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  • 1. Date of Issue: March 1996 Affected Publication: Chapter 5, “Metering,” Section “Accessory Equipment for Liquid Meters” the API 4, of Manual o Petroleum Measurement Standards, Third Edition, September1995 (1st printing) f ERRATA On Page 7, the last sentence in 5.4.13.2 was inadvertently cut 08it should read CISfollows: 5.4.13.2 SECURITY FOR TURBINEMETERS Common seal points for turbine meter installations are the mechanical counter enclosures. pickup mounting fittings, preamplifier housings, electrical conduit covers, and control box covers. Sealing electrically operated systems that have many accessories, power supplies, and readouts becomes burdensome; the equipment is often housed a buildingor in enclosure that can be locked or sealed to meet the system’s needs.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 2. Manual of Petroleum Measurement Standards Chapter 5-Metering Section 4-Accessory Equipment for Liquid Meters THIRD EDITION, SEPTEMBER 1995 American Petroleum institute 1220 L Street. Northwest Washington, D.C. 20005 1’ 1COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 3. A P I MPMS*5.4 95 m 0732270 0548963 806 m Manual of Petroleum Measurement Standards Chapter 5-Metering Section 4-Accessory Equipment for Liquid Meters Measurement Coordination THIRD EDITION, SEPTEMBER 1995 American Petroleum InstituteCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 4. SPECIAL NOTES 1. API PUBLICATIONS NECESSARILY ADDRESS PROBLEMS OF A GENERAL NATURE. WITH RESPECT TO PARTICULAR CIRCUMSTANCES, LOCAL, STATE, AND FEDERAL LAWS AND REGULATIONS SHOULD BE REVIEWED. To 2. API IS NOT UNDERTAKING MEET THE DUTIES OF EMPLOYERS, MANU- FACTURERS, OR SUPPLIERS TO WARN OR PROPERLY TRAIN AND EQUIP THEIR EMPLOYEES AND OTHERS EXPOSED CONCERNING HEALTH AND SAFETY RISKS AND PRECAUTIONS, NOR UNDERTAKINGTHEIR OBLIGATIONS UNDER LOCAL, STATE,OR FFDERAL LAWS. 3. INFORMATION CONCERNINGSAFElY AND HEALTH RISKS AND PROPER PRECAUTIONS WITH RESPECTTO PARTICULAR MATERIALS AND CONDI- TIONS SHOULD BE OBTAINED FROM EMPLOYER, THE MANUFACTURER THE OR SUPPLIEROF THAT " L , OR THEMATERTAL S A F E T Y DATA SHEET. 4. NOTHING CONTAINED IN ANY API PUBLICATIONIS To BE CONSTRUED AS GRANTING ANY RIGHT, BY IMPLICATION OR OTHERWISE, FORTHE MANU- FACTURE,SALE,ORUSEOFANYMETHOD,APPARATUS, OR PRODUCT COVERED BY LETTERS PAIENT. NEITHERSHOULD ANYTHING CONTAINED IN THE PUBLICATION BE CONSTRUED AS INSURING ANYONE AGAINST LIABILITY FOR INFRTNGEMENT LETTERS P A m . OF 5. GENERALLY,APISTANDARDS ARE REVIEWEDANDREVISED, REAF- - , OR WITHDRAWN AT LEAST EVERYFIVE Y A S S 0 " E S E R. A ONE- TIME EXTENSION OF UP TO TWO Y E A R S WILL BE ADDED TO THIS REVIEW CYCLE. THIS PUBLICATION WILL NO LONGER BE IN EFFECT FIVE YEARS AFTER ITS PUBLICATION DATE AS AN OPERATIVE S T N A R D OR, WHERE API AN EXTENSION HAS BEEN GRANTED, UPON REPUBLICATION. STAIZTSOF THE PUBLICATION CAN BE ASCERTAINED FROM THE API AUTHORING DEPART- MENT [TELEPHONE (202) 682-8000].A CATALOG OF API PUBLICATIONS AND MATERIALS IS PUBLISHEDANNUALLY AND UPDATED QUARTERLY BY API, 1220 L STREET, N.W., WASHINGTON, D.C.2005.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 5. FOREWORD This five-part publication consolidates and presents standard calculations for metering petroleum liquids using turbine or displacement meters.nt of measure in this publication Uis are in International System(SI) and United States Customary (USC) consistent with units North American industry practices. This standardhas been developed through the cooperative efforts of many individuals from industry under the sponsorship of the American Petroleum Institute and s G the a Processors Association. API Chapter 5 of the Manual of Petroleum Measurement Standards contains the following sections: Section 1, “General Considerations for Measurement by Meters” Section 2, “Measurement of Liquid Hydrocarbons by Displacement Meters” Section 3, “Measurement of Liquid Hydrocarbons by Turbine Meters” Section 4, “Accessory Equipment Liquid Meters” for Section 5, “Fidelity and Security Flow Measurement Pulsed-Data Transmission of Systems” be so. API publications may used by anyone desiring to do Every effort been made has by the Institute to assure accuracy and reliability ofdata contained herein; however, the the Institutemakes no representation, warranty, guarantee in connection this publication or with and hereby disclaims any liability o responsibilityfor loss or damage resulting from r its use o for the violation of any r federal, state, or municipal regulation which this publication with may conflict. Suggested revisions to publication are invited and should be submitted this to Measure- ment Coordination, Exploration and Production Department, American Petroleum Institute, 1220 L Street, N.W., Washington, D. C. 20005. iiiCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 6. ............. ................. CONTENTS Page SECTION &ACCESSORY EQUIPMENT FOR LIQUID METERS 5.4.1Intmduction ........................................................................................................... 1 5.4.2 Scope ..................................................................................................................... 