1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58ICS 23.020.40Cryogenic vessels Cryogenic insulation performance BRITISH STANDARDBS ISO 21014:2006BS
2、 ISO 21014:2006This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 March 2007 BSI 2007ISBN 978 0 580 50426 6Amendments issued since publicationAmd. No. Date Commentscontract. Users are responsible for its correct application.Compliance with a
3、British Standard cannot confer immunity from legal obligations.National forewordThis British Standard was published by BSI. It is the UK implementation of ISO 21014:2006. The UK participation in its preparation was entrusted to Technical Committee PVE/18, Cryogenic vessels.A list of organizations re
4、presented on PVE/18 can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a Reference numberISO 21014:2006(E)INTERNATIONAL STANDARD ISO21014First edition2006-08-01Cryogenic vessels Cryogenic insulation performance Rcipients cryogniqu
5、es Performances disolation cryognique BS ISO 21014:2006ii iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Terms and definitions. 1 3 General conditions for all methods 2 4 Measuring the heat leak by the loss of product method 3 4.1 General. 3 4.2 Test procedure 3 4.3 Determination of the h
6、eat leak in units of energy per unit time 4 4.4 Determination of the heat leak as a percentage loss of product per 24 h 4 5 Determination of the holding time for open systems from heat-leak data . 4 6 Holding times for closed systems 5 6.1 Determination of the equilibrium holding time from heat-leak
7、 data 5 6.2 Calculation of the equilibrium holding time from heat-leak data 5 6.3 Static experimental holding time 6 7 Test report . 7 Annex A (normative) Conversion of measured volumetric gaseous flow to mass flow 8 Annex B (normative) Correction of measured mass flow rate with regard to deviation
8、from reference conditions. 9 Annex C (normative) Equivalent loss determination for products other than the test product 14 Bibliography . 15 BS ISO 21014:2006iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies
9、). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and no
10、n-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Par
11、t 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting
12、 a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 21014 was prepared by Technical Committee ISO/TC 220, Cryogenic vessels. BS ISO 21014:20
13、06vIntroduction Traditionally, there have been different methods of defining the insulation performance of cryogenic vessels. It is therefore necessary to harmonize such methods for different cryogenic vessels. Figure 1 shows a logic diagram to help in the understanding of this International Standar
14、d. Figure 1 Logic diagram BS ISO 21014:2006blank1Cryogenic vessels Cryogenic insulation performance 1 Scope This International Standard defines practical methods for determining the heat-leak performance of cryogenic vessels. The methods include measurement on both open and closed systems. This Inte
15、rnational Standard neither specifies the requirement levels for insulation performance nor when the defined methods should be applied. These requirements may be defined in design or operational standards/regulations. 2 Terms and definitions For the purposes of this document, the following terms and
16、definitions apply. 2.1 open system during test system kept at a constant pressure (e.g. atmospheric pressure) in which the gas produced by the evaporation of the test fluid is continuously released to atmosphere 2.2 closed system during test system in which the mass of the contents is kept constant
17、with no input or output of product 2.3 heat-leak rate quantity of heat transferred per unit time from the ambient air to the contents of the inner vessel NOTE In an open system, the heat leak causes a loss of product; in a closed system, it causes a rise in pressure. 2.4 holding time open system tim
18、e expected to elapse, for a specified degree of filling, from initial filling level until the vessel is empty (no more liquid) calculated from heat-leak data 2.5 holding time closed system time elapsed, for a specified degree of filling, from establishing the initial filling condition until the pres
19、sure has risen, due to heat leak, to the set pressure of the pressure-limiting device NOTE 1 For transportable vessels, this holding time is determined without the effects of stratification. NOTE 2 A pressure-limiting device can be a safety valve, a rupture disc, a back-pressure regulator, or any ot
