Actuation of sprinklers at high ceiling clearance facilities

As buildings with a high ceiling clearance are becoming increasingly common, making proper assessments of whether or not the ceiling sprinklers would actuate becomes very critical to designing adequate fire protection systems for such buildings. Two sets of fire test data under high ceiling clearances pertinent to growing 3-dimensaional fires and steady plane pan fires were analyzed to estimate maximum ceiling heights from the given fire sources that would allow actuation of ceiling sprinklers. The threshold fire sizes that would actuate ceiling sprinklers at a given ceiling clearances were also computed for growing fires and steady pan fires. Comparisons of the estimated threshold fire sizes between the growing fires and the pan fires indicate that assessing sprinkler actuations based on pan fire tests, which is a commonly used practice, will be likely to lead to a wrong conclusion. The analysis shows that a much smaller fire size than what pan fire tests might indicate would be needed to actuate sprinklers on high ceilings.     

SMART Sprinkler Protection for Highly Challenging Fires—Part 2: Full-Scale Fire Tests in Rack Storage

An experimental study was conducted to demonstrate the concept of a new sprinkler protection system using Simultaneous Monitoring, Assessment and Response Technology (SMART). Part I of this study focuses on the system design and function evaluation at the component level. The present work is Part II of the study, focusing on full-scale suppression tests to evaluate the performance of SMART sprinkler technology in protecting rack storage fires. The selected fuel was cartoned unexpanded plastic (CUP) commodity representing an intermediate level of fire hazard. The storage height increased from 3 tiers (9.1 m) to 5 tiers (10.7 m) to 7 tiers (12.2 m) in the three tests. The sprinkler activation was initiated by a smoke detector and a ceiling temperature rise threshold. The fire location was calculated as the thermal centroid based on ceiling temperatures. A group of six sprinklers, closest to the calculated fire location, was activated simultaneously. Subsequent fire development was monitored through visual observation as well as ceiling temperature data. Test results show that the SMART sprinklers can provide adequate protection for the CUP commodities stored up to 7-tiers (12.2-m) high within a rack storage under the tested conditions. The water densities used in these tests were approximately 50% of those in existing protection recommendation. These results lay the foundation for exploring potential applications of the SMART sprinklers to Highly Challenging Fires.     

Field test and evaluation of residential sprinkler systems: Part I

A series of full-scale fire tests involving sprinkler installations was conducted in 1979 and 1980 in a two-story residence in Los Angeles, CA, and in a mobile home in Charlotte, NC. Previous laboratory tests, including full-scale room fire tests, had indicated that a prototype “quick-response” sprinkler was effective in controlling residential home fires. More full-scale fire tests under less controlled and more operational conditions were considered necessary to confirm or deny these scientific and engineering judgments. The prime objective of the program was to test the performance of alternative sprinkler designs to “control” the development of fire in single-family dwellings and mobile homes. National Fire Protection Association Editor's Note: This paper is the first of three papers reporting on full-scale residential sprinker fire tests conducted under Grant 79027 for the U.S. Fire Administration by the National Fire Protection Association. In this paper, the objectives of the test program are outlined; the test facilities, Prototype sprinkler, water supplies, sprinkler system design, and instrumentation are described; and the scenarios for the total of seventy-six tests conducted are summarized. The second paper (February 1984 issue) will focus on the results of the test and the conclusions drawn from them and the third (May 1984 issue) will cover a study of the comparative activation times of sprinklers and smoke detectors in the mobile home tests. Mr. Cote is Assistant Vice President (Engineering & Technical Services) for the NFPA. He served as project manager for the test series insofar as the NFPA had overall management responsibilities for the program.     

Analyzing the impact of in-rack sprinklers in a warehouse fire: A demonstration of the role optimization has in mitigating damage

This study presents a tool that illustrates the potential and role that optimization can have in fire protection design and performance. Specifically, the tool uses validated engineering correlations to simulate a warehouse fire, and evaluates whether it is controlled by modeling the placement and number of sprinklers – both in-rack and ceiling. Using initial model inputs that include storage configuration, commodity type, water supply, and sprinkler type, we allow a fire to ignite and simulate its growth behavior and corresponding effects on a nearby target array. For any initial set of input parameters, our tool demonstrates the minimum number and location of available in-rack sprinklers to control the flame spread. With reasonable run times, our work yields new insights into the design of sprinkler systems and, more broadly, the usefulness of optimization in fire protection design.     

