_RP_550-1-7-1974_scan.pdf

Manual on Installation of RefineryInstruments and Control SystemsPart I-Process Instrumentation and ControlSection 7-Transmission SystemsAPI RECOMMENDED PRACTICE 550THIRD EDITION,1974American Petroleum instituteWashinglon,D.C.20037American Petroleum Institute2101 L Street.NeWashington.D.C.20037PREFACEThis section is one of a series which make up RP 550,Manual on Installation ofRefinery Instruments and Control Systems.RP 550 is composed of four paris:Part I-Process Instrumentation and ControlPart 11-Process Stream AnalyzersPart 111-Fired Heaters and Inert Gas GeneratorsPart IV-Steam GeneratorsPart I assays the installation of the more commonly used measuring and controlinstruments,as well as protective devices and related accessories;Part II presents adetailed discussion of process stream analyzers;Part IlI covers installationrequirements for instruments for fired heaters and inert gas generators;andPart IV covers installation requirements for instruments for steam generators.These discussions are supported by detailed information and illustrations tofacilitate application of the recommendations.With this third edition,the format of RP 550,Part I has been changed tofacilitate continuity of presentation,convenience of reference,and flexibility ofrevision.Each section is now being published individually as follows:Section I凡owSection 2-LevelSection 3-TemperatureSection 4-PressureSection 5-Automatie ControllersSection 6-Control Valves and AccessoriesSection 7-Transmission SystemsSection 8-Scals,Purges,and WinterizingSection 9-Air Supply SystemsSection 10-Hydraulic SystemsSection 11-Electrical Power SupplySection 12-Control CentersSection 13-Alarms and Protective DevicesIn the preparation of these documents,it was necessary to decide on a logicalmethod of presentation:should each point be explained as fully as possible orshould extensive cross-referencing be done between sections?.The final documents contain a combination of these methods of presentation.An attempt has been made to make each section as complete as possible,withcross-referencing done only where very extensive repetition.would have beenrequired.Users of this recommended practice are cautioned to obtain a complete setof sections in order to efficiently accomplish any cross-referencing that is requiredfor a full understanding of the subject matter.FOREWORDThis recommended practice is based on the sccumulated knowledge and experi-ence of engineers in the petroleum industry.Its purpose is to aid in the installa-tion of the more generally used measuring.control,and analytical instruments;transmission systems;and related accessories in order to achieve safe,continuous,accurate,and efficient operation with minimum maintenance.Although theinformation contained herein has been prepared primarily for petroleum refineries,much of it is applicable without change in chemical plants,gasoline plants,andsimilar installations.Successful instrumentation depends upon a workable arrangement which incorpo-rates the simplest systems and devices that will satisfy specified requirements.Sufficient schedules,drawings,sketches,and other data should be provided to enablethe constructor to install the equipment in the desired manner.The various indus-try codes and standards,and laws and rulings of regulating bodies should be fol-lowed where applicable.The information contained in this publication does notconstitute,and should not be construed to be,a code of rules or regulations.API specifications standardsare published as an aid to procurement of stan-Furthermore,it does not grant the right,by implication or otherwise,for manu-dardized equipment and materials.These specifications are ot intended to inhibitfacture,sale,or use in connection with any method,apparatus,or product coveredpurchasers and producers from purchasing or producing products made to specifica-by letters patent;nor does it ensure anyone against liability of infringement oftions otber than API.letters patent.Nothing contained in any API specification is to be construed as granting anyFor maximum plant personnel safety,transmission systems are employed toright,by implication or otherwise,for the manufacture,sale,or use in connectioneliminate the piping of hydrocarbons,acids.and other hazardous or noxiouswith any method,apparatus,or product covered by letters patent,nor as insuringmaterials to instruments in control rooms.Proper installation is essential inanyone against liability for infringement of letters patent.order to utilize the full capabilities which are built into the instrument ortransmission system.API specifications may be used by anyone desiring to do so,and every effort hasbeen made by the Institute to assure the accuracy and reliability of the data con-In the installation of an instrument.the various components must be accessibletained in them.However,the Institute makes no representation,warranty,orfor efficient maintenance and certain of these elements must be readable for goodguarantee in coanection with the publication of API specifications and herebyoperation.Orifices,control valves,transmitters,thermocouples,level gages,andexpressly diselaims any liability or responsibility for toss or damage resulting fromlocal controllers,as well as analyzer sample points,generally should be readilytheir use:for the violation of any federal,state,or municipal regulation with whichaccessible from grade,permanent platforms,or fixed ladders.In this manual,an API specification may conflict;or for the infringement of any patent resultingspecial consideration is given to the location,accessibility,and readability of theelements.from the use of an API specification.Users of the various sections of this manual are reminded that in the rapidlyadvancing field of instrumentation