First, a huge thank you to everyone who's expressed interest and purchased the Toolkit - I very much appreciate the fantastic response to the launch over the last three weeks!
It's a short post this week - I've been developing a Trapeze Hanger tool that sizes and schematically details trapeze hangers. This will likely be the first of three posts while developing this tool.
Questions for you at this point in time:
(1) What other possible standard trapeze materials do you use that could be helpful as part of this tool?
(2) What would you like to see shown in the detail?
(3) If the detail could be easily translated to AutoCAD from this calculator, could it be something helpful for your projects? If so, what would you want shown and identified?
Click here to test and comment on the Trapeze Hanger tool, thanks in advance!
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Based on some feedback and good ideas I've been experimenting with graphing fire pump & flow test curves with usable data outputs. Below is the first iteration for drawing a fire pump curve alongside a water supply curve.
Determining ideal fire pump configurations for sprinkler and standpipe systems can be
an important part of optimizing fire suppression design
Here's the help I could really use from you - what else would be included in your ideal pump curve?
Would you prefer this be on a logarithmic x-axis?
Want 175 & 300 psi limit lines shown?
Would you want to see at what height in a building the 175 psi threshold would occur - on this graph?
System demand and hose?
I'm open to any and all ideas - in the end I think it'd be great if this tool was the quickest & best method for summarizing and analyzing fire pump output. Share your ideas in the comments here, thanks in advance!
This week's resource was a fun one to put together.
Frequent Questions about NFPA 13 vs. 13R
I've been asked a handful of times in early project planning phases on whether NFPA 13R would be allowed in lieu of NFPA 13 for a project. In short, the two standards have very different objectives and as a result require very different means.
While those who ask are generally looking for ways to save on construction for the project, the differences are important and worth discussing early in a project.
Designed for Different Purposes
It's important to note that NFPA 13R systems are designed primarily with the intent for life safety (extending the amount of time occupants have to escape a burning building). It's stated purpose is to additional "prevent flashover in the room of fire origin, where sprinklered" (NFPA 13R 2019 1.2.2).
Unlike NFPA 13, NFPA 13R works to make the installation of the sprinkler system more affordable and accessible for residential occupancies by targeting the areas of highest fire risk to life safety with sprinkler systems. Swapping NFPA 13 and NFPA 13R is not simply a one-for-one exchange, as their goals are overall quite different.
Summary of Differences
Here's the summary of differences I use between NFPA 13, 13R, and 13D as a downloadable PDF (at the bottom of this page). References to the building code are to the International Building Code, as it's typically the most prevalent used in the US.
As always, there's far more detail to many of these requirements than can be summarized in two pages - so be sure to use the supplied section references to gather more information on specifics for your project.
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I've never trimmed a dry valve nor have I tested or drained a system myself. I'll also admit that for longer than I should have I never investigated the details of a dry valve.
Hopefully with today's post if you've been in that same boat there's enough to better understand the basic components of a dry pipe valve.
How Dry Pipe Valves Function
1. The valve is in the closed position (clapper inside the valve is horizontal) and air pressure keeps the clapper closed.
2. A sprinkler activates, releasing air pressure at the sprinkler.
3. Air pressure within the dry pipe system begins to reduce.
4. After sufficient air pressure is reduced, the water pressure below the clapper becomes greater than the pressure above the clapper, and the valve opens upward.
5. Water flows through the opening in the valve, past the clapper, and into the system.
6. After entering through the valve, the water gravitates towards the opening in the system where the air pressure is being released, and discharges through the sprinkler at the fire interface.
The clapper is the interface between the air and the water within a dry pipe valve.
It's purpose is to remain closed when air pressure is sufficient in the system, and open when the air pressure falls.
The surface area of the clapper is disproportionately larger on the air side than the water side - which is intentional. To hold the clapper closed, the force on the clapper must be greater on the air side than the water side. Since force is pressure x area, a larger surface area on the air side means the air can be kept at a much lower pressure and still keep the clapper assembly closed - often to a ratio of 4:1 or 5:1 (allowing 40 psi of air to 120 psi of water pressure, for instance).
The External Reset Knob shown in this model is used in lieu of priming water, which otherwise sits on top of the clapper and helps distribute pressure across the top interface of the clapper.
