Sprinkler Protection Research Articles

Laboratory-scale testing of titanium powder fire extinguishment using water

Metal powders, such as those used in additive manufacturing, can pose a high fire hazard due to faster heating times relative to larger ingots or parts. Current industrial standards recommend special agents for manual extinguishment of metal powder fires and not automatic protection systems such as sprinklers. In this work, laboratory-scale experiments were conducted to understand the behavior of titanium powder fires when subjected to water sprays. Aluminum powder, although combustible when dispersed in air, could not be ignited in the configurations tested. Powder was ignited in a straight channel to evaluate flame propagation rate and characteristics during spray application. Additionally, piles of powder were ignited to assess the possibility of extinguishment in scenarios with larger flames. These exploratory experiments revealed that upon water delivery, ejected powder plumes caused intensification of the fire. These powder plumes were caused by the vaporization and expansion of water trapped beneath the powder surface. Most importantly, it was determined that a water flux threshold exists where cooling from the water spray can overcome intensification effects and yield effective fire suppression. Contrary to existing recommendations, automatic sprinkler protection may be effective for metal powders in storage applications, however future investigation is required at larger scales.

A model-based approach to estimate sprinkler protections for warehouse storage

Experimental and modeling efforts are made to develop a new approach to estimate sprinkler protection requirements for warehouse storage. The approach incorporates different models to predict water penetration effectiveness and critical delivered flux, as well as fire plume/ceiling jet correlations to predict the required sprinkler discharge density and number of sprinkler activations for an adequate protection in various storage configurations. The objective is to develop a reliable and repeatable means to estimate protection requirements for varying practical scenarios (target) based on limited large-scale fire tests (baseline). The newly proposed approach is validated using large-scale fire tests with solid-piled plastic pallets. The validation shows good agreement between modeled results and experimental data with an error less than 20%, when the suppression ratio was similar between target and baseline tests. Overall, this work should be viewed as a step towards a more cost-effective framework for designing fire protection systems.

Two dimensional temperature distributions in a ceiling jet generated by a finite line-source fire: An experimental study

The temperature distributions of ceiling jets are fundamental characteristics in enclosure fire dynamics. It is also the basics in the designs of fire safety devices in buildings, like detection, sprinkler, smoke control and standard fire protection. However, the only exists equation is for the radial ceiling jet temperature profile induced by a point source. There are no studies on line source despite the fact that the non-axisymmetric sources are the more common fires in buildings. This paper, for the first time, investigates the temperature profiles in ceiling jet induced by a finite line-source fire plume impinging upon an unconfined ceiling. Experiments are carried out with a buoyant jet fire and a pool fire. The temperature profile under the ceiling was measured along with flow condition visualized by a laser sheet. It is found that the temperature profile is two-dimensional and decays slower in the y-direction (perpendicular to line source longer side) than that in the x-direction (parallel to line source longer side). The characteristic length scales for characterizing the temperature profiles in the two directions are then proposed on the basis of the dimensions of the plume impinging zone. An equation is derived to describe the two-dimensional temperature profile based on the characteristic length scales. The present study provides basic data and a new equation for temperature profiles of ceiling jet induced by finite line-sources for building fire science.

Fire Hazard Analysis of Modern Vehicles in Parking Facilities

Vehicle fires in parking structures developing into large conflagrations are rare but can result in severe economic losses. It is important to understand the hazard posed by modern vehicle fires to determine whether current fire codes for parking garages are mandating adequate fire protection requirements. There has been an increase in the fire hazard from changes in vehicle design and increased use of plastics and other combustible materials in vehicle construction, along with denser parking of vehicles in parking structures. This manifests as faster flame spread within the vehicle, easier ignition and more rapid fire spread to neighboring vehicles. Based on the findings, test data from vehicles older than 2000–2005 model years should not be used as basis for development of codes and regulations. Open parking structures emerge as the main area of concern regarding fires in modern vehicles. The lack of any requirements for active protection systems in the fire codes, and trends in vehicle and garage design suggest that large, devastating fires in these structures could become increasingly common. The spread of fire between vehicles, especially from the initial to the second and third vehicles, is critical in determining the extent of the fire and the ability of the fire department to successfully control and extinguish. Future research should be conducted into earlier detection, sprinkler protection, and fire spread between vehicles to address the hazard.

