Evaluating the performance of fixed water-based fire protection systems for passenger train and metro cars

Transcription

1 Evaluating the performance of fixed water-based fire protection systems for passenger train and metro cars Teemu Kivimäki Marioff Corporation Oy Vantaa, Finland Jukka Vaari VTT Technical Research Centre of Finland Espoo, Finland ABSTRACT A test procedure for evaluating the fire protection performance of water-based fixed fire fighting systems for passenger train and metro cars will be presented. Well defined materials are applied in both test configurations that are intended to provide realistic but conservative fire scenarios for the applications. Results are presented for two different water mist systems tested according to the proposed test procedure. Water mist systems are an attractive choice for these applications specifically due to their lower weight and space requirements. KEYWORDS: Water mist systems, fire protection, test procedure, passenger train cars, metro cars INTRODUCTION There are few rail fire accidents in the headlines almost every year although serious disasters that include loss of lives happen rarely. One of the most severe train accidents in the 21 st century is the Kaprun disaster in Austria, on 11 th November 2, where a fire occurred in an ascending railway car in the tunnel of the Gletscherbahn in Kaprun. The disaster claimed the lives of 155 people, leaving only 12 survivors. Another disastrous accident was the Daegu subway fire in South Korea, on 18 th February 23. The fire was started by an arsonist who ignited a stopped metro car at the Jungangno Station of the Daegu Metropolitan Subway in Daegu. In total some 198 people lost their lives and at least 147 were injured. Today most passenger trains are equipped with manual extinguishers that provide first aid protection in case of a small fire. With an emergency stop the train can be stopped and people evacuated quickly from the train. It has been argued, though, that this simplistic approach would not be possible e.g. if the train is crowded or in a tunnel. Fixed fire fighting systems would be a logical way for improving the fire safety in trains in all cases. In metros the approach is very similar to passenger trains. Although metros have typically less fire load than trains there can still be catastrophic consequences if a fire breaks out in a crowded metro car between stations. Also, manual extinguishers in metros might be subject to vandalism and therefore not available for use. Again a fixed fire fighting system could be considered appropriate to approve the safety of people and business. Trains and metros as such pose technical challenges to any fixed fire fighting systems installed onboard due to space and weight constraints. When setting performance criteria to such systems these practical boundary conditions cannot be ignored. The objective should be to find a technically feasible solution with sufficient performance to provide time for evacuation also in cases where the train or metro may be in a long tunnel and unable to stop for several minutes. 329

2 Since there is currently no internationally recognized authority for rail industry that would define the boundary values and requirements for fire protection systems in trains or metros, Marioff Corporation Oy has worked together with VTT Technical Research Centre of Finland to develop a repeatable and reproducible fire test procedure for evaluating the performance of water-based fire protection systems both for passenger train and metro cars. Such procedures would give end-users and authorities an objective way to evaluate the fire fighting performance of different water-based systems. TEST PROCEDURE The intention of the test program was to develop a test procedure with challenging and realistic fire scenarios for evaluating the fire fighting performance of water-based systems in train and metro cars. The procedure applies both to deluge-type systems and automatic sprinkler-type systems. The procedure is similar to guidelines published by the International Maritime Organization (IMO) for evaluating water-based suppression systems on board ships because those guidelines are well defined and widely recognized with a lot of practical experience [1 4]. The development process took almost half a year during which over 7 full scale fire tests were conducted. The test fuel package consisted of well-defined, non-fire retardant generic materials to ensure reproducibility and repeatability of the tests. The materials were the same that are applied in many IMO guidelines [1 3] but also in widely recognized land-based water mist fire test procedures published by CEN, FM and UL [5 8]. In reality, especially in modern trains and metros, the seats and other materials are fire retardant, but a challenging non-fire retardant fuel package provides a well-justified worst case scenario with a safety factor built in it and it takes into account also the variable luggage passengers bring in with them. Flammable liquid pool fires were not included in the test procedure because if a fire is started by an arsonist spilling flammable liquid to the car, it results in a large but short-lived initial fire. Solid combustibles that are likely to be ignited by the liquid fire provide the actual hazard with respect to duration and fire spread. The qualitative primary objective of the fire fighting system is to suppress the fire and provide tenable conditions for as long as it takes to stop the train or metro and evacuate the passengers. Issues to be taken into account in the duration evaluation include the space and/or power limitations in a train or metro and the worst case scenario of the time needed to stop the train/metro in a safe place, e.g. if the fire occurs in a tunnel. Test compartment for trains and metros For both the train and metro tests, a representative mock-up enclosure was used. It was considered appropriate to use an ISO standard shipping container where two doors, one at each end, were assembled. The test compartment with inner dimensions is presented in Figures 1 and 2. Train and metro fuel packages The train and metro fuel packages were designed to simulate a typical long-distance passenger train and subway metro cars. The fuel package consisted of an ignition source, mock-up seats with polyether foam simulating the seat padding, combustible walls with plywood panels simulating combustible clothes, curtains etc hanging on the walls, and polyether foam on the luggage rack for observing fire spread (Train setup only). All solid materials in the fuel package were conditioned for at least 72 hours in a controlled environment. In both test setups and in each test the fuel package was assembled in the middle of the mock-up as presented in Figures 1 and 2. 33

