1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58pressure signal transmissions between primary and secondary elementsICS 17.120.10Fluid flow in clos
2、ed conduits Connections for BRITISH STANDARDBS ISO 2186:2007BS ISO 2186:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 May 2007 BSI 2007ISBN 978 0 580 50759 5Amendments issued since publicationAmd. No. Date CommentsThis publication do
3、es not purport to 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.National forewordThis British Standard was published by BSI. It is the UK implementation of ISO 218
4、6:2007. The UK participation in 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.INTERNA
5、TIONALSTANDARDISO2186Second edition2007-03-01Reference numberISO 2186:2007(E)Fluid flow in closed conduits Connections for pressure signal transmissions between primary and secondary elementsDbit des fluides dans les conduites fermes Liaisons pour la transmission du signal de pression entre les lmen
6、ts primaires et secondairesBS ISO 2186:2007iiiiiContents Page1 Scope 12 Normative references 13 Terms and definitions 14 General principles . 14.1 Safe containment 14.2 Piping specification 24.3 Isolation (block) valves . 34.4 Valve manifolds . 34.5 Installation . 44.6 Pressure taps . 54.7 Impulse l
7、ine size 54.8 Insulation . 65 Horizontal piping installations . 65.1 Gases 65.2 Liquids 65.3 Condensing vapours, e.g. steam . 76 Vertical piping systems . 76.1 General . 76.2 Gases 76.3 Liquids 76.4 Condensing vapours, e.g. steam . 87 Piezometer ring 88 Special cases . 8Annex A (informative) Guidanc
8、e on pipe diameters for long impulse lines . 10Annex B (informative) Impulse-line dynamics . 11Annex C (informative) Elevation head example calculation . 12Annex D (informative) Supplementary figures . 13Bibliography . 20BS ISO 2186:2007ivForewordISO (the International Organization for Standardizati
9、on) is a worldwide federation of national standards bodies(ISO member bodies). The work of preparing International Standards is normally carried out through ISOtechnical committees. Each member body interested in a subject for which a technical committee has beenestablished has the right to be repre
10、sented on that committee. International organizations, governmental andnon-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the InternationalElectrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are dr
11、afted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standardsadopted by the technical committees are circulated to the member bodies for voting. Publication as anInternational Stan
12、dard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patentrights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 2186 was prepared by Te
13、chnical Committee ISO/TC 30, Measurement of fluid flow in closed 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 2186:2007vIntroductionThe primary devices are flow meters d
14、escribed in ISO 5167 (all parts).A secondary device in this context receives a differential pressure signal from a primary device and can displaythe differential pressure value and convert it into a signal of a different nature, i.e. an analogue or digital signal,to transmit the value of the differe
15、ntial pressure to another location.BS ISO 2186:2007blank1Fluid flow in closed conduits Connections for pressure signal transmissions between primary and secondary elements1ScopeThis International Standard sets out provisions for the design, lay-out and installation of a pressure signaltransmission s
16、ystem, whereby a pressure signal from a primary fluid flow device can be transmitted by knowntechniques to a secondary device safely and in such a way that the value of the signal is not distorted ormodified.2 Normative referencesThe following referenced documents are indispensable for the applicati
17、on of this document. For datedreferences, 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 conduits Vocabulary and symbolsISO 5167-1:2003, Measurement of fluid flow by
18、 means of pressure differential devices inserted in circular cross-section conduits running full Part 1: General principles and requirementsISO 5167-2, Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full Part 2: Orifice platesI
19、SO 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 nozzlesISO 5167-4, Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits runni
20、ng full Part 4: Venturi tubes3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 4006 and ISO 5167-1 and thefollowing apply.3.1 secondary devicedevice which receives a differential pressure signal from a primary device, may display the differential pressu
21、revalue and may convert it into a signal of a different nature, i.e. an analogue or digital signal, to transmit the valueof the differential pressure to another location4 General principles4.1 Safe containmentThe differential pressure signal shall be transmitted in a safe manner within a pipe or tub
22、ing to the secondarydevice. This requires that the fluid between the primary and secondary device be safely contained. Safecontainment of the fluid requires conformity to the applicable standards and codes and requires the selection ofthe proper materials of construction, the fabrication methods and
23、 practices and any required gaskets andBS ISO 2186:20072sealing materials. For on-line maintenance or verification, design shall cover safe means for proof of isolation,depressurization, flushing and removal/replacement of secondary instrumentation.4.2 Piping specificationThe pipe or tubing installe
24、d between the primary and secondary device should comply with applicable nationalstandards and codes of practice.NOTE 1 National regulations can also apply.A process-piping specification should include the specification for the isolation valve (or block valve) closest tothe primary device. The speci
25、fication for the piping or tubing between this isolation valve and the secondarydevice, including any additional valves in this piping, may differ from the piping specification for the isolationvalve. This is because the small size, and often the more limited temperatures involved on the instruments
26、econdary piping, justifies these differences.The break (change) in piping specification between the process and the instrument (or secondary) side isnormally at the process isolation valve on its secondary connection end (see Figure 1). If the process-pipingspecification requires flanged connections
27、, then the process end of the isolation valve is flanged and the matingflange on the secondary side is an instrument connection or may have another approved fitting.NOTE 2 An approved hydrostatic test can be required for piping systems to prove the integrity of the pressure-containingparts of the pi
