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What are Some Different Arrangements for Fire Sprinkler Systems?
INTRODUCTION Sprinkler systems are available in a few different arrangements when it comes to design and layout. In this module, we’re going to go over the various arrangements a sprinkler system can have. Fire sprinkler systems really only have three arrangements: TREE SYSTEMS, LOOP SYSTEMS, AND GRIDDED SYSTEMS. Also, we’re using the term arrangement here because when we talk about a system “type”, we usually would mean a wet-pipe, dry-pipe, preaction or deluge system. NFPA 13 doesn’t use the term arrangement, but that’s what we mean here. A fire sprinkler system can utilize any one of these arrangements. It could also be a combination of them. Let’s go over how to identify each of these systems if you encounter them in the wild. TREE SYSTEM A Tree system gets its name due to the similarities in shape. A tree system is arranged similarly to the trunk and branches of a tree. The water supply (comparable to the roots) feeds the express or feed main (the main trunk) to the cross main (if more than one trunk on the tree) which in turn feeds the branch lines (or the branches of the tree). Tree systems can be basic, or could have the feed main split to serve different portions of a structure. Tree systems were the most common throughout the history of fire sprinkler systems. They are efficient. They’re still common today for slim buildings, small buildings, or low-demand hazards. We’ll talk about that in more detail later. LOOPED SYSTEM A loop system is similar in design to a tree system with multiple feed mains tied together at each end. Loop systems provide two ways for the main piping to feed water to the lines. Loop systems work better hydraulically than a tree system, because the looped main has to flow less water on each pipe in order to work. Dry and preaction systems are allowed to be looped, so loop systems end up being more common for hydraulically demanding dry and pre-action systems. GRIDDED SYSTEM A gridded system is designed and installed using parallel cross mains that are connected using the branch lines. The Primary cross main, or front main, is fed from the water supply. Water is sent through the branch lines to the secondary cross main (or back main). When a sprinkler is activated, water is distributed efficiently through each of the branch lines to the secondary cross main, and back through the branch line with the fused sprinkler. Grid systems perform the best hydraulically, so they are common for demanding wet-pipe sprinkler systems or in very large wet-pipe systems. SUMMARY This is a quick overview of the three pipe arrangements found in sprinkler design. We have tree, looped, and gridded systems. Over the next few modules, we’re going to go over where these systems will be commonly found, as well as the limitations these systems may have from a code standpoint. I’m Chris Logan, this is MeyerFire University.
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Mark Gantz
4/7/2024 02:56:47 pm
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