3 Figure 1 Fuel package in the train setup. Figure 2 Fuel package in the metro setup and indicative nozzle arrangements in the compartment. Materials The fuel packages were constructed using well-defined, non-fire retardant generic materials to ensure that the tests are challenging, reproducible and repeatable. The material specifications were taken from existing fire test procedures in IMO Res.MSC.265(84) and CEN TS 14972:28 [2, 5]. Ignition source In each test the fire was ignited by an igniter which was made of insulating fibreboard soaked in 12 ml of commercial heptane (LIAV 11 industrial solvent, supplied by Neste Oil Oyj) [1, 2]. The igniter was placed on the relevant train/metro seat as shown in Figure

4 Figure 3 Seat with igniter. Left: Train. Right: Metro. Seats The frame of the seats was made of steel consisting of rectangular bottom and backrest frames constructed of steel angles and solid steel plates. Each seat was formed of two polyether foam pieces. The backrest was placed on top of the seat cushion and steel angles were used at the backrest to prevent the foam from falling during the test. Schematic picture of the train seat arrangement is given in Figure 1 and a photo is shown in Figure 3. The same seat frames were used in the metro setup but in the metro case the seats were arranged along the wall as presented in Figures 2 and 3. The polyether foam was non-fire retardant with a density of approximately 33 kg/m³. When tested at VTT in accordance with ISO the polyether foam gave results as given in Table 1. Table 1 Cone calorimeter test for foam in accordance with ISO Test conditions Irradiance: 35 kw/m² Horizontal Position Sample thickness: 5 mm No frame retainer was used Test results Time to ignition 4 6 s 3 min average Heat release rate HRR (23 ± 1) kw/m 2 Effective heat of combustion > 24 MJ/kg Total heat release (43 ± 1) MJ/m 2 Walls In both test setups the incombustible wall of the mock-up was covered with uncoated birch plywood panels in such way that no air gap was left behind the panel and the incombustible walls. A schematic view of the installation is presented in Figures 1 and 2. The flame spread properties of the plywood wall panels were determined at VTT according to IMO Res.A.653(16) [4]. Three samples were investigated. The main fire characteristics are given in Table 2. The ignition times for the three samples were 32 s, 35 s, and 35 s. The flame spread times to 35 mm for the three samples were 81 s, 81 s, and 83 s. The flame spread index (FSI) of the plywood was not verified but when measured in accordance with the Standard for Test for Surface Burning Characteristics of Building Materials (UL 723) the birch plywood should correspond to FSI

5 Table 2 Flame spread test for plywood in accordance with IMO Res.A.653(16). CFE kw/m 2 Q sb MJ/m 2 Q t MJ Q p kw Sample Sample Sample Mean Luggage rack In the train setup a luggage rack was attached 19 cm above the floor. Polyether foam pieces with the characteristics of Table 1 were arranged on the luggage rack as presented in Figure 2. Fire tests The approach in the train and metro suppression tests was to run the tests with two nozzle arrangements: the fire was started (i) close to the location of one nozzle (A1) and (ii) between two nozzles (B2) as shown in Figure 2. The different nozzle arrangements were done by moving the nozzles in proportion to the fuel package. Deluge system Two free-burn tests were conducted first to define the pre-burn time in suppression tests 1 and 2 in Table 3. In the train setup the flame attachment time to the first polyether target on the luggage rack was recorded and in the metro setup the time recorded was the flame attachment to the wall. The preburn time in the suppression tests was defined as 3 s less than the average flame attachment time recorded in the free-burn tests [3]. The deluge system was manually activated at the end of the preburn period. Sprinkler system When automatic sprinklers were used the pre-burn times in suppression tests 1 and 2 in Table 3 was defined by the sprinkler sensitivity. The tests were conducted for at least 1 min after the system was activated, and any remaining fire was manually extinguished. Table 3 Basics of the test program (Train and Metro). Test Number Ignition location Ignition source Pre-burn time Deluge system 1 Seat, at one nozzle (A1) Igniter Determined with a 2 Seat, between two nozzles (B2) Igniter free-burn test Instrumentation The instrumentation arrangement was the same for both setups. The following parameters were measured during the tests: Gas temperature with.5 mm bare K-type thermocouples arranged as shown in Figure 4. Water pressure at the ceiling level close to the hydraulically most remote operating nozzle. Oxygen level 16 cm above the floor as shown in Figure 4. The fire damage was photographed after each test. 333

