Overview of a Year of Battery Fire Testing by DNV GL for Con Ed, NYSERDA and FDNY

Transcription

1 2017 NFPA Conference & Expo Overview of a Year of Battery Fire Testing by DNV GL for Con Ed, NYSERDA and FDNY Presented by: Nick Warner, Sr. Test Engineer, DNV GL Dalan Zartman, President, Rescue Methods Fire Safety Testing Overview With the Cooperation of: 2 1

2 Introduction Test Setup Toxicity and Ventilation How bad are these things? How should I size my ventilation? What other less obvious risks exist? Extinguishing Are other agents effective? Reignition and cascading. Is it real? Ventilation and extinguishing Overhaul and firefighting operations 3 Test Setup 4 2

3 Test Setup, Cell Level Gas sampling was performed three ways: GasmetDX4000 FTIR collected: O2, CO, NO, CO2, NO2, SO2, CH4, Ethylene, Benzene, Toluene, Propane, Ethane, HCl, HF, HCN Based on DNV GL s ARPAeAMPED work MSA Ultima Sensors recorded: O2, H2, F2/Cl2, LEL Gas bag sampling was performed minimally as gas bag data aligned with FTIR data Besides gas sampling, a thermopile of eight thermocouples was built around the battery in addition to inlet and outlet temperatures, ambient chamber temps, and thermocouples placed directly on the battery Batteries were heated by x4 1kW ceramic radiant heaters. In cases where batteries vented but did not ignite, two hot point ignitors were placed in the upper chamber that triggered at 50% LEL. 5 Test Setup, Cell Level Morning Pride PPE swatches were placed in the unit as well to assess effect of battery fire on the gear. This material was to FDNY spec (A full set of turnout gear was also placed on a mannequin during a module test burn) Occasional surface swabs were taken from inside the chamber as well. Testing showed typical fire residue as well as trace amounts of nickel, cobalt, and manganese (as would be expected from NCM batteries). No swabs were taken after LTO or LFP tests, but results were not expected to differ (Fe and Tiare less toxic as well) Direction of misting nozzle from extinguisher Approximately 25% of the cells tested did not conflagrate or generate enough gas to burn as a result of chemistry, SOC, constraint, or overall size. Thus testing focused on those that did. 6 3

4 12/05/2017 Examples of Cell Fires 1 Flashover (triggered by ignitors) after venting with no self ignition 3 2 Images 1-3 show a pouch cell as it swells, vents and self ignites (pictures approximately 3 seconds apart) 7 Module Fire Burn Room Setup Two Firecams and a thermal imaging camera were placed inside the room, an additional camera and thermal imaging camera were setup outside The FTIR sensor probe was put through the wall to record off gas, while two other MSA Altair 5 gas sensors were placed around the unit. All firefighters around the unit wore MSA Altair 4 gas sensors Thermocouples were placed up one side of the wall to record thermal layers Thermocouples 8 4

5 Module Fire Burn Room Ventilation In addition to video and data acquisition as well as extinguishing, we were also interested in qualitatively testing certain ventilation strategies To accomplish this, five ~1sqft holes cut into the room, high and low on each side of the room and one on the roof. In addition, we mostly test negative ventilation, but also supplemented with positive ventilation in some instances. 9 Module Burn Example Data 10 5

6 Module Scale Testing Pictures *One mannequin and one fan were thoroughly harmed in the making of these videos 11 Ventilation 12 6

7 Ventilation Considerations Of primary interest were flammable and toxic gases. The limits of the FTIR were such that most flammable gases could not be measured reliably in their LEL ranges. Though all were reliably measured through their IDLH ranges A catalytic bead LEL with nonspecific cal was used for LEL measurements The primary toxic gases monitored were CO, HCl, HF, HCN, Benzene, Toluene Gas were observed in DNV GL s ARPAeAMPED testing project Ultimately the fires showed similar or less output of those gases than a plastics fire of comparable mass Though peak values are high because of the nature of the failures/fires, they are short lived and longer term values are lower than equal masses of plastic HClis the main driver for ventilation requirements based on IDLH but CO is produced in greater quantities and poses a longer term risk (minutes to hours) 13 Example Off Gas Data Representative Gas Sample 1 CO HCl HF HCN Very similar batteries, very different results Representative Gas Sample 2 CO HCl HF HCN time (s) 2000 Different form factor, chemistry and much larger than 1 and 2, mixed results in terms of similarity Representative Gas Sample time (s) time (s) CO HCl HF HCN Ultimately normalizing for mass and Whmade more sense than trying to distinguish by chemistry and form factor. Electrolyte and plastics are the larger driver of off gas and exist equally regardless of electrode chemistry 14 7

