First - last week I put together a draft PDF cheatsheet for fire alarm design in elevators. Lots of great response to that tool. One major flub on my part - I didn't actually link to it. Here's an actual working hyperlink (fingers crossed).
K-Factor & Pressure Versus Area & Density
One of the hand calculations I do frequently when laying out sprinkler systems is comparing the k-factor, minimum pressures, and resulting flow for the sprinkler. It comes up all the time with residential-style, extended coverage, special application, and storage sprinklers.
Many hydraulic calculation programs do this comparison automatically. That being said, it is important to understand and compare the minimum flow from sprinklers for a hydraulic calculation.
Reducing unnecessary flow from a sprinkler reduces the total calculated flow from a system, which has major impacts on pipe sizing for some branch lines, cross mains, feed mains, and even the underground service size.
Driver #1: K-Factor and Minimum Pressure
There are two drivers for the actual minimum flow that must come from a fire sprinkler.
The first driver is the K-Factor and Minimum Pressure. This equation is
Q = k√P
Q = Flow (gpm)
k = Sprinkler k-Factor
P = Pressure (psi)
With a 5.6 k-factor and a minimum pressure of 7.0 psi (as is required by NFPA 13), we get a flow of 5.6 x √7 = 14.8 gpm
There's a wide array of k-factors available on the market, and a wide variety of minimum sprinkler pressures too. Extended coverage, residential, attic, storage, and ESFR all vary in required minimum pressures.
Driver #2: Area and Density (When Using the Density/Area Design Approach)
When reviewing cutsheets for sprinklers it's easy to take a k-factor and minimum pressure and assume that you then know the minimum requirements for a sprinkler and you're done. If you're using design criteria that only uses that approach, then you may actually be done.
However, if you're using the density/area approach of NFPA 13 then you also have to ensure the sprinkler is actually delivering the minimum density for the area its protecting.
It's easy to skip over this step. If you've ever laid out residential-style sprinklers, then you probably already know this.
Residential-style sprinklers can have small k-factors and relatively low minimum pressures to cover a reasonable floor area. However, these sprinklers can be used in NFPA 13, 13R, or NFPA 13D systems. 13R and 13D specifically can allow densities less than 0.10 gpm/sqft. The cutsheets often offer the minimum pressure for a given k-factor and floor area coverage, but the cutsheet may be assuming a 0.05 gpm/sqft density.
When we have higher densities (such as residential-style sprinklers in an NFPA 13 design), we have to consider this second driver for sprinkler flow.
The equation for density/area coverage is also straightforward:
Q = D x A
Q = Flow (gpm)
D = Minimum Density (gpm/sqft)
A = Area Covered by Sprinkler (sqft)
A sprinkler spaced at 15 ft x 15 ft with a minimum design density of 0.10 gpm/sqft requires a flow of 22.5 gpm.
With this, a k-5.6 sprinkler at 7 psi, spaced 15 x 15 feet with a 0.10 gpm/sqft density will actually need to flow 22.5 gpm.
Here's how this scenario looks when graphed:
The red line above represents the hydraulic pressure/flow relationship that a k-5.6 sprinkler offers. As the minimum pressure increases, the flow will increase. Similarly, as the flow needed through the sprinkler increases, the minimum pressure required to deliver that flow also increases.
For this scenario, the actual flow through the sprinkler must be the higher of the two amounts, or 22.5 gpm which will occur at 16.1 psi (see the blue lines above).
This means for a light-hazard, typical sprinkler we're demanding that the pressure at the sprinkler is over double what the code minimum is!
Will this difference break your calculation? No, it won't.
But let's look at another example where these decisions become a little more critical.
Take a Viking VK460 residential sidewall sprinkler. It's a 5.8 k-factor and has varying coverage areas with varying pressure and flow requirements.
Based on a 12 ft x 12 ft spacing, the minimum pressure required under the product data is 7.6 psi.
The Sprinkler-Driven minimum flow becomes Q = k√P = 5.8 x √7.6 = 16.0 gpm.
Assuming an NFPA 13 design, the Density-Area minimum flow becomes Q = 0.10 gpm/sqft x (12 ft x 12 ft) = 14.4 gpm.
In this scenario, the flow is Sprinkler-Driven. The actual flow through the sprinkler is driven by the k-factor and minimum pressure, and not the density/area point.
This same sprinkler, however, at a 16x20 spacing, looks a little different.
Based on a 16 ft x 20 ft spacing, the minimum pressure required under the product data is 20.1 psi.
The Sprinkler-Driven minimum flow becomes Q = k√P = 5.8 x √20.1 = 26.0 gpm.
Assuming an NFPA 13 design, the Density-Area minimum flow becomes Q = 0.10 gpm/sqft x (16 ft x 20 ft) = 32.0 gpm.