1 5.4.3FieldofApplication .............................................................................................. 1 5.4.4Definitions ............................................................................................................ 1 5.4.5ReferencedPublications ....................................................................................... 1 5.4.6 Selecting Accessory EQuipment for Meters ......................................................... 1 5.4.7Shaft-Driven (Mechanical)Accessories ............................................................... 1 5.4.7.1Adjuster(Calibrator) ...................................................................................... 1 5.4.7.2 Register .......................................................................................................... 2 5.4.7.3 Printer ............................................................................................................. 2 5.4.7.4TemperatureCompensator ............................................................................. 2 5.4.7.5 Pulse Generator.............................................................................................. 2 5.4.7.6RemoteTransmission ..................................................................................... 2 5.4.7.7Preset D e.................................................................................................. ei v 2 5.4.7.8Gear-ChangeAdapter ..................................................................................... 2 5.4.7.9 Rigid Extension .............................................................................................. 2 5.4.7.10AnalogGenerator ......................................................................................... 2 5.4.7.1 1 Rate-of-Flow Indicator ................................................................................. 2 5.4.7.12SwivelAdapter ............................................................................................. 2 5.4.7.13AngleAdapter .............................................................................................. 2 5.4.7.14 Dual Adapter ................................................................................................ 3 5.4.7.15Right-AngleTakeoff ..................................................................................... 3 5.4.7.16Shifter Adapter ............................................................................................. 3 5.4.7.17Combinator ................................................................................................... 3 5.4.7.18Key-LockCounter ........................................................................................ 3 5.4.7.19 Differential Drive ......................................................................................... 3 5.4.7.20ComputingCounterPfinter .......................................................................... 3 5.4.8Pulse-Driven(Electronic)Accessories ................................................................. 3 5.4.8.1 Electronic Adjuster (Calibrator or Scaler) ..................................................... 3 5.4.8.2Readout .......................................................................................................... 3 5.4.8.3Printer ............................................................................................................. 3 5.4.8.4FlowComputer ............................................................................................... 3 5.4.8.5PresetTotalizer ............................................................................................... 4 5.4.8.6ProvingCounter ............................................................................................. 4 5.4.8.7Flow-RateIndicator ....................................................................................... 4 5.4.8.8FrequencyConverter ...................................................................................... 4 5.4.8.9StepperDrive .................................................................................................. 4 5.4.8.1 O Temperature Compensator ........................................................................... 4 5.4.8.11Combinator ................................................................................................... 4 5.4.8.12ComputingCounterFrinter .......................................................................... 4 5.4.9 Interface Connections to Pulse-Driven Accessories ............................................. 4 5.4.9.1ShieldedCable ............................................................................................... 4 5.4.9.2Preamplifier .................................................................................................... 4 5.4.10InstallingPulse-DrivenAccessories ................................................................... 5 5.4.11ProtectiOnControlEquipmentConditioners ........................... ........................... 5 5.4.11.1Strainers-Filters ......................................................................................... 5 5.4.11.2AirorVaporEliminators .............................................................................. 