The Knob incorporated in this dry valve is depressed to "unlatch" an open clapper, allowing it to reset back into its normal, closed position. It is a convenient function where a user doesn't have to open the face of the valve in order to reset it.
Low Body Drain Valve
The low-body drain valve allows the air-side of the valve to be drained completely with the clapper closed. Since the main drain valve is below the clapper, the clapper must be opened for the main drain to be used to drain the system.
Main Drain & Intermediate Chamber
The main drain is used to drain water from the system, and is located below the clapper assembly.
For dry valves, some models permit the main drain to be used to test the waterflow pressure switch without opening the clapper.
In other models, there's an intermediate chamber between the water and air side which is normally dry. When water enters the intermediate chamber after the valve opens, the waterflow pressure switch senses water pressure and activates. In this configuration, there's usually a ball valve that can be used to test the waterflow pressure switch and fill the intermediate chamber without opening the dry valve.
The water supply pressure gauge and the system air pressure gauge are included to monitor the incoming water supply pressure and the system air pressure. These gauges are usually attached to a gauge test valve with a plug that permits removal and cleaning of the gauge orifice.
There are typically two pressure switches on the dry pipe valve assembly. The first is a pressure switch which monitors the air supply. When the air supply on the system drops to a pre-determined level, this pressure switch will typically send a supervisory signal to the fire alarm control panel, allowing an early warning that the dry valve is about to open and flood the system.
The second pressure switch is included to activate when there is water in the intermediate chamber or is flooding the system. This is typically an alarm signal that also activates fire alarm notification in a building.
Supply Shut-Off Valve
This valve is typically separate from the dry pipe valve, but allows the system to be shut off after a fire has been sufficiently suppressed. It also can be closed when a system needs to be isolated, such as for a modification, repair or remodel.
Outside of the dry valve assembly, an air maintenance device allows the incoming air to be regulated to a preset air pressure and for that pressure to be maintained in the system.
In order to supply the air, or in many cases now nitrogen, an air compressor or nitrogen generator are provided to supply pressured air or nitrogen into the system.
While this valve is only one model, many of the components between dry valves are designed similarly. For further reading and detail on dry valves, I'd recommend reading NFSA's Layout, Detail and Calculation of Fire Sprinkler Systems (2nd Edition by Kenneth E. Isman, P.E.) and any product data for a dry valve you're reviewing, installing, or specifying.
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When conducting or reviewing hydraulic calculations, I very often face scenarios where the initial (very first) hydraulic demand exceeds the potential for the water supply.
At that point I lose all hope and add a fire pump to the job.
Just kidding, of course - there's at least a half dozen hydraulic elements I analyze and refine to better match the capabilities of the water supply to the design of the sprinkler system.
Refining Hydraulic Calculations with K-Factors
One of the more fine-tooth aspects I look at is the k-factor used on the sprinklers.
The k-factor for a fire sprinkler is the discharge coefficient, or in normal human terms just relates to the amount of water that is permitted through the sprinkler.
The k-factor is dependent upon the orifice diameter of the sprinkler - a low k-factor (such as K2.8) restricts the flow of water, while a larger k-factor (such as K22.4, K25.2, or K28.0) permit much more water to flow through. K-factors were originally created to be multiples of the discharge of a K5.6 sprinkler. A K2.8 sprinkler, for example, is 50% discharge of a K5.6 sprinkler, while a K11.2 sprinkler is 200% of the discharge of a K5.6. NFPA 13-2016 Table 184.108.40.206 shows this well.
Use In Design
We find K5.6 sprinklers in light hazard all the time. Residential sprinklers often have k-factors less than 5.6. ESFR and CMSA require minimum K11.2 (NFPA 13-2016 220.127.116.11). ESFR are tied directly to the hazard it protects.
Back to refining the hydraulics in a system - increasing the k-factor of a sprinkler allows more water to flow through a sprinkler with less pressure loss. This becomes very important when trying to reduce pressure loss in a system.
Light Hazard Example
A light hazard system (0.10 gpm/sqft) with widely spaced sprinklers (at 225 sqft each) would require a minimum flow through each sprinkler of 22.5 gpm (0.10 gpm/sqft x 225 sqft = 22.5 gpm).
