1、PD CEN/TR 16988:2016 Estimation of uncertainty in the single burning item test BSI Standards Publication WB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06PD CEN/TR 16988:2016 PUBLISHED DOCUMENT National foreword This Published Document is the UK implementation of CEN/TR 16988:2016. The UK par
2、ticipation in its preparation was entrusted to Technical Committee FSH/21, Reaction to fire tests. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are res
3、ponsible for its correct application. The British Standards Institution 2016. Published by BSI Standards Limited 2016 ISBN 978 0 580 90291 8 ICS 17.200.01 Compliance with a British Standard cannot confer immunity from legal obligations. This Published Document was published under the authority of th
4、e Standards Policy and Strategy Committee on 31 August 2016. Amendments issued since publication Date Text affectedPD CEN/TR 16988:2016TECHNICAL REPORT RAPPORT TECHNIQUE TECHNISCHER BERICHT CEN/TR 16988 July 2016 ICS 17.200.01 English Version Estimation of uncertainty in the single burning item test
5、 Messunsicherheit - Thermische Beanspruchung durch einen einzelnen brennenden Gegenstand (SBI) This Technical Report was approved by CEN on 4 July 2016. It has been drawn up by the Technical Committee CEN/TC 127. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, C
6、yprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
7、Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2016 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. CEN/TR
8、 16988:2016 EPD CEN/TR 16988:2016 CEN/TR 16988:2016 (E) 2 Contents Page European foreword . 4 1 Scope 5 1.1 General 5 1.2 Calculation procedure . 5 1.2.1 Introduction 5 1.2.2 Synchronization of data 5 1.2.3 Heat output 5 2 Uncertainty 9 2.1 Introduction 9 2.2 Elaboration of terms and concepts 11 2.2
9、.1 Mean and variance . 11 2.2.2 Estimation of the confidence interval for the population mean . 12 2.2.3 Sources of uncertainty 12 2.2.4 Standard uncertainties for different distributions 12 2.2.5 Combined uncertainty 15 2.2.6 Expanded uncertainty 16 2.2.7 Uncorrected bias 16 2.3 Combined standard u
10、ncertainties . 17 2.3.1 Combined standard uncertainty on sums . 17 2.3.2 Combined standard uncertainty on averages 18 2.3.3 Combined standard uncertainty of a product and a division . 19 2.3.4 Combined standard uncertainty on the heat release rate (Q) . 20 2.3.5 Combined standard uncertainty on the
11、depletion factor () 22 2.3.6 Combined standard uncertainty on the initial O 2-concentration (X D O2) . 22 2.3.7 Combined standard uncertainty on the volume flow rate (V D298) 23 2.3.8 Combined standard uncertainty on the air density ( air) 24 2.3.9 Combined standard uncertainty on specimen heat rele
12、ase rate (Q specimen) 24 2.3.10 Combined standard uncertainty on the average heat release rate (Q av) . 24 2.3.11 Combined standard uncertainty on FIGRA . 25 2.3.12 Combined standard uncertainty on THR600s . 25 2.3.13 Combined standard uncertainty on the volume flow (V(t) . 25 2.3.14 Combined standa
13、rd uncertainty on the smoke production rate (SPR) 25 2.3.15 Combined standard uncertainty on specimen smoke production rate (SPR) . 26 2.3.16 Combined standard uncertainty on the average smoke production rate (SPR av) 26 2.3.17 Combined standard uncertainty on SMOGRA 26 2.3.18 Combined standard unce
14、rtainty on TSP600s 27 2.4 Confidence interval classification parameters 27 2.5 Standard uncertainty on the different components 28 2.5.1 Uncertainty on the data acquisition (DAQ). 28 2.5.2 Transient error . 28 2.5.3 Aliasing error . 28 2.5.4 Uncertainty on data synchronicity 29 2.5.5 Uncertainty on
15、the component E and E . 30 2.5.6 Uncertainty on the component . 36 2.5.7 Uncertainty on the component p atm . 36 2.5.8 Uncertainty on the component T room . 36 2.5.9 Uncertainty on the component 38 PD CEN/TR 16988:2016 CEN/TR 16988:2016 (E) 3 2.5.10 Uncertainty on the component c . 38 2.5.11 Uncerta
16、inty on the component A and L 39 2.5.12 Uncertainty on the component q gas 40 2.5.13 Uncertainty on the component k t 40 2.5.14 Uncertainty on the component k p . 43 2.5.15 Uncertainty on the component p 44 2.5.16 Uncertainty on the component T ms . 44 2.5.17 Uncertainty on the component I 46 Annex
17、A (informative) List of symbols and abbreviations . 48 PD CEN/TR 16988:2016 CEN/TR 16988:2016 (E) 4 European foreword This document (CEN/TR 16988:2016) has been prepared by Technical Committee CEN/TC 127 “Fire Safety in Buildings”, the secretariat of which is held by BSI. Attention is drawn to the p
18、ossibility that some of the elements of this document may be the subject of patent rights. CEN shall not be held responsible for identifying any or all such patent rights. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association.
