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1、BRITISH STANDARD BS ISO 2186:2007 Fluid flow in closed conduits Connections for pressure signal transmissions between primary and secondary elements ICS 17.120.10 ? Licensed Copy: London South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy, (c) B
2、SI BS ISO 2186:2007 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 May 2007 BSI 2007 ISBN 978 0 580 50759 5 National foreword This British Standard was published by BSI. It is the UK implementation of ISO 2186:2007. The UK participation i
3、n its preparation was entrusted by Technical Committee CPI/30, Measurement of fluid flow in closed conduits, to Subcommittee CPI/30/2, Differential pressure methods. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport t
4、o include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. Amendments issued since publication Amd. No. DateComments Licensed Copy: London South Bank University, London Sou
5、th Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy, (c) BSI INTERNATIONAL STANDARD ISO 2186 Second edition 2007-03-01 Reference number ISO 2186:2007(E) Fluid flow in closed conduits Connections for pressure signal transmissions between primary and secondary elements Dbit des f
6、luides dans les conduites fermes Liaisons pour la transmission du signal de pression entre les lments primaires et secondaires BS ISO 2186:2007 Licensed Copy: London South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy, (c) BSI ii Licensed Copy:
7、London South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy, (c) BSI iii Contents Page 1Scope 1 2Normative references 1 3Terms and definitions 1 4General principles . 1 4.1Safe containment 1 4.2Piping specification 2 4.3Isolation (block) valves .
8、 3 4.4Valve manifolds . 3 4.5Installation . 4 4.6Pressure taps . 5 4.7Impulse line size 5 4.8Insulation . 6 5Horizontal piping installations . 6 5.1Gases 6 5.2Liquids 6 5.3Condensing vapours, e.g. steam . 7 6Vertical piping systems . 7 6.1General . 7 6.2Gases 7 6.3Liquids 7 6.4Condensing vapours, e.
9、g. steam . 8 7Piezometer ring 8 8Special cases . 8 Annex A (informative) Guidance on pipe diameters for long impulse lines . 10 Annex B (informative) Impulse-line dynamics . 11 Annex C (informative) Elevation head example calculation . 12 Annex D (informative) Supplementary figures . 13 Bibliography
10、 . 20 BS ISO 2186:2007 Licensed Copy: London South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy, (c) BSI iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bod
11、ies). 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
12、 non-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,
13、Part 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 cast
14、ing 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 2186 was prepared by Technical Committee ISO/TC 30, Measurement of fluid flow in clos
15、ed conduits, Subcommittee SC 2, Pressure differential devices. This second edition cancels and replaces the first edition (ISO 2186:1973), which has been technically revised. BS ISO 2186:2007 Licensed Copy: London South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 200
16、7, Uncontrolled Copy, (c) BSI v Introduction The primary devices are flow meters described in ISO 5167 (all parts). A secondary device in this context receives a differential pressure signal from a primary device and can display the differential pressure value and convert it into a signal of a diffe
17、rent nature, i.e. an analogue or digital signal, to transmit the value of the differential pressure to another location. BS ISO 2186:2007 Licensed Copy: London South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy, (c) BSI blank Licensed Copy: Lon
18、don South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy, (c) BSI 1 Fluid flow in closed conduits Connections for pressure signal transmissions between primary and secondary elements 1Scope This International Standard sets out provisions for the
19、design, lay-out and installation of a pressure signal transmission system, whereby a pressure signal from a primary fluid flow device can be transmitted by known techniques to a secondary device safely and in such a way that the value of the signal is not distorted or modified. 2Normative references
20、 The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 4006, Measurement of fluid flow in closed co
21、nduits Vocabulary and symbols ISO 5167-1:2003, Measurement of fluid flow by means of pressure differential devices inserted in circular cross- section conduits running full Part 1: General principles and requirements ISO 5167-2, Measurement of fluid flow by means of pressure differential devices ins
22、erted in circular cross- section conduits running full Part 2: Orifice plates ISO 5167-3, Measurement of fluid flow by means of pressure differential devices inserted in circular cross- section conduits running full Part 3: Nozzles and Venturi nozzles ISO 5167-4, Measurement of fluid flow by means o
23、f pressure differential devices inserted in circular cross- section conduits running full Part 4: Venturi tubes 3Terms and definitions For the purposes of this document, the terms and definitions given in ISO 4006 and ISO 5167-1 and the following apply. 3.1 secondary device device which receives a d
24、ifferential pressure signal from a primary device, may display the differential pressure value and may convert it into a signal of a different nature, i.e. an analogue or digital signal, to transmit the value of the differential pressure to another location 4General principles 4.1Safe containment Th
25、e differential pressure signal shall be transmitted in a safe manner within a pipe or tubing to the secondary device. This requires that the fluid between the primary and secondary device be safely contained. Safe containment of the fluid requires conformity to the applicable standards and codes and
26、 requires the selection of the proper materials of construction, the fabrication methods and practices and any required gaskets and BS ISO 2186:2007 Licensed Copy: London South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy, (c) BSI 2 sealing mat
27、erials. For on-line maintenance or verification, design shall cover safe means for proof of isolation, depressurization, flushing and removal/replacement of secondary instrumentation. 4.2Piping specification The pipe or tubing installed between the primary and secondary device should comply with app
28、licable national standards and codes of practice. NOTE 1National regulations can also apply. A process-piping specification should include the specification for the isolation valve (or block valve) closest to the primary device. The specification for the piping or tubing between this isolation valve
