AUTHOR: Brian O'Connor

Hangers and Support of Sprinkler System Piping

With all of the hard work and effort that goes into designing and installing a sprinkler system, we want to make sure it’s going to stay in place for years to come. Designing the support of such a system is no easy task but if done right can help save lives and property. Hangers need to do three things:  connect to the building itself, typically to structural members; be long enough to reach the pipe they are supporting; and securely attach to the sprinkler system piping. Some hangers accomplish this with one piece while other types of hangers require multiple components. There are requirements for the specific hanger components, for example threaded rods, u-hooks and eye rods all need to be a certain thickness based on the size of the pipe they are supporting. Likewise, there are specific requirements on the type of fasteners that are based on the pipe size and material that the fasteners go into (wood, concrete or steel). This image shows a typical hanger assembly. It consists of a C-clamp that secures the threaded rod onto the building, the rod itself that reaches down to the pipe and the adjustable swivel ring that secures the rod to the pipe. As an added bonus there is a retainer strap that will help the C-clamp stay on the building in the event of an earthquake. This blog will address general requirements that cover most installations but it’s important to note that this blog doesn’t contain all of the requirements for hanging and bracing. To see all of the requirements for hanging and bracing be sure to read chapter 17 of NFPA 13. There are several different types of sprinkler piping support, this blog will discuss hangers (including trapeze hangers) pipe stands and riser clamps. Trapeze Hangers Trapeze hangers are a type of sprinkler piping support that consists of a length of pipe or angle iron that serves as a trapeze bar between multiple structural members which then support the sprinkler system piping. This is usually used for larger pipe so the load can be shared between two structural members or when you need to support pipe that is not directly underneath a structural member.  The requirements in NFPA 13 for trapeze give you a certain section modulus that the trapeze member needs to have, and this is based on the length of the trapeze and the size of the pipe it’s supporting. That section modulus is then translated into either a pipe or angle iron size that is needed for the trapeze member. Installation of Pipe Hangers Two main concepts to consider when it comes to the installation of pipe hangers is the location of hangers on branch lines and the maximum distance between hangers. Maximum distance between hangers needs to be in compliance with the table below. This is done to ensure that there are not long stretches of unsecured piping. Note that nonmetallic piping should follow the hanger spacing requirements located in the product listing. There is more to know about installing hangers than just placing them at their maximum intervals. The following requirements are in place to ensure hangers can properly support the sprinkler system before, during and after activation. Minimum number of hangers – there needs to be at least one hanger on each piece of pipe. Clearance to hangers – the distance between a hanger and an upright sprinkler needs to be at least 3 inches (75mm). This is done to prevent the hanger from becoming an obstruction to sprinkler discharge. Unsupported lengths – the maximum unsupported length between the end sprinkler and the last hanger in the line needs to comply with the table below. Keep in mind that there are different requirements for pendent sprinklers where the maximum static or flowing pressure exceeds 100 psi. Unsupported armover – the horizontal length of an unsupported armover can’t exceed 24 inches (600mm) for steel pipe and 12 in (300 mm) for copper tube. Once again, there are different requirements once the pressure exceeds 100 psi. Pipe Material Pipe Size Maximum Unsupported Length Steel 1 in (25 mm) 36 in (900 mm) 1 ¼ in (32 mm) 48 in (1200 mm) 1 ½ in (40 mm) or larger 60 (1500 mm) Copper 1 in (25 mm) 18 in (450 mm) 1 ¼ in (32 mm) 24 in (600 mm) 1 ½ in (40 mm) or larger 30 in (750 mm)   Support of Risers Risers, which are the vertical supply pipes in a sprinkler system, typically consist of large heavy pipes that are filled with a great deal of water. Due to the weight and force of water flowing through the piping, it is essential to be able to secure them from moving. Typically, risers are supported by a friction-type clamp that rests on or is secured to the floor slab. However, risers can also be supported with riser clamps that are fastened to the building structure or with hangers that support the horizontal piping at the top of the riser. When risers are installed in multistory buildings, they need to be supported at the lowest level and at each alternative level above that, as long as the distance between the supports doesn’t exceed 25 ft (7.6 m). Riser supports also need to be provided at the top of the riser as well as above and below offsets. Pipe Stands Sometimes it is impractical or infeasible to