Design and Development of Corrosion Resistance Coating for Pipes in Fire Protection Sprinkler Systems : A Review

Fire pumping systems are often used in most buildings for firefighting, whether they are residential, commercial, industrial or of any other kind. Such systems are responsible for the water flow and pressure necessary for manual or automatic devices designed to build safety. Therefore, ensuring their availability when an unexpected fire event occurs is very critical. But due to the presence of dissolved oxygen in the water-filled in the pipes, corrosion takes place at some point in time. This will lead to several types of failures in the system if the system is not properly designed with the right material for the environmental conditions and water quality, which in turn will render the system ineffective. This paper discusses the reasons for corrosion in the piping of fire sprinkler systems and their mitigation.

Fire Hazard of Lithium-ion Battery Energy Storage Systems: 1. Module to Rack-scale Fire Tests

Lithium-ion batteries (LIB) are being increasingly deployed in energy storage systems (ESS) due to a high energy density. However, the inherent flammability of current LIBs presents a new challenge to fire protection system design. While bench-scale testing has focused on the hazard of a single battery, or small collection of batteries, the more complex burning behavior of a commercially design module (collection of batteries) or rack (collection of modules) is still largely unknown. In this study, a series of small- to large-scale free burn fire tests were conducted on ESS comprised of either iron phosphate (LFP) or lithium nickel oxide/lithium manganese oxide (LNO/LMO) batteries. Small-scale tests showed that a thermal runaway event could lead to a self-propagating fire for both the LFP and LNO/LMO batteries with a significantly greater heat release rate (HRR) generated from the LNO/LMO battery. Intermediate- and large-scale tests showed that the burning of a single module was sufficient to involve all other modules within the same ESS rack for both types of battery chemistries. The different burning behavior of the two battery chemistries was further demonstrated with the LNO/LMO battery generating a maximum HRR nearly three times that of the LFP battery. To better understand the hazard associated with these fires, a multi-point source model was used to analyze the radiative heat exposure to the environment. The end result is an experimentally validated data set that can be used to estimate the heat exposure to objects surrounding an ESS fire, such as ESS racks across an aisle space in a large deployment, or other nearby combustibles. These data also provide the basis for evaluating the effectiveness of sprinkler protection at reducing the fire hazard and protecting the surroundings.

Experimental investigation of human tenability and sprinkler protection in hospital room fires

SummaryThe effectiveness of sprinklers in protecting hospital patients in the room of fire origin was investigated by 14 experiments with a residential‐grade sprinkler system, and by two free‐burns. The fire load was UL 1626 corner fire. Tenability conditions were evaluated for the UL 1626 corner fire using gas temperature and species concentration measurements, and by calculating the fractional effective dose (FED) and fractional irritant concentration (FIC) with the comprehensive model of Purser and a more simplified method of ISO 13571. In the sprinklered tests, the average FED at 15 minutes was 0.8 ± 1 with 95% confidence, when using the Purser's method, and 0.2 ± 0.2 with ISO 13571. The difference was mainly caused by the assumption in the Purser's method that all NOx gases behave like NO2. Ignoring the NO contributions decreased the Purser's FED values very close to those of ISO 13571. In nonsprinklered tests, the FED and FIC values indicated definite incapacitation and possibly death 3 minutes after ignition. The sprinklers effectively increase the possibility of surviving, but the toxic effects may still be dangerous. In hospital and health care environments, many of the exposed persons may have lower‐than‐average tolerance.