no publication of this type can be complete,norcan any written document be substituted for qualified engineering analysis.Certain systems are not covered herein because of their very specialized natureand limited use.When one of these systems gains general usage and installationreaches a fair degree of standardization,this section will be revised to incorporatesuch additional information.Acknowledgment is made of the work of all the engineers and operating andmaintenance personnel who,through years of study,observation,invention,andsometimes trial and error,have contributed to the technology of instrumentation.Suggested revisions are invited and should be submitted to the director of theDivision of Refining,American Petroleum Institute.2101 L Street,N.W.Wash-ng0n,D.C20037.Copyright 1974 American Petroleum InstituteCONTENTSSECTION 7-TRANSMISSION SYSTEMS7.1 ScopePage7.2 General17.2.1 Advantages of Transmitted Signals.7.2.2 Transmission System Design Considerations.7.3 Pneumatic Systems7.3.1 General7.3.2 Standard Pneumatie Signal Ranges07.3.3 Tubing and Fitting Materials.7.3.3.1 General1007.3.3.2Single Metallie Tubes7.3.3.3Single Plastic Tubes.7.3.3.4Bundled Metallie Tubes17.3.3.5 Bundled Plastic Tubes7.3.4 Installation37.3.4.1 General473.4.2Processing73.4.3Collection Point73.4.416Transmission.7.3.5 Cleaning and Pressure Testing7.35.1 General.27.352Cleaning7.3.5.3 Pressure Testing27.4 Systems for Electric Signals.7.4.1 General227.4.1.1 Standard Electrie Signal Ranges.7.4.2 Regulatory Codes and Recommended Practices.74.2.1Classified Areas and Listed Equipment.7.4.2.2Grounding of Equipment Cases and Circuits247.4.3 Reducing Electrical Interference.7.4.3.1 Sources of Electrical Interference7.43.2Minimizing Unwanted Voltages in Signal Transmission25Circuits257.433Instruments To Be Interconnected7.4.426Engineering Factors for Wire Type Selection7.4.4.1 Industrial Process Controls with Milliampere Signals67.4.42Industrial Process Controls with Voltage Signals.27.4.4.3 Industrial Process Controls and Computers.277.4.4.4 Low-Impedance Sensors to Industrial Process Con-trols.97.445Low-Impedance Sensors to Computers.7.44.6pH Glass Electrodes to Industrial Process Controls.7.4.4.7Telemetering or Supervisory Equipment.397.4.4.8Industrial Process Controls Using A-C Signals.3Page4.9Turbine Meters4.10 Magnetic Flow TransmitterPART I-PROCESS INSTRUMENTATION AND CONTROL4.11 A-C Powered Strain Gage Sensors4.12 Chromstographssifications for Wires and CablesSECTION 7-TRANSMISSION SYSTEMS5.1Wire Size2222225.2Stranded Wire7.1 Scopeship may influence a loops actual performance.5.3Insulation3Section 7 discusses recommended practices for the2.Reliability of air and electric power supplies.5.4Temperature Ratinginstallation of pneumatic and electric measurement and3.Routing and installation of tubing,wiring.and pip-5.5Overall Jacket.control signal transmission systems.Leased wire anding so as to reduce the possibility of damage from fire5.6Preferred Type of Shieldingradio transmission are not discussed.The methodsoverheating from hot process lines or equipment,and5.7Number of Crossovers.described are those generally used throughout themechanical abuse.5.8Wire and Pair IdentificationUnited States.They are based on the assumption that59Communication Wires4.Materials and construction to resist corrosion dueical Applications and Wire Type Useddes on Separation.14141515536measuring transmitters,transducers,valve positioners,control valves,and other field-mounted devices areto chemicals in the atmosphere or splatter from newproperly installed in accordance with the recommen-construction or maintenance work.7.1 Similar Signal Levels.dations in the other sections of this manual.It is also5.Provisions for manual control,testing.and ready7.2Signal and Power Wiringassumed that the wiring.piping,and tubing at the con-access to instruments for maintenance.7.3Proximity to A-C Fields.imetrical Arrangement of Circuits.et of Transmission Distance of Installation6077trol panel comply with requirements in API RP 550.Part I,Section 12-Control Centers.Fig.7-1through 7-4.illustrate comparative pneumatic andhods of Installing.electronic arrangements for a typical processing plant10.1Trays38installation.10.2 RacewaysLEGEND10.3 Messenger CablesEVEL ALARM10.4 Lightning Protection7.2 General105 Wiring for Field-Mounted Process Instruments.4VALVE POSITIONER-TYPE 132 C310.6 Junction Boxes77.2.1 ADVANTAGES OF TRANSMITTED SIGNALSELECTRO-PNEUMATIC TRANSDUCER TYPE 138 C310.7 Control Room Wiring51PRESSURE TRANSMITTERThe use of transmission systems that permit opera-7DFFE线PRESSURE T我AN5 MTTER10.8 Grounding.44410.9 Wiring Terminations and Installation Practices.“LG更LTRA制雪打TTERtion of one or more large process units from a remoteRECEIVERcontrol center increases personnel safety and con-INDICATINS RECEIVERY67venience.Because the measuring device or transmitterCONTROL WALVEis at,or as near as possible to,the point of measure-ment,certain advantages accrue.This arrangement re-duces to a minimum:CONTROL VALVE WITH YOKE-MOUNTED CONTROLLER1.The amount of connecting piping carrying processfluids,which may be unstable,corrosive,toxic,viscous,or subject to freezing.Tg,将TH OKE MOUNTED COT胶n2.The need for purging.sealing.heat tracing.andwinterizing.DUAL CONTROL WLVE WITH MECHANICAL LINKAGE3.The presence of hazardous or noxious fluids in,if nottotally exeluded from,the control center.DFFERENTIAL TYPE LEVEL INSTRUMENT7.2.2 TRANSMISSION SYSTEM DESIGN CONSIDERA-LOCAL INSTRUMENTSTIONSEXTERNAL DISPLACEMENT TYPE LEVEL INSTRUMENTMajor factors in transmission system design thatshould be considered are:INSTRUMENT AIR SUPPLY LNE1.The relationship of time constants between processNUMBER OF LINES REPRESENTEDand transmission and control lines,since this relation-MULT-TUBE CABLE CABLE NR留