support sprinkler piping from the ceiling. When that is the case, pipe stands can be used to secure piping from the ground, for example, when supporting a back flow prevention device. When pipe stands are supporting piping from the ground, there are maximum heights in which the stands can support. The table below lists these limitations. Most pipe stands are much shorter and usually only used to support large pipe closer to the ground. When the system piping is 10 inch (250 mm) schedule 40 or smaller, it can be supported by a 2 inch (50 mm) schedule 40 pipe as long as the pipe stand isn’t any longer than 4ft (1.2m) (see figure below). The distance between pipe stands follows the same rules as the distance between hangers. Also, similar to pipe hangers it’s important to properly attach the pipe stand to the ground as well as attach the pipe stand to the system piping.   Performance Based Approach As an alternative to the prescriptive based requirements mentioned above you can follow the performance-based approach for installing hangers and pipe stands. With this method, hangers or pipe stands certified by a professional engineer to meet the five conditions listed below can be an acceptable alternative to the other requirements in the hanging and bracing chapter of NFPA 13. This approach is typically only used where listed hangers can not be used for a particular building arrangement or system configuration. Hangers need to be able to support five times the weight of the water filled pipe, plus 250 lbs (115kg) at each point of piping support. The points of support need to be able to support the system Hanger spacing needs to be in compliance with the table (referenced earlier in the blog) Hanger components need to be either iron an iron alloy (such as steel) Engineering calculations need to be submitted to the AHJ as requested. Conclusion In addition to hangers, riser supports, pipe stands and other types of components that support the sprinklers against the pull of gravity, sprinkler systems sometimes also need to be able to be resistant to seismic activity.  Check out our recent blog for information on seismic protection of sprinkler systems. 

Types of Sprinklers

As the saying goes, you need the right tool for the right job, and this applies to selecting the right types of sprinklers to be used in a sprinkler system. This blog is designed to be a helpful reference and contains most of your sprinkler options along with a helpful description of each. While there are several different types of sprinklers, each sprinkler will have a characteristic related to their spray pattern, orientation, and response time that can vary and is addressed below. It is also important to note that although there are a wide variety of different nozzles that can be used as part of an NFPA 13 system this blog only addresses sprinklers. Before we jump into some of the varying characteristics of a sprinkle here is a quick note about basic sprinkler operation. A sprinkler works by having a heat-activated element made of either a glass bulb or a fusible metal link that will activate and discharge water when heated to a designated temperature. Sprinklers are tested and listed for specific uses, and they need to be used in accordance with their listing. SPRAY PATTERN When a sprinkler is activated, a plug is released, and water moves through an orifice at a certain flow and pressure. That water then collides with the deflector which is designed to create a certain spray pattern. Most sprinkler spray patterns fall into one of the following categories. Standard Spray Sprinklers. The standard spray sprinkler is installed in accordance with specific coverage area limitations and is available in pendent, upright, and sidewall configurations. Because the standard spray sprinkler is proven to be effective for a broad range of hazards and applications by adjusting the water discharge density, it is popular and, to a certain degree, serves as the benchmark for sprinkler measurement and performance. Extended Coverage Sprinklers. As the title suggests, these sprinklers have a larger, or extended, coverage area when they discharge. This can help save material and labor costs because you do not need to install as many sprinklers. The trade-off is that they might require a water supply with a higher pressure to discharge at the higher flow rate necessary to cover the larger area they were designed for. Extended coverage sprinklers also come in several orientations and response types. Old Type Sprinklers: Old style sprinklers are only permitted for special situations such as the protection of fur storage vaults. These sprinklers have a unique water distribution, where about half the water is directed upwards and half is directed down. This typically allows these sprinklers to be installed in either the pendent or upright position.   