The Impact of Thermal Runaway on Sprinkler Protection Recommendations for Warehouse Storage of Cartoned Lithium-Ion Batteries

This study investigates the appropriateness of applying the standard large-scale fire test protocol developed for ordinary combustibles for energetic batteries. A large-scale fire test was recently conducted to determine sprinkler protection guidance for warehouse storage of lithium-ion batteries. The specific battery tested had a 20 Ah capacity, polymer pouch format, lithium iron phosphate chemistry and was at a typical state-of-charge (50%) for long-term storage. The batteries were packaged in single-wall corrugated containerboard cartons on hardwood pallets, as received from the supplier. Each carton contained 20 batteries separated by nested polystyrene plastic dividers. Acceptable ceiling-level sprinkler protection was achieved for 4.6 m (15 ft) tall rack storage under a 12.2 m (40 ft) ceiling using K-Factor of 320 L/min/bar^½ (22.4 gpm/psi^½), quick-response, sprinklers at a discharge pressure of 2.4 bar (35 psig). The effect that thermal runaway of the Li-ion batteries had on the design and outcome of the large-scale fire was evaluated. A focus was placed on the role of thermal runaway during three stages of the fire; ignition leading to sprinkler operation, active sprinkler protection, and conditions after the sprinkler system was turned off. An external ignition source was used in cases where induced thermal runaway, which refers to rapid self-heating of a battery under abuse conditions, did not lead to combustion of the battery contents. Through a combination of experiments and review of literature data, it was found that thermal runaway within a pallet load of cartoned batteries would result in a similar fire hazard as that associated with external ignition scenarios typically used in large-scale fire testing. Regardless of chemistry, evidence shows that fire propagation beyond the battery or carton of origin occurs external to the carton due to limited available air within the carton to support combustion. In addition, intermediate-scale testing showed that sprinkler water would be effective at suppressing a fire at a later stage of battery involvement than was achieved in the large-scale test. This work reinforces the sprinkler protection guidance resulting from the successful large-scale fire test.     

Computational fluid dynamics studies on the effectiveness of sidewall sprinklers to suppress the fire at the undercarriage of mass rapid transit train

This paper reports the computational fluid dynamics (CFD) studies of sidewall automatic fire sprinklers installed adjacent to and in close proximity to the trains to suppress the fire at the undercarriage of the trains in the stabling yard, for the sake of protection of the train assets. Plume cooling due to water spray from fast response sprinklers is simulated with the sprinkler model available in Fire Dynamics Simulator (FDS). Concurrently, fire suppression due to the interaction between the water and fire source is simply modelled with the assumption of an exponential reduction of the prescribed burning/pyrolysis rate. The objective is to gain some insight about the effectiveness of sidewall sprinklers proposed to prevent the fire from spreading to adjacent trains. CFD simulation results demonstrate that it is highly likely that the undercarriage fire will spread to both the connected train-car and its adjacent train, if only overhead sprinklers are provided in the design. Due to the obstruction posed by the train, water cannot reach the fire source. Sidewall sprinklers are very effective to detect, control, suppress and even extinguish the fire, hence preventing the spread of fire. When sidewall sprinklers are installed on both sides of the trains, further asset protection may be extended successfully to the connected train cars. This study implies that the installation of sidewall sprinklers may be a practical solution for the protection of train assets in the stabling yard.     

Economic Performance of Residential Fire Sprinkler Systems

A benefit–cost analysis is performed to measure the expected present value net benefits (PVNB) resulting from the installation of a residential fire sprinkler system in a newly constructed, single-family house. The benefits and costs associated with installation and use of a fire sprinkler system are compared across three prototypical single-family house types: colonial, townhouse, and ranch. Each of the house types varies by design, size, and fire sprinkler affordability. Six fire sprinkler system designs are evaluated: a multipurpose network system, three stand-alone systems, and two stand-alone systems equipped with a backflow preventer. The sprinkler designs vary by installation cost (materials and labor cost) and required annual maintenance, but all were designed to meet the NFPA 13D standard. The estimated benefits of fire sprinklers include reductions in the following: the risk of civilian fatalities and injuries, homeowner insurance premiums, uninsured direct property losses, and uninsured indirect costs. Results show that residential sprinkler systems not requiring expensive annual upkeep or maintenance are economical. The expected PVNB in 2005 dollars is estimated as $2,967 for the colonial-style house, $3,099 for the townhouse, and $4,166 for the ranch-style house, given installation of the lowest life-cycle cost sprinkler system in each of the house types. A sensitivity analysis that measures the variability of the results to changes in the modeling assumptions confirms the robustness of the baseline analysis.

