Walk-in commercial coolers and freezers present a unique challenge for fire sprinkler systems. Today I'm walking through some of the common issues and tips I've encountered when protecting these units.
Challenge #1: Ice Plugs
The most common and potentially dangerous issue with fire protection in walk-in coolers and freezers is the potential for ice plugs to delay or impair entirely sprinkler discharge.
The thermal mass of water allows for high absorption of heat as compared to other materials and liquids, which is one of the reasons water works so well in suppressing fires. This same property, however, acts as a major inhibitor to activation when large ice plugs form at the sprinkler coverplate or frame.
Ice blocks can prohibit effective and responsive fire protection from gaps in a continuous thermal barrier.
Why Do Ice Plugs Form?
Any gap or compromise between the sprinkler (or pipe) and the insulative cooler/freezer lid can allow moist warm air to enter the cooler/freezer near the compromise. Once this intrusion occurs, the moist air reaches the chilled freezer temperature, the moisture condenses into water and then freezes, forming an ice block.
Those who regularly work in or survey these walk-ins no doubt notice ice plugs.
Tips for Preventing Ice Blocks
Preventing ice blocks is all about quality and lasting seals between the dry sprinkler shaft and the adjacent insulation.
In theory, if any clearance around the dry sprinkler is sufficiently insulated (such as with spray foam) and this foam stays in place for years without movement, then ice blocks couldn't occur.
However, such as is the case in many large retailers or groceries, the tops of the coolers and freezers are subject to some movement from personnel or storage on top of the units themselves. Even with very minor deflection, fixed sprinklers and pipe can shift away from the insulation, cause a gap in insulation, and form ice blocks.
Giving Ice The Boot
Some manufacturers (such as Tyco) offer rubber boots that adhere to the top of the cooler/freezer and tighten to the dry pendent sprinkler, which helps accommodate movement of the lid over time and ensures a better seal against the sprinkler shaft. While a little pricier than a foam insulation can, these can be quick to install and can offer a better seal against the cooler/freezer lid.
Rubber "boots" can simplify installation and provide a consistent seal along the top of a cooler/freezer.
Providing a boot for sealing isn't the only way to better accommodate movement. Flexible drops at the point of connection to horizontal piping, or even Victaulic's new flexibly dry sprinkler can help accommodate movement and afford flexibility to the final sprinkler location, without impairing the insulation.
Challenge #2: Dry Pendent Connections to Tees
A commonly overlooked requirement of dry pendent sprinklers is their point of connection to pipe above. Because the inlet of the runs just beyond the thread of the sprinkler's tube, we can't thread a dry pendent sprinkler directly into an elbow; instead product data requires the connection to be a tee or adapter (for CPVC connections) that have dimensions which don't contact the valve seat. It's a very often overlooked part of the dry pendent installation that's easy to miss.
Challenge #3: Refrigeration Equipment as Obstructions
Very often, the refrigeration equipment is a part of the cooler/freezer supplier's equipment package, and not indicated on mechanical HVAC plans. This poses a frequent challenge for both upfront engineering design and shop drawing, as these shop submittals showing the locations of the units aren't often compiled until very late in the construction phasing.
Without good information on the dimensions of the equipment, it's often difficult for sprinkler layouts to incorporate the equipment without being obstructed under NFPA 13. Coordinating this with the supplier, or anticipating locations with sprinklers in front and rear of the unit help mitigate this late-forming issue.
Size and placement of refrigeration equipment isn't often known until late in the design/shop drawing process, so their final installation often provides obstructions to sprinkler discharge
I know I'm not the only one to come across nuances with fire protection in these cooler and freezer units. What challenges do you come across with cooler/freezer protection, and what tips do you have? Discuss here.
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I receive feedback regularly from many users and observers - and I'm very grateful for both!
Sprinkler Database Interest & Feedback
One member recently reached out about the Sprinkler Database and said:
"I appreciate all the work you’ve done on that site. The sprinkler database has helped tremendously when looking for specialty sprinklers, specifically available storage sprinkler is odd configurations!"
It's a tool that is basic in premise but can save tons of time when you're looking to compare sprinklers, find a specific type of sprinkler, or see if a solution exists for your specific problem. Here's a quick overview
Fire Pump Database
With the interest and feedback from the Sprinkler Database, it was only a matter of time before I expanded this into other areas. You may already have seen the Backflow Database, but now we have a beta version of a Fire Pump Database.
With the fire pump database you can now search for fire pumps of various configurations, drivers, sizes, and then instantly link to CAD and Revit models, performance curves, website links, product data, and dimensions. The current beta version includes AC, Armstrong, and Aurora Fire Pumps.
All-inclusive Toolkit members can log in and use the database now.
Know a Contact for Patterson or Peerless?
If you work for or know a great contact for Patterson Fire Pumps and Peerless Fire Pumps, please let me know their contact information. I'm looking to partner with both of these companies to also help connect users to their products.
Toolkit Sale Through November 30th
Interested in getting the Toolkit and access to all of our tools? Join between now and Friday the 30th for $30 off your first year's subscription. Just use coupon code CYBER18 when you checkout here before Friday November 30th.
Lastly, if you're in the US, I hope you have a great Thanksgiving!
Things are busy around here - despite the PE Prep "offseason" beginning, I've been working on improvements and construction of a handful of promising tools.
One basic but very much needed update is an improvement to the Obstruction Calculator. Now, you can enter either the horizontal distance of a sprinkler or the vertical distance of the sprinkler, and get minimum and maximum feedback based on each.
During design, many of us know the depth of the sprinkler and depth of the obstruction prior to determining where (horizontally) the sprinkler is going to be located away from an obstruction. Now the tool helps support that effort.
If you're a Toolkit user, you have immediate access to these updates and can download the latest updates on the dashboard here.
As always, thank you to those who have sent ideas and feedback! Stay tuned for next week on a new database launch for Toolkit users.
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First, a big thank you to those who commented and emailed ideas and topics that contributed to the latest tool for this site - the Trapeze Calculator.
With only a few "knowns" (pipe diameter and schedule, and distances to nearest structure), you can now quickly calculate the section modulus that's required, visit options for the trapeze bar, and see these options schematically in a to-scale detail.
Have multiple pipes on a trapeze? Calculate the section modulus required for each, add the two moduli together, and simply override the Section Modulus Required value below to see your options.
Get CAD Details
Want a CAD version of the detail? Sure thing - the downloadable All-Access Toolkit allows you to save and print these calculations as PDFs, which can then be imported directly into AutoCAD and use the ALIGN function to scale it to your drawing.
Already a Toolkit user? Install the latest version from your dashboard to get the updates to this tool. No new activation code is necessary.
Don't see the tool below? Try it out here -
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Joseph Meyer, PE, is a Fire Protection Engineer in St. Louis, Missouri. See bio on About page.