19、 PD CEN/TR 16988:2016 CEN/TR 16988:2016 (E) 5 1 Scope 1.1 General The measuring technique of the SBI (single burning item) test instrument is based on the observation that, in general, the heats of combustion per unit mass of oxygen consumed are approximately the same for most fuels commonly encount
20、ered in fires (Huggett 12). The mass flow, together with the oxygen concentration in the extraction system, suffices to continuously calculate the amount of heat released. Some corrections can be introduced if CO 2, CO and/or H 2O are additionally measured. 1.2 Calculation procedure 1.2.1 Introducti
21、on The main calculation procedures for obtaining the HRR and its derived parameters are summarized here for convenience. The formulas will be used in the following clauses and especially in the clause on uncertainty. The calculations and procedures can be found in full detail in the SBI standard 1.
22、1.2.2 Synchronization of data The measured data are synchronized making use of the dips and peaks that occur in the data due to the switch from primary to main burner around t = 300 s, i.e. at the start of the thermal attack to the test specimen. Synchronization is necessary due to the delayed respo
23、nse of the oxygen and carbon dioxide analysers. The filters, long transport lines, the cooler, etc. in between the gas sample probe and the analyser unit, cause this shift in time. After synchronization, all data are shifted so that the main burner ignites by definition at time t = 300 s. 1.2.3 Heat
24、 output 1.2.3.1 Average heat release rate of the specimen (HRR 30s) A first step in the calculation of the HRR contribution of the specimen is the calculation of the global HRR. The global HRR is constituted of the HRR contribution of both the specimen and the burner and is defined as + = ) ( 105 ,
25、0 1 ) ( ) ( ) ( HRR a_O2 298 total t t x t V E t D (1) where total HRR ( ) t is the total heat release rate of the specimen and burner (kW); E is the heat release per unit volume of oxygen consumed at 298 K, = 17 200 (kJ/m3); 298 () D Vt is the volume flow rate of the exhaust system, normalized at 2
26、98 K (m3/s); a_O2 xis the mole fraction of oxygen in the ambient air including water vapour; () t is the oxygen depletion factor. The last two terms a_O2 x and + ) ( 105 , 0 1 ) ( t t express the amount of moles of oxygen, per unit volume, that have chemically reacted into some combustion gases. Mul
27、tiplication with the volume flow gives the PD CEN/TR 16988:2016 CEN/TR 16988:2016 (E) 6 amount of moles of oxygen that have reacted away. Finally this value is multiplied with the Huggett factor. Huggett stated that regardless of the fuel burnt roughly a same amount of heat is released. The volume f
28、low of the exhaust system, normalized at 298 K, V D298(t) is given by ) ( ) ( ) ( ms 298 t T t p k k cA t V t D D = (2) where c0,5 1,5 0,5 00 (2 / ) 22, 4 K m kg T = A is the area of the exhaust duct at the general measurement section (m2); t kis the flow profile correction factor; converts the velo
29、city at the height of the bi-directional probe in the axis of the duct to the mean velocity over the cross section of the duct; k is the Reynolds number correction for the bidirectional probe, taken as 1,08; () pt Dis the pressure difference over the bi-directional probe (Pa); ms () Ttis the tempera
30、ture in the measurement section (K). The oxygen depletion factor () t is defined as ) ( O ) ( CO 1 ) s 90 . s 30 ( O ) s 90 . s 30 ( CO 1 ) ( O ) ( CO 1 ) s 90 . s 30 ( O ) ( 2 2 2 2 2 2 2 t x t x x x t x t x x t = (3) where 2 O() xtis the oxygen concentration in mole fraction; 2 CO ( ) xtis the car
31、bon dioxide concentration in mole fraction; Ys.Zs mean taken over interval Y s to Z s. The mole fraction of oxygen in ambient air, taking into account the moisture content, is given by = 46 ) s 90 . s 30 ( 816 3 2 , 23 exp 100 1 s) s.90 30 ( O ms 2 a_O2 T p H x x (4) where 2 O() xtis the oxygen conc
32、entration in mole fraction; H is the relative humidity (%); p is the ambient pressure (Pa); Tms(t) is the temperature in the general measurement section (K). Since we are interested in the HRR contribution of the specimen only, the HRR contribution of the burner should be subtracted. An estimate of
33、the burner contribution HRR burner(t) is taken as the HRR total(t) during the base line period preceding the thermal attack to the specimen. A mass flow controller ensures an identical HRR through the burners before and after switching from primary to the main burner. The average HRR of the burner i
34、s calculated as the average HRR total(t) during the base line period with the primary burner on (210 s t 270 s): PD CEN/TR 16988:2016 CEN/TR 16988:2016 (E) 7 ) s 270 . s 210 ( HRR HRR total av_burner = (5) where HRRav_burner is the average heat release rate of the burner (kW); HRRtotal(t) is the tot
