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SINTEF NBL as Reaction to fire 2012-03-26
NBL F12102- Restricted
Report
Test of stove guard SFC300RF in combination with stove alarm SA102RF Test based on requirement specification from the Swedish Institute of Assistive Technology (SIAT) Authors Sindre Fjær
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SINTEF NBL as SINTEF NBL as
Address: Postboks 4767 Sluppen NO-7465 Trondheim NORWAY
Telephone:+47 73591078 Telefax:+47 73591044
[email protected] www.nbl.sintef.no Enterprise /VAT No: NO 982 930 057 MVA
Report
Test of stove guard SFC300RF in combination with stove alarm SA102RF Test based on requirement specification from the Swedish Institute of Assistive Technology (SIAT)
KEYWORDS: Fire Safety Stove guard
VERSION
1.1 DATE
2012-03-26
AUTHOR(S)
Sindre Fjær
CLIENT(S)
Innohome Ltd CLIENT’S REF.
Matti Myllymäki
PROJECT NO.
107565 NUMBER OF PAGES/APPENDICES:
16
ABSTRACT
The stove guard SFC300RF in combination with the stove alarm SA102RF was tested according to requirement specification for stove guards worked out by the Swedish Institute of Assistive Technology in 2004. The test results are assessed on basis of experience gained from a project SINTEF NBL has performed for the Norwegian Directorate for Civil Protection and Emergency Planning (Direktoratet for samfunnssikkerhet og beredskap) from 2009 to 2011. The tests performed did not lead to fire. There were relatively small variations in temperature in the situations where the stove guard released the alarm. The stove guard SFC300RF in combination with stove alarm SA102RF cut off the electric power supply with satisfactory margin without unnecessary alarm before spontaneous ignition temperature in the scenarios tested was reached. Modifications of the sensitivity level for the Norwegian market, notified by the manufacturer, will improve this margin. Interaction with supplementary modules as CO-detector and smoke alarms, in addition to possibilities for interaction with existing alarm systems, will increase the possibilities for preventing fire to occur.
PREPARED BY
Sindre Fjær SIGNATURE
CHECKED BY
Anne Steen-Hansen SIGNATURE
APPROVED BY
Anne Steen-Hansen SIGNATURE
REPORT NO.
NBL F12102 ISBN
CLASSIFICATION
Restricted CLASSIFICATION THIS PAGE
Restricted
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Document history VERSION DATE VERSION DESCRIPTION
0.1 0.2 1.0 1.1
2012-02-20 2012-03-20 2012-03-22 2012-03-26
First draft Corrections made after comments from the client Final version Corrections made due to new information about client
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Table of contents
1 Introduction ......................................................................................................................................................................................................................... 4 1.1 Background ..............................................................................................................................................................................................................4
2 Test setup .............................................................................................................................................................................................................................. 5 2.1 Equipment .................................................................................................................................................................................................................5
2.1.1 Stove ..........................................................................................................................................................................................................5 2.1.2 Cooking vessels .................................................................................................................................................................................5 2.1.3 Oil .................................................................................................................................................................................................................5 2.1.4 Stove guard ...........................................................................................................................................................................................6
2.2 Instrumentation ....................................................................................................................................................................................................8 2.3 Tests.............................................................................................................................................................................................................................8
2.3.1 Test 1 – Empty frying pan ...........................................................................................................................................................8 2.3.2 Test 2 – Frying pan with oil ........................................................................................................................................................9 2.3.3 Test 3 – Steel pot with oil ......................................................................................................................................................... 10 2.3.4 Test 4 – Frying pan with oil and pots with boiling water ..................................................................................... 11 2.3.5 Test 5 – Large cast-iron pot with oil .................................................................................................................................. 12
3 Results ................................................................................................................................................................................................................................... 13 3.1 Adjustment of the temperature measurements in frying pan ........................................................................................... 13
4 Discussion .......................................................................................................................................................................................................................... 15
5 Conclusion ........................................................................................................................................................................................................................... 16
References ........................................................................................................................................................................................................................................ 16
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1 Introduction
1.1 Background SINTEF NBL AS received an inquiry 04.01.2012 on behalf of Innohome Ltd concerning testing of a new stove guard. A project performed for the Directorate for Civil Protection and Emergency Planning (Direktoratet for samfunnssikkerhet og beredskap) (DSB) showed that the various stove guards reacted in different ways to superheated cooking vessels (1). Innohome Ltd wants to prove that their stove guards solve the problems illustrated in the report from the DSB-project. One of the conclusions from the DSB-project is that there is a need for a standardized test method for testing and approval of stove guards. Such a test method does not exist today. Therefore an adjusted test is performed based on a requirement specification for stove guards worked out by the Swedish Institute of Assistive Technology and issued in 2004 (2). The test is based on the description given in 8.4 Spisvaktens bryttemperatur/värmesensor in this specification.
