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Leaders in Flexible Drops

8/31/2016

Two weeks ago we covered Benefits and drawbacks of flexible sprinkler drops, and last week we covered Considerations with flexible sprinkler drops. This week we offer a summary of industry leaders in the U.S. market with flexible drop technology. Know someone we're missing? Contact us so we can be sure to provide a thorough summary.

Summary of Leaders in Flexible Drop Technology in the U.S. Market

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Supplier	Lengths (inches)	Approvals	Max. Sprinkler K-Factors	Bend at Nut?	Max 90 Deg. Bends (applicable sizes)	Min. Bend Radius	Source / Website / Pressure Loss
EasyFlex	24, 36, 48, 60, 72	UL/FM	K5.6 for 1/2" outlet (UL/FM) K8.0 for 3/4" outlet (UL/FM)	No bend within 2.52 inches from connection nut	1 (24) 2 (36) 3 (48) 4 (60, 72)	4 inch (UL) 8 inch (FM)	Link
FlexHead	24, 36, 48, 60, 72	UL/FM	K5.6 for 1/2" outlet (UL/FM) K14.0 for 3/4" outlet (UL/FM) K22.4 for 1" outlet (FM)	No limit	3 (24, 36) 4 (48, 60, 72)	3 inch (UL) 8 inch (FM)	Link
Sidewinder	30, 48, 60	FM	None Listed	Not within 2.5" of connection nut or reducer	3 (30, 48, 60)	6 inches (FM)	Link
SprinkFlex	28, 40, 48, 59, 71	UL/FM	K8.0 for 1/2" reducer (UL) K11.2 for 3/4" reducer (FM) K5.6 for 1/2" outlet (FM) K8.0 for 3/4" reducer (FM)	Not within 2" of connection nut	2 (28) 3 (40, 48, 59, 71)	3 inch (UL) 8 inch (FM)	Link
VicFlex	31, 48, 60, 72	UL/FM	K8.0 for 1/2" reducer (UL) K14.0 for 3/4" reducer (FM) K5.6 for 1/2" outlet (FM) K14.0 for 3/4" reducer (FM)	No limit	3 (31) 4 (36, 48, 60) 5 (72)	2 inch (UL) 7 inch (FM)	Link

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Considerations with Flexible Sprinkler Drops

8/25/2016

Last week we covered Benefits and Drawbacks of Flexible Sprinkler Drops, and this week's post covers things to consider when using the technology.

Maximum Bends

The listing for each product limits the maximum number of bends that the installation can use
The greater number of bends allowed will help allow for flexibility in the actual installation (to avoid obstructions), but the greater number of bends used also significantly impacts friction loss within the drop.
It's important to also verify the actual number of bends used in installation so that the install does not violate the manufacturer's listing.

Maximum K-Factors

There are limits to sprinkler k-factors provided with flexible drops. These limitations are listed in the product data for each drop.

Minimum Bend Radius

In order to prevent kinking, the UL Listing and/or FM Approval process dictates a minimum bend radius. This is listed in the manufacturer's product data.
It's important to also verify minimum bend radius for field inspections so that the install does not violate the manufacturer's listing.

Bending Near Mounting Nut

Some manufacturers require a minimum distance before a bend is allowed at the nut near the mounting bracket. This distance varies across manufacturers (we'll explore more next week) and is available in the product data.
Some manufacturer's combat this limitation by providing a 90 degree elbow immediately at the reducing fitting near the mounting bracket, which offers flexibility in the hose direction directly above the sprinkler.

Flexible Drops have limitations on minimum bend radius, the maximum number of bends allowed, and bending near the mounting nut

Hanging

Flexible sprinkler hose fittings exceeding 6 feet in length are required to use a hanger attached to structure (NFPA 13 2016 Section 9.2.1.3.3.3, which was added in the 2016 edition)

Pressure Loss

We'll see this in more detail next week, but pressure loss within the flexible hoses have significant hydraulic impact, and vary widely across different products.
Pressure loss needs to be incorporated in the hydraulic calculations.

Types
Braided

Braided hose is defined by the external braiding which wraps and protects the interior corrugated hose.
This arrangement better retains internal water pressure and prevents deformation of the hose, prevents overbending of the flexible hose, and ends up being more flexible (workable) than non-braided hose
Braided type is required by FM 1637 Standard. This approval process requires 50,000 cycle tests (under ISO 10380)

Non-Braided

Corrugated hose only
Can be prone to extension (corrugations can pop-out)
Can be prone to kinking
Can be very stiff (only tested to 100 cycles under UL test)

Next week I'll briefly dive into the currently available products developed by leaders in the U.S. marketplace.