In order to flow 22.5 gpm, a sprinkler with a k-factor of 5.6 now requires 16.1 psi to do so (Q=k√p, or rearranged, p=(Q/k)^2). This is 9.1 psi higher than 7 psi, or the minimum that NFPA 13 requires.
In order to flow 22.5 gpm, a sprinkler with k-factor of 8.0 only requires 7.9 psi to do so, or less than 1 psi more than the minimum NFPA 13 requires.
In this scenario, flowing the same amount of water (22.5 gpm) results in a 8.2 psi difference in the pressure required at the most remote sprinkler. Can 8.2 psi be important? Absolutely!
Similarly, consider Ordinary Hazard Group 1 (0.15 gpm/sqft) and Ordinary Hazard Group 2 (0.20 gpm/sqft) systems.
For Ordinary Hazard Group 1 and sprinklers spaced at 130 sqft, a K8.0 sprinkler requires 5.1 psi less than a K5.6 sprinkler (7.0 psi vs 12.1 psi).
This same methodology applies to extended coverage sprinkler requirements, specific densities for traditional storage design, and more.
The K-Factor Selector
Want to quickly compare fire sprinkler k-factors across different design densities and sprinkler spacing? Easy. Here's the calculator I've created that quickly compares pressure requirements and flow rates across different sprinkler k-factors.
Want all these tools in a downloadable, printable & PDF-saving capability? Great! The MeyerFire Toolkit will include this tool as well. You can download and try it out now through September for free.
Other than the Toolkit, users of the comprehensive Fire Sprinkler Database can sort & search among k-factors as one of the parameters when comparing sprinklers.
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Aside from being the historically-preferred location for canine bladder relief, fire hydrants serve an important function in providing access to a water supply system.
Fire Hydrants fall within one of two types; wet and dry barrel.
Dry Barrel, as implied, is not water-filled until the hydrant valve is opened. Dry hydrants are overwhelmingly the most popular type of hydrant within the United States to provide insulate using depth to prevent freezing portions of the water supply.
Wet Barrel hydrants, though infrequent, are used in portions of southern California and Florida. These hydrants have one or more operating stems which run horizontal at each outlet. As implied, wet barrel hydrants are water-filled at all times.
The conical cap for the hydrant, or bonnet, holds the operating stem nut in place and protects the hydrant from mechanical damage and water penetration.
The branch pipe serving the hydrant from the city main is one restriction for the overall capacity of a hydrant. While older systems often connect hydrants with 4-inch branch pipe, a minimum of 6-inch pipe should be used to limit pressure loss and permit greater flow capacity. Our friction loss tool can be helpful in estimating loss through these pipes.
The flange at the base of the hydrant is the point of connection for the hydrant to the rest of the barrel.
While the dimension from the bonnet to the flange of the hydrant is standard, the height of the flange becomes important during installation as it determines the height of the outlets. Because hydrants need to be quickly accessed during an active fire, hydrant outlets need to be installed tall enough to allow a full-revolution of a hydrant wrench from the lowest outlet.
Some jurisdictions paint hydrants or hydrant bonnets to identify the capacity of the hydrant.
NFPA 291, the Recommended Practice for Fire Flow Testing and Marking of Hydrants, suggests hydrant colors as Red/Class C, Orange/Class B, Green/Class A, and Light Blue/Class AA for Less than 500 gpm, up to 1,000 gpm, up to 1,500 gpm, and 1,500 gpm and more, respectively (NFPA 291-2019 18.104.22.168).
A traditional dry barrel fire hydrant contains three outlets: two 2 1/2-inch (65 mm) side outlets and a single 4 1/2-inch (115 mm) or 6-inch (150 mm) "pumper" outlet. The latter outlet gets its name as it is often the preferred choice for the fire department to connect and feed pumper trucks.
The size and number of the outlets serve as one limit to the capacity of the hydrant. While the typical hydrant described above is the most common type, other combinations certainly exist - downtown St. Louis, for instance, have hydrants with only a single pumper outlet.
The stem nut is the key to operating the valve within the hydrant. Typically shaped as a pentagon, the stem nut will turn the operating stem of the hydrant and raise the valve to an 'open' position when turned with a hydrant wrench.