Application of a judgement method to regulatory impact assessments for sprinkler protection to English high‐rise residential buildings

SummaryWhen proposing a widespread investment in a safety measure, it is common for some form of regulatory impact assessment to be undertaken. In this study, the cost‐effectiveness of two proposals made by government bodies in England are investigated. The first is made by the London Assembly Planning Committee (LAPC) to retrofit London's existing high‐rise residential buildings (HRRBs) with sprinkler systems. Similarly, the Ministry of Housing, Communities and Local Government (MHCLG) has called for evidence to support reducing the trigger height for sprinkler provision in new HRRBs. The redundant concept of a value for a preventable fatality is addressed using the J‐value methodology. The baseline results show a J‐value above unity for both proposals, suggesting that they are potentially not cost‐effective. A sensitivity analysis highlights the embedded uncertainty and the implications for the J‐value. For the MHCLG proposal, a large increase in annual fatalities for HRRBs would be required to support a reduction in trigger height for the inclusion of sprinklers. However, reasonable modification of some inputs results in a J‐value below unity for the LAPC proposal, suggesting that this may be a cost‐effective safety investment. It may be argued that this proposal be implemented to err on the side of caution.

Experimental investigation into fire behaviour of glazed façades with pendant type sprinklers

Façade systems play an important role in fire compartmentation of a building and reducing the likelihood of fire spreading through and outside of the building walls. The use of sprinklers in building regulations often allows for smaller building separation. However, no additional benefits are usually given to additional internal sprinkler protection of the external glass façade using standard pendant sprinklers. Four compartment fire experiments were performed with non-fire-rated aluminium façades with two- and three-layered Insulating Glass Units (IGU), protected by pendant-type sprinklers (DN15, K-factor = 80, T = 68 °C). Sprinklers were in row 14–55 cm from the glazing, with 1.514–1.83 m separation distance. In all experiments, façades achieved satisfactory performance in terms of glazing integrity, insulation and reducing the thermal radiation. Under a non-uniform water distribution, parts of the glass were dry (1.7%–15.7% of IGU area), where we have observed soot deposition and local damage to fire exposed glass layer, but no loss of the structural integrity. The temperatures on the unexposed side did not exceed 86 °C, the peak measured temperature of the internal glass surface was 173 °C. The performed experiments confirmed the capability of standard pendant-type sprinklers to enhance the fire protection features of a building façade.

Time-resolved fire heat release rate under a ceiling based on ceiling layer measurements

Measurement of time-resolved fire heat release rate (HRR) is important to characterize fire growth and suppression. Under certain conditions, such as large fire tests conducted under a ceiling with sprinkler protection, quantification of a time-resolved HRR is still a challenging problem. This work attempts to develop a new methodology of estimating convective and chemical HRRs for a fire under a ceiling. The instantaneous measurements of gas temperature, velocity and species concentration in the ceiling layer are used to calculate the HRRs. To verify the proposed method, two heptane pan fire tests were conducted under a ceiling and the chemical HRR was calculated from the fuel mass loss data. The results demonstrate that the proposed method can provide a time-resolved chemical HRR that is comparable to that obtained from the fuel mass loss rate. The fraction of convective HRR to chemical HRR also agrees well with the test data obtained under a calorimeter. The application to rack-storage fires under a ceiling with sprinkler suppression shows that the proposed method can provide the fire growth in the free-burn period and consistent trends for the fire development with water application.

An Efficacy Evaluation of Water Mist Protection Against Solid Combustible Fires in Open Environment

CEN and NFPA standards have accepted water mist for protecting solid combustible fires more challenging than light hazard fires in open environment, but with little data in the public domain to support such applications. Therefore, a series of exploratory experiments was conducted to evaluate the efficacy of fire suppression in open environment by water mist sprays for a rack storage of corrugated cardboard cartons on wood pallets (Fire A), and for a palletized storage of cartoned plastics stacked on wood pallets (Fire B). Both are in the accepted hazard categories by both standards. Representative water mist sprays were employed to provide water application densities of 4.1 mm/min and 6.1 mm/min for Fire A, and 8.1 mm/min for Fire B. These sprays had downward thrust forces ranging from 18 N to 73 N per spray, and volume median droplet diameters from 75 µm to 345 µm. A standard ½-in. pendent sprinkler was also employed to provide the suppression performance references for these two fire hazards. In each experiment, four open sprinklers or nozzles were centered 1.7 m above the fuel array with nozzle spacing ranging from 2.6 × 2.6 m to 3 × 3 m. All experiments were conducted under a 20-MW calorimeter with no ceiling presence. Water discharge in each experiment was started at a designated fire convective heat release rate of 1000 kW. The experiments indicated that, for the same application density, not all water mist sprays having different characteristics would lead to a comparable fire suppression result. Therefore, each water mist system should be tested individually for the same intended protection. Furthermore, the results showed that when water mist protection was effective, it required application densities comparable to those of sprinkler protection to provide comparable fire suppression results in open environment under the present experimental conditions.

