easy to create and save pipe data files.

Heaters may be installed anywhere along the pipeline, including at pump stations.

Liquid may be injected or delivered at various points along the pipeline.

Several batches of different liquids transported in series in the pipeline can be modeled.

Pipe may be modeled above ground or below ground or a combination of both.  Isothermal simulation is included.

Drag Reduction can be simulated for specified sections of the pipeline.

Pressure drop calculations may be based on Moody, Colebrook, Hazen-Williams, MIT or Miller equations.

The pipeline may have several pump stations with pumps in series or parallel at each pump station. Calculations can be performed with or without considering pump curve data. There may be a maximum of 5 pumps at each station. Pumps can be in series or parallel configuration. 

The amount of pump impeller trims required to minimize throttling can be calculated.

Variable speed pumps may be modeled.

Individual pump curve data can be viewed, edited and plotted on the screen or the printer.

The maximum pipeline throughput for a given MAOP can be calculated for a specified pump station configuration.

The hydraulic pressure gradient can be plotted superimposed on the pipeline elevation profile. 

The pipeline may have branches and parallel loops. Maximum number of branches and loops is limited to 50. Each branch pipe may have up to 500 data points compared to a maximum of 1000 sets of data points for the main pipeline.  Flow injection and stripping are allowed on the branches.

 Running the Program
A toolbar consisting of icons for commonly used menu items is available below the menu bar. These menu items or commands can be accessed by clicking on the icons. As the mouse is moved over an icon, a tool tip help appears explaining the function of each icon.

The Liquid (Beaker) icon is used for entering the liquid injection and delivery data along the pipeline. Also includes a Liquid Properties Database that can be updated regularly with liquid properties (specific gravity and viscosity versus temperature).

The Graph icon is used for selecting the different graph types for hydraulic pressure gradient, temperature profile along the pipeline.

You can use the e-mail icon         on the toolbar to send the results of calculations to a colleague or contact SYSTEK in the event of a problem with the software. The Notepad icon is to launch Windows Notepad, if you want to do some quick text editing or cut and paste results.

The pull down menus (such as File, Edit etc.) can be accessed by using the mouse or pressing Alt together with the underlined letter of each menu item ( F for file, O for option etc.).

The pull down menu under File, lets you create, open, close, save or print data files.  The pull down menu under Edit  lets you Cut, Copy or Paste  selected (highlighted) data from the spreadsheet to the Windows clipboard or from clipboard to the current cursor location in the spreadsheet.   Accelerator keys, such as Ctrl-X for Cut and Ctrl-I for Insert row are available for several menu items. 


The pull down menu under Options has the following :

Units - For selecting English or Metric units of calculation. Also to specify the unit of measurement for the distance along the pipeline, the pipeline flow rate and units for pump curve data.

Pump curves - For choosing pump curve data for checking data or getting a graphical plot of the pump curve. Also includes options for predicting pump performance for speed changes and impeller diameter changes  and calculating impeller size or speed required to match a given design point (Q, H).

Formula - For selecting the pressure drop formula to be used. Options include Colebrook-White, Miller, Hazen- Williams, Moody friction factor and the MIT equations.

Batching - For specifying different liquid batches and properties. 

Drag Reduction - For using drag reducer in the pipeline. 

Interpolate - To interpolate the elevation of pipeline at an intermediate mile post.

The pull down menu under Stations has the following:

Under Pump Stations, data such as name, location, the ON/OFF status,  pump curve data and minimum pump suction pressure are input.  If pump curves are not used, a fixed pump efficiency may be specified for each pump station for calculating the HP required. 
 You may also choose to include liquid heating due to pump inefficiency.  
 

Heater Station  - for entering individual heater station data. 

The Valve Stations is used for specifying minor pressure drop devices. These include valves, fittings and other custom components such as meters and filters along the pipeline. The K-values needed for calculating the minor losses through valves and fittings are built into the program. You may also specify the actual pressure drop through a valve, fitting or custom device. In the latter case, the K-value is not used.  A tank may be specified instead of a pump station at the beginning of the pipeline.

The pull down menu under Conductivity is used for entering the thermal conductivity of pipe, soil and insulation and the insulation thickness and pipe burial depth along the pipeline.

The pull down menu under Branches/Loops has the following:

Branches - for entering the branch piping data. 
Loops   -  for entering the information on pipe loops.

