1、BRITISH STANDARD BS 7550-2: 1993 ISO 9091-2: 1992 Calibration of spherical tanks for refrigerated light-hydrocarbon fluids in ships Part 2: Triangulation method UDC 629.12.011.52:665.725:531.731.089.6BS7550-2:1993 This British Standard, having been prepared under the directionof the Petroleum Standa
2、rds Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 15 May1993 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference PTC/12 Draft for comment 90/56139 DC ISBN 0 580 21802 3 Committees responsible for this Br
3、itish Standard The preparation of this British Standard was entrusted by the Petroleum Standards Policy Committee (PTC/-) to Technical Committee PTC/12, upon which the following bodies were represented: Department of Trade and Industry (Gas and Oil Measurement Branch) Department of Trade and Industr
4、y (National Engineering Laboratory) Institute of Petroleum Royal Institution of Naval Architects Salvage Association The following body was also represented in the drafting of the standard, through sub-committees and panels: Society of International Gas Tanker and Terminal Operators Ltd. Amendments
5、issued since publication Amd. No. Date CommentsBS7550-2:1993 BSI 10-1999 i Contents Page Committees responsible Inside front cover National foreword ii Introduction 1 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Precautions during measurement 2 5 Equipment 3 6 Preparation 3 7 Measurement 5 8
6、 Coordinate system 7 9 Calculation 8 10 Data processing 13 11 Calculation procedure 13 12 Calibration table 13 Annex A (informative) Safety precautions 15 Annex B (informative) Calibration uncertainty 15 Annex C (informative) Example of main gauge table at 1.60 C 17 Annex D (informative) Example of
7、trim correction table 18 Annex E (informative) Example of list correction table 19 Annex F (informative) Example of correction table for tank shell expansion or contraction 20 Figure 1 Example of marking 3 Figure 2 Set-up of instruments for determining the height of the base point 4 Figure 3 Locatio
8、n of benchmarks and target 4 Figure 4 Example of shoe arrangement for platform 5 Figure 5 Setting of subtense bar 6 Figure 6 Measurements with the theodolite on point A 6 Figure 7 Measurement of the target 7 Figure 8 Coordinate system for calculation 8 Figure 9 Data for calculation of the coordinate
9、s of base points (A, B) 9 Figure 10 Data measured for coordinate determination 9 Figure 11 Data for calculation of relative lengths 10 Figure 12 Calculation order 10 Figure 13 Horizontal angles for determining base point coordinates 11 Figure 14 Coordinates of a target 11 Figure 15 Transformation fr
10、om local coordinate (x, y, z) system to basic coordinate (x, y, z) system 12 List of references Inside back coverBS7550-2:1993 ii BSI 10-1999 National foreword This Part of BS 7550 has been prepared under the direction of the Petroleum Standards Policy Committee. It is identical with ISO9091-2:1992
11、Refrigerated light hydrocarbon fluids Calibration of spherical tanks in ships Part 2: Triangulation measurement, published by the International Organization for Standardization (ISO). ISO9091-2 was prepared by Subcommittee 5, Measurement of light hydrocarbon fluids, of Technical Committee28, Petrole
12、um products and lubricants, in which the United Kingdom participated. BS 7550 consists of the following Parts: Part 1: Method of stereo-photogrammetry; Part 2: Triangulation method. Part1 is identical with ISO9091-1:1991. CAUTION. Attention is drawn to the Health and Safety at Work etc. Act1974, and
13、 the need for ensuring that the method specified in this Part of BS7550 is carried out with suitable precautions. The procedure described in this Part of BS 7550 is intended to be carried out by appropriately qualified and experienced persons or other suitably trained and/or supervised personnel. No
14、rmal safety precautions should be observed throughout the use of the method. Attention is drawn to the additional safety precautions given inAnnex A. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correc
15、t application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-reference International Standard Corresponding British Standard ISO 8311:1989 BS 7627:1993 Method for calibration by physical measurement of membrane tanks and prismatic tanks in ships
16、for carriage of refrigerated light-hydrocarbon fluids (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 20, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incor
17、porated. This will be indicated in the amendment table on the inside front cover.BS7550-2:1993 BSI 10-1999 1 Introduction Large quantities of light hydrocarbons consisting of compounds having one to four carbon atoms are stored and transported by sea as refrigerated liquids at pressures close to atm
18、ospheric. These liquids can be divided into two main groups: liquefied natural gas (LNG) and liquefied petroleum gas (LPG). Bulk transportation of these liquids by sea requires special technology in ship design and construction to enable such transportation to be safe and economical. Measurement of
19、cargo quantities in ships tanks for custody transfer purposes has to be of a high order of accuracy. The two parts of this International Standard, together with other standards in the series, specify methods of internal measurement of ships tanks from which tank calibration tables can be derived. Fo
20、r internal measurement, methods of liquid calibration, physical measurement, optical measurement and stereo-photogrammetry, etc. are in general use. Liquid calibration cannot be used for large spherical tanks designed to operate at near atmospheric pressure with refrigerated light hydrocarbons becau