SPRINKLER ORIENTATIONS Sprinklers are designed to be installed in a certain orientation. While this allows additional design flexibility it is also important to ensure that sprinklers are installed in the orientation in which they are designed to be installed. Pendent Sprinkler: A sprinkler designed to be installed in such a way that the water stream is directed downward against the deflector. Pendent sprinklers are very common but standard pendent sprinklers can’t be used with dry pipe systems because water can get trapped between the sprinkler and branch line piping causing ice to block the flow of water. Upright Sprinkler: Upright sprinklers have a spray pattern that appears similar to that of a pendent sprinkler. The difference is that upright sprinklers are mounted to the top of branch lines or sprigs and installed in such a way that the water spray is directed upwards against the deflector. Upright sprinklers can be used in dry pipe systems because water can’t get trapped. Sidewall Sprinkler: Sidewall sprinklers typically are installed along a wall and discharge water away from the wall into the room or space. Sidewall sprinklers can be mounted on the side, bottom, or top of a branch line, as specified in their listings. The discharge pattern resembles one-quarter of a sphere, with a small portion of the discharge directed at the wall behind the sprinkler. Recessed Sprinkler: A sprinkler in which all or part of the body is mounted within a recessed housing. Some recessed sprinklers are meant to be partially recessed into a wall or ceiling while others are designed to be completely flush with the wall or ceiling. Only sprinklers designed and listed to be installed as a recessed sprinkler can be installed recessed. Concealed Sprinkler: A recessed sprinkler with cover plate. The cover plate is typically soldered to the frame that screws or pushes into the sprinkler assembly. The solder is designed to melt at a lower temperature than the sprinkler activation temperature. When the solder melts, the cover plate falls off allowing the sprinkler head deflector to drop below the ceiling height and distribute water after the sprinkler activates. SPRINKLER RESPONSE TYPES Sprinkler response types are determined by their Response Time Index (RTI). This is a method of measuring thermal sensitivity under standardized test conditions. In addition to sprinkler response time, sprinklers also can have different thermal elements that are designed to activate at varying temperatures. For more information on thermal characteristics of sprinkler check out our latest blog that covers that very topic. Quick Response (QR) Sprinkler: A type of spray sprinkler that has a thermal element with an RTI of 50 (meter-seconds)1⁄2 or less and is listed as a quick-response sprinkler for its intended use. A quick-response sprinkler is similar to a standard response sprinkler, except that it possesses a fast-response operating element, so when exposed to the same temperature change, a quick response sprinkler will operate faster than a standard response sprinkler. QR sprinkler technology was developed from residential sprinkler technology. QR sprinklers are tested against the same criteria as standard-response sprinklers. The difference in the size of the operating elements of QR sprinklers and standard-response sprinklers should be noted. Where glass bulbs are used for standard spray sprinklers, the diameter of the bulb of a QR sprinkler is typically less than that of a standard-response sprinkler. Where a metallic alloy is used, the operating heat responsive element of a standard-response sprinkler has more mass than the element used in a QR sprinkler. Standard Response Sprinkler: Sprinklers defined as standard response have a thermal element with an RTI of 80 (meters-seconds)1⁄2 or more. SPECIAL SPRINKLERS Residential Sprinkler: A type of fast-response sprinkler having a thermal element with an RTI of 50 (meters-seconds)1⁄2 or less that has been specifically investigated for its ability to enhance survivability in the room of fire origin and that is listed for use in the protection of dwelling units. Residential sprinklers are designed to prevent flashover, so the spray pattern throws water much higher. Residential sprinklers are required to pass wall wetting tests in addition to floor distribution. Dry Sprinkler: Sometimes referred to as dry barrel sprinklers, dry sprinklers are used in areas where the sprinklers and piping are subject to near-freezing temperatures such as freezers or balconies. A dry sprinkler or dry barrel sprinkler is a sprinkler that is secured in an extension nipple that has a seal at the inlet end to prevent water from entering the nipple until the sprinkler operates. Dry sprinklers are used so a wet pipe system can serve an area that is subject to freezing by holding the water back in a space that can be maintained above freezing. Open Sprinklers: Open sprinklers are used in deluge systems. They are not activated by individual thermal elements, instead the system water supply is held back by a deluge valve that is automatically opened (most often by activation of a heat detection system). This is meant to deliver a large amount of water over a specific area in a short amount of time. They are typically used for protection against high-hazard or rapidly spreading fires. Institutional Sprinkler: Installing sprinklers in a correctional or institutional facility can be tricky since they need to be tamper-proof. Institutional sprinklers are specially designed to prevent people from