Unless mechanically restrained, thrust blocks serve as a way to distribute the hydraulic force of the pipe network into the soil. Our thrust block calculator can be helpful in sizing these blocks.
When in the 'open' position, the valve at the bottom of a dry barrel hydrant rises to plug drain holes and simultaneously permit water to fill the barrel of the hydrant.
When in the 'closed' position, the valve lowers to block water passage and re-open drain holes at the bottom of the hydrant. These drain holes act as weeps which slowly drain the hydrant barrel and help prevent freezing.
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One of the popular aspects of fire sprinkler installations that is overwhelmingly familiar to fitters in the field yet something I hardly understood back as a new graduate is pipe connections. Today I'm breaking out some of the popular methods of joining steel pipe in fire sprinkler systems.
While copper, CPVC and PEX are listed for use in fire sprinkler systems (PEX is only for NFPA 13D systems), black steel pipe remains the most popular pipe material for commercial fire sprinkler applications, at least within the United States.
For steel pipe, the primary means of connecting the pipe include threaded fittings, grooved fittings, plain-end compression fittings, flanged connections, and welding.
Plain End Pipe
Steel pipe when initially formed has flat cut, unpolished ends. This is generally referred to as plain end pipe.
Plain end pipe can be connected by compression fittings or push-on fittings, which bite into the pipe to prevent separation. While popular for other building systems, use of plain end pipe and compression or push-on fittings are not used in sprinkler systems due to the relatively high pressures sprinkler systems experience.
Perhaps the most common current method of joining fire sprinkler pipe for smaller pipe diameters, threaded pipe makes use of helical crests that screw into a female threaded fitting.
To create threaded pipe, a plain-end pipe is cut with a threaded machine decreasing the thickness of the pipe wall. As a result, the areas remaining below and adjacent to the thread become weaker and more susceptible to corrosion breakthroughs with the thinner wall of pipe.
As compared to grooving or welding pipe, the pipe wall thickness must be thicker to accommodate the cut-in threads (ASME B1.20.1) for threaded pipe. NFPA 13 22.214.171.124 (2002-2016 Editions) addresses minimum pipe thicknesses for threaded pipe up to 300 psi, unless the pipe is separately listed for fire sprinkler use:
When connecting threaded pipe, joint compound or pipe tape is applied to the male thread to avoid water leakage.
While threading larger pipe was common throughout the early to mid twentieth century, the weight of Schedule 40 pipe and difficulty of turning large diameter threaded pipe makes threading an uncommon choice for larger diameter sprinkler pipe today.
Grooved pipe is a popular method of pipe joining invented by Victaulic with roots in both World Wars to deliver water and petroleum with faster, more reliable method of pipe connection.
Grooved pipe is formed by either cutting into the pipe (cut groove) or by pressing an indentation into the pipe (roll groove).
Cut groove pipe results in a lesser pipe thickness, weakening the pipe and also offering less protection against corrosion.
Roll grooving, while keeping the pipe wall thickness, also poses issues in low-sloped dry and pre-action systems as the rolls on the interior side of the pipe create areas to trap water and create an air-water interface for corrosion to occur.
Grooved pipe has a number of inherent advantages. Smaller pipe thicknesses are permitted for grooved pipe, resulting in thinner pipe which makes transporting, carrying, and lifting into place easier. Minimum thicknesses for Grooved Pipe:
With thinner, lighter pipe and easy grooved coupling options, labor can be less difficult and significantly quicker.
Welded & Flanged Pipe
A less common but additional option for restraining pipe is welding. Pipe can be welded as an outlet - where a welding equipment cuts a hole in one pipe whereafter another pipe segment is held in place and the two are welded together.
Welding has a few advantages - it can be (and often is) performed in a fabrication shop, does not require any additional fittings, and can allow for more custom pipe arrangements.
For instance: a 4-inch x 4-inch x 1/2-inch outlet for a pressure gauge connection might be a special order reducing tee (ie: costly); as a welded outlet, it could be quickly and easily welded into place with the outlet easily threaded or grooved.
Welding is not limited to outlets, however. "Slip-on flanges" can be welded to the hub side of the flange to a piece of pipe, allowing two flanged fittings to be bolted together with a gasket in-between.