21、se the hydrostatic pressure exerted by the calibrating liquid may exceed the design pressure when filled higher than a certain level. This part of ISO9091 covers a calibration technique applicable to spherical tanks equipped with a central pipe/instrumentation column. 1 Scope 1.1 This part of ISO909
22、1 specifies a triangulation method for the internal measurement of spherical tanks in liquefied gas carriers. 1.2 This part of ISO 9091 also sets out the calculation procedures for compiling the calibration tables to be used for the measurement of cargo quantities. 2 Normative references The followi
23、ng standards contain provisions which, through reference in this text, constitute provisions of this part of ISO9091. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO9091 are encouraged to invest
24、igate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 7507-1:, Petroleum and liquid petroleum products Calibration of vertical cylindrical tanks Part 1: Strapping method 1
25、) . ISO 8311:1989, Refrigerated light hydrocarbon fluids Calibration of membrane tanks and independent prismatic tanks in ships Physical measurement. 3 Definitions For the purposes of this part of ISO9091, the following definitions apply. 3.1 base point centre point of the theodolite set above the t
26、raverse point 3.2 basic pentagon pentagon connecting base points 3.3 basic target portable target mounted on a tripod with a tribrach 3.4 benchmark point on which a staff is erected to determine the height of the theodolite above the south pole 3.5 calibration process of determining the total capaci
27、ty or partial capacities of a tank corresponding to different levels 3.6 calibration table; main gauge table table, often referred to as a tank table or a tank capacity table, showing the capacities of or volumes in a tank corresponding to various liquid levels measured from the gauge reference poin
28、t, with the ship on an even keel and upright 3.7 datum point position used as the datum in the preparation of a calibration table NOTE 1This position may differ from the gauge reference point. 3.8 deadwood Any tank fitting which affects the capacity of a tank. 3.8.1 positive deadwood fitting whose c
29、apacity adds to the effective capacity of the tank 1) To be published.BS7550-2:1993 2 BSI 10-1999 3.8.2 negative deadwood fitting whose volume displaces liquid and reduces the effective capacity 3.9 equator largest horizontal circumference of a spherical tank 3.10 gauge reference point point from wh
30、ich the liquid depth is measured 3.11 latitude horizontal circumferences on the surface of the sphere parallel to the equator 3.12 longitude vertical circumferences on the surface of the sphere passing through the north and south poles 3.13 list transverse inclination of a ship 3.14 north pole zenit
31、h, or highest point, of a spherical tank shell, an imaginary point in most spherical tanks due to the pipe tower or other appurtenances 3.15 pipe tower large-diameter pipe coaxial with the tanks north-south axis, containing pipes for loading and discharging, measuring instrumentation, ladder, wiring
32、 and other in-tank facilities 3.16 port left-hand side of a ship facing forward 3.17 south pole nadir, or lowest point, of a spherical tank 3.18 starboard right-hand side of a ship facing forward 3.19 target position distinctively marked on the inside surface of the tank for the triangulation method
33、 (see6.1) 3.20 traverse point position on the inside surface of the tank above which a theodolite is set for determining the coordinates of a target 3.21 trim longitudinal inclination of a ship 4 Precautions during measurement 4.1 Utmost care and attention shall be exercised in taking measurements a
34、nd anything unusual occurring during the measurement which might affect the results shall be recorded. The calibration method described in this part of ISO9091 may be applied to ships whether afloat or in dry-dock. However, its use in dry-dock may be preferable, because trim or list, if any, will re
35、main the same throughout the measurement. 4.2 If any unusual distortions are found in the tank shell, additional measurements shall be taken by the calibrator to obtain sufficient data for correct calculation in the calibration table, and the calibrators notes should be provided in connection with s
36、uch extra measurements. 4.3 Duplicate measurements of angles shall be taken to check whether they agree within16s, and if they do not agree, measurement shall be continued until two consecutive readings agree. The average of the two shall be recorded. If consecutive measurements do not agree, the re
37、ason for the disagreement shall be clarified and, if necessary, the entire calibration procedure shall be repeated. If the measurement has been interrupted, the last angle measurement taken should be repeated. If the new angle values do not agree, within the required tolerance of16s, with the earlie
38、r measurements, then the earlier set should be rejected. 4.4 Measurement shall be carried out when the temperature fluctuation of the wall is limited to the minimum. NOTE 2Temperature fluctuations should be checked during measurement procedures. 4.5 Measurements shall not be carried out when there i
39、s any motion of the ship, or vibration of the tank. If calibration is carried out before installation of the tank in the hull of the ship, the distance between predetermined points on the interior of the tank shall be measured after installation to ensure that no distortion of the tank has occurred.
