A few weeks ago I received a call from a sprinkler contractor who needed to provide a water supply graph for a flow test he conducted.
I had a canned sheet I had developed for my own flow tests, but it was a basic graph that showed a curve and didn't match the traditional N^1.85 hydraulic graphs common for water supply curves. Since then I've tinkered and come up with an accurate chart that takes flow test input values, calculates total flow and draws the curve along the N^1.85 chart.
The N^1.85 chart is particularly useful for fire suppression systems because the Hazen-Williams formula is based on the relationship that pressure relates to flow to the 1.85th power.
Take a look at the N1.85 Water Supply Curve tool here and let me know what you think in the comment section below.
When the x-axis, or the hydraulic flow is then scaled to the 1.85th power, hydraulic curves become straight lines which becomes easier to graph and compare. Prior to everyone carrying a computer in their pocket, these graphs were likely much easier to use for summaries and comparisons.
The water supply information is what is provided as part of a two-hydrant flow test. The design input information would be the system demand side and can be used for quick comparisons.
Personally, I only use this setup for flow test reports and water supply comparisons. Fire sprinkler hydraulic calculation software takes care of the graphs and outputs I need after I've completed the hydraulic calculations.
On a side note, I've had several people ask about getting access to all of the tools I've created to use on their own computer with the ability to produce printable output for record keeping. Thanks again to those who asked - that concept is in the works and I'm hoping to bring about some version of all-inclusive software in the next couple months.
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Joseph Meyer, PE, is a Fire Protection Engineer in St. Louis, Missouri. See bio on About page.