Limited-water-supply sprinklers for manufactured (mobile) homes

A prototype limited-water-supply (LWS) sprinkler has been developed for manufactured (mobile) homes in a research program sponsored by the United States Fire Administration. The LWS sprinkler is designed to be installed at a 2.44 m (8-foot) spacing and to have a total water supply of 380 (100 gallons). The installation spacing was determined in a series of freeburn fire tests that indicated that the heat release rate at sprinkler actuation could be halved by reducing the sprinkler spacing from 3.66 m to 2.44 m (12 feet to 8 feet). A series of eight fullscale fire tests, including a corner living room scenario similar to that used in the Los Angeles Residential Test Program, was conducted to evaluate the performance of the prototype sprinkler. In five of the tests, room tenability was maintained during the 10-minute period following the actuation of a single sprinkler at a flow rate of 38 pm (10 gpm). In three tests, tenability was maintained with multiple sprinkler actuation (2 or 3 sprinklers) and a total system flow rate of 49 pm (13 gpm). The spray of the sprinkler was characterized in terms of its water flux distribution and drop size distribution. The thermal sensitivity requirements of the sprinkler are to be based upon RTI, C, and temperature rating, which would ensure that sprinkler actuation would occur at fire sizes comparable to those encountered using the prototype LWS sprinkler in this study.     

水喷淋保护下防火玻璃作为防火分隔物的试验研究

针对我国大空间建筑日益增多，而防火分隔手段相对匮乏，不能满足建筑防火设计需求的现状，通过实验证明了在水喷淋作用下高强度单片铯钾防火玻璃作为防火分隔的安全性，通过实验提出在实际运用中具体的使用参数（包括喷头选型、单位面积上水流量、压力、喷头的具体参数），该实验为高强度单片铯钾防火玻璃作为防火分割物应用于大空间建筑提供了有益的实验支持。     

对不同安装高度、工作压力下喷头布置间距的探讨

依据《自动喷洒与水喷雾灭火设施安装》提供的ZST-15型喷头洒水曲线和《自动喷水灭火系统设计规范》(GB50084-2001)(2005版)中的相关规定,分析在保证作用面积内不留洒水空白点和喷水强度的前提下,喷头在不同安装高度、工作压力下所应采取的合理布置间距。     

Fixed Fire Protection Systems in Tunnels: Issues and Directions

Fire protection practices for highway tunnels have been undergoing significant changes in the last decade, largely in response to a number of catastrophic fires that caused tunnel authorities to thoroughly review their fire safety assumptions. One of the fire safety issues currently receiving much attention includes the installation of “active” fire protection systems in addition to the “passive” fire protection features that were until recently considered to be sufficient to mitigate fire risk in tunnels. Passive fire protection measures include the use of fire resistive construction materials which help protect the critical structural elements from damage due to high temperatures. Active fire protection systems include fixed piping systems to deliver water sprays, such as deluge sprinklers and water mist, or other water-based agents such as compressed air or high expansion foam (CAF or Hi-Ex respectively). Active fire protection systems for tunnels are currently referred to as water based fixed fire fighting systems, or FFFS for short. Fire research suggests that measures based solely on passive protection are not likely to be sufficient to protect life and property to the degree warranted by the high monetary and strategic value of modern tunnel infrastructure. Full-scale fire testing and engineering analysis indicate that FFFS have the potential to reduce the impact of a severe fire on the tunnel structure from catastrophic to manageable at an affordable cost. Fire testing with CAF and Hi-Ex foam systems has shown them capable of actually extinguishing very large fires, including hydrocarbon pool fires. Systems based on water sprays on the other hand are not expected to extinguish fires, but rather to control the fire, limit fire growth and heat release rate, prevent fire propagation and provide thermal management. Although there are a few years of experience internationally that have proven sprinkler and deluge sprinkler system to be effective in mitigating tunnel fires, recent testing of FFFS in Europe has concentrated on water mist. One reason is the perception that water mist systems may involve less complex piping and agent storage than CAF or Hi-Ex foam, and may provide equivalent or superior performance with less water and smaller pipes than conventional sprinkler deluge systems. However, many engineering challenges remain to be resolved, such as how much credit to grant to the FFFS in terms of reduced criteria for passive protection, and how exactly to integrate active protection systems with traditional fire safety measures such as the ventilation systems. This article examines some recent developments in understanding how active fire-fighting systems might alter the impact of fires in tunnels.     