6 5.4.11.3 Control of Flow ............................................................................................ 6 5.4.12Monitors .............................................................................................................. 6 VCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 7. Page 5.4.12.1 Thermometers .............................................................................................. 7 5.4.12.2 TemperanmRmmre-Averaging Instruments ............................................. 7 5.4.12.3 Temperature Recorders ................................................................................ 7 5.4.12.4 Pressure Gauges ........................................................................................... 7 5.4.12.5 Pressure Recorders ....................................................................................... 7 5.4.12.6 Hydrometers................................................................................................. 7 5.4.13 Security ............................................................................................................... 7 5.4.13.1 Security for Displacement Meters................................................................ 7 5.4.13.2 Security for TurbmeMeters ......................................................................... 7 viCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 8. Chapter &Metering SECTION &ACCESSORY EQUIPMENT FOR LIQUID METERS 5.4.1 Introduction API API Chapter5 4of theManual of Petroleum Measure- . Manual of Petroleum Measurement Staruiards ment Standards is intended to be a guide for the selection Chapter 4 3 “Small Volume Provers” ., Chapter 4.6, “Pulse Interpolation” and application of accessory equipment thatused with is Chapter 5.2, “Measurement of Liquid Hydrocarbons by liquid hydrocarbon meters obtain accurate measurements to and optimum service life. Selecting the kinds of accessory Displacement Meters” equipment that are described in this chapter depends on the Chapter 5 3 “Measurement of Liquid Hydrocatbons by ., function, design, purpose, and manner in whichspecific a Turbine Meters” measurement installation to be used. is Chapter 7.2, ‘‘Dynamic Temperature Determination” This publication does not endorse or advocate the prefer- Chapter 9, “Density Determination” ential use of any specific typeequipment or metering of Chapter 12.2, “Calculation of Liquid Petroleum Quan- system, nor does intend to restrict the development of any it tities Using Dynamic Measurement Methods and Volu- particular meter, instrument, or accessory equipment. metric Correction Factors” 5.4.2 Scope 5.4.6SelectingAccessoryEquipment for Meters This section of P I MPMS Chapter5 describes the char- A acteristics of accessory equipment generally used with Accessory devices should selected so that trouble will be displacement and turbine meters in liquid hydrocarbon not arise from the following: service. Havinga knowledge of these characteristics helps a Environment. Temperature and humidity extremes should . the designers and operators turbine and displacement of be evaluated, and the installation should be protected accord- meter installationsto provide satisfactory volume measure- ingly. Electrical safety factors (including the hazardous area ment results. Certain minimum requirements devices that for radio classification), electromagnetic and frequency interfer- monitor temperature, density, and pressure discussed in are ence, weatherproofing, funguspmfing,and corrosion should this chapter. System hardware, such valves, vents, and as be considered. this manifolding, is not discussed in chapter. b. Maintenance.Easy access should provided for mainte- be nance, and spareparts that havebeen recommended by the 5.4.3 Field of Application manufacturer should be obtained. The field of application of this section all segments of is c. Compatibility. The readout device or register must be the petroleum industry require dynamic measurement of that compatible with the meter and transmission system. its liquid hydrocarbons by displacement turbine meters. or d. Installation.All equipment must be installed andoperated according to the manufacturer’s recommendations and must 5.4.4 Definitions conform toall applicable regulations and codes. Terms used in this publication are defined in 5 4 4 1 ... through 5 4 4 3 .... 5.4.7 Shaft-Driven (Mechanical) Accessories 5.4.4.1 Accessory equipment is any device that enhances the utility of a measmmentsystem, includingreadouts,regis- A variety of shaft-driven accessories are applied to t r ,monitors, and liquid- or flow-conditioning equipment. es displacement meters and sometimes to turbine meters. A mechanical linkage, usuallygear train,transmits force and a 5.4.4.2 A readout is a device that displays numbers or motion from the rotating measurement element to the exte- symbols and incorporates electric or electronic measures. rior of the meter, where the accessories are attached. Care 5.4.4.3 A register is a mechanical device that displays should be exercised in selecting the number and type of numbers. accessories so excessive torque, which can overload the that 5.4.5 Referenced Publications meter, is avoided. This sectiondiscusses some of the acces- sory devices that are now being used. standards are cited in The c m n t editions of the following this chapter: 5.4.7.1 ADJUSTER (CALIBRATOR) 1COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 9. 