Modification of Water Application Rates and Intermittent Control for Sprinkler Frost Protection

Abstract. To validate the feasibility of an automated frost protection sprinkler system, a sprinkler irrigation system with an optimal water application rate was designed, constructed, and tested in a tea field. A modified calculation model of the water application rate was provided by simulation with different values of airflow velocity, air temperature, air humidity, and spray water temperature. An intermittent control strategy was provided using a modified model that included the start and stop time of the system and adjustment of the water application rate. Tea field experiments were conducted to evaluate the effect of frost protection based on this control strategy during frost night events. The results showed that a variable water application rate was better suited for frost protection, and the modified intermittent control automatically regulated the water application rate. In early spring and winter heavy frost nights, the canopy temperature (Tc) of the irrigated area remained above -1.2°C and 0°C, respectively, which is higher than the critical damage temperature for tea plants. The Tc of the irrigated area was approximately 2.8°C higher than that of a non-irrigated area. Moreover, the irrigated area with the modified model had a slower temperature rise after sunrise compared with the non-irrigated area, which was beneficial for frost protection. This sprinkler control strategy is an effective frost protection method that could be applied for in tea fields in the Yangtze River region. The calculation and simulation procedure of the water application rate would be applied for constructing sprinklers for different micrometeorological environments. Keywords: Frost protection, Intermittent control, Spraying water temperature, Sprinkler irrigation system, Tea, Water application rate.

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/bar½ (22.4 gpm/psi½), 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.

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.

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.

Effects of storage height on critical delivered flux of representative fuels

Fire suppression experiments were conducted to determine the critical delivered fluxes (CDFs) of representative fuels. The objective was to evaluate the CDF-based commodity classification for sprinkler protection purposes with emphasis on the effects of storage height. The experiments were carried out in 2- and 5-tier double-row, rack storage configurations, which, together with previous 3-tier work, provide a complete set of CDF measurements at different storage heights. The experimental results show that the 5-tier CDFs correlate well with full-scale sprinkler testing experiences. The comparison of CDFs also reveals the storage height effects for different fuels: the CDF values scale linearly for the cartoned commodities, while nonlinearities are observed for the uncartoned plastic commodities. Based on these results, a commodity classification method is proposed to assess solid combustible materials in the real world with separate treatment of cartoned and uncartoned fuels.

Characterization of interactions between hot air plumes and water sprays for sprinkler protection

One important aspect of the complex sprinkler protection process is the interaction between the water spray and the fire plume. In order to provide suitable data for the development and validation of a LES-based fire protection models, such as FireFOAM, a series of small-scale experiments were conducted to examine the interaction of hot air plumes and water sprays through combined gas–liquid velocity and droplet size measurements. Laser-based particle image velocimetry (PIV) was used to acquire the spatially-resolved velocity data; and a shadow imaging system (SIS) was used to measure the water droplet size and volume flux. Hot air plumes with three convective heat release rates (1.6, 2.1 and 2.6kW) were selected to interact with a water spray at a discharge rate of 0.084Lpm. The velocity field of the hot air plume and ceiling flow with/without water spray, the droplet size and volume flux of water spray with/without hot air plume were measured. The interaction between the hot air plume and water spray was characterized by the location of the interaction boundary with the momentum ratio of the hot air to that of the spray. The results showed that that the momentum ratio and the evaporation effect due to hot air on the water droplets played a significant role to change the interaction structure and the ceiling layer pattern.