20、her device installed to limit the system pressure under normal operating conditions. 2.5.1 equilibrium holding time holding time calculated from a specified heat leak assuming that liquid and vapour are constantly in equilibrium (without stratification) BS ISO 21014:20062 2.5.2 longest equilibrium h
21、olding time equilibrium holding time calculated from heat-leak data for a vessel when filled with the quantity of product giving the longest holding time 2.5.3 static experimental holding time time it takes starting from atmospheric pressure, or from a stated pressure in the case of fluids where the
22、 starting pressure cannot be atmospheric pressure (e.g. 10 bar for CO2), to reach the set pressure of the pressure-limiting device with the tank initially filled to its maximum allowable filling mass 2.6 maximum allowable filling mass initial mass that results in the tank becoming hydraulically full
23、 (98 % for all fluids except helium and 100 % for helium) at the point that the pressure-limiting device operates NOTE For fluids in a supercritical condition, the maximum allowable filling mass will be a function of the holding time and will be stated. 3 General conditions for all methods The measu
24、rements specified in this International Standard shall be carried out under the following conditions. 3.1 The cryogenic fluid used for testing shall be agreed upon between the involved parties. Liquid nitrogen may normally be used, except in cases where the vessel to be tested is designed for a spec
25、ific cryogenic fluid. 3.2 The liquid and gaseous phases shall be in equilibrium at the beginning of a test. When a test is carried out at a higher pressure than atmospheric pressure, it is important that the liquid equilibrium pressure is not lower than this test pressure. 3.3 The test environment s
26、hall be stable and constant during the test. It shall be as close as possible to the following reference conditions: ambient temperature, 15 C; atmospheric pressure, 1 013 mbar. For products other than carbon dioxide and nitrous oxide: vessel reference pressure, 1 013 mbar. For carbon dioxide and ni
27、trous oxide: vessel reference pressure, 15 bar (gauge). 3.4 The vessel and its contents shall have reached a stable temperature before the beginning of the measuring period. Equilibrium conditions are obtained after a period of stabilization, the duration of which depends on the size of the vessel a
28、nd the type and configuration of the insulation. 3.5 All accessories of the vessel which can influence the result of the measurement shall be clearly defined and specified in the report. 3.6 All instrumentation used shall be verified by calibration. 3.7 It is not necessary to use the method defined
29、in this International Standard to evaluate the insulation performance resulting from small modifications; this may be done by simple extrapolation. BS ISO 21014:200634 Measuring the heat leak by the loss of product method 4.1 General There are two methods of measuring the heat leak: direct measureme
30、nt of loss of mass; indirect measurement of loss of mass by measuring the gaseous volumetric discharge rate. The filling level shall be 10050 %+of the maximum filling level at the start of measurement, unless otherwise stated. The ambient temperature, ambient barometric pressure and the operating pr
31、essure at the top of the vessel shall be recorded throughout the test so as to be used for correction purposes. The temperature sensor(s) shall be placed in the immediate proximity of the tank being tested, but sited such that they are unaffected directly by cold gas discharged from the vents. The m
32、inimum measurement duration shall be 24 h after stable conditions have been reached. During the test, precautions shall be taken to avoid agitation of the liquid, except for tanks designed for land transport mode. When measuring the rate of discharge of gas escaping from the vessel by a flow meter,
33、it is essential that the entire gas flow passes through the meter. The gas flow rate shall be determined as a mass flow rate by using either of the following: mass flow meter; volumetric flow meter (an appropriate method is shown in Annex A). 4.2 Test procedure The test procedure shall be as follows
34、: a) precool the vessel; b) leave for a first stabilization period; c) adjust the filling to the intended starting level (e.g. 10050 %+); d) connect the instrumentation (e.g. gas flow meter); e) leave for a second stabilization period; f) take a sufficient number of readings to establish an acceptab