2 CHAPTER E T E R I N G ~" A mechanical meter adjuster,or calibrator, changesthe remain uncompensated. drive-system gear ratio between the volume-sensing portion of the meter and the primary register. The calibrator adjusts 5.4.7.5PULSE GENERATOR the registerso that it is direct reading(htis, it provides a ta A pulse generator provides pulses ain quantity thatis unity meter factor). For example,precisely 100.0 units of if directly proportionalto meter throughput. Pulsing devices volume are delivered by a meter, the register shouldbe can have various types of output signal, including switch adjusted to indicate 100.0 units. Adjusters may be gear closures, square-wave signals, and sine-wave signals. The changing, friction driven, or clutch driven: depending on thedevices can also have various frequency outputs. Low design, the adjustment range cover from1 to 10 percent may frequency is usually required registration; high frequency for of throughput. is required for meter proving. Different types of adjusters are capable of handling different torqueloads. Friction-driven and clutch-driven 5.4.7.6REMOTE TRANSMISSION adjusters show decreased sensitivity and repeatability when A remote-transmission device is used to transmit a torque is increased Increased torque reduces lifea l types lin measurement signal to a remote device, sucha driving as of adjusters. If adjustment to a unity meter factor notis device, that in turn can operate most meter shaft-driven required, the adjusting device should be omitted from the accessories. meter, and a direct drive shaft to the register should be installed. 5.4.7.7 PRESET DEVICE A preset device can be preset for any quantity meter of 5.4.7.2 REGISTER throughput. At the preselected quantity, the device will stop A shaft-drivenprimary register is attached directly to the the flow of liquid will perform desired functions automat- or meter. The primary register displays the selected standard ically. It may ormay not be an indicating device. units of measurement, such as gallons, barrels, or cubic metres; the registerl o displays fractions of these units, as if 5.4.7.8GEAR-CHANGE ADAPTER required. A primary register may be a totalizer only a or speed A gear-change adapter changes the output shaft by totalizer with a separate nonresettable register.primary A a fixed ratio and is sometimes usedto achieve a given output register is usually secured and sealed meter to prevent to the for accessory devices. tampering (see 5.4.13). 5.4.7.9 RIGID EXTENSION 5.4.7.3 PRINTER A rigid extensionis a convenience device used to elevate A shaft-ven primary printer may accompanya primary meter accessories some distance above the meter itself. The register. Theprimary printer fecordson a measurement ticket used device is also to isolate meter accessories from adverse the amount of liquid thatis delivered. The ticketprinted in is environmental conditions the meter. at standard unitsof measurement, suchas gallons, barrels, or cubic meters, and in herions of these units, required. if 5.4.7.1 O ANALOGGENERATOR Impact M pressure-roller printersare capable of printing one or more paper copies. The number of copiesl m t d is i i e a An analog generator allows a meter to generateDC by the type of paper the clarityh t is required.Mechan- and ta speed. voltage that is proportional to meter The generators ical printers usually show the lowest digit to the nearest voltage signalcan be used to remotely indicate or control whole number. Ticket forms are inserted, printed, and flow rateor related t s s ak. removed manually. 5.4.7.1 RATE-OF-FLOW 1 INDICATOR 5.4.7.4 TEMPERATURE COMPENSATOR A rate-of-flow indicator is a mechanical device that is A tempexam compensatoris a variable-ratio mechanism mounted on a meter and indicates the meters flow rate by located in the meters drive i .It has a temperature sensor t an r driving a tachometer-typeindicator. that works with the variable-ratio mechanism correct the to flowing volume to standard reference temperature, 6O0E 5.4.7.12 SWIVEL ADAPTER 15"C, or 0 C The temperature compensator mustset for 2°. be A swivel adapter is a convenience device that allows the appropriate of themal coefficientof expansion the liquid accessories mounted above the swivel torotate without hydrocarbon t a is measured. ht changing indication or registration. The location of the temperature compensatorin relationto primary or other accessory readout devices depends on 5.4.7.13 ANGLE ADAPTER which of the devices to be compensated and which to are are An angle adapteris a convenience device that allowsaCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 10. A P I MPMS*5.4 95 m 0732290 0548970 T46 I SCTlON ACCESSOW OW EQUIPMENT FOR LIQUID METERS 3 counterlprinter to mounted at angle for better accessi- immediately. The device mayalso be equipped with a ticket be an bility and visibility. (See printer for preparing invoices. 5.4.8.12 for information about electrically driven computing counterdprinters.) 