INTRODUCTION There are two program files provided on the disk. The program named NETWORK.EXE is designed to work on IBM compatible computers that are limited to 640 Kbytes of memory. The program called NETEXP.EXE will work on IBM compatible computers that have EXPANDED memory. A driver is required ( such as LIM-386 ) in your CONFIG.SYS file to enable the program to use the upper memory of your computer. The NETEXP program can use up to 8 Mbytes of expanded memory to handle networks with over 2000 pipes. The basic network program is limited by memory to systems of less than 1000 pipes. The programs work best on systems with hard disks, since the programs makes use of frequent disk operations to read in the various screens in the program. To install the programs simply copy all the files on the disk to a subdirectory of the hard disk. The files with extensions PIC and INP are required as well as the EXE files for the program to operate. NETWORK ANALYSIS Large complex networks of pipes and pumps are a common feature of many chemical plants, both for the distribution of process streams and utilities such as cooling water. Large networks also are found in the petroleum, natural gas, and water distribution systems. A pipe network consists of groups of pipes and piping components that are joined together at Nodes. The network can consist of loops typical of water distribution systems or highly branched systems typical of flare systems. It is of interest to calculate the steady state behavior of the network under various conditions of output flowrates, pump pressure heads etc. The solution of pressure drop in a single phase line is simple, but pipe networks are extremely difficult to solve by hand techniques due to the iterative nature of determining the interactions of the flow on various upstream and downstream loops and branches. The problem consists of determining all unknown Node pressures and pipe flow rates given the information known about the network. This information consists of the layout of the pipe network including the manner in which the pipes are connected. The pipes diameters, and length. All fittings on the pipes. The charactistics of pumps in the system. And all known flows and pressures that are fixed at specified Nodes. The first attempts on this problem were based upon the Hardy Cross method. In the precomputer days the Hardy Cross method was used. This method applied Newtons method considering individual loops of piping and laboriously solving them one equation at a time until convergence was reached. This method was generally slow and frequently did not work. The method used in this program is based upon Newton-Raphson techniques with internal correction factors applied to improve convergence. The Newton-Raphson approach is the fastest method to achieve solution, but it requires a reasonably accurate estimate of the initial pressure profile in the network to arrive at a solution. Consequently, the network program will estimate the unknown node pressures from the information supplied for fixed node pressures and flow rates. PROGRAM OPERATION The most important work needed to operate this program is done with the computer off. It is first necessary for you to sketch up the network that you wish to solve before using the computer. This sketch must show all pipes and nodes and all the nodes and pipes must be numbered. The sketch should also show elevations if a liquid system with varying grade levels is to be solved. The sketch should show all pumps, fittings, control valves and other known pressure drops. All flows into and out of NODES should be shown if they are to be specified. All pressures to be specified should be added to the sketch. This sketch should be as neat and complete as possible, particularly for a large network, since errors and extensive changes may require the network to be reentered. An approximate guesstimate of the pressure profiles for the various nodes should be made. The program can generate its own initial guesses however from limited information on fixed pressures, however the users estimates will be used when provided. The program is started from the hard disk by typing the name of the program NetWork.EXE from the DOS command line. If the Expanded Memory version is to be used type the name NETEXP.EXE at the DOS command line. The program will load and the Main Menu screen will be shown on the monitor. The various features of the program are addressed by pressing the command keys F1 to F10 from the main menu. The programs operation is terminated by pressing the ALT key followed by the Q key. MAIN MENU F1 HELP F2 INPUT FLUID DATA F3 INPUT PIPE DATA F4 INPUT NODE DATA F5 REVIEW INPUT DATA F6 REVIEW RESULTS F7 NEW PROBLEM F8 PRINTER OPERATION F9 DISK OPERATIONS F10 RUN PROGRAM ALT Q = QUIT PROGRAM The function of the various keys are described as follows: F1 The F1 key will show a help screen that give a abbreviated instructions to the program. F2 The F2 key is used to input the general physical properties of the fluid that flows through the lines. F3 The F3 will input the Pipe information F4 The F4 key will input the Node information F5 The F5 key will allow you to review a summary of the input information. F6 The F6 key will review a summary of the results for both Nodes and Pipes. F7 The F7 key will erase all information on the network and allow you to run a new case. Save the data before pressing the F7 key. F8 The F8 key will print out the input or results of the network calculation F9 The F9 key permits disk operations such as saving the network input data, Loading a new data set from the directory or changing the directory. The network data should be saved before printing the data. F10 The F10 key will run the program to solve the network. It is recommended that the input data be saved before running the program. FLUID INPUT After you have pressed the F1 key a window will pop up that will request that you press either the F1 key to select a liquid or the F2 key to input the gas properties. The program will work with either liquids or gases, but not both. If the F1 key was pressed then a window will pop up requesting that you input the liquids density in Lb/Ft3 and the viscosity in Centipoise. If the F2 key was pressed a window will pop up that requests the Molecular Weight, Temperature, Viscosity in