28、ping system.NOTE 3 Some installations require provision for “rodding out” of the process connections. This is the use of a rod or otherphysical device to remove materials blocking the free flow of fluid in the impulse lines. Safety precautions apply.Key1primary side2 secondary side3 specification br
29、eak, where the piping specifications change between secondary and primary4 conduit running full5 primary head creating device6 isolation valves7 impulse line connecting pipe8manifold9 secondary device10 bleed valves, typical11 alternative location of equalization valveFigure 1 Primary and secondary
30、at same elevation, preferred installationBS ISO 2186:200734.3 Isolation (block) valvesIsolation (block) valves are required to separate the entire measurement system from the main pipeline, whennecessary, but they should not affect the pressure signal.It is recommended that isolating valves should b
31、e located immediately following the pressure tappings of theprimary element. If condensation chambers are installed, isolation valves may also be fitted immediatelyfollowing the condensation chambers. However, if condensation chambers are used, it is important to check thatthey are emptied regularly
32、 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 pressure and temperature.b) There shall be a careful choice of both valve and packing, particularly in th
33、e case of dangerous or corrosivefluids and with gases such as oxygen.c) Valves shall be chosen that do not affect the transmission of a pressure signal, particularly when that signalis subject to any degree of fluctuation.Ball valves or gate valves should be used where possible, as globe-style block
34、 valves can create a pocket of gasor liquid if they are installed with the valve stem in the vertical plane.NOTE This pocket can result in a distortion of the pressure difference, which can result in an error in the indicatedmeasurement. Installation with the valve stem at an angle of from the verti
35、cal normally solves this problem.4.4 Valve manifoldsValves are often installed to permit operation, calibration and troubleshooting of the secondary device withoutremoving it. Some typical valve manifold configurations are shown in Figure 2.These valves are useda) to isolate the secondary device fro
36、m the impulse lines;b) to open a path between the high and low pressure sides of the secondary device. The secondary devicezero (no flow signal) can be adjusted at operating pressure with one block valve closed and the bypassvalve(s) open;c) to drain or vent the secondary device and/or the impulse p
37、iping to the drain or to atmosphere.Manufactured valve manifolds can reduce cost and save space. Valve manifolds integrate the required valvesand connections into one assembly. Valve manifolds shall be installed in the orientation specified by themanufacturer to avoid possible errors caused by trapp
38、ed pockets of gas or liquid in the body.90BS ISO 2186:200744.5 InstallationThe installation design should minimize the separation between the primary and secondary devices. Theconnecting piping is variously referred to as “impulse lines”, “gauge lines”, “instrument tubing” or “instrumentpiping”.The
39、detailed design for the installation of the flow meter secondary system should consider instrumenttroubleshooting and calibration. To accurately convey the pressure difference, the instrument lines shall be asshort and direct as possible and the two lines should be the same length.NOTE 1 For circums
40、tances where the instrument lines are necessarily long, guidance on the preferred line diameter isgiven 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 enablemaintenance and calibration. Installat
41、ions providing this access shall not increase measurement uncertaintiesby being excessively long with excessive fittings.Key1 secondary instrument2 manifold block3 block valve4 equalizer valve5 vent, drain and calibration plug6 vent, drain and calibration valve (optional if dashed)7 vent, drain and
42、calibration valve8 process sideFigure 2 Typical manifold configurationsBS ISO 2186:20075Any difference in elevation between the primary device pressure taps and the secondary device results in apressure difference between the two ends of the impulse lines due to the hydrostatic pressure of the fluid
43、column in the impulse lines.NOTE 2 This 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 lines isidentical. If the fluids in the two lines are not identical in density, a difference in pressure is
44、 generated. Densitydifferences arise when there is a temperature difference between the fluids in the two impulse lines. It isrecommended that, if possible, the two impulse lines be fastened and insulated together, when it is required toavoid significant temperature differences between them.NOTE 3 N
45、on-identical fluids in the two impulse lines can also give rise to density differences.The impulse lines shall be installed so that the slope is in one direction only (upward or downward depending onthe fluid; see Clauses 5 and 6. If a change to the slope direction is unavoidable, then only one such
46、 change shallbe made. In this case, a liquid trap shall be installed at the lowest point in gas service and a gas trap shall beinstalled at the highest point in liquid service.Where possible, the impulse lines should be “bled” or “vented” after installation to clear the impulse lines offluids left d
47、uring construction or after hydrostatic testing or cleaning. Bleed valves may be included in the valvemanifolds or in the secondary device body, or installed as needed.NOTE 4 Periodic bleeding can be required if the characteristics of the fluids in the impulse lines change over time with fluidageing
48、 and with diffusion or leakage into or out of the impulse lines.It is good practice to design the installation to allow for natural draining of liquids or venting of gases.Errors caused by tap-elevation differences and pressure and temperature effects on the secondary device arereduced if the zero f
49、low indication and transmission secondary instrument signal output is adjusted while thesystem is at the operating pressure and temperature and there is no flow through the system.NOTE 5 Depending on the installation and materials used, non-flowing fluid in the piping can exchange sufficient heat tothe environment to change the temperature up to tens of degrees Celsius towards ambient over a distance of hundreds ofmillimetres and hundreds of degrees Celsius over a distance of a metre.4.6 Pressure tapsThe pressure tap