5.4.7.14DUAL ADAPTER A dual adapter used to mounttwo sets of shaft-driven is 5.4.8 Pulse-Driven (Electronic) accessories ona single meter. The device often usedwith is Accessories so a temperaturecompensator on one side that both compen- A variety of pulse-driven accessories can be used with sated and uncompensated meter readings available. are both displacement and turbine meters. pulses generated The by high-resolution pulsers for displacement meters and the 5.4.7.15RIGHT-ANGLE TAKEOFF inherent pulses generated by most turbine meters represent A right-angle takeoff is a device in the meter’s drive train discrete units of volume and be used to provide input can that is used to provide a rotating external output for shaft signals to the equipment discussed in 5.4.8.1 through operating mechanical accessories that are mounted exter- 5.4.8.12. nally to the meter. 5.4.8.1ELECTRONIC ADJUSTER (CALIBRATOR 5.4.7.16SHIFTER ADAPTER OR SCALER) two A shifter adapteris used for mounting sets of shaft- a An electronic adjuster, also called factoring counter, driven accessories on single meterso t a only one set of a ht a manipulates the pulse signal to achieve unit meter factor shaftdriven accessories canbe driven ata time. The device for direct reading of volume. The device is generally capable is generally used in conjunction with tender change in of being calibrated to onepart in 10,OOO. pipeline operation, where the total volume of tender must a be retained while registration in process on the alternate is 5.4.8.2 READOUT printer or register. The means of shifting, which may be An electrically driven primary readout indicates volumes manual or mechanical, transfers the meter drive from train in the desired standard units of measurement, such as one set of accessories to the other. The adapter can be gallons, barrels, or cubic meters; it also indicates fractions of equipped withan optional indicatorto show its position. these units, ifrequired. The accuracy of the readout depends on system resolution, which is proportional to the number of 5.4.7.17 COMBINATOR pulses per unit volume. A combinator is used to combine the output of two or Electromechanical registersare limited in speed. Their more meters into a single output that can be used to then adequacy should therefore be considered before a decision is drive desired accessories. made about installation. Electronic readouts not limited are in speed, but they depend onelectrical power for proper 5.4.7.18KEY-LOCK COUNTER performance. During a power failure, standby power is A key-lock counter usually used in conjunction is with the needed to verify and meter registration if mechanical retain a unattended operation ofa bulk-plant metering system. The means is not available. a equipment provides totalizer for any persan who has a t e u h rized access to the system. Access is gained through keys 5.4.8.3 PRINTER and locks that connect the totalizer to the meter train, drive Several types of electrical printers available. The two are which actuates the system. common ones include electromechanical mechanisms in the final stages. The first is designedso that each adjacent type 5.4.7.19 DIFFERENTIAL DRIVE digit advances the next digit into position it would in a as A differential drive is used to detect the differencein This mechanical totalizer. type of printer simple, inexpen- is two output between meters in batching or blending systems.sive, and widely used, but it has limited speed and longevity. The device is generally mounted on one meter and equipped The second type of printer includes individual digit with a drive connection from another meter. modules that a in a rest position until they called on mi n are to print the throughput volume that is storedain memory. 5.4.7.20 COMPUTING COUNTERPRINTER This type of printerhas high resolution, high speed, and A computing counter/printer is generally on tank used exceptional longevity. trucks that make home deliveries that total price can be so provided whena delivery is completed. The deviceshaft- a is 5.4.8.4FLOW COMPUTER driven computing mechanism that can be manually set to Many types of electronic flow computers available that are enter price per unit volume and applicable taxes. the At accept meter output signals, and other sensor signals, to conclusion of the delivery, the extended price is available calculate volume or mass flow quantitiesas required. FlowCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 11. 4 C m +METERINGI computers display, transmit, and print data that can be used 5.4.8.10TEMPERATURE COMPENSATOR foroperationalorcustodytransferpurposes. A flow an A temperature compensator combines input signal computer can be designed for single meter run a bank of a or from a volume meter and input from a temperature sensor an meters. to provide a corrected output standard reference tempera- to In addition to meter signals, some flow computers accept 60°F,15OC, or 20°C. ture, signals from pressure, temperam, and density devices that allow the calculation of gross and net flow rates and totals. 