35、al heat release rate of specimen and burner (kW). HRR of the specimen In general, the HRR of the specimen is taken as the global HRR, HRR total(t), minus the average HRR of the burner, HRR av_burner: For t 312 s: av_burner total HRR ) ( HRR ) ( HRR = t t (6) where: HRR(t) is the heat release rate of
36、 the specimen (kW); HRRtotal(t) is the global heat release rate of specimen and burner (kW); HRRav_burner is the average heat release rate of the burner (kW). During the switch from the primary to the main burner at the start of the exposure period, the total heat output of the two burners is less t
37、han HRR av_burner (it takes some time for the gas to be directed from one burner to the other). Formula (24) gives negative values for HRR(t) for at most 12 s (burner switch response time). Such negative values and the value for t = 300 s are set to zero, as follows: For t = 300 s: HRR(300) 0 kW = (
38、7) For 300 s t 312 s: HRR ) ( HRR , kW 0 . max ) ( HRR av_burner total = t t (8) where max.a, b is the maximum of two values a and b. Calculation of HRR 30s In view of the calculation of the FIGRA index, the HRR data are smoothened with a flat 30 s running average filter using 11 consecutive measure
39、ments: 10 ) 15 ( HRR 5 , 0 ) 12 ( HRR . ) 12 ( HRR ) 15 ( HRR 5 , 0 ) ( HRR s 30 + + + + + + = t t t t t (9) where HRR 30s(t) is the average of HRR(t) over 30 s (kW); HRR(t) is the heat release rate at time t (kW). 1.2.3.2 Calculation of THR(t) and THR 600s The total heat release of the specimen THR
40、(t) and the total heat release of the specimen in the first 600 s of the exposure period (300 s t 900 s), THR 600s, are calculated as follows: PD CEN/TR 16988:2016 CEN/TR 16988:2016 (E) 8 3 ) ( HRR 1000 1 ) ( THR a s 300 a = t t t (10) 3 ) ( HRR 1000 1 THR s 900 s 300 s 600 = t (11) whereby the fact
41、or 1 000 is introduced to convert the result from kJ into MJ and the factor 3 stands for the time interval in-between 2 consecutive measurements, and where THR(t a) is the total heat release of the specimen during the period 300 s t t a (MJ); HRR(t) is the heat release rate of the specimen (kW); THR
42、 600s is the total heat release of the specimen during the period 300 s t 900 s (MJ); (equal to THR(900). 1.2.3.3 Calculation of FIGRA 0.2MJ and FIGRA 0.4MJ (Fire growth rate indices) The FIGRA is defined as the maximum of the ratio HRR av(t)/(t 300), multiplied by 1 000. The ratio is calculated onl
43、y for that part of the exposure period in which the threshold levels for HRR av and THR have been exceeded. If one or both threshold values are not exceeded during the exposure period, FIGRA is equal to zero. Two combinations of threshold values are used, resulting in FIGRA 0,2MJ and FIGRA 0,4MJ. a)
44、 The average of HRR, HRR av, used to calculate the FIGRA is equal to HRR 30s, with the exception of the first 12 s of the exposure period. For data points in the first 12 s, the average is taken only over the widest possible symmetrical range of data points within the exposure period: For av 300 s:
45、HRR (300 s) 0 t = = (12) For av 303 s: HRR (303 s) HRR(300 s 306 s) t = = (13) For av 306 s: HRR (306 s) HRR(300 s 312 s) t = = (14) For av 309 s: HRR (309 s) HRR(300 s 318 s) t = = (15) For av 312 s: HRR (312 s) HRR(300 s 324 s) t = = (16) For av 30s 315 s: HRR ( ) HRR ( ) t tt = (17) b) Calculate
46、FIGRA 0,2MJ for all t where: (HRR av(t) 3 kW) and (THR(t) 0,2 MJ) and (300 s 3 kW) and (THR(t) 0,4 MJ) and (300 s t 1 500 s); both using: PD CEN/TR 16988:2016 CEN/TR 16988:2016 (E) 9 = 300 ) ( HRR . max 000 1 FIGRA av t t(18) where: FIGRA is the fire growth rate index HRR av(t) is the average of HRR
47、(t) as specified in a) (kW); As a consequence, specimens with a HRR av not exceeding 3 kW during the total test have FIGRA values FIGRA 0,2MJ and FIGRA 0,4MJ equal to zero. Specimens with a THR not exceeding 0,2 MJ over the total test period have a FIGRA 0,2MJ equal to zero and specimen with a THR n
48、ot exceeding 0,4 MJ over the total test period have a FIGRA 0,4MJ equal to zero. 2 Uncertainty 2.1 Introduction According to EN ISO/IEC 17025 3, which sets out the general requirements for the competence of testing and calibration laboratories, and EN ISO 10012 7, which sets out the requirements for
49、 assuring the quality of measuring equipment, uncertainties shall be reported in both testing and calibration reports. The general principles for evaluating and reporting uncertainties are given in the ISO Guide to the Expression of Uncertainty in Measurement (GUM) 6, but need to be applied to the specific case of fire testing. Due to the harmonization of fire testing in the
