When teaching the basics of sprinkler layout, I find it far too easy to jump right to talking about sprinkler spacing distances and the coverage area in relatable terms.
SPRINKLER SPACING AS 225 SQFT & 15x15
I say that a sprinkler is limited by a coverage area limit, and by a maximum spacing. I then introduce an example for Light Hazard with an acoustical ceiling tile, and explain that the limits are 225 sqft and 15-ft x 15-ft.
That's all technically correct. And, as an example, it's a common one for those of us that work regularly with light commercial buildings.
However, by giving that example, there is a whole series of assumptions built in that I completely gloss over.
UNDERSTANDING THE PATH
Experienced Designers & Engineers will tell you (they've told me), that to teach the fundamentals correctly we really need to start with all the considerations and assumptions that go into a sprinkler layout.
Is the structure combustible, noncombustible, or limited-combustible?
Is the construction Obstructed or Unobstructed?
Are we assuming standard-spray sprinklers, or something like ESFR or Extended Coverage?
I've gotten caught making basic mistakes - spacing sidewalls inappropriately because I just assumed that a 14x14 spacing applied regardless of the construction type.
I could be wrong here, but my guess is that even experienced people have made the same mistakes I have on sprinkler spacing because we've glossed over the combustible nature of the ceiling.
A new sprinkler spacing flowchart. Click above to download.
A PDF FLOWCHART
Partially to satisfy my own curiosity, and partially because we're getting into a lot of detail with teaching these concepts on the University platform (all our PDF resources are there), I've broken out these different paths and decision trees in a new pdf flowchart. Click above to download the full PDF version.
Unlike some of the other charts and checklists we've created, this probably isn't one I'm going to be referencing daily. There's typically only a few common limitations that apply to most of the work that I do.
However, just as a concept, I find it interesting how the considerations of combustible/noncombustible construction, obstructed and unobstructed, exposed members versus non-exposed members all play a part in how NFPA 13 tells us to properly protect each space. This can be helpful as a teaching tool in introducing the spacing concepts.
Hope you have a great rest of your week!
This week I'm happy to debut an update to one of our popular tools, the K-Factor selector, which is a part of the Toolkit.
This tool quickly calculates the actual pressure and flow across different types of sprinklers. It's helpful when we're trying to select the best-possible sprinkler for a hazard.
Even for light hazard areas, a standard k5.6 sprinkler may not be the 'optimal' sprinkler, from a hydraulic perspective. We touched on this when looking at whether the flow through a sprinkler is governed by the density and area or by the k-factor and minimum pressure.
In short, the minimum flow through a sprinkler can be driven by the coverage area of the sprinkler multiplied by the density of the hazard, or, it can be driven by the k-factor of the sprinkler and the minimum pressure that sprinkler requires.
In either case, it's important to make a quality selection for the k-factor if we want to reduce the required pressure and flow that a system will demand. Less flow usually means less friction loss, which can result in more efficient systems and smaller pipe sizes (saved cost of material and labor).
The updates to this tool make it mobile and tablet friendly, and also now clearly indicate what the 'optimal' sprinkler k-factor is for flow and for pressure (hint: they're not always the same). If you're a Toolkit user, just click the image above to see the updates. Thanks!
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Joe Meyer, PE, is a Fire Protection Engineer out of St. Louis, Missouri who writes & develops resources for Fire Protection Professionals. See bio here: About