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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Toolkit Release in a Few Weeks
We're just a few weeks away from the Toolkit release. It'll contain everything that's in the tool now, plus the popular Sprinkler Database and the ability to post any question to the Daily followers.
The MeyerFire Toolkit contains all of the quick tools I use regularly, which can be printed or saved as PDFs.
Haven't seen the Sprinkler Database? Watch this quick video:
If you've demo'd the MeyerFire Toolkit and have any ideas or suggestions, it's not too late! Please email any ideas for improvement at email@example.com.
Vote on the Next Project
Here's the top five ideas for next development. Click here to vote below to rate the idea and help guide the direction of tools & resources:
Floor-Mounted Obstruction Calculator
While it doesn't come up all that often, floor-mounted items can create obstructions for sprinklers just as anything hanging from a ceiling. This calculator is a quick-assessment tool similar to the popular Sprinkler Obstruction Calculator.
Access: Free to Everyone / Downloadable for Toolkit Members
Fitting Hydraulic Loss Calculator
This tool is an expansion of the popular Friction Loss Calculator, but compares loss across various sizes with more output analytics. Trying to decide whether a backflow preventer was calculated correctly? Will you need a 3" or 4" sprinkler riser? Will the choice between various flex drop suppliers matter? This is the tool for you.
Access: Free to Everyone / Downloadable for Toolkit Members
Fire Pump Database
This comprehensive database lists all of the various models of fire pumps available on the marketplace. Just like the Sprinkler Database (currently available to Sprinkler Database subscribers), this database allows users to quickly search and filter all current fire pumps on the markets. Links from the database go straight to manufacturer's websites, product data, CAD details, and Revit models.
Access: Free to Toolkit Members
Trapeze Hanger Calculator
This tool is a quick-sizer with analytics for designing & sizing trapeze hangers for fire sprinkler systems.
Access: Free to Everyone / Downloadable for Toolkit Members
This site is created to help you excel in fire protection. It's all about a supportive community & fast tools to help you do great work in fire protection.
Next week I'll be covering big-picture differences between NFPA 13, NFPA 13R, and NFPA 13D. If you haven't already subscribed, you can do so here. Have a great week.
In hindsight it seems silly that early as a designer I didn't take time to understand some of the basic nuances and differences in pipe fittings.
Performance Spec Beginnings
Like a good handful of engineers in the industry, I began early in my design days doing bid/performance specification work - outlining big picture issues and project nuances - while leaving the system layout and detailing to the fire sprinkler contractor. It lends itself to understanding code surprisingly well, but lacks the hands-on experience to understand how systems are actually built.
Understanding Each Component
Why is understanding the fitting components important? When I started laying systems out there's some natural rules that develop due to availability of the materials. If you want a basic, labor efficient, and cost-effective system, then it's imperative to understand what materials are commonly available and cost effective - and materials are considered "special order" (ie: expensive and longer lead-times).
After doing shop drawing/fabrication design, finding ways to create clean designs with commonly available components is a very important part of the design process.
Overview of Components
In today's article I'm covering the basic, traditional threaded pipe fittings.
Likely the most familiar component - an elbow has two openings traditionally 90-degrees apart, with female threads on both ends. Elbows can vary in angles - while the most common are 90-degree and 45-degree, cast-iron fittings also offer a 22-1/2 degree threaded elbow.
The 'turn' on the elbow also can vary, particularly with cast-iron elbows. "Long-turn" elbows have a larger radius and make a more gradual curve, which could have hydraulic benefits should the application justify it.
"Street Elbows", typically available as a malleable-iron fitting, is an elbow with a female thread on one side and a male thread on the other. They can be particularly helpful when an elbow is needed to come directly off a welded branch line without a riser nipple in-between the branch pipe and the elbow. I don't know where "street" elbows get their name, but I like to think it comes from a dark and cloudy past of use in 1920's style gangster street battles.