Flanged pipe and fittings are common around fire pump assemblies, as NFPA 20 annex material even notes that "flanges welded to pipe are preferred" despite screwed, flanged mechanical joints or other approved fittings are allowable (NFPA 20 2003-2007 126.96.36.199, 2010-2013 4.13.2, 2016 4.14.2, 2019 4.15.2).
Different installing contractors often have different preferences on fabricating pipe. Personally I've worked with some who prefer to have welded outlets along 21-foot lengths of pipe and groove as much as allowed for a job to use lighter, thinner pipe, including through branch piping. Others prefer some flexibility of threaded pipe to make quick changes in the field and provide a more traditional, tightly-connected threaded system.
What do you commonly see? Does your team have preferences for fabrication methods? Discuss this here.
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Last week I introduced a new Thrust Block Calculator and explored some of the concepts around the design and function of Thrust Blocks.
Here's the new expanded thrust block calculator. With similar inputs as before, we're now able to calculate the thrust block volume required, as well as determine the height and width required for the thrust block.
Toolkit is Here
Well it's here! The MeyerFire Toolkit is past a beta version and ready for you.
To celebrate here's the latest version I've created and free access that runs through the end of September. You can download the complete Toolkit with installation instructions below:
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One fundamental aspect of fluid movement is thrust force, which is created when a flow path bends, tees, wyes, dead ends, or reduces. In order to counter the unbalanced forces that are created at these locations, the pipe and fittings must be mechanically restrained from separating, welded together, or otherwise fixed from movement.
Push-On Underground Joints
One popular method of preventing pipe separation for underground pipe is gasketed push-on joints for underground pipe that do not have special locking devices, but permit pipe to be installed in any direction and at any point along the path.
Role of Thrust Blocks
In order to prevent the internal pressure from forcing the pipe and fittings to separate, blocking (or "thrust blocks") provide stability and allow the surrounding soil to accept the thrust force from the pipe assembly.
Soil conditions vary in its ability to handle forces. Thrust blocks allow a narrow point force to be spread and distributed across larger areas of soil down to a pressure that the soil can bear.
Thrust blocks take the point force created from the change in direction of the water (static and dynamic)
and distribute that force to the soil.
The tool below is an early part of a larger effort to determine the thrust block detailing. In the coming weeks, I would like to add block height, width, volume and visualizations to detail the parameters.
Don't see the tool below? Click here.
For those who work routinely with thrust block and their calculations under NFPA 13, what else could I add to this tool to be more useful? Comment here or email me at email@example.com if you have any ideas.
The Toolkit - Launches Next Week
The long-awaited Toolkit launches next week - complete with this and other tools in a downloadable software package. Be the office hero with quick and printable tools, as well as access to the Sprinkler Database and the ability to post questions to users on the Daily Discussion forum.
Look out for news regarding the launch next week.
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Shop drawings (or installation drawings, fabrication drawings, or working plans) are a cornerstone of the fire protection industry. Prepared by or under the installation contractor, this design package contains the most important details concerning the design of fire sprinkler systems.
NFPA 13 has specific requirements to what is required for a shop drawing submittal. It is enforceable by the Authority Having Jurisdiction anywhere that NFPA 13 is used as the reference standard.
Below is a basic checklist for items that are required to be indicated in a shop drawing package, with references to whichever edition of NFPA 13 is being used.
There's many items required to be included in a set of shop drawings beyond just the basic design parameters.
Don't Be A Jerk
Unfortunately I have seen these references abused - an engineer rejecting submittals for not including a graphic scale, for instance, which does nothing to improve the technical content of the submittal but does adequately upset every person involved in a project.
It is a rare submittal that achieves and includes every single aspect of the checklist (how often do you see a full-building section, for instance?). However, if you're a review party, review engineer, or shop drawing designer/engineer, this re-organized checklist with references may help clarify expectations for the design package.
Shop Drawing Checklist
When using this tool, select the edition of NFPA 13 used in the red box on the right-hand side. The references and checkboxes will autopopulate based upon your selection.
Don't see the tool below? Click here to see it.
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Joseph Meyer, PE, is a Fire Protection Engineer in St. Louis, Missouri. See bio on About page.