attaching anything to it that could inflict harm on themselves or others. They are also made with components that cannot be easily converted into makeshift weapons. Corrosion Resistant Sprinkler: A sprinkler fabricated with corrosion-resistant material, or with special coatings or platings, to be used in an atmosphere that would normally corrode sprinklers. Corrosion-resistant sprinklers are either covered with a decorative or corrosion-resistant coating or are designed for a specific function. Additional consideration of corrosion resistance should be given to any attached escutcheon. Stainless steel and aluminum escutcheons are often preferred over mild steel in harsh environments. STORAGE SPRINKLERS Most sprinklers are designed to control a fire. This means that they apply water to a fire to prevent it from growing out of control. This is done in order to allow the occupants to evacuate the building and firefighters to arrive and fully extinguish the fire. There is only one type of sprinkler that is designed to fully extinguish a fire. When it comes to the sprinklers used in the protection of storage areas you will notice that the names of the sprinklers indicate whether they control the fire (control mode) or suppress the fire (early suppression). Control Mode Density Area (CMDA): A type of spray sprinkler intended to provide fire control in storage applications using the density/area design criteria. Control Mode Specific Application (CMSA) These are designed for applications such as storage occupancies. These designs, along with most other types of sprinklers, are intended to control the fire, not suppress it. CMSA sprinklers are a type of spray sprinkler that can produce characteristic large water droplets and that is listed for its capability to provide fire control of specific high-challenge fire hazards. This term is meant to incorporate a wide variety of sprinklers capable of fire control in high challenge fire scenarios. Note that CMSA Sprinklers are tested for use in specific storage configurations and need to be used in accordance with their listing. You might hear some people refer to CMSA sprinklers as large-drop sprinklers. Early Suppression Fast Response (ESFR). Similar to CMSA sprinklers ESFR sprinklers are designed for storage occupancies. Although, ESFR sprinklers are designed for fire suppression rather than control. These are designed to protect rack storage without the need for in-rack sprinkler protection. The ESFR concept is to apply enough water to the burning fuel during the early phases of a fire and penetrate the developing fire plume, achieving suppression. ESFR sprinklers have a thermal element with an RTI of 50 (meters-seconds)1⁄2 or less and are listed for their capability to provide fire suppression of specific high-challenge fire hazards. Caution must be exercised to avoid confusing ESFR sprinklers with other types of sprinklers that are equipped with fast-response operating elements. A non-ESFR sprinkler with a fast-response element is not specifically designed to achieve fire suppression. The relationship among thermal sensitivity, actual delivered density, and required delivered density needs to be considered. Intermediate Level Sprinkler: A sprinkler equipped with integral shields to protect its operating elements from the discharge of sprinklers installed at higher elevations. Intermediate Level Sprinklers are typically designed for use in rack storage sprinkler systems where their thermal elements need to be shielded from the water spray of sprinklers above. Other applications where one might find Intermediate Level Sprinklers include areas beneath open gridded catwalks. RECENT TECHNOLOGY Here are some additional sprinkler types that have recently been brought to the market, they are not as common as some other types of sprinklers but it is important to be aware of them. Polymer sprinklers: A residential fire sprinkler comprised of mainly polymeric materials. These are typically slightly lighter than metallic sprinklers and are lead free, allowing them to be used in a system that uses potable water. As of the writing of this article these sprinklers are limited to being used in NFPA 13D systems. Electrically Operated Sprinklers: Electrically operated sprinklers are a technology in which the primary means of operation is through an electrical signal provided by an electronic control system using specialized detection and control algorithms. These systems are typically used in high challenge storage applications. The systems utilize a combination of heat and smoke detectors to pinpoint the precise location of a fire, which enables the system to actuate (open) the proper number of sprinklers to control and/or suppress the fire. If you enjoyed this blog be sure to check out our blog on the Thermal Characteristics of Sprinklers as well as our blog on the different Types of Sprinkler Systems. Important Notice: Any opinion expressed in this blog is the personal opinion of the author and does not necessarily represent the official position of NFPA or its Technical Committees. In addition, this piece is neither intended, nor should it be relied upon, to provide professional consultation or services.

