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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3 Comments

mustafa

7/7/2019 04:09:11 am

need experience in the installation as to avoid sprinkler movement or damage the ceiling when the sprinkler activated.

Ben O'Regan

7/24/2019 02:01:55 am

These things are quite expensive and it's really hard to justify the cost. It takes a sprinkler fitter about half an hour to construct a similar arrangement using conventional rigid pipe and threaded fittings - so for most jobs, rigid pipe is more cost effective.

I have known a contractor use these when they were fitting out a small office in a high rise and only had a small window of opportunity to access the site. The owner was willing to pay extra for having the job done quickly and the flexible connections help get the project time down slightly, because the contractor had the sprinkler pipe pressure tested even before the ceiling grid was installed.

The other place I've seen these is in clean rooms. The flexible coupling helps keep the ceiling air tight if the ceiling moves relative to the sprinkler pipe.

Gregory A Bartels

3/16/2020 03:09:44 pm

I have many experiences with flex drops as a foreman/supervisor in the field over the years. They do have a much higher material cost-but there are many advantages over hard pipe. With some training and planning of the installation-the productivity, flexbility, and efficency of getting the job done is much better over traditional hard piped armovers and drops. Plus, the contractor is much cleaner during the finishing phases-avoiding threading oils, cuttings and dirty water when locating the finished sprinklers into the ceilings. If the job is roughed in with the flex assemblies installed with the sprinkler, the contractor can test the system, and finish the sprinklers later without having to drain the system of water. A typical fitter could locate center tile from 15-30 sprinklers in tiles per day using hard pipe and fittings, slower if the armovers required hangers. With flexible drop assemblies, a fitter could finish 50-100 or more flexible drop assemblies in a day, perfect center of tile, without staining tiles or finishes with cutting oils, dirty water, or dirty fingerprints from greasy gloves.
Plus, on design-build jobs, moving sprinklers due to lowered ceilings or field changes was very easy compared to hard pipe.
Drawbacks-higher materal cost, avoiding poor installation with number and radius of bends to hose, poor hydraulic flow of hoses, avoiding other trades removing or trying to move finished sprinklers later.
Greg Bartels

Benefits and Drawbacks of Flexible Sprinkler Drops

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