8 What We Looked For Concentration (ppm unless otherwise noted) NFPA Codes (F=flammability, H=health, R=reactivity, S=special) Chemistry Relevant Detected LEL (Lower IDLH Solubility in Auto Ig. F H R S Ref. Batteries State Explosion (Immediately Water Temp (deg Limit) Dangerous to (mg/l) C) Life and Health) Methane CH 4 Li-ion Gas 50,000 5, NJ DOH Carbon CO All Gas 12,500 1, CDC.gov Monoxide Benzene All except Gas 12,000 3, CDC.gov PbA Ethane Vanadium Gas 30, CDC.gov Redox Ethylene C 2H 4 Li-ion Gas 27, Matheson MSDS Hydrogen H2S Pb Acid, Liion Gas 40, CDC.gov Hydrogen H2S VR, PbA Gas 4, , CDC.gov Sulfide Hydrogen HF All except Gas - 30 miscible CDC.gov Fluoride PbA Hydrogen HCl All Gas CDC.gov Chloride SO2 SO2 VR, PbA Gas , CDC.gov Hydrogen HCN All except Gas - 50 miscible CDC.gov Cyanide PbA Nickel Ni Li-ion Residue / Powder Manganese Mn Li-ion Residue / Powder Cobalt Co Li-ion Residue / - - Insoluble Powder Lithium Li Li-ion Residue / W Powder V2O5 Dust V2O5 VR Residue - 35 mg/m^ CDC.gov Pb Vapor, Pb PbA Residue mg/m^3 10^-5 to CDC.gov salts, dust Battery Peak Gas Release In many cases, cells generated large amounts of gas both flammable and toxic internally before venting. As soon as the batteries vented, a large, but short lived, burst of gases was detected. These bursts caused high peak values of a range of toxic gases including HCl, HF, CO and HCN. Again though, these bursts were short lived (on the order of seconds to one minute). 16 8

9 Battery Average Gas Release However, over the total event duration, the average levels of the gases were much lower In many cases literature did not provide sufficient data, so representative samples of plastics were burned to compare them to the batteries In many cases, the average long term exposure over several minutes, when normalized for mass, is higher in pure plastics fires. For that reason, in many cases, recommended ventilation requirements are not higher than those already recommended for similar scenarios 17 Example Ventilation Requirements These tables show the projected required air change overs per hour during events of varying sizes and for different sized environments In many cases, the existing regulations for similar systems call for ventilation that is sufficient for smaller failures Though CO is typically generated in greater quantities, HClis next and has a lower IDLH, making it the main driver for ventilation requirements 18 9

10 Extinguishing 19 Cell Level Extinguishing Test Setup A 2.5gal pressurized water can was controlled via an electronic solenoid valve. The extinguisher was typically filled with 1 gallon of agent, mixed to manufacturer specs, and the valve was opened the until the extinguisher exhausted itself All manufacturers approved of the extinguisher setup and specs An eight second pulse of water was used in one test to verify a theory about gas management All testing was done on pouch cells as they proved best at sustaining a fightable fire. Cells were unconstrained and left exposed, as opposed to being constrained as they would in regular systems Unconstrained cells did show higher volatility than constrained cells in testing without extinguishing 20 10

11 Cell Level Findings Summary All agents were effective at immediately knocking out the fire All water based agents that were deployed fully (~30 seconds) experienced flashover mid cycle. The 8 second pulse put out the fire but did not experience the flashover It is known from previous testing that cells, even when extinguished, continue to generate gas while hot It is believed that this fact, coupled with the direction of the extinguisher, drove flammable gas toward the top of the chamber, which was unsuppressed, and triggered the ignitors It is not believed this will be an issue in actual applications, as there should not be an ignition source in those scenarios However, it is important to note that flammable gas generation remains an issue during extinguishing 21 Extinguishing Agent Effectiveness Top of Cell Bottom of Cell Again, all agents extinguished the fire, but water showed marginally better performance than the other agents at continued cooling after the fact. This was reflected on different cell types. Water also showed better cooling ability 22 11

12 Recommended Water Usage for Sprinklers Based on heat release rate, expected propagation of fire through the system, the deployment of sufficient cascading protections and the aggressive & proactive deployment of suppression, sizing of sprinklers in large scale systems can be as small as.2gpm/kg of battery 23 Required Water Use for Fire Fighting: Worst Case Scenario Why is this so much worse than expected? 24 12