5.4.8.1 1 COMBINATOR have The flow computer should provisions to acanately cali- A combinator accepts two or more simultaneous input brate input or output signals. Security maures should be sum oa. frequencies and displays their ttl provided to preventunauthorizedaccess and almation of the flow computer memory or user confguration. Security may 5.4.8.12COMPUTING COUNTEWRINTER be hardware, such key locks or switches, sohare pass- as or A computing counter/printer generally usedon tank is words. Also, the flow computer should have means of trucks that make home deliveries that the total so price can internal processor and circuit error checking to ensure the becomputedandprinted as soon as thedelivery is integrity of calculated results. completed. This electrically driven device also equipped to is 5.4.8.5 PRESET TOTALIZER manually enter price per unit volume and applicable taxes, to thereby allowing the extended pricebe available immedi- A preset totalizeris a totalizing counter that actuates a ately when the transaction is completed. The device is avail- contact closure when the measured volume equals a value able witha ticket-printing function for preparing invoices. that was preselected on a manually adjustable counter. 5.4.8.6 PROVING COUNTER 5.4.9 Interface Connections to Pulse- Driven Accessories A proving counteris a high-resolution digital-pulse total- Interface connections, d e s c r i ï in this chapter, the as are izer that provides a display the high-frequency pulsed of output from the meter. Pulse totalizers are started and connections between the meter’s volume-sensing device stopped with an odoff gating circuit that operated from is (usually electromechanical) and its driven equipment. the prover’s mounted detector or detectors, which identify 5.4.9.1 SHIELDED CABLE the passing of calibrated volume of fluid. totaker may a The be an electromechanical counter or an electronic counter. If The signal from a volumetric meter in a measurement the counter is attached to a small volume prover,as d s r b d ecie system is in the formof a pulse train. The accuracy of the in API MPMS Chapter 4 3 the device will constitute a ., measurement system depends on the security with which the sophisticated electronic system that the capability to has pulse signals transmitted and received. are quantify fractons of a pulse cycle, using the pulseintepla- may Noise is a spurious signal that be picked up either tion techniques discussed in API MPMS Chapter 4.6. electrically or magnetically the transmission lines or by equipment. It can be picked up electrically through capaci- 5.4.8.7 FLOW-RATE INDICATOR tance coupling to other conductors; it can be picked up A flow-rate mdicator converts an input signal visual to a magnetically through induction. The amount of noise and the display of flowrate m the desired units. The device used is cost of removing it depend on the type of equipment, the for general operational information and to monitor system length of the transmission line, and the proximity of the flow rate during meter proving. s uc .Acceptable pulse transmission usually be main- o re can tained between volumetric meters that coupled within are 5.4.8.8 FREQUENCYCONVERTER 1000 feet of each other and electronic equipment hasthat A frequency converter converts an input frequency,aor shielded twisted-pair conducton signal of ample strength if a pulse train, to a proportional analog signal for reuansmission (2100 millivoltspeak to peak) is transmitted. Shieldingshall to other devices, such as recorders or controllers,a require t t h be grounded at the receiving end to prevent ground-loop only analog inputsignals. so effects. The cables should be routed that proximity to sources of electrical interference is avoided. 5.4.8.9 STEPPER DRIVE A stepper drive converts frequency inputto an accept- a 5.4.9.2 PREAMPLIFIER able form for driving a stepper motor. The stepper motor A preamplifier may be used to shape the pulse the of then rotates at a speed that is proportional to the input meter outputso that the performance of downsueam acces- frequency. The device be used t drive various mechan- can o sories will be enhanced. If a long transmission line is ical devices that require rotary input (for example, coun- required,a preamplifier should considered. The preampli- a be t r , ticket printers, and compensators). es fier should always located at the meter, the source of the be COPYRIGHT American Petroleum Institute Licensed by Information Handling Services
  • 12. signal, so ta the original low-level signal be amplified ht will pulse producer,or meter, shallbe sensitive enough operate to and increased toa satisfactory level. The shield conductor when the pulse amplitudes generated over the rated flow are shall be grounded at the receiving end only to prevent range. ground-loop effects. b. Frequency. The readout device shall able to cope with be the maximum output frequency of the pulse producer, or 5.4.1 O InstallingPulse-Driven meter, when it reaches its highest expected flow rate. Accessories c. Width. After shaping, the duration of every pulse gener- 5.4.10.1 A system that transmitsdata consists of at least ated by the pulse producer, r meter, shall long enought o be o three components:a meter (pulse producer), transmission a be detected and counted by the readout device. line (pulsecarrier), and a readout device (pulse counter and d. Shape. A sine-wave output shall not be used, without display). Thesethree components must compatible, and be preamplification and