SMART Sprinkler Protection for Highly Challenging Fires—Part 1: System Design and Function Evaluation

An experimental study was conducted to prove the concept of a new protection system—a sprinkler system that uses Simultaneous Monitoring, Assessment and Response Technology (SMART). The present work focuses on the system design and function evaluation at the component level. The objective is to demonstrate the feasibility that the SMART sprinkler system can provide adequate protection to highly challenging fires. The new protection system has several key functions including multi-sensor detection, real-time fire location calculation, dynamic sprinkler activation and wireless communication coordinating the system components. A series of fire detection, sprinkler activation and fire suppression tests were carried out to evaluate these system functions. Results show that a combination of smoke and temperature sensors can detect the fire at a very early stage, with the fire size reduced by one order of magnitude, and provide sufficient data to locate the fire. A thermal centroid based algorithm can determine the fire location within less than 50% of the sprinkler spacing on average. The sprinkler activation (six units) concentrating water discharge in the vicinity of the fire can suppress and even extinguish the fire under certain experimental conditions. These results confirm that the design objectives have been achieved. The experimental data also provide crucial information to assess system performance in full-scale tests.     

The Response Time of Different Sprinkler Glass Bulbs in a Residential Room Fire Scenario

The response time of fire sprinklers is essential for their performance, especially in applications where life safety protection is desired. The earlier the sprinkler activates, the smaller the size of the fire. Most commercial residential sprinklers are fitted with 3 mm, 68°C glass bulbs. However, thinner sprinkler glass bulbs with lower operating temperatures are available. The aim of this study was to determine the response time—and the corresponding heat release rate—of different glass bulbs in a residential room fire scenario. A series of tests were conducted inside a compartment measuring 3.66 m by 3.66 m having a ceiling height of 2.5 m. The compartment was either enclosed or had two walls removed to provide a more ventilated scenario. A propane gas burner was positioned at one of the corners. The mass flow rate of the gas was controlled such that either ‘slow’, ‘medium’ or ‘fast’ fire growth rate scenarios were simulated. In each test, nine Response Time Index (RTI) and operating temperature combinations were tested. Each test was replicated three times. In addition, two commercial fire detectors were tested. The results show that the fire is considerably smaller upon activation with a combination of a low RTI and a low operating temperature, as compared to the 3 mm, 68°C glass bulb typically used for residential sprinklers. The operating temperature proved to have a larger impact on the results than the RTI. The heat from the fire was typically detected by the fire detectors prior to the activation of the sprinkler glass bulbs, especially for the ‘slow’ and ‘medium’ fire growth rate scenarios.     

Temperature and velocity correlations in room fires for estimating sprinkler actuation times

Automatic sprinklers are increasingly used in residential occupancies to provide active fire protection. These sprinklers, known as quick response and residential sprinklers, may be located either at the ceiling (pendent-style) or on a wall (sidewall-style). Though several fire models are available for estimating actuation times for sprinklers located under unobstructed ceilings, these use engineering correlations that do not apply to residential-sized rooms. Thus, data are needed for estimating sprinkler actuation times for residential occupancies.This paper reports on fire tests that were conducted in various sized rooms to obtain temperature and velocity data for 73 kW, 100 kW, and 147 kW fires. The data were then used to develop nondimensional correlations for temperature and velocity at the sprinkler locations. The temperature data revealed a significant temperature transient in the hot gas layer, and thus a nondimensional correlation describing the transient phenomenon was developed. These correlations compared reasonably well with experimental data, and they were used to estimate the sprinkler actuation times. The estimates were in reasonable agreement for the pendent sprinkler, except for the smallest fire in a 4.27 m by 4.27 m occupancy. The estimates for sidewall sprinkler acuation were significantly lower than experimental values. This may have been due to the sprinklers' heat losses, which were not accounted for in the calculation.     