13 Need for Cascading Protection: Reignition Insufficient cascading protection allowed a hot, deep seated core to remain as the surface was cooled. Lack of cascading protection allowed this heat to rapidly spread back through the battery and reignite remaining active mass. It took far more water than usual to cool the battery and flame had to be put out several times. Once the battery completely cooled though, it remained stable for weeks. This reignition took place on the order of seconds to minutes, not hours and days HOWEVER:Based on literature review and project experience, batteries do not magically reignite on their own once properlycooled. Previous examples of reigntion ALWAYS involve external electrical, thermal or mechanical stimuli 25 Need for Cascading Protection: Proof These are results from a gas phase extinguishing agent test. Two pouch cells were stacked together. Though the fire did extinguish, the hot battery continued to generate flammable gas. At one point, enough oxygen seeped into the bottom of the chamber for a small flash to occur in the lower part of the chamber. This verified discussions with fire services that even if the fire is out, the reintroduction of oxygen into the gas filled space would pose a flashover/backdraft risk. DNV GL recommends any system equipped with an inert gas/clean agent system that has not demonstrated sufficient cascading protection be supported by a water based sprinkler system 26 13

14 Four Tile Video As the video will show, the effectiveness of extinguishing is somewhat dependent on ventilation and it becomes difficult in this case to extinguish this battery with sprinklers when ventilation is not operating 27 Firefighting Operation and Overhaul 28 14

15 Overall Lessons Learned and Recommendations During testing, especially module testing, a handful of important points were discovered that should be shared with all first responders: Ventilation is key. It was demonstrated time and again that batteries will continue to generate flammable gas so long as they stay hot, but a key component of that gas is CO, which is generated until the batteries are completely cooled through to their core While storing batteries in the back 30 of the trailer, after placing four or five batteries, CO levels hit over 100ppm even with a small man door open Batteries were submerged to test the effectiveness of that method for cooling and neutralizing damaged cells. Batteries continued to off gas CO for extended periods while submerged. May also have included H2. For these reasons, DNV GL recommends SCBA be worn during all stages of the fire, including overhaul, and that ventilation be maintained through overhaul as well, especially in confined areas 29 Does Submerging Batteries Help? Submerging batteries after they burned seemed to prove effective at cooling the batteries and neutralizing the thermal threat. However, even after submerging batteries, many continued to show voltage across surviving cells, suggesting they remain electrically active Also, during submersion, batteries continued to off gas, mostly CO, but possibly also H2. Though no where near LEL or even IDLH levels, submerging several batteries in a confined space may prove problematic without ventilation During submersion, ph typically dropped to ~6, however, one severely burned battery increased ph to 11 after several hours and to 13 after several days It is still not clear what occurred differently 30 15

16 Residual Battery Voltages After Fire Some of these voltage measurements were taken after submersion. Besides the obvious risks associated with AC connections, which can be easily cut and verified, DC voltage risks may remain in systems that are partially damaged or destroyed where stranded energy can not be discharged or isolated 31 Surviving Live Batteries Even after severe fire and while looking heavily destroyed, there may be live cells remaining in the pack For that reason, DNV GL recommends against the use of piercing nozzles and irons and advises great caution when cutting on battery systems Damaged batteries arced and in some cases nearly self welded themselves to the steel test grate when trying to move them from the trailer to the pool. Extreme caution should be advised if this method is to be applied, and should be done after verifying the system is truly electrically neutralized Cells are still intact and live Special thanks to Franklin County Bomb Squad for X-Ray images 32 16

17 Additional DC Electrical Risks Besides the obvious AC risks and risks associated with stranded DC energy, a large scale burn conducted by DNV GL and RM separate from this project showed other weaknesses in systems that should be addressed Though this large scale system performed incredibly well when exposed to fire, and the design extended time to battery ignition significantly, the cables in the unit saw their insulation degrade, leading to arcing in a high temperature environment that may already be generating gas. This may also pose electrical risks in partially damaged systems that are less apparent and not subject to just handling of the batteries 33 QUESTIONS? Nick Warner Nicholas.warner@dnvgl.com SAFER, SMARTER, GREENER 34 17

18 2017 NFPA Conference & Expo CEUs: To receive CEUs for this session, scan your badge at the back of the room before leaving Evaluation: Complete a session evaluation on the mobile app. (Search app store for NFPA 2017 C&E. ) Handouts: Handouts will be available via the mobile app and at nfpa.org/conference Recordings: Audio recordings of all sessions will be available free of charge via NFPA Xchange. 18