35、le thermal equilibrium before the start of the measuring period; g) determine the mass of the vessel contents at the start of measuring period, if direct measurement of the mass is used; h) record readings for a minimum of 24 h; i) determine the loss of product in mass units (when gaseous flow is me
36、asured) in accordance with Annex A; j) reduce to reference conditions in accordance with Annex B. BS ISO 21014:20064 4.3 Determination of the heat leak in units of energy per unit time The rate of product loss (kg/s) during the measurement period, corrected to the reference conditions in accordance
37、with Annexes A and B, shall be converted to an equivalent heat leak, Q, as given in 4.4. To calculate the heat leak with a product other than the test product, compensation using linear extrapolation in accordance with Annex C may be applied, but only if the difference between the boiling temperatur
38、e of these products at the reference conditions does not exceed 20 K. 4.4 Determination of the heat leak as a percentage loss of product per 24 h Based on the result obtained in accordance with 4.3, the heat leak as a percentage loss of product per 24 h is calculated as follows. a) Correct the measu
39、red heat leak to the reference condition for the test product by linear extrapolation, as specified in 4.3. b) Calculate the equivalent loss of the test product per day in accordance with the following formula: glgfg86 400 ( )100 %vvQLvh F= where F is the maximum allowable filling mass of the test p
40、roduct (kg); L is the equivalent loss of product as a percentage of F per day; Q is the heat leak (W); hfgis the latent heat of vaporization (J/kg) at the vessel reference pressure (see 3.3); gis the specific volume of vapour (m3/kg) at the vessel reference pressure (see 3.3); lis the specific volum
41、e of saturated liquid (m3/kg) at the vessel reference pressure (see 3.3); 86 400 is the number of seconds per day. All product-related data shall be taken at correct reference conditions for the specified product. Annex C may be used to determine the equivalent loss of product as a percentage of ful
42、l tank content per day, for a product other than the test product. 5 Determination of the holding time for open systems from heat-leak data The holding time, in days, for open systems is equal to 100Lfor the specified product. BS ISO 21014:200656 Holding times for closed systems 6.1 Determination of
43、 the equilibrium holding time from heat-leak data The system is in thermal equilibrium, i.e. the liquid and gas phases are saturated and at a temperature corresponding to the saturation pressure at all times. The calculation process shall incorporate correctly the temperature and pressure dependence
44、 of the thermodynamic properties. The data source used for calculations shall be identified and the actual value shall be shown in the calculation. Thermodynamic data from bibliography items 1, 2 or 3 may be used. The influence of phase change in the system has to be accounted for in a proper manner
45、. The thermal mass of the vessel shall be neglected in the calculation, which results in shorter holding times. For a degree of filling less than that used for the longest holding time, the holding time shall be defined as the time elapsed between when the initial filling condition is established an
46、d when the pressure-limiting device opens. Heat-leak data corrected in accordance with Annex C may be used when different products are concerned. 6.2 Determination of the optimum equilibrium holding time from heat-leak data The equilibrium holding time for a specific product shall be calculated from
47、 heat-leak data as follows. a) Correct the heat leak, Q, measured in accordance with Clause 4, to the reference conditions for the specified product by linear extrapolation (see Annex C). b) Determine the reference quantity of the specified product as follows. 1) When the critical pressure is greate
48、r than the pressure of the pressure-limiting device, the reference quantity is the quantity of product which fills, at operating temperature, 98 % of the volume of the tank below the inlet of the pressure-limiting device under conditions of the pressure-limiting devices recipient opening. 2) When th
49、e critical pressure is less than the pressure of the pressure-limiting device, the reference quantity of the product depends directly on the holding time required. c) The equilibrium holding time, H, in hours shall be calculated from the first law of thermodynamics for a constant volume system. eg eg el el ig ig il il()()3 600mu mu mu muHQ+= and ()()eleg eg elVMvmvv=()()egelel egVMvmvv=( )()iligig elVMvmvv=BS ISO 21014:20066 ()()igilil igVMvmvv=where V is the container gross volume (m3); M i