The menu bar item on the extreme right titled Help provides information about the program, such as version number, user registration and general help on the program. 


Notes

In the main program window, choose File from the menu bar. Choose Open to open an existing file. Select Pipe data file from the next dialog box and you are then presented with the File/Open dialog box to choose the name of the pipe data file. As a convention, pipe data files are designated with a file name extension of .DAT. Similarly, pump curve data files are designated with a file extension of .PMP. Therefore,  a pipeline data file may be MYPIPE001.DAT whereas a pump curve data file may be shown as DIMPTON.PMP.

Type MyPipe001.DAT in the dialog box. The sample pipeline data file opens up. This pipe data file contains the pipeline information for the sample problem.

 

               


The pipe delivery pressure at the end of the pipeline and the minimum pipeline pressure are input in the main screen above.
If a new pipe data file is to be created from scratch, choose File followed by New. A blank editing window (spreadsheet) will be presented for entering the data. Input the pipeline data similar to the sample problem. 

To save changes, Select File /Save from the menu bar. 

For further explanation on creating data files,  creating pump files, using drag reduction etc. check  the manual provided. 

 Entering Liquid Properties, Pressures etc.

Next select Liquid from the icons or menu bar. This screen lets you input distance, flow rate, temperature and the product that flows through the pipeline. 

                           

To input the properties of the product, double click on the product cell. This opens up the database screen for inputting the properties such as specific gravity, viscosity and specific heat of the liquid. The program requires liquid specific gravity as a decimal number. Liquid viscosity can be input in centistokes, SSU, SSF or centipoise. 

 

Entering Pump and Driver Data
The pump station data (names, locations,  number of pumps, their configuration, pump curve data and the installed HP) are entered under the menu item Stations as follows:                            

                   

 Next, click on the Calculator icon to start calculations. In the resulting dialog box enter the date, project title, case number and select the necessary checkboxes and press ok.

The check box designated as MAOP check indicates that the calculated pipeline pressures will be checked to insure that they are below the Maximum allowable Operating Pressure (MAOP) of the pipeline.

The project title may be a maximum of 4 lines. Press the Tab key to move from each line to the next to enter the additional lines for the project title. Notice that the pipe data file name and the corresponding output file names are shown as MyPipe001.DAT and MyPipe001.OUT respectively. If the input pipe data file were XYZ.DAT, the corresponding results of calculation will be stored in a file 
named XYZ.OUT.

The calculated results are included at the end of the  manual under the heading Sample Output.

     

           

If pump trim calculations were specified, the trimmed pump curve data is automatically saved as a modified file name. For example the pump curve COMPTON.PMP will be trimmed and the modified file name would be COMPTONTRM.PMP.

If the throttle pressure is excessive, sometimes the results of the pump impeller trim calculations will display a warning message "TOO MUCH TRIM REQUIRED!". This means that the pump is too big for the particular application and trimming is not economical. A smaller pump needs to be specified. See next section on making changes to the data file, for running different cases.

Each column in the spreadsheet is for a specific data for the pipeline. Each row represents a specific location along the pipeline. As the cursor (arrow) keys are moved around in the spreadsheet cells, the status bar at the bottom of the screen briefly describes the information to be entered in each cell. After each numeric entry, press Enter and move to the next cell by using the arrow keys. The first column is for the distance measured from the origin of the pipeline, such as mile post. Each subsequent location of the pipeline is measured from the beginning of the pipeline and hence the first column is the cumulative length of each point on the pipeline measured from the beginning, also designated as mile post location (m.p.). 

Note that unlike other hydraulic simulation models, the distances are cumulative and not pipe segment lengths. 

The second column is for the elevation of the pipe at that mile post location, measured above some datum, such as sea level. The third, fourth and fifth columns represent the pipe outside diameter, pipe wall thickness and pipe roughness at this location. The pipe diameter, wall thickness and roughness entered at a specific location represent those for the pipe segment downstream of that milepost location. Thus, if the first two milepost locations are 0.0 and 15.0, the diameter, wall thickness and roughness entered at 0.0 milepost are for the pipe segment from 0.0 to the 15.0 location. The diameter, wall thickness and roughness entered at milepost 15.0 are for the next pipe segment starting at milepost 15.0. Accordingly, for the very last milepost location (the last data row 
of the spreadsheet) the diameter, wall thickness and roughness entered should be a duplicate of the immediately previous location, since there is no pipe segment downstream of the last milepost. 