Commodity Classifications in NFPA 13

Commodity classifications are used to categorize the contents of storage occupancies so that the appropriate sprinkler system design can be identified. Commodity classifications are determined by not only the product but also the packaging of that product, the container those packaged products are in, and even the pallet type. This can get a little complicated, so I’ll run through a quick example. We have glass jars stored in a double layered carboard box with cardboard dividers and it is sitting on a reinforced plastic pallet. Even though the glass jars are only a Class I commodity, the cardboard box and plastic pallet increases the fuel load so that it should be considered a Class IV. Commodity Classifications are broken down into Classes I through IV and Group A though C plastics with Class I being the lowest hazard level and Group A expanded plastics being the highest hazard level. Class I: A Class I commodity is defined as a noncombustible product that meets one of the following criteria: Placed directly on wood pallets Placed in single-layer corrugated cardboard boxes, with or without single-thickness cardboard dividers Shrink-wrapped or paper-wrapped as a unit load Class II: A Class II commodity is defined as a noncombustible product that is in slatted wooden crates, solid wood boxes, multiple-layered corrugated cardboard box, or equivalent combustible packaging material. Class III: A Class III commodity is defined as a product fashioned from wood, paper, natural fibers, or Group C plastics with or without cartons, boxes, or crates. A Class III commodity shall be permitted to contain a limited amount (5 percent or less by weight of nonexpanded plastic or 5 percent or less by volume of expanded plastic) of Group A or Group B plastics. Class IV: A Class IV commodity is defined as a product that meets one of the following criteria: Constructed partially or totally of Group B plastics Consists of free-flowing Group A plastic materials Cartoned, or within a wooden container, that contains greater than 5 percent and up to 15 percent by weight of Group A nonexpanded plastic Cartoned, or within a wooden container, that contains greater than 5 percent and up to 25 percent by volume of expanded Group A plastics Cartoned, or within a wooden container, that contains a mix of Group A expanded and nonexpanded plastics and complies with the graph section at the end of the blog Exposed, that contains greater than 5 percent and up to 15 percent by weight of Group A nonexpanded plastic Exposed, that contains a mix of Group A expanded and nonexpanded plastics and complies with the graph section at the end of the blog PLASTICS Plastics are a little more straightforward since there is a specific list of what each group contains. Classifying plastics gets complicated when the commodity being stored is a combination of different groups of plastics, but the graphs at the end of this blog should be able to help alleviate some of that work. Group C Plastics: Group C plastics are treated as Class III Commodities and consist of the following: Fluoroplastics (PCTFE — polychlorotrifluoroethylene; PTFE — polytetrafluoroethylene) Melamine (melamine formaldehyde) Phenolic PVC (polyvinyl chloride — flexible — PVCs with plasticizer content up to 20 percent) PVDC (polyvinylidene chloride) PVDF (polyvinylidene fluoride) Urea (urea formaldehyde) Group B Plastics: Group B plastics are treated as Class IV Commodities and consist of the following: Chloroprene rubber Fluoroplastics (ECTFE — ethylene-chlorotrifluoro-ethylene copolymer; ETFE — ethylene-tetrafluoroethylene-copolymer; FEP — fluorinated ethylene-propylene copolymer) Silicone rubber Group A Plastic: Group A plastics are further subdivided into expanded and nonexpanded Group A plastics and consist of all of the plastics listed in the table below. ABS (acrylonitrile-butadiene-styrene copolymer) FRP (fiberglass-reinforced polyester) Polycarbonate PVC (polyvinyl chloride — highly plasticized, with plasticizer content greater than 20 percent) (rarely found) Acetal (polyformaldehyde) Natural rubber Polyester elastomer Acrylic (polymethyl methacrylate) Nitrile-rubber (acrylonitrile-butadiene-rubber) Polyethylene Butyl rubber Nylon (nylon 6, nylon 6/6) Polypropylene PVF (polyvinyl fluoride) Cellulosics (cellulose acetate, cellulose acetate butyrate, ethyl cellulose) PET (thermoplastic polyester) Polystyrene SAN (styrene acrylonitrile) EPDM (ethylene-propylene rubber) Polybutadiene Polyurethane SBR (styrene-butadiene rubber) HELPFUL DEFINITIONS One of the biggest issues I see when people are starting to learn about sprinkler design for storage occupancies is that they don’t know the terminology. It is important to fully understand the definitions for the terms used in the storage chapters of NFPA 13, Standard for the Installation of Sprinkler Systems. I recommend looking at the definition chapter of NFPA 13 to make sure you understand exactly what a term means because oftentimes it means something different than what you would expect. Here are a couple of definitions that are important to understanding this blog. Expanded Group A Plastics: Those plastics, the density of which is reduced by the presence of air pockets dispersed throughout their mass. Some examples include packing peanuts or acoustic foam. Nonexpanded is everything else that is not covered under the definition of expanded. Free Flowing Group A Plastics (protect as Class IV): Those plastics that fall out of their containers during a fire, fill flue spaces, and create a smothering effect on the fire. Examples include powder, pellets, flakes or random-packed small objects. Free flowing plastics are those small objects that fill a box or a subdivision within the box without restraint. The theory is that during a fire. The objects will freely