Since tapes cannot be telescoped (changing sizes down the lateral) in IRRICAD you will need to simulate tapes as spraylines to achieve this feature. This is a brief description of how to simulate tapes with suitable spraylines so that analysis and design can be carried out for blocks with tape that have multiple sizes.
SUMMARY
Entries to simulate the tape need to be made in the pipe and outlet databases.
In the pipe database add a pipe with the internal diameter as the tape entry (do not forget to give it a unique warehouse code). The roughness for the pipe can be determined from trials to achieve the same headloss through the pipe that the tape gives. To do this, in a clean design, run out a tape a set length (similar to the run length in the design), e.g. 300ft (100m). Then run out your new pipe the same length. Connect with a large submain pipe and a control valve. Turn off "Minor Losses" in Design|Zone Design Configuration, analyze the zone, and check the Zone Full report. Change the roughness factor for the new pipe until it achieves the same headloss through the pipe that the tape is giving.
In the outlet database, make an entry for the tape outlet. The constant and index for this can be derived in a number of ways:
CREATING THE SIMULATED DESIGN
It is generally better to duplicate your tape design and make the changes required to simulate the tapes on a separate copy. Make a copy of your design by using File|Save As and save the design under new name. In the copy of your design, replace the existing tapes with connected spraylines using the tape pipe and tape outlet you created for this purpose. To do this select the block and then select Tools|Tapes to Spraylines and select you new pipe and new outlet. Sprinklers are always assumed to be at ground level. If in your design they are not at ground level, you must select an outlet connector with the appropriate height previously entered in the "Height" field (in the database) to ensure that IRRICAD uses that height in the pressure calculations at the sprinkler. Note the height entered into the database is the height above ground, not the length of the outlet connector from a buried submain to the height of the outlet. For subsurface outlets (e.g. subsurface dripline) the height above ground will be negative (-ve).
If you are going to design the submain with this method, then it is important to determine what nominal pressure you need to assign to the outlets so that the resulting flow for your simulated tape matches the tape specifications. You need to do this because the inlet pressure is specified for tapes and you need to get the average pressure that will normally be less than the inlet. The simplest way to do this is to layout a single simulated tape (with the same length and slope of the tapes in your block) connected to a very short (no headloss) submain and valve. The valve pressure then is fixed in Design|Zone Design Configuration to the tape inlet pressure you wish to use. Guess a pressure for the outlets (e.g. half way between the minimum pressure allowed and the inlet pressure) analyze the simulated tape (normal analysis, not detailed). You can then adjust your guess and re-analyze until the flow for your simulated tape matches that for a real tape of the same length, slope and inlet pressure.
If you have an existing submain you wish to analyze, then it is unnecessary to go through the above process. Simply make a guess at the nominal pressure of your outlets and then use detailed analysis to analyze the system. This does not apply to normal analysis where you need to use the method outlined above.
SIZING / ANALYSIS
The Simulated block can now be sized or analyzed. It is advisable, after sizing, to run detailed analysis (do not forget to set the valve pressure in Zone Design Configuration) as a check.
SUMMARY
- Enter the required data into the database as a sprayline and nozzle.
- Duplicate your design, replace existing tapes with spraylines and nozzles.
- If using LP Design to size the submain, guess a nominal pressure, analyze and adjust as required so it simulates the tape as close as possible.
- If the submain has been manually selected, guess at a nominal outlet pressure and use detailed analysis to analyze.
Entries to simulate the tape need to be made in the pipe and outlet databases.
In the pipe database add a pipe with the internal diameter as the tape entry (do not forget to give it a unique warehouse code). The roughness for the pipe can be determined from trials to achieve the same headloss through the pipe that the tape gives. To do this, in a clean design, run out a tape a set length (similar to the run length in the design), e.g. 300ft (100m). Then run out your new pipe the same length. Connect with a large submain pipe and a control valve. Turn off "Minor Losses" in Design|Zone Design Configuration, analyze the zone, and check the Zone Full report. Change the roughness factor for the new pipe until it achieves the same headloss through the pipe that the tape is giving.
In the outlet database, make an entry for the tape outlet. The constant and index for this can be derived in a number of ways:
- Directly from tape manufacturers data.
- From manufacturers data using Outlet Flow curve fitting utility.
- Assuming the index is 0.5 and calculating the constant by substitution in the equation (this method is normally accurate enough) Flow (lph) = Const * Pressure (m) ** (0.5) (for PC emitter the index is 0 and the constant is equal to the flow rate)
- Contact AEI Software.
CREATING THE SIMULATED DESIGN
It is generally better to duplicate your tape design and make the changes required to simulate the tapes on a separate copy. Make a copy of your design by using File|Save As and save the design under new name. In the copy of your design, replace the existing tapes with connected spraylines using the tape pipe and tape outlet you created for this purpose. To do this select the block and then select Tools|Tapes to Spraylines and select you new pipe and new outlet. Sprinklers are always assumed to be at ground level. If in your design they are not at ground level, you must select an outlet connector with the appropriate height previously entered in the "Height" field (in the database) to ensure that IRRICAD uses that height in the pressure calculations at the sprinkler. Note the height entered into the database is the height above ground, not the length of the outlet connector from a buried submain to the height of the outlet. For subsurface outlets (e.g. subsurface dripline) the height above ground will be negative (-ve).
If you are going to design the submain with this method, then it is important to determine what nominal pressure you need to assign to the outlets so that the resulting flow for your simulated tape matches the tape specifications. You need to do this because the inlet pressure is specified for tapes and you need to get the average pressure that will normally be less than the inlet. The simplest way to do this is to layout a single simulated tape (with the same length and slope of the tapes in your block) connected to a very short (no headloss) submain and valve. The valve pressure then is fixed in Design|Zone Design Configuration to the tape inlet pressure you wish to use. Guess a pressure for the outlets (e.g. half way between the minimum pressure allowed and the inlet pressure) analyze the simulated tape (normal analysis, not detailed). You can then adjust your guess and re-analyze until the flow for your simulated tape matches that for a real tape of the same length, slope and inlet pressure.
If you have an existing submain you wish to analyze, then it is unnecessary to go through the above process. Simply make a guess at the nominal pressure of your outlets and then use detailed analysis to analyze the system. This does not apply to normal analysis where you need to use the method outlined above.
SIZING / ANALYSIS
The Simulated block can now be sized or analyzed. It is advisable, after sizing, to run detailed analysis (do not forget to set the valve pressure in Zone Design Configuration) as a check.