29、 and the secondary device, including any additional valves in this piping, may differ from the piping specification for the isolation valve. This is because the small size, and often the more limited temperatures involved on the instrument secondary piping, justifies these differences. The break (ch
30、ange) in piping specification between the process and the instrument (or secondary) side is normally at the process isolation valve on its secondary connection end (see Figure 1). If the process-piping specification requires flanged connections, then the process end of the isolation valve is flanged
31、 and the mating flange on the secondary side is an instrument connection or may have another approved fitting. NOTE 2An approved hydrostatic test can be required for piping systems to prove the integrity of the pressure-containing parts of the piping system. NOTE 3Some installations require provisio
32、n for “rodding out” of the process connections. This is the use of a rod or other physical device to remove materials blocking the free flow of fluid in the impulse lines. Safety precautions apply. Key 1primary side 2secondary side 3specification break, where the piping specifications change between
33、 secondary and primary 4conduit running full 5primary head creating device 6isolation valves 7impulse line connecting pipe 8manifold 9secondary device 10bleed valves, typical 11alternative location of equalization valve Figure 1 Primary and secondary at same elevation, preferred installation BS ISO
34、2186:2007 Licensed Copy: London South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy, (c) BSI 3 4.3Isolation (block) valves Isolation (block) valves are required to separate the entire measurement system from the main pipeline, when necessary, bu
35、t they should not affect the pressure signal. It is recommended that isolating valves should be located immediately following the pressure tappings of the primary element. If condensation chambers are installed, isolation valves may also be fitted immediately following the condensation chambers. How
36、ever, if condensation chambers are used, it is important to check that they are emptied regularly and that they do not become a source of leaks due to corrosion. When specifying an isolation valve, practical considerations include the following. a)The valve shall be rated for the pipe design pressur
37、e and temperature. b)There shall be a careful choice of both valve and packing, particularly in the case of dangerous or corrosive fluids and with gases such as oxygen. c)Valves shall be chosen that do not affect the transmission of a pressure signal, particularly when that signal is subject to any
38、degree of fluctuation. Ball valves or gate valves should be used where possible, as globe-style block valves can create a pocket of gas or liquid if they are installed with the valve stem in the vertical plane. NOTEThis pocket can result in a distortion of the pressure difference, which can result i
39、n an error in the indicated measurement. Installation with the valve stem at an angle of from the vertical normally solves this problem. 4.4Valve manifolds Valves are often installed to permit operation, calibration and troubleshooting of the secondary device without removing it. Some typical valve
40、manifold configurations are shown in Figure 2. These valves are used a)to isolate the secondary device from the impulse lines; b)to open a path between the high and low pressure sides of the secondary device. The secondary device zero (no flow signal) can be adjusted at operating pressure with one b
41、lock valve closed and the bypass valve(s) open; c)to drain or vent the secondary device and/or the impulse piping to the drain or to atmosphere. Manufactured valve manifolds can reduce cost and save space. Valve manifolds integrate the required valves and connections into one assembly. Valve manifol
42、ds shall be installed in the orientation specified by the manufacturer to avoid possible errors caused by trapped pockets of gas or liquid in the body. 90 BS ISO 2186:2007 Licensed Copy: London South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy
43、, (c) BSI 4 4.5Installation The installation design should minimize the separation between the primary and secondary devices. The connecting piping is variously referred to as “impulse lines”, “gauge lines”, “instrument tubing” or “instrument piping”. The detailed design for the installation of the
44、flow meter secondary system should consider instrument troubleshooting and calibration. To accurately convey the pressure difference, the instrument lines shall be as short and direct as possible and the two lines should be the same length. NOTE 1For circumstances where the instrument lines are nece
45、ssarily long, guidance on the preferred line diameter is given in Annex A. See additionally 4.7.1, 4.7.2 and 4.7.3. Access to the impulse lines, the valves, the valve manifold and the secondary device is required to enable maintenance and calibration. Installations providing this access shall not in
46、crease measurement uncertainties by being excessively long with excessive fittings. Key 1secondary instrument 2manifold block 3block valve 4equalizer valve 5vent, drain and calibration plug 6vent, drain and calibration valve (optional if dashed) 7vent, drain and calibration valve 8process side Figur
47、e 2 Typical manifold configurations BS ISO 2186:2007 Licensed Copy: London South Bank University, London South Bank University, Fri Jun 01 01:33:20 GMT+00:00 2007, Uncontrolled Copy, (c) BSI 5 Any difference in elevation between the primary device pressure taps and the secondary device results in a
48、pressure difference between the two ends of the impulse lines due to the hydrostatic pressure of the fluid column in the impulse lines. NOTE 2This effect is usually greater for liquids than for gases. The impulse lines shall be installed in such a way that the hydrostatic pressure in the two impulse
49、 lines is identical. If the fluids in the two lines are not identical in density, a difference in pressure is generated. Density differences arise when there is a temperature difference between the fluids in the two impulse lines. It is recommended that, if possible, the two impulse lines be fastened and insulated together, when it is required to avoid significant temperature differences between them. NOTE 3Non-identical fluids in the two impulse lines can also give rise to density di