fall out of the box and either smother the fire or fall away from it, removing themselves as fuel. Since the burning rate is reduced and fuel load has been lessened, free-flowing plastics are permitted to be treated as a Class IV commodity. Exposed: Commodities not in packaging or coverings that absorb water. For example, a cardboard box or wooden container can both absorb water so they would not be considered exposed. However, something that is wrapped in plastic sheeting could be considered exposed since plastic sheeting doesn’t absorb water. Cartoned - A method of storage consisting of corrugated cardboard or paperboard containers fully enclosing the commodity. GRAPHS The following tables come from NFPA 13 to help with navigating how a commodity should be classified when it contains Group A plastics. Note that the X axis is percentage by volume while the Y axis is percentage be weight.  The first graph addresses exposed commodities while the second graph addresses commodities that are cartoned or within a wooden container (non-exposed). PALLETS When commodities are tested, they are tested on wooden pallets. This means that wooden pallets are assumed to be used in commodity classifications, however if plastic pallets are used, they increase the commodity classification by two classes. Although, if the plastic pallet is made of polypropylene or high-density polyethylene and marked as “nonreinforced” then the commodity classification only needs to be increased by one classification. Plastic Pallet Increase (+2) Class I --> Class III Class II --> Class IV Class III --> Group A Plastics Class IV --> Cartoned nonexpanded Group A plastic Group A Plastics --> Group A Plastics (No increase)  Unreinforced Polypropylene or High-Density Polyethylene Plastic Pallet Increase (+1) Class I --> Class II Class II --> Class III Class III --> Class IV Class IV --> Cartoned nonexpanded Group A plastic Group A Plastics --> Group A Plastics (No increase) Determining the classification for commodities in storage occupancies can get complicated at times but I can not stress how important of a step this is during the sprinkler design process. It is also imperative that the owner understands what the building is designed to handle as well as what can and can not be stored in the facility once it is built. I hope you enjoyed the blog. Comment below if you have questions and be sure to share this with friends and colleagues who might find it helpful.
Energy Storage System

Battery Energy Storage Hazards and Failure Modes

Around the globe energy storage systems are being installed at an unprecedented rate, and for good reasons. There are a lot of benefits that energy storage systems (ESS) can provide, but along with those benefits come some hazards that need to be considered. This blog will talk about a handful of hazards that are unique to energy storage systems as well as the failure modes that can lead to those hazards. While there are many different types of energy storage systems in existence, this blog will focus on the lithium-ion family of battery energy storage systems. The size of a battery ESS can also vary greatly but these hazards and failure modes apply to all battery ESS regardless of size. HAZARDS As with most electrical equipment there are common hazards that need to be addressed as part of operation and maintenance such as a potential for electrical shock and arc flash. These should always be accounted for when working in and around energy storage systems. More information on how to work with electrical equipment safely can be found in NFPA 70E, Standard for Electrical Safety in the Workplace. Thermal Runaway – Thermal runaway is the uncontrollable self-heating of a battery cell. It begins when the heat generated within a battery exceeds the amount of heat that can be dissipated to its surroundings. The initial overheated cell then generates flammable and toxic gasses and can reach a heat high enough to ignite those gasses. This phenomenon can cascade to adjacent cells and progress through the ESS, thus the term “runaway”. Off Gassing – The gasses that ae released from battery energy storage systems are highly flammable and toxic. The type of gas released depends on the battery chemistry involved but typically includes gases such as: carbon monoxide, carbon dioxide, hydrogen, methane, ethane, and other hydrocarbons. If the gas is able to reach it’s lower explosive limit before finding an ignition source then there is the potential for an explosion. An example of this occurred in Surprise, Arizona back in 2019. Stranded Energy – Standard energy is the term used for when a battery has no safe way of discharging its stored energy. This commonly occurs after an ESS fire has been extinguished and the battery terminals have been damaged. This is a shock hazard to those working with the damaged ESS since it still contains an unknown amount of electrical energy. Stranded energy can also lead to reignition of a fire within minute, hours, or even days after the initial event. FAILURE MODES There are several ways in which batteries can fail, often resulting in fires, explosions and/or the release of toxic gases. Thermal Abuse – Energy storage systems have a set range of temperatures in which they are designed to operate, which is usually provided by the manufacturer. If operating outside an acceptable temperature range, the ESS may not work as intended, may result in premature aging of the battery, and can even cause a complete failure that can lead to fire and explosions. Thermal abuse is caused by external sources, it is the result of contact with burning or overheated adjacent cells, elevated temperatures, or exposure to other external heat sources associated with both storage of the cells or the environment in which the ESS is installed. Electrical Abuse – Electrical abuse takes