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2 Test setup
2.1 Equipment
2.1.1 Stove The stove used for the tests was a BEHA Ambassadør with ceramic top. Diameter and effect of the hot-plates are shown in Table 1. The requirement specification describes cast-iron plates, but this is considered to have little impact on the result, besides the fact that heating and cooling of the plates will take longer time with cast-iron plates than with a ceramic top. The stove was placed towards the wall and a hood was mounted above the stove. The hood was not connected to ventilation or electricity, but was only used as an installation for the stove guard to be mounted to. Table 1: Diameter and effect of the hot-plates
Plate Diameter [cm] Effect [W] Left rear 14.5 1200 Right rear 21 2100 Left in front 18 1700 Right in front 14.5 1200
2.1.2 Cooking vessels The cooking vessels used are described in table 2. These cooking vessels have various size compared with the cooking vessels described in the specification from the Swedish Institute of Assistive Technology. The vessels were placed in such a way that the stove guard was not exposed for heat from the hot-plates. Table 2: Cooking vessels used in the tests
Cooking vessel Material Diameter [cm] Height [cm] Small steel pot Steel 18 12.5 Medium steel pot Steel 20 11.5 Large steel pot Steel 22 13.5 Large cast-iron pot Iron 24 14 Frying pan Teflon 19 4
2.1.3 Oil Rapeseed oil was used in all tests except for the test with empty frying pan. 150 ml was used in the large cast-iron pot, while 100 ml was used in the remaining tests with oil. According to the specification from the
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Swedish Institute of Assistive Technology sunflower oil is to be used. Gained experience from stove fire tests indicates that there are small variations in ignition point for these oils. Preferably the oil shall not ignite in these tests; therefore parameters connected to ignition are of no relevant importance.
2.1.4 Stove guard The stove guard system tested, consisted of two parts; stove guard SFC300RF (see Figure 1) and stove alarm SA102RF (see Figure 2). The stove guard shall be mounted together with the technical plug following the system (see Figure 1), while the stove alarm shall be mounted above the hot-plates according to the instructions from the manufacturer. The system has a user instruction with 16 levels which learns to recognise the normal environment and how the user uses the hot-plates after implementation of the system. Default setting is level 5, and all tests were performed on this level unless other levels are indicated. The alarm unit adjusts its sensitivity according to how it is adjusted in an alarm situation. By pressing the manual call point once in case of unnecessary alarm, the alarm will learn that the actual situation was safe and adjust its sensitivity level and accommodate to the situation. The stove alarm SA102RF functions by measuring temperature changes above the cooking zone. It is programmed to recognize temperature changes which occur faster than by normal cooking. A rapid change in temperature indicates that the stove is overheated and this trigger off the alarm before damage occurs. Fast temperature changes occur only in dangerous situations. By normal cooking the temperature changes will occur slower, and the food and the pot will be heated slower than an empty hot-plate or a dry pot or pan. The alarm will also trigger if the total temperature exceeds to a dangerous level. When a dangerous situation occurs, the stove alarm gives a pre warning for 1 minute. During this time the alarm signal can be reset by pressing twice on the test button. If the alarm is not reset, the alarm unit gives the stove guard a signal to cut off the electricity or gas supply to the stove or hot plates. The stove guard SFC300RF is installed in the stove socket. For gas stoves, a valve (accessible as extra equipment) is installed in the gas supply. The stove guard has an alarm output which can be connected to other alarm systems. The stove guard has an intelligent timer controlling the cooker use and the gas/electricity use of the stove. The system identifies automatically if the user varies the energy consumption on the stove, and "notices" that the user is present. It identifies when a hot plate is not adjusted for a longer period, for example when a hot plate has been turned on by accident or if one has forgotten to turn it off. The function starts automatically and cuts the electric power supply after 30 – 150 minutes, dependent on effect consumption and type of hot plate. It is programmed to only react in dangerous situations. Normal use of the stove for a longer period will not activate the system. If the intelligent timer cut off the electric power supply to the stove, the stove guard will give an acoustic signal. The signal can be reset by turning off the hot plates and press the button on the alarm unit. The stove guard will also recognize other acoustic alarm systems connected to the installation, as smoke, CO, gas alarms etc., and will cut the electricity- or gas supply in case of an alarm. Representatives from Efa Elektro AS and Innohome Ltd provided for the mounting and installation of the stove guard system during the test.
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SINTEF NBL has not tested all functionalities of the stove guard. Description of the tests made of the functionalities of the stove guard is given in chapter 2.3.