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Benefits and Drawbacks of Flexible Sprinkler Drops

8/17/2016

While not a code requirement, flexible sprinkler drops have quickly become a major innovation for the fire sprinkler industry. This week's post explores logistical advantages and drawbacks of the technology.

Components

Components of a Flexible Sprinkler Drop Assembly

Advantages

Reduced labor cost

Flexible sprinkler drops can significantly reduce the time to installation. A single return bend on branch piping can be composed of at least seven distinct pieces which include some that must be cut and joined. A flexible sprinkler drop does not require the assembly nor coordination required to locate in specific positions within a ceiling.

Faster project completion

Time savings can lead to an overall faster-completed project.

Allows for ceiling/lid movement over time

Lowering of a ceiling or hard lid can occur over time due to settling, loads placed on the ceiling, or even activity above the ceiling (such as workers above a cooler/freezer). This difference in ceiling position for hard piped sprinklers can cause unwanted obstructions between the new ceiling position and the fixed-in-place sprinkler. Flexible drops allow the sprinkler to move with the ceiling.

Flexible Sprinkler Drop Ceiling Movement

Flexible sprinkler drops allow the sprinkler to stay in the appropriate position with ceiling movement or following seismic events

Seismic performance

In a seismic event, sprinklers on flexible drops can continue to provide protection below a ceiling

Does not require oversized escutcheon

Unless a ceiling is rigidly braced, sprinklers must be allowed 1/4 inch clearance on all sides in buildings with Seismic Category C (ASCE 7 Section 9.6.2.6.2.1) or 1 inch of free movement in all horizontal directions in buildings with Seismic Design Category D, E, and F (ASCE 7 Section 9.6.2.6.2.2(e)).
This requirement necessitates either (1) an oversized escutcheon to cover the required clearance (which may not exactly enamor your architect), (2) a swing joint above the sprinkler, or (3) a flexible drop. While each solution meets code, flexible drops can accommodate the required movement without oversized escutcheons (NFPA 13 2016 9.3.4.11.1).

For facilities with Seismic Design Category D, E, or F, movement must be allowed between a sprinkler and its surroundings. Oversized escutcheons are one method to allow the movement but conceal the surrounding gap.

Remodel friendly

Use of flexible sprinkler assemblies allow easy relocation of sprinklers within a short distance with ceiling modifications without re-cutting, attachment or demolition of existing pipe and fittings.

Disadvantages

Material Cost

A flexible armover assembly can run $160-$400 per assembly, while traditional pipe and fittings can run half that cost or less on materials.

Hydraulic Demand

As we'll explore in next week's post, the hydraulic demand can be dramatically more significant than a return bend, adding the equivalent of up to 100 feet of 1-inch schedule 40 piping in friction loss.

What is your experience?
Join the conversation and discuss what you see as advantages or disadvantages of flexible sprinkler assemblies for this post at www.meyerfire.com.

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Next week I'll explore points to consider with flexible sprinkler drops in design and inspection that I've come across in my research.

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Slope Requirements for Fire Sprinkler Pipe

8/10/2016

Pipe slope is a critical element in reducing water collection following a sprinkler system drain. Water removal is important in that the largest detriment to sprinkler system life, corrosion, occurs across interfaces between air and water. Here is a quick summary of the minimum pipe slope requirements for fire sprinkler systems.

	Non-Refrigerated	Refrigerated
Wet Systems	Branch & Main Pipe: Level (NFPA 13 2002 8.15.2.2.1, 2007/2010/2013/2016 8.16.2.2.1)	N/A
Dry Systems	Mains: 1/4 inch per 10 feet Branches: 1/2 inch per 10 feet (NFPA 13 2002 8.15.2.3.1, 2007/2010/2013/2016 8.16.2.3.1)	Branches & Mains: 1/2 inch per 10 feet (NFPA 13 2002 8.15.2.3.4, 2007/2010/2013/2016 8.16.2.3.3)
Pre-Action Systems	Mains: 1/4 inch per 10 feet Branches: 1/2 inch per 10 feet (NFPA 13 2002 Edition does not require slope for pre-action systems in non-freezing areas per 8.15.2.3.3, 2007/2010/2013/2016 does require slope per 8.16.2.3.2)	Branches & Mains: 1/2 inch per 10 feet (NFPA 13 2002 8.15.2.3.4, 2007/2010/2013/2016 8.16.2.3.3)

Advantages of Return Bends in Fire Sprinkler Systems

8/3/2016

Components of a Return Bend
A return bend is the piping arrangement for pendent sprinklers where piping stems from the top of the branch pipe (riser nipple), runs horizontally (arm over), and then down to the sprinkler (drop).