place when a battery is overcharged, charged too rapidly, or externally short-circuited. This can also occur if the battery is discharged too rapidly or if the battery is over discharged below its specified end voltage. Electrical abuse can lead to an inoperable ESS, overheating, fire, and explosion. Mechanical Abuse – Mechanical abuse occurs if the battery is physically compromised when the battery is crushed, dropped, penetrated, or otherwise distorted to failure by mechanical force. Internal Faults – Internal faults can result from inadequate design, the use of low-quality materials, or deficiencies in the manufacturing process. It might be worth noting that the failure rate for lithium-ion cells is said to be on the order of one in a million. Environmental Impacts – Environmental impacts can lead to battery failure. This can be the result of ambient temperature extremes, seismic activity, floods, ingress of debris or corrosive mists such as dust (deserts) or salt fog (marine locations), or rodent damage to wiring.  Some locations subjected to rapid temperature variations such as in the mountains can experience dewing leading to damage within the ESS located outdoors if not well-controlled. While there are numerous applications and advantages to using battery energy storage systems it is important to keep in mind that there are hazards associated with these installations. Understanding the hazards and what leads to those hazards is just the first step in protecting against them. Strategies to mitigate these hazards and failure modes can be found in NFPA 855, Standard for the installation of Energy Storage Systems. NFPA also has a number of other energy storage system resources including the following: Fact sheet on ESS PV and ESS training ESS resource page Blog on residential ESS
Man in a warehouse

Unique Fire Protection Challenges Found in Warehouse/Distribution Centers

NFPA research shows that warehouse fires happen at a frequent rate with an average of 1,410 warehouse fires, two deaths, 20 injuries, and an estimated $159.4 million in direct property damage annually. To avoid becoming part of these statistics it is essential that a fire protection system is correctly designed, installed, inspected, maintained, and tested. Warehouse environments require additional considerations for sprinkler system design. This is due to the nature of how warehouses are designed and used. This blog will look at a handful of unique fire protection challenges found in warehouses and other distribution centers. For more specific information on how to design a sprinkler system see NFPA 13, Standard for the Installation of Sprinkler Systems. Commodity classification The most obvious unique characteristic of a warehouse is that the purpose of the building is to store a large number of goods and products. This can increase the fire load by a significant amount. This is why it is essential, when designing an automatic sprinkler system for a warehouse, that the items being stored are assigned the proper commodity classification. When determining the commodity classification, it is important to include not only the product itself but also the packing material as well as the container and pallet. The different commodity classifications are as follows: Class I – a noncombustible product that is either stored in single layer cardboard boxes or shrink wrapped or paper wrapped. The product can either be stored with or without wooden pallets. Class II – A noncombustible product stored in either wooden crates or multiple-layered cardboard boxes. The product can either be stored with or without wooden pallets. Class III – A product made from wood, paper, natural fibers, or Group C plastics. This can be stored with or without wooden crates and pallets. Class IV – A product that can be made from a mixture of Group B plastics with wood, paper, natural fibers or Class C plastics. The product is allowed to be made from a small percentage of Group A Plastics Group C Plastic – Certain plastics such as PVC. This is treated the same as a Class III Commodity Group B Plastic – Certain plastic rubbers such as silicone. This is treated the same as a Class IV commodity. Group A Plastic -   The most flammable plastics and natural rubbers. This group is further subdivided into expanded or nonexpanded plastics. This is treated differently from all other commodity classifications. In rack sprinklers Warehouses are the only location where you will find sprinklers both at the ceiling level as well as in racks closer to ground level. This is a unique way to get water in the racks and applied to a fire before it is able to grow beyond the capabilities of the sprinkler system. Some higher hazard commodities will require in-rack sprinklers while other commodities have the option to include rack sprinklers and decrease the robustness of the ceiling sprinklers. Prewetting Most sprinkler systems rely on the concept of prewetting as a critical component in controlling a developing fire. Prewetting is when the sprinkler system activates and wets the fuel in front of the fires path, slowing down the fire growth. The issue with warehouses is that they can contain encapsulated products, which are impervious to prewetting (think of something that is wrapped in plastic on all sides). Due to this challenge the sprinkler system would have to be designed to be robust enough to be able to control a fire without prewetting. Obstructions In warehouses there is the potential for Early Suppression Fast Response (ESFR) sprinklers to be used. ESFR sprinklers rely on getting water to the fire quickly, this means both activating earlier than normal sprinklers and discharging water at a higher velocity. Because of this unique design feature, it makes it even more important to ensure that these sprinklers are clear of obstructions. If