Fire tests to evaluate CPVC pipe sprinkler systems without fire resistance barriers

Nine full-scale fire tests were conducted to assess the adequacy of exposed chlorinated poly vinyl chloride (CPVC) pipe and fitting sprinkler systems installed in light hazard occupancies. The tests were conducted in an enclosure using six different types of automatic sprinklers including QREC pendent and sidewall sprinklers, a pendent residential sprinkler, and a sidewall residential sprinkler. Two types of fires, fast growing and slow growing, were used as test fires.The sprinkler in each test was operated with the normal operation pressure until the test fire was almost completely suppressed. Next, to assess the integrity of piping systems after fire exposure, the water pressure was increased to 12.1 bar and maintained for 10 min and then were visually inspected for any leakage while hydrostatic pressure was maintained at 12.1 bar. No leakage was detected in any of the tests.The results of the tests indicate that sprinkler systems based on exposed CPVC pipe and fittings can be safely installed in light hazard occupancies and will provide adequate protection when installed to all the relevant standards.     

Response characteristics of glass bulb sprinkler heads mounted in a paint spray booth

The response of sprinklers mounted in a paint spray booth is usually influenced by paint covering the heat-sensitive element. To avoid this problem, sprinklers are often covered to prevent the paint from accumulating on the heat-sensitive element. The influence of various numbers of paint layers and different types of covers on the response time of two different types of glass bulb sprinkler heads has been investigated. Both wind-tunnel tests and large-scale fire tests were performed in the test series.It was found that covers delayed the activation of the sprinklers considerably, though a faster response was obtained with a quick response sprinkler than with a standard response sprinkler. It was found that the accumulated paint on the heat-sensitive element also affected the response time, but not nearly as much as the covers. It was also found that a paint layer covering both the glass bulb and the frame acted as a glue; the consequence was that the spray pattern of the sprinkler was considerably affected.     

Field test and evaluation of residential sprinkler systems: Part III

A series of full-scale fire tests utilizing prototype “quick-response” sprinklers was conducted in a two-story residence in Los Angeles, CA, and a mobile home in Charlotte, NC. A prime objective of the program was to test the performance of alternative sprinkler designs to “control” the development of fire in single-family dwellings and mobile homes. Part of the mobile home test series focused on a study of the comparative activation times of sprinklers and smoke detectors installed in the same areas under a variety of test conditions. The results of that phase of the test program are given here. National Fire Protection Association REFERENCE: Cote, arthur E., “Field Test and Evaluation of Residential Sprinkler Systems”, Fire Technology, Vol. 20, No. 2, May 1984, p. 41. Mr. Cote is Assistant Vice President (Engineering & Technical Services) for the NFPA. He served as project manager for the test series insofar as the NFPA had overall management responsibilities for the program.     

Influence of fire source locations on the actuation of wet-type sprinklers in an office fire

An experiment is conducted on a full-scale model office and an actual sprinkler system to explore the influence of fire source locations on sprinkler actuation. The office space is a brick structure that measures 5.7 m in interior length, 4.7 m in width and 2.4 m in ceiling height, and equipped with a sprinkler system. The investigated fire source (100 kW LPG burner) locations include the room center, wall centers, room corner, and other locations at different distances from sprinklers. The results show that actuation of the sprinklers is affected by the fire source locations and the heat conduction properties of the glass temperature-sensing bulb. Average actuation time of all the tests is 102 s, around 40 s faster than if the fire source is located in the room center. For fire sources in corners, sprinklers are quickly activated at the experimental time 75 s, showing concentrated hot gas flow.     

机器学习在煤粉着火敏感性预测中的应用

摘 要：为探究机器学习模型预测煤粉云最低着火温度（Minimum Ignition Temperature,MITc）的可行性,收集Godbert-Greenwal炉测试得到的煤粉云最小着火温度和影响因子数据,并分析了影响因子的关联性。利用AUC/ROC、Kappa系数、敏感性、特异性、MAE、RMSE等指标对三种机器学习模型在煤粉云最小着火温度和着火概率两方面的预测效果进行评价。结果发现：RSM模型的预测效果最差;RF模型在预测煤粉云MITc和着火概率时具有较好的精度和稳定性;Bagging模型在预测着火概率时AUC值均大于0.85,但预测MITc时效果较差。结果为煤粉云着火敏感性预测提供了一种新的研究思路。     

自动喷水灭火系统的抗震设计

自动喷水灭火系统的抗震措施应在设计和安装时予以考虑,以确保在地震发生次生火灾时能正常发挥作用,保护财产安全.自动喷水灭火系统抗震设计的方式主要有抗震支撑、柔性连接及设置间隙三种方式.