Centipoise, the Compressibility factor Z and the K ratio (Cp/Cv) of the gas. The fluid properties can also be altered for each line on the pipe input section of the program, but these general properties must be added first. This step is the first activity that you need to perform in inputting the problem description. PIPE INPUT DATA The F3 key is pressed to input the pipe data. The pipe input screen will come on the monitor and request the total number of pipes to be input. After you give the total number of pipes the cursor will move to each field to be filled in for the first pipe in the network. After all the input data is filled in for the first pipe, press the F4 key to proceed to the next pipe. The pipes are numbered automatically by the program. If you wish to edit a previously filled in pipe then press the F3 key to go backwards. It is possible to move rapidly to a specified pipe for editing by pressing the F1 GOTO key. This is useful for large networks. You can move rapidly through various fields on the pipe input screen by using the up and down arrow keys. For a given pipe it is necessary to input the following data otherwise the program will fail in execution. Required information includes the entering node and exit node, as well as descriptive data on the pipe such as the nominal diameter, pipe length, and pipe roughness. Other information such as fittings and check valves etc. is optional but needed to obtain accurate results. The node numbers in and out give the direction of flow in the pipe. Flow in the pipes from the inlet node to the outlet node is a positive number in the network solution. The order of the node numbers is arbitrary except if a pump, check valve or flow controller is included in the pipe description. In this case, it is necessary to give the correct direction of flow. The pipe internal diameter are automatically provided by the program from the pipe schedule selected when the nominal diameter is filled in. PIPE SCHEDULES..F2 KEY Different pipe schedules can be selected by pressing the F2 key. If the F2 key is pressed then a screen is shown that offers several selections of standard schedules. Select the one you want by entering the number corresponding to it. The schedules can be selected for each individual pipe. The standard schedule if none is selected from the menu is SCH 40. The pipe roughness is also provided for new C.S. pipe from the pipe schedule. This value can be overridden by the user. FITTINGS.. F5 KEY If the F5 key is pressed then a screen will come up that gives the equivalent feet (L/D) for several common fittings. These values were taken from the Crane manual. You select the fitting by inputting the number of fittings followed by pressing the enter key. The arrow keys will rapidly move the cursor to the different fittings. The fitting screen can be printed out by pressing the F9 key. Return to the pipe input screen by pressing the F10 key. The number of equivalent feet will be shown on the pipe screen for the fittings described. Additional pressure drop in the line in PSI can be specified to simulate a control valve or heat exchanger or other obstruction in the line. It is also possible to specify a flow regulator in the line to limit the flow to a specified maximum GPM. However, The flow controller option can cause convergence problems and it is recommended to first solve the network without a flow controller to assist in generating good pressure estimates. Expect that the number of iterations will be considerably increased if the flow controller option is selected. The physical properties of the fluid in the pipe as specified in the general fluid input option are shown on the screen. You may override these values by inputting different values for density, or viscosity etc. and the program will use them when calculating this line. Do NOT input gas properties on liquid flow problems or vice versa. CHECK VALVES..F6 KEY Check valves can be specified by pressing the F6 key. If the line has a check valve then the inlet and outlet node numbers must be correctly specified. The is no flow possible against the check valve. PUMP..F7 KEY If a pump is to be specified then only the inlet and outlet node should be specified. The length and diameter terms have no meaning in a pump specification and will be ignored by the program. The pump outlet pipe should be connected to the pump node out specification. The pumps A & B values are calculated by the program by pressing the F7 key. A screen will come on the requests information on the pump curve, specifically the GPM and Pump discharge pressures. At least 3 points, and a maximum of 10 points must be specified for the program to calculate the A & B values for the equation Pout = A - B*GPM^2. Press the F1 key to calculate the coefficients and to see the calculated pressure values for the input flow. When you press the F10 key to return the A & B values will be entered on the pipe screen. DELETE..F8 KEY The F8 key will delete a the pipe that is shown on the screen, and all downstream pipes will be renumbered. ADD PIPES..F9 KEY The F9 key will allow you to add additional pipes to the network beyond the number originally specified. The new pipes will be added at the end. NODE INPUT F4 KEY Pressing the F4 key from the Main Menu will bring up the node input screen. The first field to be inputted is the total number of nodes in the network. The total must be inputted followed by the return key. The program then requests the following information for each Node. After all the Node information is filled in press the F4 key to proceed to the next node. The editing features for Node input is the same as for the Pipe Input screen. The Elevation of the node is relative to a arbitrary grade level. This is important for liquid flow problems if hydrostatic head is to be considered in the pressure drop calculations. The pressure of the node in PSIA for gases, PSIG is satisfactory for liquids. Reasonably accurate pressure estimates are needed for the network to converge. Pressures are required if the pressure at the node is to be specified, for example where the main liquid flow into the network enters, or at exit points. To Specify if the pressure is to be fixed at the Node press the F1 key. The F1 key is a toggle switch, and can be used to convert pressure estimates to specified