Components of a return bend in a fire sprinkler system

Where Required
Raw Water Sources, Mill Ponds, Open-Top Reservoirs

Required to avoid sediment and mineral deposit accumulation (NFPA 13 2002 Edition Section 8.14.18.1, 2007/2010 8.15.18.1, 2013/2016 8.15.19.1)

Dry Systems

Although in theory return bends would trap air and prevent water from traveling to a pendent sprinkler, in practice many installers have found water trapped at pendent sprinklers in dry systems even when on return bends. This is in part why return bends on dry systems as well as sprinklers are required to be located in heated areas. (NFPA 13 2002 7.4.1.4, 2007/2010/2013/2016 7.3.2.5)

Where Not Required
Deluge Systems

Deluge systems already provide an open orifice, so sediment accumulation to the extent that the system would be plugged is typically not a concern. (NFPA 13 2002 8.14.18.3, 2007/2010 8.15.18.3, 2013/2016 8.15.19.3)

Where Dry Pendent Sprinklers Are Used

Sediment accumulation may be less of an issue at the sprinkler, but could still be a concern at the edge of the dry shaft. (NFPA 13 2002 8.14.18.4, 2007/2010 8.15.18.4, 2013/2016 8.15.19.4)

Wet Pipe Where K-Factors are 11.2 or greater

In theory large orifices would be more difficult for accumulation of sediment to block. (NFPA 13 2013/2016 8.15.19.5)

Return bends are used primarily to prevent sediment accumulation in the drop to the sprinkler.

So Why Use Return Bends?
1. Sediment Accumulation

Prevent mineral deposit, pipe scale, and sediment accumulation (NFPA 13 2002 8.14.18.2, 2007/2010 8.15.18.2, 2013/2016 8.15.19.2)

2. Sprinkler Installation Flexibility

By piping from the top of the branch pipe instead of the side, sprinklers have the flexibility to be located at the center of tile or a specific location with greater tolerance for the sprinkler installer

3. Remodel and Shell Friendly

Where shell spaces are provided with upright sprinklers, return bends can typically be installed without modifying the branch piping
When systems undergo remodels, taping the top of the branch piping allows for flexibility in future sprinkler placement.

Use of return bends on outlets at the top of branch pipe makes relocation and exact-location placement easier for installers.

Things to Consider
Hangers

Hangers are required to prevent upward movement on the arm over piping when:
- the arm over is steel, exceeds 12 inches, and system pressure exceeds 100 psi (NFPA 13 2002/2007/2010/2013/2016 9.2.3.5.2)
- the arm over is steel and exceeds 24 inches (NFPA 13 2002/2007/2010/2013/2016 9.2.3.5)

Minimum Outlet Dimension

New systems require outlets to be minimum 1-inch, but can have temporary bushings serving upright sprinklers (NFPA 13 2002 8.14.19.1, 2007/2010 8.15.19.1, 2013/2016 8.15.20.1)

Minimum Riser Dimension on Existing Systems

For hydraulically designed systems, nipples less than 1 inch are allowed but cannot exceed 4 inches in length, and must be incorporated in hydraulic calculations (NFPA 13 2002 8.14.19.4, 2007/2010 8.15.19.5, 2013/2016 8.15.20.5)
For pipe schedule systems, nipples less than 1 inch are allowed but also cannot exceed 4 inches in length (NFPA 13 2002 8.14.19.3, 2007/2010 8.15.19.4, 2013/2016 8.15.20.4)

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Further Reading
Minnesota Public safety Issue | Link
NFPA 13 | Link

A New Look

8/2/2016

I'd like to open the blog today with a different flavor of technical information alongside visuals which I hope you enjoy. Early in my career I realized that the value an engineer has is in the knowledge he or she gains and can then convey in order to help others.

Traditional thinking is that experience is the only way to gain knowledge and build value. While that may be true in large part, those who wish to learn without compromise naturally have more to gain and more to offer others. In this blog I hope to note takeaways I've gathered and topics which I hope to explore in more detail as part of my effort to be a relentless learner. It is my way of cementing details I've explored while garnering feedback and learning from knowledge of others.

If you have not already subscribed, you can do so by visiting the Blog and simply entering your email on the right hand side. Thanks for being a part of the journey.

Leaders in Flexible Drops

Considerations with Flexible Sprinkler Drops

Benefits and Drawbacks of Flexible Sprinkler Drops

Slope Requirements for Fire Sprinkler Pipe

Advantages of Return Bends in Fire Sprinkler Systems

A New Look

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