Reducing Elbows & Tees
Elbows, like tees, come in reducing styles, where one opening is simply a different (reduced) size from the original opening. This is a very helpful and friendly feature with threaded fittings, as there are many different reducing elbow and reducing tee sizes that makes their use with branch lines easy.
Identifying Reducing Fittings
To label the size of a reducing tee or elbow, there's a specific order to the different openings.
A 1 x 1/2 reducing elbow, for instance, emphasizes that the primary opening is 1-inch and the smaller opening is 1/2-inch. While this terminology doesn't matter much for a traditional elbow that can be quickly spun around, it's more important for reducing street elbows and certainly for tees.
Reducing tees are labeled by their primary opening (opening A, above), then the opposite side (B, above), and then the last outlet in-between and perpendicular to the first two (opening C, above). If a branch line goes from 1-1/4" in diameter, to a 1" pipe, while serving a 1/2" threaded sprinkler at the intersection, then this reducing tee would be a 1-1/4" x 1" x 1/2" (A x B x C).
Crosses can be helpful when sprinklers split on either side of a continuous branch line. Crosses also offer a good reminder that just because a cross exists, doesn't mean it exists in the wide variety of combinations that could possibly be necessary.
Ductile iron crosses, for instance, are commonly in three sizes 2 x 2 x 1 x 1, 1-1/2 x 1-1/2 x 1 x 1, and 1-1/4 x 1-1/4 x 1 x 1. Cast iron are generally available in a wider variety, even offering sides C and D below in different sizes. It's important to caution, however, that just being available doesn't mean an item is commonly available as 'off the shelf'.
The naming convention for crosses is the primary side (largest, A above) x opposite side (B, above) x adjacent north side (C, above) x remaining south side (D, above). A cross that connects a 2-inch branch pipe to a 1-1/2-inch branch pipe while also splitting out to serve two 1" armovers would be a 2 x 1-1/2 x 1 x 1 fitting.
Riser Nipples to Avoid Crosses
One trick to avoid semi-custom crosses entirely is to consider using two tees at the intersection. Running a riser nipple from one line to another slightly above it can make use of more common reducing tees and give the designer some flexibility that crosses don't always offer.
Order of Threading
One other item to consider with crosses is the order of threading. It's important not just to select fittings that functionally work for a design, but that can physically be threaded in a sequence that can actually be accomplished in the field.
One classic situation fitters understand all too well that designers don't is the order of threading. Without a union, you can't have two risers connect into the same main drain with threaded fittings. Likewise, without a union, a gridded system can't only use threaded connections.
Why? It's all about the order of installation. Threads can only be accomplished in one circular direction (righty-tighty, lefty-loosey, right?). Because of this, threading one end will lock in pipe without the ability to then rotate the pipe on the other end.
Now introducing the union. Sent by the pipe gods, the union has a female threaded connection on both ends with a swivel disc (for lack of a better term) in-between, that allows rotation between the two female inlets. This swivel ability allows threading to occur on either side of the union without the opposite side needing to turn. As cited in the above examples, unions are used to make closed connected systems threadable.
The more basic counterpart to the union, the coupling connects two male segments by way of two female inlets.
If you ever get this mixed up and happen to order unions instead of couplings - don't worry - you'll get a call from someone in the field who will be 'happy' to straighten things out. At least that was the case for me the first and last time I accidentally swapped the two.
Also known as 'reducers' and 'bell reducers', reducing couplings connect two male threaded segments off different sizes. In the sprinkler industry these are far and away the most popular fitting used to connect a sprinkler to a sprig, drop, or armover.
The actual styles and look can vary, but in basic premise there's two different sized inlets with a hex or another flanged point to attach a wrench and turn the coupling relative to a pipe or sprinkler.
Less common in steel systems than in CPVC systems (where there's many less fitting options), bushings are similar to reducing couplings except that one side is male and the other is female.