40、 If distortion has occurred, the calibration shall be repeated.BS7550-2:1993 BSI 10-1999 3 4.6 The paint used to mark the targets shall be manufactured from materials which are resistant to liquids at cryogenic temperatures. 5 Equipment 5.1 Basic target A target mounted on a tribrach indicating a ba
41、se point. 5.2 End-to-end rule A rule graduated in centimetres and millimetres, to be used to measure deadwood, etc. The rule should bear the identification of a recognized standardizing authority or certificate of identification. 5.3 Measuring tape A tape bearing the identification of a recognized s
42、tandardizing authority or a certificate of identification. 5.4 Optical level An optical level having an erect image, a magnification of 20 or greater, capable of being focussed to1,5m or less and with a spirit-level sensitivity of40s per2mm or less. 5.5 Staff A scale graduated in millimetres to be e
43、rected on a benchmark. 5.6 Steel rule A rule, to be used to measure clearances, etc., graduated in millimetres. The rule should bear the identification of a recognized standardizing authority or certificate of identification. 5.7 Subtense bar A subtense bar having a length greater than5% of the dist
44、ance between the base points with a length uncertainty of less than0,01% of its length. 5.8 Surface thermometer A thermometer used to measure the temperature of the surface of the tank with an accuracy of 0,5 C in order to convert the coordinates of the targets at the temperature at the time of meas
45、urement to those at the certified reference temperature. 5.9 Theodolite A theodolite, recommended to have an erect image with a minimum circular reading of1s and a spirit plate level sensitivity of20s per2mm or less. 5.10 Tribrach A levelling platform, mounted on the tripod, with three levelling scr
46、ews and a clamping device to fasten the theodolite. 6 Preparation 6.1 Marking of targets During construction of the tank and prior to the installation or the pipe tower, targets (seeFigure 1) shall be stencilled on the inside surface of the tank shell at each intersection of latitude and longitude a
47、t20 intervals. The marking error shall be less than10mm in both vertical and horizontal directions. 6.2 Basic pentagon 6.2.1 Determination of traverse points Mark five traverse points so that each target can be measured from at least four traverse points without being obstructed by the pipe tower. 6
48、.3 Marking of benchmark Mark the benchmark at an arbitrary position near the south pole of the tank (seeFigure 2). 6.4 Set-up of measuring instruments (see Figure 2) 6.4.1 Set staffs upright on the benchmark and on the south pole of the tank. 6.4.2 Set up a level (for the basic target) using a tripo
49、d and tribrach, on an arbitrary point at which the staff on the south pole can be observed through the opening of the pipe tower (seeFigure 3). 6.4.3 Set up a levelled tribrach (for the base point) on a tripod at each of five traverse points (seeFigure 4). Figure 1 Example of markingBS7550-2:1993 4 BSI 10-1999 Figure 2 Set-up of instruments for determining the height of the base point Figure 3 Location of benchmarks and targetBS7550-2:1993 BSI 10-1999 5 7 Measurement 7.1 Elevation of base point from south pole