The next column entry is the maximum allowable operating pressure (MAOP) for the pipe at that milepost location. If you double-click  with the cursor in the cell containing the MAOP, a dialog box opens up. This dialog box can be used to verify or calculate the MAOP of the pipe. It also calculates the hydrostatic test pressures for pipe hoop stresses of 90% and 100% of the specified minimum yield strength (SMYS) of pipe material. 

The status bar at the bottom of the spreadsheet window briefly describes the expected data in each cell. 

Note: A maximum of 1000 points are allowed in the pipe data file and a maximum of 50 pump stations can be specified. 
 


A pump curve file is created by entering the flow rates, heads and efficiencies of the pump at several points from the pump manufacturer’s performance curve. From the File/Open menu, choosing a pump file name (e.g. DEMO.PMP) will open up the pump curve data in a spreadsheet. To create a new pump curve, open an existing pump data file, make changes to the data and use the Save As option from the File menu to save under the new file name. 

From the spreadsheet editor, double-clicking  with the cursor on the pump data file name, will open up a second spreadsheet for editing the pump data, after confirmation. 

The maximum set of data points allowed on a pump curve is 15 sets. For each pump station, a maximum of 5 pumps either in series or parallel can be specified. Therefore 5 pump curve data files can be specified per pump station on the main spreadsheet describing the pipeline data.

The Batching dialog box shows some typical information for a hypothetical pipeline system. The program automatically displays the current pipeline line fill volume. For each liquid batch, enter the batch size (in barrels) followed by the corresponding specific gravity and viscosity in the appropriate spreadsheet cells.

               

Click the Calculate Batch Location button and the program adjusts the last batch size to fill the pipeline volume and the beginning and ending mile post location for each liquid batch is calculated and displayed. If the batch sizes are too large for the pipe line fill volume, a warning message is displayed and you are given an opportunity to correct the input data. Since the program automatically calculates the beginning and ending mile post location of each batch (and the corresponding interpolated pipeline elevation ), this information can optionally be inserted in the main pipeline spreadsheet. The pipe data file is thus updated automatically. When the pipeline data file is loaded the next time, the newly created mile post locations will show up on the spreadsheet. 

Once the above batch configuration is specified, hydraulic calculations can be performed by clicking on the Calculate icon. You can then simulate movement of the batches along the pipeline by altering the batch sequence, sizes and locations and re-running the calculations.

For a batched pipeline system, all liquid input should originate at the beginning of the pipeline. No intermediate injection or delivery points are allowed in a batched pipeline system in the current version of LIQTHERM.


 Quick Pressure Drop 

Upon clicking the icon with the letter "Q", the “Quick Pressure Drop” option screen opens up.

          

           

This is for quick calculation of isothermal pressure drop in a pipe segment. For a given flow rate, pipe diameter, pipe length, elevations, specific gravity and viscosity, the Quick Calc Option calculates the inlet or outlet pressure, given one of the two pressures. If the outlet pressure is specified, the inlet pressure is calculated and vice versa. You may also choose the pressure drop formula (such as Colebrook-White, Hazen-Williams etc.) to be used. Liquid viscosity may be specified in centistokes, centipoise, SSU etc. The pipe roughness is specified in the pull down menu as in the main program.

Technical Support

If you have a question about LIQTHERM, first refer to the Tutorial section in the User Manual. If you cannot find the answer in the Tutorial Section or the Troubleshooting section of the User Manual, contact SYSTEK as described here. Please have your program disk and serial number handy. Free Technical Support is provided only for the first 60 days of the date of software purchase. After the initial free technical support period, you may purchase an Annual Program Maintenance and Technical Support Plan. Please call SYSTEK for pricing options.

We welcome comments and suggestions from users. Please give us your thoughts on how LIQTHERM can be improved further. Our goal is to make this software the most user-friendly program available for engineers. 

You may send us your comments by regular mail or email.

Contact SYSTEK as follows:

SYSTEK Technologies, Inc.
Phone: (928) 453-9587
Fax:    (928) 453-3583
Email:  info@systek.us
Web site: www.systek.us

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