6 Figure 4 Measurement arrangement (Train and Metro). Acceptance criteria The principal qualitative objective of the suppression system is to stop the fire spread and suppress the fire. For quantitative evaluation the UL 1626 [8] was applied for relevant parts as the suppression systems in trains and metros can also be considered life safety systems. As per the life safety criteria in the UL 1626, the temperatures shall be limited for the required time as follows: The maximum peak temperature 16 cm above the floor shall not exceed 93 C. The maximum temperature 16 cm above the floor shall not exceed 54 C for more than any continuous 2-minute period. In addition, the suppression systems shall prevent ignition of targets as follows: In the train tests, the flame shall not be attached to the foam on the luggage rack In the metro tests, the flame shall not be attached to the combustible wall EXPERIMENTAL RESULTS Fire suppression tests and free burn tests were conducted on simulated passenger train car and metro car setups as described earlier. Two HI-FOG water mist systems (one deluge-type system, one automatic sprinkler-type system) were tested for each application. Both systems were of limited duration operated with gas cylinders and a limited water supply that can be fit in a train or metro car. The deluge system was based on a gas-driven pump unit. The sprinkler system was based on an accumulator unit. Free-burn tests For each fuel package, one free-burn test was conducted until the fire had consumed most of the fuel. The purpose of these tests was to demonstrate the fire spread potential of the fuel package designs, and to provide a baseline for evaluating the capability of the suppression systems to limit fire spread and to manage gas temperatures. Figure 5 presents the ceiling gas temperatures (T1-T4, see Figure 4) for the free-burn tests. For both fuel packages the data is presented as a running average over 3 seconds. The temperatures started decreasing after 4 minutes (train) and 8 minutes (metro) because the fires were running out of fuel. The oxygen concentrations in both free-burn tests dropped close to 12 % within 5 min from ignition. Figure 6 and 7 show the fire development and post-fire conditions for both free-burn tests. Overall the 334

7 Fourth International Symposium on Tunnel Safety and Security, Frankfurt am Main, Germany, March 17-19, 21 fuel packages exhibited sufficient fire spread potential to present a meaningful test for the capability of suppression systems to limit fire spread. Figure 5 Ceiling gas temperatures for the free-burn tests. Left: Train. Right: Metro. Figure 6 Train setup. Left: 6 s after ignition (wall ignited at 58 s). Right: Post-test condition. Figure 7 Metro setup. Left: 135 s after ignition (wall ignited at 95 s). Right: Post-test condition. 335

8 Suppression tests In each test, a single row of four ceiling-mounted pendent nozzles was installed along the centerline of the mock-up. The spacing between nozzles was 3. m, and the distance to walls was 1.2 m, yielding a protected area of 7.2 m 2 per nozzle. The K-factor for all nozzles was 1.45 lpm/bar ½. Tables 4 and 5 present a summary of the main test results. In the train tests, the pre-burn time of 57 s for the deluge system was determined based on tests 1 and 2. Similarly, in the metro tests, the preburn time of 1 min 14 s for the deluge system was determined based on tests 7 and 8. For the sprinkler systems, the pre-burn time corresponds to the activation time of first sprinkler. Table 4 Test Summary of the test results for train setup. Wall Suppression Pre-burn Test type ignition system (min:s) (min:s) Target ignition (min:s) Maximum peak temp 16 cm above the floor 1) Max 3 s avg ceiling temp 1 n/a Free-burn n/a 1:7 1:33 n/a n/a 2 n/a Free-burn n/a :47 1:24 n/a n/a 3 deluge B2 :57 n/a 2) not ignited 45 C (T7) 165 C (T2) 4 deluge A1 :57 n/a 2) not ignited 37 C (T5) 74 C (T1) 5 sprinkler B2 1:7 :5 not ignited 44 C (T5) 125 C (T2) 6 sprinkler A1 :44 n/a 2) not ignited 39 C (T5) 76 C (T3) Ref. freeburn 351 C (T5) 648 C (T2) Table 5 Test Summary of the test results for metro setup. The column seats damaged shows the number of seats involved in fire vs the total number of seats installed for the test. Wall Maximum peak Pre-burn Seats Test type ignition temp 16 cm (min:s) damaged (min:s) above the floor 1) Suppression system Max 3 s avg ceiling temp 7 n/a Free-burn n/a 1:38 n/a n/a n/a 8 n/a Free-burn n/a 1:51 n/a n/a n/a 9 deluge B2 1:14 not ignited 4 / 7 43 C (T7) 12 C (T2) 1 deluge A1 1:14 not ignited 4 / 7 49 C (T5) 92 C (T2) 11 sprinkler B2 :38 not ignited 4 / 7 39 C (T7) 88 C (T2) 12 sprinkler A1 :48 not ignited 3 / 7 37 C (T6) 55 C (T2) Ref. freeburn 374 C (T5) 55 C (T3) 1) All suppression tests in Tables 4 and 5 passed the quantitative temperature criteria (93 C / 54 C). 2) Wall ignition time not recorded. Post-test inspection showed that wall had ignited. All tests were successful in terms of suppressing the fire and also in terms of the quantitative acceptance criteria. Ignition between two nozzles (B2) was invariably worse of the two nozzle arrangements in terms of damage to the fire load as well as gas temperatures. When comparing the ceiling gas temperatures between Table 4 and 5 it can be seen that the temperatures are, in most cases, higher in the train setup. This was mostly due to faster fire propagation in the train setup. The worst and the best performance of the tested water mist systems of Tables 4 and 5 will be 336