The demand through this sprinkler now becomes density-driven, and notice the actual pressure required to achieve this density is now 30.4 psi. If you have a poor water supply then these decisions can begin to really impact your hydraulic calculations.
Do you need to assess whether your sprinklers are driven by the k-factor and pressure or density/area? No - many hydraulic calculation programs cover this already.
These differences to become critical though with sprinkler selection, reducing the system demand, reducing the system pressure, and refining a design to end up with the most efficient system possible as an end result.
This Tool Available Now
If you're a Toolkit user, you can give this new tool a try today. Click here for online access to it.
This tool comparison tool allows different k-factor inputs, minimum pressures, density and areas with immediate graphed comparisons.
This tool will also be available for download with the latest Toolkit release here in a few weeks. More on that to come.
Thank you for reading and have a great, safe week!
Last spring I created a beta test tool for soffit obstructions to sprinklers. It was fairly basic using the dimensional rules for a soffit against a wall for a standard-spray pendent or upright sprinkler.
Thanks to some feedback and more input on this tool, I'm happy to debut it with new features. I've added code references from the 2007 to 2019 editions of NFPA 13, the different style sprinklers, and an updated visual diagram.
This tool is useful when there's a dropped soffit against a wall to determine whether the sprinkler will throw sufficiently underneath the soffit.
In the coming weeks I'll break out a code path for determining when each of these tools are used. For now, if you're familiar with the NFPA 13 Sections for Obstructions Against Walls then you'll recognize this tool's quick usefulness.
This tool stems from the Figures (b) and (c) for Obstructions Against Walls found in NFPA 13 Section 188.8.131.52.2 for Standard Spray Sprinklers, 184.108.40.206.2 and 220.127.116.11.4 for Extended Coverage Sidewall and Pendent/Uprights, and Sections 18.104.22.168.2 and 22.214.171.124.4 for Residential Sidewalls and Pendent/Uprights.
I'll have it hosted for free use for a couple months before it transitions to the Toolkit package. For today it's live here and on thecloud access for all current Toolkit users. Interested in getting access to every tool? Get the Toolkit here.
Know someone that might be interested in this tool? Send them a link! It's greatly appreciated.
Have a great week!
Awhile back I researched and built a translator for various versions of NFPA 13.
It's built to quickly find where a code section has migrated between different editions of the standard. There's a free version here which connects the 2016 and the 2019 Editions of NFPA 13.
Based on feedback and the positive response to that tool, I've just finished a similar edition translator for all of the published versions of the International Building Code. It covers Chapters 1 through 11, 15 and 30. Here's a quick video of how it works:
If you're interested in giving this a try, you can get it as part of a 30-day trial for the MeyerFire Toolkit here. https://www.meyerfire.com/toolkit-trial.html.
It's been busy around here tinkering with new tools since I went on my own in October of 2019. I am not by nature a programmer, but as the son of two accountants I'm pretty sure Microsoft Excel is just in my blood.
I've gotten lots of positive feedback from users on the Toolkit and I'm happy to announce this week some major improvements aside from the new IBC translator:
1. A La Carte Tools Coming
Some users aren't designers or engineers and would only use one or two tools. I get it. In the next couple weeks I'll be breaking out individual tools and pricing them for less, separately. The first one offered this way is the Water Supply Analysis tool that will be up this week.
2. Instant Activation Codes
One of the biggest frustrations I've had on the development side is with quirky activation code servers. They drive me nuts. Over the past month I've dramatically simplified the process, so that new purchases automatically get clear activation codes exactly 2 minutes after their purchase. Clean and simple and it's working much better than before.
3. Toolkit Going to $195 in February
With over a half-dozen new tools, the price of the Toolkit is going up to $195 starting in February. If you're interested but haven't bought yet, pick up a license now and you'll lock in your $150 subscription.
4. New Licenses Are Multi-Device & Sharable with Coworkers
Lastly, based on the biggest piece of feedback I've gotten, with the $195 price-bump starting in February a single license will allow multiple installs, so that you can use on multiple devices and with members of your company.
If you have a design staff with multiple users, it only makes sense that you're able to use and share files with coworkers.
If you have a single-user license now and want to upgrade, shoot me an email at firstname.lastname@example.org and we'll get the upgrade set up. Should you want to learn more about the Toolkit, you can do so here.
Hope you have a great rest of your week!
This time of year is just the best.
I feel extremely fortunate to have three young kiddos at home, a supportive and all-around great family, and an extremely rewarding career in fire protection and doing what I do here at MeyerFire.com. Whether you subscribe, dabble occasionally on the forum, or just stop in to use tools here and there, THANK YOU for a really wonderful 2019.
One of the tasks of wrapping up a year is revisiting what resonated the most in 2019 of all the content here. If you just joined in this year or know someone who would benefit from this content, please consider sending a link.
I've been on a bit of a tool creation kick lately. Sorry, I just get excited sometimes.