. Figure 1. Stove guard SFC300RF
Figure 2. Stove alarm SA102RF (marked with an arrow)
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2.2 Instrumentation All temperature measurements are done with mantled thermocouples type K with diameter 1.5 mm. The thermocouple in the steel pot was fixed with Kapton tape, while the thermocouple in the cast-iron pot was fixed with clasps welded to the bottom of the pot. The thermocouple in the Teflon frying pan was fixed by squeezing it to a hole with diameter 2 mm in the surface due to limited possibilities to weld or fix it with tape on Teflon. The stove alarm was placed in a height of about 50 cm above the stove top.
2.3 Tests 4 tests are performed according to the method described in chapter 8.4 in the requirement specification from the Swedish Institute of Assistive Technology. In addition to these tests, a test is performed with the large cast-iron pot used in the project for the Directorate for Civil Protection and Emergency Planning, in order to compare the results with the stove guard tested in that project. In all tests the hot plate with the pot was turned on full effect at the start of the test. Between every tests the stove was cooled to room temperature. The room temperature in the laboratory was 20 °C during the tests.
2.3.1 Test 1 – Empty frying pan This test was performed with an empty frying Teflon pan on the rear right plate as shown in Figure 3. The hot plate was turned on full effect when the test started. A thermocouple was fixed by squeezing it to a hole with diameter 2 mm in the surface of the pan.
Figure 3: Test 1 – Empty frying pan
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2.3.2 Test 2 – Frying pan with oil This test was performed on the same hot plate as in test 1. The only variation from test 1 was that the frying pan was filled with 100 ml rapeseed oil before the test started. See Figure 4.
Figure 4: Test 2 – Frying pan with oil
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2.3.3 Test 3 – Steel pot with oil This test was performed with the medium cooking vessel on the left hot plate in front. The cooking vessel was filled with 100 ml rapeseed oil before the test started. The thermocouple was fixed with Kapton tape. See Figure 5.
Figure 5: Test 3 – Steel pot with oil
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2.3.4 Test 4 – Frying pan with oil and pots with boiling water This test was performed with a frying pan with oil, two small pots filled with 2 litres of water and a large pot filled with 3 litres of water. The water was first brought to boiling and kept controlled boiling, until the hot plate with the frying pan with 100 ml oil was turned on full effect. See Figure 6.
Figure 6: Test 4 – Frying pan with oil and pots with boiling water.
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2.3.5 Test 5 – Large cast-iron pot with oil In order to compare this stove guard with the stove guards tested in the project for the Directorate for Civil Protection and Emergency Planning, a test was performed with one of the cooking vessels used in that project. The thermocouple was kept in place with a little clasp welded to the bottom. The bottom of the pot was covered with rapeseed oil. See Figure 7.
Figure 7: Test 7 – Large cast-iron pot with oil
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3 Results At each test, the temperature was measured in the frying pan/pot/cast-iron pot when the stove guard gave a pre alarm, and when the stove guard alarmed and cut off the electric power supply to the stove. See Table 3. Table 3: Temperatures measured at pre alarm, alarm and highest temperature in each test
Test no
Pre alarm [°C]
Alarm [°C]
Highest temperature measured [°C]
1 346 359 361 2 329 350 351 3 315 335 342 4 304 326 331 5 338 365 367
3.1 Adjustment of the temperature measurements in frying pan The thermocouple in the frying pan was mounted in the pan itself, and not in the oil of reasons explained in the chapter about instrumentation. This is a source for misinterpretation of the result compared with measurements in the oil. Therefore a small test was performed where the temperature in the oil was compared with the temperature in the frying pan when the thermocouple was held manually in the oil, see Figure 8.
Figure 8: Test set up when comparing temperatures in oil and frying pan
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Figure 9: Temperatures in oil and frying pan The plates were cold and the hot plate was turned on full effect when the test started. The frying pan was placed as shown in Figure 4. The results show a difference in temperature between 20 and 50 °C as shown in Figure 9, dependent on temperature by heating of room tempered oil and frying pan. The difference is 25 °C in the area where the stove guard reacts. The results are shown in Table 4. Table 4: Adjusted levels of temperatures in oil and frying pan
Test no
Pre alarm [°C]
Alarm [°C]
Highest measured temperatures [°C]
1 346* 359* 361* 2 304 325 326 4 279 301 306
*) In test 1 the surface temperature might differ from the temperature measured, but this is not checked. In test 1 there is no oil that can ignite.