9 presented in more detail. The train setup, deluge system and ignition between two nozzles (test 3) gave the worst performance and the best performance was achieved in the metro setup, sprinkler system and ignition at one nozzle (test 12). Test 3: Train, Deluge, Ignition between two nozzles (B2) Figure 8 presents the gas temperatures for the test, presented as a running average over 3 seconds. The deluge system was activated at 57 s (small drop in ceiling temperatures) and the maximum ceiling temperature 165 C at T2 (Table 4) was reached at 3 min 2 s. Soon after reaching the maximum ceiling temperature all temperatures started to drop because of the suppression and cooling effects of the water mist system. Temperatures 16 cm above the floor remained below 44 C during the 2 min system activation. The oxygen concentration in Figure 9 indicates that the oxygen level remained sufficient for survival in the car during the whole test. Fire propagation was prevented and all the targets on the luggage rack remained unburned as presented in Figure Temperature ( C) T2 T3 T1 T4 T1 T2 T3 T4 Temperature ( C) T7 T5 T6 T5 T6 T7 T Figure 8 Time (min) Time (min) Left: Gas temperatures at ceiling level. Right: Gas temperatures.8 m (T5-T7) and 1.6 m (T8) below ceiling. Figure 9 Oxygen concentration. 337

10 Figure 1 Left: Fire development 45 s after ignition. Middle and right: Fire damage. Test 12: Metro, Sprinkler, Ignition at one nozzle (A1) Figure 11 presents the gas temperatures for the test, presented as a running average over 3 seconds. The first and only sprinkler activated at 48 s (small drop in ceiling temperatures), the fire was immediately suppressed and ceiling temperatures only slightly increased and remained somewhat higher than ambient. Temperatures 16 cm above the floor remained below 4 C. The test was conducted for 1 min during which the fire was suppressed and the fire propagation was prevented. The oxygen concentration in Figure 12 remained over 2 % the whole test period. Three out of seven seats were damaged and wall was not ignited as shown in Figure 13 so the sprinkler system prevented the ignition of target properly. 2 1 Temperature ( C) T2 T1 T2 T3 T4 Temperature ( C) T5 T5 T6 T7 T Figure 11 Time (min) Time (min) Left: Gas temperatures at ceiling level. Right: Gas temperatures.8 m (T5-T7) and 1.6 m (T8) below ceiling. 338

11 Fourth International Symposium on Tunnel Safety and Security, Frankfurt am Main, Germany, March 17-19, 21 Figure 12 Figure 13 Oxygen concentration. Left: Fire development at system activation (48 s). Middle and right: Fire damage. SUMMARY The fuel package provided reproducible and repeatable tests and challenging fire scenarios for any water-based protection system compatible with the space, weight and power limitations onboard a train or metro car. Qualitatively, the fire was clearly suppressed and the fire spread and damage was limited in all suppression tests. Quantitative temperature criteria taken from the UL 1626 life safety standard would be well justified to be applied in the train and metro tests but, in the tests presented, they were far less challenging than the criteria set for limiting the spread of fire to targets. Based on the full test program, a formal fire test procedure has been formulated and is available upon request. ACKNOWLEDGEMENTS The authors would like to thank Dr. Maarit Tuomisaari of Marioff Corporation Oy for guidance in setting up the fire test procedure and helpful discussions during the preparation of this paper. 339