One applications I've come across that's made good use of bushings is in a new installation installing upright sprinklers were a future ceiling will be provided. Since a minimum 1-inch outlet is required for sprinklers below a ceiling (NFPA 13-2106 126.96.36.199), the 1-inch outlet can be provided but installed with a bushing that can screw directly into the 1-inch outlet and still accommodate the 1/2-inch thread of a standard upright sprinkler.
Plug & Cap
One of the concepts that prompted this article was a discussion my wife and I had about the differences between plugs and caps (yes, I do think about this stuff all the time). In short, plugs have a male connection while caps have a female. They both generally serve the same purpose - to stop the flow of anything in the pipe network.
I don't come across caps in threaded systems much, primarily because of the availability of reducing fittings that size each component to its need. Caps are common for temporary drops in ceilings to close up a system while waiting for ceilings to be installed. Caps are also used when a branch pipe needs to be extended beyond the last sprinkler to catch a hanger.
Plugs are used quite a bit - at remote auxiliary drains that aren't piped to a discharge location, for three-way valves serving water gauges, or on tees connected to dry sprinklers.
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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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New Backflow Preventer Database
I've started a new database for backflow preventers in a similar way to the popular fire sprinkler database.
Backflow preventers are and have been a mainstay on fire sprinkler systems to protect the public water supply from backsiphonage. They're required by both the International Plumbing Code (608.16.4) and the Uniform Plumbing Code, two popular enforced codes in the US and elsewhere.
The new Backflow Preventer Database is in beta and available to current Sprinkler Database subscribers.
Backflow preventers have a number of different parameters. There's differences in types (double check, double check detector, reduced pressure zone, and reduced pressure detector), materials, listed rating, sizes, connections (flanged, grooved), valve types (outside screw and yolk or OS&Y, non-rising stem or NRS, butterfly valves, or ball valves), orientations (horizontal, vertical, n-pattern, y-pattern, z-pattern), and various certifying agencies (UL, FM, ASSE, CSA, NSF, USC).
Most of my curiosity and the reason for building to the tool was (1) to determine what is actually available on the market today, (2) what are the differences between types and models, and (3) how can I easily access manufacturer websites, product data, CAD details, and Revit families with one-click. That curiosity led to the new Backflow Database.
While it's still in an early beta-testing mode users who are already subscribed to the Sprinkler Database can now access the Backflow Database by logging in.
If you're a Sprinkler Database user, give it a try and let me know what improvements I can make. Right now the database includes Wilkins, Ames, and Febco models. Have a manufacturer you'd like to see? Have ideas for updates? Email me at firstname.lastname@example.org or comment here. Thanks in advance!
Vote on New Tools & See What Else is Coming Soon
Around here we're always in development on new and improved tools to help designers, reviewers, inspectors, installers, and engineers in the fire protection industry.
You can now see, and vote, on upcoming tools that are in development for MeyerFire.com. The "Coming Soon" page is now live under "Tools" on the website header.
Take a look at upcoming tools, rate each, and share ideas that we can work towards on this new area of the website.
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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 188.8.131.52 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 184.108.40.206). 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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Quick updates for this week - thanks to helpful recent suggestions I've updated the Friction Loss Calculator to include several NFPA 13-provided fittings as well as fluid velocity among various sizes.
With a flow rate and length of pipe, you'll see fluid velocity as it's own column in feet/second. While both NFPA 13 and FM Global do not have any limitations on fluid velocity, it's a good point of reference to reference how quickly a fluid is moving through the pipe.
The brief list of fittings at the bottom allow you to compare friction loss across a number of different assembly sizes, so you can compare runs of pipe or assemblies at various sizes all at the same time.
Can't see the tool above? See it here:
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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 220.127.116.11).
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 18.104.22.168 (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 22.214.171.124, 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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Joseph Meyer, PE, is a Fire Protection Engineer in St. Louis, Missouri. See bio on About page.