0
50
100
150
200
250
300
350
0 2 4 6 8 10 12 14 16 18
Tem
pera
ture
/ C
elsi
us
Time / Minutes
Frying Pan Oil Difference
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4 Discussion The requirement specification from the Swedish Institute of Assistive Technology describes that in test 1 to 3, the electricity shall be cut off at a temperature of 275 °C ± 10 °C and in test 4 the temperature should be cut off at this temperature. In average the stove guard (adjusted as described in chapter 3.1) gave a pre alarm at 321 °C and alarm at 339 °C with little variation, while test 4 gave pre alarm at 279 °C and alarm at 301°C. This indicates that the stove guard gives an alarm signal later than the specification requires at level 5 which is default setting from the manufacturer. When alarm signal is given, the user can give a message to the stove guard by pressing the button twice if the alarm is correct, or once if the alarm is not correct, and by this reduce the sensitivity level. This result indicates that the sensitivity level should be set lower. The four tests in the requirement specification from the Swedish Institute of Assistive Technology give various levels of heat radiation. Especially test 4, which has 3 cooking vessels with boiling water in addition to a frying pan with oil, gives a different total radiation heat than tests with only one hot plate in use. Heat radiation from the cooking vessel in test 3 will give a greater difference compared to test 1 and test 2 if the heat detector is placed with diagonal access (in cases where the detector is placed low on the wall in stead of in the hood). The learning function is meant to take various places of mounting into account. In the tests made by SINTEF NBL, the stove alarm was placed under the hood as shown in Figure 2. The results indicate that the stove guard does not vary much in response when comparing each test. Interrupt temperature is somewhat higher than given in the requirements from the Swedish Institute of Assistive Technology in general, but still with sufficient margin to ignition of cooking oils. The spontaneous ignition temperature for cooking oils is normally between 400 - 450 °C. Fire did not occur in any of the 5 tests performed. Among the tests based on specifications from the Swedish Institute of Assistive Technology, there was a margin of more than 60 °C to lower temperature for spontaneous ignition for the most common cooking oils. This result was not within the criteria from the Swedish Institute of Assistive Technology, but SINTEF NBL is still of the opinion that there is a sufficient margin to possible ignition. The temperatures measured in the cast-iron pot were higher than temperatures in test 1 to 4. Compared to the results from the stove guards described in SINTEF NBL report "Brann til middag" (SINTEF-rapport NBL A11111), the results indicate that the tested stove guard, as also for other stove guards on the Norwegian marked, has somewhat high temperatures, but still with sufficient margin to spontaneous ignition. The advantage with the tested stove guard compared to the tests of stove guards reported in "Brann til middag", is the flexibility and a low variation in temperatures leading to alarm. This ensure a constant performance ability at various situations. The manufacturer informed after test that default settings shall be reset so that level 1 will represent Norwegian learning level 5. This is due to the fact that Norwegian stoves have lower effect than the Finish stoves, to which the manufacturer has adjusted the stove guard. The reason for this can be that Norway has more stringent requirements to fuses for stoves than in Finland. The manufacturer estimates that this will lead to that the stove guard will give alarm 10 °C earlier, based on their own tests. SINTEF NBL has not verified this. The stove guard can cut off the electric power supply by its own, without the stove alarm connected. This function was not tested by SINTEF NBL. The manufacturer informs that the stove guard can interpret and react on alarm signals from other external detectors, as smoke alarms and CO-detectors. A combination between various detectors might increase safety considerably by analyzing several parameters for fire hazard. The stove guard can also be connected to
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existing alarm systems for integration and increased safety. This might for example detect smoke development from pizza boxes and other combustible material which is mislaid on the hot plates. SINTEF NBL has not tested this extended functionality.
5 Conclusion Fire did not occur in any of the tests performed. There were relatively small variations in temperature when the stove guard led to alarm in the different scenarios. The stove guard SFC300RF in combination with stove alarm SA102RF cut off the electric power supply with satisfactory margin without unnecessary alarm before spontaneous ignition temperatures were reached in the scenarios tested. This margin might be even better by the changes of learning level for the Norwegian marked, as notified by the manufacturer. Cooperation with supplementary modules as CO-detector and smoke alarm, in addition to the possibilities for interaction with existing alarm system, will increase the possibilities for preventing a fire.
References 1. Stølen, Reidar, et al.: Brann til middag? Undersøkelse av sikringstiltak mot branner på komfyr (Fire for
dinner? A study of measures to prevent fires on stoves). Trondheim : SINTEF NBL as, 2011. SINTEF-report NBL A11111
2. Kravspesifikasjon Spisvakter, baskrav. 21 51 15 Övervakningssystem. Giltig från och med 2004-03-01. s.l. : Hjälpmedelsinstitutet, 2004. (Requirement specification from the Swedish Institute of Assistive Technology)
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