the sprinklers were prevented from reaching the fire during the early stages of fire growth the sprinkler could be ineffective. Change management Warehouses are likely to have items with varying commodity classifications being stored. Sprinkler design can account for this by either designing to the highest hazard commodity or by creating separate zones for higher and lower hazard commodities. Either way, when warehouses change what they are storing it is essential that the new products do not exceed the hazard level that the sprinklers were designed for. Flammable liquids and gasses Another unique fire protection challenge for warehouses is that there might be large quantities of hazardous materials such as flammable liquids and gasses. These types of materials typically fall outside of the scope of NFPA 13 and into other NFPA documents such as NFPA 30, Flammable and Combustible Liquids Code, NFPA 55, Compressed Gases and Cryogenic Fluids Code, NFPA 52, Vehicular Natural Gas Fuel Systems Code or NFPA 58, Liquified Petroleum Gas Code. These codes contain requirements on the specific containers, building construction, and/or sprinkler design required for the storage of these more hazardous materials. These are just some of the many unique fire protection challenges for warehouse and other similar distribution centers. For more information check out our Warehouse Fact Sheet. Also, come check out NFPA’s 125th Anniversary Conference series on November 16, which will feature presentations on automatic warehouse storage and retrieval systems, the importance of water supply assessment, a review of the changes to the 2022 edition of NFPA 13, and other relevant systems, storage, and suppression topics. Buybox:Title:Featured training|OLS1322SPR

Transformer Fire Protection

While superheroes and the big box office may have everything thinking about robots when we talk about transformers, they are actually a much more important device that is essential for the transmission, distribution, and utilization of alternating current electric power. What are transformers and what do they do? In basic terms a transformer is a device that transfers electric energy from one AC circuit to another, either increasing or reducing the voltage. This is done for several reasons, but two main purposes are to reduce the voltage of conventional power circuits to operate low-voltage devices and to raise the voltage from electric generators so that electric power can be transmitted over long distances. They have been in use for a long time and are an essential piece of our electrical infrastructure. The most common transformer that people often see are located on telephone poles. Why are transformers hazardous? Transformers are often times filled with oil for insulation, to prevent electrical arcing and to serve as a coolant. This oil is similar to mineral oil and very flammable. When a transformer fails it can lead to an intense fire and violent explosion (feel free to check out one of the many videos online on exploding transformers). Transformers can hold anywhere between a few gallons to thousands of gallons. Transformers can be installed indoors or outdoors, but indoor transformers typically are not filled with oil while outdoor transformers often are. Oil insulated transformer protection methods Some of the main considerations when talking about transformer fire protection are fire walls & separation, water based fire protection systems, containment, drainage and lightning protection. Fire Wall & Separation Ideally, we want to prevent transformers from catching fire, but in the event one does catch fire or explode we want to limit the damage and potential spread of fire. This can be done by several means, the most common being physical separation and fire walls. NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations,  recommends that transformers with more than 500 gallons (1900 L) of oil be protected by a fire wall rated for 2 hours that is extended 1ft (300 mm) vertically and 2ft (600 mm) horizontally beyond the transformer. In lieu of a fire wall, physical separation is recommended anywhere from 5 to 25 ft (1.5 to 15 m) based on the oil capacity of the transformer. Fire Protection Systems NFPA 15, Standard for Water Spray Fixed Systems for Fire Protection, contains requirement on how transformers should be protected using a water spray system. If requires  0.25 gpm/ft2 [10.2 (L/min)/m2] of water to be discharged onto the envelope of the transformer itself and 0.15 gpm/ft2 [6.1 (L/min)/m2]  on the surrounding area for exposure protection. The water supply for such a system needs to be able to keep up with the designed flow rate of the system as well as 250 gpm (946 L/min) for a hose for the duration of 1 hour. Another important protection feature is a containment pit and drainage system to help retain any spilt transformer oil or discharge from a fixed water spray system. If a containment area is designated, then the fire wall should at least extend to the edge of that area. Since lightning is a potential ignition source for a transformer fire lightning protection should also be provided. For more information on how lightning protection works see NFPA 780, Standard for the Installation of Lightning Protection Systems. Transformer failures can be extremely dangerous but with the right precautions in place fires can be controlled to limit damage to the surrounding components, minimize plant downtime and improve survivability of plant staff. There is a lot more that goes into panning and designing a safe transformer installation, but this addresses the main concepts and ideas. For more information on fire protection recommendation for power generating plants check out NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations.

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