Numerical Simulation of Sprinkler Suppression of Rack Storage Fires

Fire suppression tests with ceiling sprinkler protection in a rack storage fuel configuration are simulated using a Computational Fluid Dynamics tool. The fuel is arranged in a double-row, six pallet-load wide and three-tier high (2×6×3) rack storage array. Each pallet load consists of three nested double-wall corrugated cardboard boxes surrounding a metal liner. Two types of ceiling sprinklers are used in this study: a pendent quick response sprinkler designated as K14, and an upright standard response sprinkler designated as K11.2. The tests are simulated using FireFOAM, which couples necessary sub-models for fire growth, sprinkler response, and fire suppression. Numerical results are compared with experiments for both free burn tests under a 20-MW calorimeter and sprinkler suppression tests under a 7.6 m high ceiling. For the free burn case, the model results show good quantitative agreement of heat release rates in all three phases, from ignition to fire growth and steady burning. For the suppression cases, the model reproduces the suppression effectiveness of the two sprinkler protection designs: K14 sprinklers suppress the fire rapidly with only one sprinkler activation, while with K11.2 sprinklers, both in the tests and simulation, the fire spreads to the pallets on the end of the fuel array with multiple sprinkler activations. The modeled sprinkler activation times are within the estimated experimental uncertainty following three repeat tests. Quantitative results characterizing sprinkler suppression performance obtained from the simulations, such as the actual delivered density (ADD) and water evaporation rate, are also reported.

An Experimental Study of Automatic Water Cannon Systems for Fire Protection of Large Open Spaces

An experimental study is conducted to evaluate the performance of automatic water cannon systems for protecting fire hazards in large-open spaces. As part of this study, typical fire hazards encountered in large-open spaces are simulated to allow for a comparison of water cannon and automatic fire sprinkler protection. Tests are performed to characterize response time, water distribution and effectiveness of protection of the selected water cannon system. Results show that, in general, water cannon can respond to fire events in large-open spaces much faster than sprinklers. Under certain conditions, water cannon can also control and/or suppress the fire. However, further improvement of automatic water cannon technology is needed to optimize system performance for various commodity fires that may occur in large-open spaces.

Sprinkler protection of non-storage occupancies with high ceiling clearance

Five large-scale fire tests were conducted to investigate the effects of ceiling clearance, sprinkler type and sprinkler discharge rate on sprinkler fire control performance of a non-storage high-ceiling-clearance scenario. The fire scenario selected for this study is to simulate fire loads of either sale booths or exhibition booths in non-storage occupancies under a high ceiling. Three ceiling heights were employed: 12, 16 and 18m. Two Large Orifice (LO) sprinklers, an Extra Large Orifice (ELO) sprinkler and a K363 Control Mode Specific Application (CMSA) sprinkler were used. All the sprinklers tested are pendent sprinklers with a nominal temperature rating of 70°C. The sprinklers were installed at 3m×3m spacing. The effectiveness of fire control of the sprinklers depends on ceiling height, sprinkler spray pattern, water drop size (as related to orifice size and discharge pressure), and sprinkler discharge rate. The test results show that the standard-response LO sprinklers at a discharge rate of 141L/min per sprinkler did not control the test fire under a 12 m high ceiling and sprinkler skipping occurred. For a ceiling height of 16 m, the quick-response LO sprinklers discharging at a rate of 182L/min per sprinkler were not effective in controlling the test fire and sprinkler skipping also occurred; however, the standard-response ELO sprinkler discharging at a rate of 209L/min was marginally effective in controlling the test fire. For a ceiling height of 18 m, the K363 CMSA sprinklers discharging at a rate of 363L/min per sprinkler either controlled or suppressed the test fire, because the sprinkler generates considerably large water drops and provides sufficient high discharge rate. The test series has demonstrated that water drop size is an important factor for achieving fire control or suppression of the high-ceiling-clearance fire scenario. With regard to the fire size at sprinkler actuation, the convective heat release rate of the fire is estimated from the gas temperature measured at ceiling level directly over ignition by using a plume correlation. Using a sprinkler with a RTI of 130 (m⁎s)1/2 under the 18 m high ceiling, the fire size at first sprinkler actuation was estimated to be 7-8 MW. The test results provide a technical basis for developing sprinkler installation rules for non-storage high-ceiling-clearance occupancies in the revised Chinese National Code of Designs for Sprinkler Systems.