This week I'm introducing a small portion of a much larger programming effort - this tool helps determine an adjusted fire sprinkler remote area based on the system type and density/area curves of NFPA 13. It can factor in the quick-response area reduction, sloped ceiling adjustment, double-interlock pre-action or dry increase, and high-temperature sprinkler decrease. I'll probably only have this up as a free version for a month or so before adding to it and incorporating the full tool in the Toolkit.
At the bottom of the tool you'll see a schematic remote area drawn with the parameters input. I'm using it when mocking up hydraulic calculations for estimation or when I'm first setting up a hydraulic calculation. Give it a shot and let me know what you think!
This week I'm pulling back the curtain a little bit and showing a tool that is very much still under development. It's a water-storage tank sizer that incorporates a handful of decisions that go into water storage tank sizing.
I'd like to get it in front of you this week as I'm looking for feedback on how to improve this tool. There's not a lot of great documentation on how to size water storage tanks, but there are plenty of variables that impact proper water storage tank sizing.
With that said, check out the tool here:
If you're in the water storage tank space and have tips or feedback, please email me at email@example.com or comment here. I'd be very much interested in ways to improve this one (or any tool for that matter).
On a side note, this and many other recent tools are going to be included with a major MeyerFire Toolkit update here in the next few weeks. We've been working quite a bit on improving the activation/subscription process which has been no small task. When that gets cleaned up I'll be happy to send out the major update for the Toolkit.
Hope you have a great rest of your week!
Occasionally, as part of the upfront engineering work I do, I'm asked to identify the quantity and approximate size of clean agent storage tanks. The final calculations and actual clean agent system design is to be completed by a specialist at a later time, but my role is to make sure they have room allocated specifically to them early in the design process.
As part of that effort in determining quantity and sizes of tanks, I'll estimate about how much agent the project will actually need.
For that purpose, I've built the Clean Agent Quantity Estimator. It's built on NFPA 2001 and its' own agent weight formulas for FM-200 and NOVEC-1230.
With a few parameters and assumptions you can very quickly get an estimate of the amount of clean agent your project would justify for a space. It's important to note here that these are estimates - actual agent weight will need to be fine-tuned once the pipe network has been laid out and sized.
Do you see this tool being useful for what you do? What would make it better? Feel free to comment below here with ideas or feedback.
Don't get these free tools? Subscribe here.
Thanks & have a great week!
Occasionally I come across projects where the contractor (my client) is looking to use listed anchors or attachments that are listed, but have various strengths associated with them.
NFPA 13 lists the maximum spacing for hangers, but this maximum spacing doesn't always address these alternative hanging methods. NFPA 13 addresses these by requiring that any hanger assembly be able to support five times the weight of water filled pipe, plus 250 pounds.
Based on this, I've created a calculator that reverses this process and calculates the maximum spacing for hangers depending upon the pipe size, type, and strength of a hanging element. As this is the first week out I only have I-P units (sorry international friends, I'll continue to work on this), but give it a spin here and let me know what you think in the comments section below.
Don't see the tool below? Click here.
Thanks and for those in the US have a great Thanksgiving week!
I was asked recently for a specific project how much flow the owner should anticipate coming from a building's main drain.
There's just a few factors that play into exactly how much water to expect. Is the drain serving as the main drain for a system? Is it only serving an inspector's test? Is the drain off a 1-inch pipe, or 2-inch? How much pressure is on the system?
These aren't often difficult to answer if you're familiar with the job, but each of these answers plays a role in determining how much water will come out of an open orifice.
This week I've simplified a few of these parameters to come up with a quick inspector's test and drain calculator for fire sprinkler systems.
With it, you can estimate the amount of flow that will come from an inspector's test (use the k-factor option) or from a drain (diameter option). For our international audience I have incorporated real units from the get-go this time. It's a free tool that's now live on the site, here.
Give it a spin and let me know what you think in the comments here.
Know others that might find this helpful? Send them a link or tell them to subscribe here.
Thanks & have a great week!
Over a year ago I released a Thrust Block Calculator online.
It that takes a small handful of inputs and offers sizing and dimensions according to NFPA 13. The tool has been a reasonable hit except for one repeated request from the field – the thrust block weight. Until now designers and engineers using the tool still had to convert the minimum required volume into the minimum weight based on the density of the concrete. Hand calc no longer!
Special thanks to Sinisa who offered the reminder after I asked for pet peeves or upgrade requests in last week’s post.
If you’ve never used the tool and would like to check it out, here’s the link to it. It's free and available now.
Last item for this week - I'm circling back to a call for water storage tank experts. If you're experienced in this space and would like to review a new tool I'm working on, please shoot me an email at firstname.lastname@example.org. Would be happy to set up beta testing.
Thanks and I hope you have a great rest of your week!
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Joseph Meyer, PE, is a Fire Protection Engineer in St. Louis, Missouri. See bio on About page.