pressures and vice versa. Additional nodes can be added to the network by pressing the F5 key. There is no provision to delete a node because this can cause considerable changes to the network since the pipes would be changed. If a node is to be deleted it will be necessary to reinput the network. The Liquid rate into or out of the node is given if a specific value is to be specified. Flows into the Node are entered a positive numbers. Flows out of the node are entered as Negative Numbers. The units for flow can be changed by pressing the F2 key. A selection window will pop up and offer alternative flow values such as GPM, LB/H, or ACFM. Only one set of units may be used for the program. They cannot be mixed. The program will use the last selection made, the default value is GPM. REVIEW INPUT F5 KEY The F5 key from the Main Menu will bring up the review input screen. There are two active windows on the screen. The top window gives the Pipe Input data, and lists the pipe number, Nodes in and out, and other data such as the pipe diameter, length, Roughness, and pump Constants if selected. The window will scroll down or up to the limit of the data by pressing the Arrow keys. The lower window give the Node Input Data. It lists the Node number, Node specification ie. Estimated pressure, Specified Pressure or Pumped ( If a liquid flow rate in or out was specified). The elevation of the Node and the Flow rate in the selected units is also shown. This window will also scroll by using the arrow Keys. The Function Keys F1 and F2 are used to pick the desired window to scroll to review the input. Initially the Pipe window is specified. After reviewing the input you can return to the main menu by pressing the F10 Key. DISK OPERATIONS Press the F9 key from the main menu to perform disk operations. Once you press this key a message is shown on the screen to press either the F1 Key to save the input data, or The F2 key to read in a new file from the disk, or the F3 key to change the default directory. The F3 key can by used for example to save the data to a different subdirectory or floppy disk if you do not wish to use the directory that the program was booted up from. Be careful to save the input data on the network as your first operation to prevent possible running problems from causing the data to be lost. Do not accidently press the F2 key if you intend to save the data because reading in a new file will cause the input data to be lost. If you are saving the data by pressing the F1 key a screen will come on requesting the name of the file. Input a maximum of 8 characters per the DOS convention, and do NOT add a period or extension to the name, Network data files are automatically given the extension NET by the program. Do NOT use a prefix for sub directories here. The F3 key is to be used for setting the default sub directories. If you are loading in and existing data set, Press the F2 key. A selection window will come up that lists the files on the disk that have the extension NET, and are network data files. The file to be loaded is selected by using the arrow keys to move the colored box to the selected file and then press the return key to load in the file. RUNNING THE PROGRAM F10 The program is run by pressing the F10 key. This should be done after a problem has been loaded from the disk, or after the data has been completely inputted, checked, and saved to the disk. While the program is running a window will pop up that gives the number of the iteration and the sum of the residuals squared for the programs convergence. The network will iterate to reach a convergence tolerance of 0.001 or for a maximum of 200 iterations. Small networks with less than say 10 pipes will usually converge very rapidly in less than 10 iterations. Large networks can take considerably longer. This window will let you watch the progress of the solution. If the residuals do not converge to zero then the solution is not accurate. If there is something wrong with the problem statement and convergence is not possible then a warning message will appear and the convergence routine will stop, and return you to the main menu. REVIEW RESULTS F6 After the program has been run, the results can be reviewed by pressing the F6 key. The Result screen is similar to the Review Input screen and works in the same manner. The Pipe Data results are scrolled by pressing the Arrow keys. and the Node Data can be selected by pressing the F2 key. The pipe results for each pipe are the Flow in the pipe, the velocity, calculated friction factors and Reynold's Numbers, Average Density of the fluid in the pipe, the Head Loss in PSI across the pipe ( Head Loss includes additional Pressure drops and Static head differences ) and the Pump Head of and Pumps in PSI. Negative number for Flow or Velocity indicate that the flow in the pipe is from the outlet to the inlet node specified. The Node Results give the pressures at each Node calculated, the Nodes Elevation and the Flows Into or Out of the Node. Flows Out are Negative Numbers, Flows In are Positive. These flows are obtained by performing material balances at each node. Small numbers like 0.01 GPM indicate convergence tolerances. The flow result at a Node should be zero unless the node has a Flow or Pressure specified. Fixed pressures indicate locations where flow is either entering or exiting the Network. PRINTER OPERATIONS F8 KEY The Printer should be On and connected to the computer before pressing this key. A window will pop up that gives you the option to print out the Input, Print the Output or to give a line feed or Form Feed to the printer. Press the Function key shown in the window to select the case. The Printer option assumes that the printer is a continuous feed printer such as an Epson. NEW PROBLEM F7 KEY If you press the F7 key a message will appear to confirm that you wish to wipe out the existing network from the computer memory and start a new problem. If you have not save the data file you should answer the question by typing the N key for No. Type a Y to start a new problem. QUITTING THE PROGRAM The program is terminated by pressing the ALT key and simultaneously pressing the Q key from the Main Menu. A message will appear asking for confirmation that you wish to quit. Press the Y key to answer yes and the program will shut off.