You're asking an indeterminate question. A few years ago I went to the trouble to acquire 5 top-rated programs and build a model of two different gathering systems into each. Since this was several years ago, I will not list the programs I tested (many of the problems I found have been corrected in intervening releases). I only found one that could be calibrated to match observed data on both systems and that is the one I use to this day (it is no longer for sale since the manufacturer went out of business).
The exercise was really useful. Some of the bonehead things I found were:
- One program had a built in bias to flow from low-numbered nodes to high-numbered nodes. This bias eliminated an excelent system modification because it wouldn't allow reverse flow. You can find this error by building a test model, running it, renumbering the nodes, and run it again -- if the output from the two runs are not identical then "Houston we have a problem" and I would reject the program without further testing.
- One program had an (undocumented) limit of 5 loop lines (one of my systems had 35).
- One program came to an Abnormal End (ABEND with indeciferable code) if you used the capability to loop a line and end up in a different point than the first line ended.
- Several programs lacked the "knobs" to "tweak" the program into compliance with the observed data (i.e., you couldn't do a calibration run).
- One of the systems had two off-take points and they would reverse the flow in the pipe between them with 1/2 psi change in one of the pressures -- three of the five programs would fail when the flow reversed.
You will be using this program to predict the outcome of millions of dollars of construction -- relying on the old adage "if its on green-and-white, its right" is simply irresponsible.
David Simpson, PE
MuleShoe Engineering
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The Plural of "anecdote" is not "data"