shaping, to operate readout device a each component must meet the specifications recommended that quires a square-wave input. by the manufacturers of the meter accessory equipment. and 5.4.1 0.8 In an electrical transmission installation, great 5.4.10.2 Electrical noise is a troublesome element in care should be exercised to maintain the signal amplitude at systems that have low-level signal outputs. Even in high- the highest level possible and to reduce the magnitude of level output systems, noise and spurious electrical signals noise. The followingsteps should be taken to maintain the must be eliminated. Noise signals are superimposed on optimum signal level: meter signals by electromagnetic induction, electrostaticr o a Minimize the length of the transmission line from the , capacitive coupling, or electrical conduction. meter to the readout device. 5.4.10.3 Great care should be exercised in effectively b. Ensure the correct impedence. isolating the meter system from external electrical influ- c. Use the most technically compatible signal transmission ences. To minimize unwanted noise,h grounding shall be er at cable that is available, recommended by the equipment as separate Bom other grounding networks. Shielding trans- the manufacturer. mission cables of meter and prover detectors is essential. d. If dictated by the transmission distance or the manufac- turers requirements, introduce signal preamplifier into the a 5.4.10.4 Every meter system must meet two requirements turbine meters transmission system. shall to operate properly. First, the readout device be sensi- e.Ensurethatvoltagessupplied topreamplifiersand tive enough respond to every pulse produced by the meter constant-amplitude pulse-generating systems of proper to are throughout its operating range. Second, the signal-to-noise magnitude and do not exceed thehaximum noise level or ratio shall be high enough to prevent spurious electrical ripple requirements specified the equipment manufac- by signals from influencing the readout device. turer. 5.4.1 0.5 A meters output signal be viewed as a Erain may f. Ensure that all pickup coils are securely mounted and of electrical pulses in which each pulse represents a discrete properly located. volume of liquid passing through the meter. One approach g. Periodically inspect and clean all terminals and connec- to producing electrical pulses to use magnetic induction to is tors. directly translate therotational motion of the meter into elec- h. Replace components that give a weakened signala as trical energy. Another approach is to supply external elec- result of deterioration. tia power toa proximity o photosensing device. rcl r With the first approach, both pulse frequency and ampli- 5.4.1 1 Protection/Control Equipment tude are genedy proportional to flowate.With the second r Conditioners approach, only pulse frequency is proportional to flow rate Protectionkontrol equipment is used with displacement since the amplitude of the output voltage is nearly constant.and turbine meters to ensure the most accurate and reliable 5.4.1 0.6 Most electronic readout devices condition a wave performance. This includes, but is not limited to, flow form to count each pulse or t measwe the frequency of meter control, pressure control, and removal of unwanted foreign o output so that flow rate can be indicated. Since signals may material, such as dirt, water, orgas. have a relatively low power level, installation conditions shall 5.4.11.1 STRAINERS-FILTERS be suitable for low power level signals. The recornmeendations described in this chapter not apply tol meters; they are do al Foreign material, such rust, scale, weldingbeads, slag, as related only systems t a have low power level signals. to ht sand, and gravel, may damage a meter system or may adversely affect its performance. A strainer is usually 5.4.1 0.7 The following pulse characteristics influence installed upstream of the meter a protective device. It as proper opration of the meter system: includes a basket or barrier (usually made of metal clothor a Amplitude. Any readout device that is connected to a , screen) that stops and collects foreign material before itCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 13. ~~~ ~ A P I MPMS*5-4 95 m 0732290 0548973 755 m 6 CHAPTER ~"METERING size enters the meter, The mesh varies according to the needs 5.4.1 1.3 CONTROL OF FLOW of the meter system; meter manufacturers can provide Most installations include manually or power-operated a criteria for selecting mesh size. valve for starting, controlling, and stopping the f o of lw A schedule shouldbe followed for cleaning screens. The liquid. In general, power-operated valves should open and purpose of the straineris defeated if the screen becomes close slowly to prevent flow and pressure surges. loaded to the point of rupturing. differential pressure A To avoid overspeeding a meter, may be necessaryto it gauge o upstream and downstream pressure gauges may r be include a control that limit the maximum rate of flow to will used to indicate the differential pressure across the strainer; the rated maximum of the meter. In multimeter installations, the differential pressure will in proportion to the amount be of a control valveis normally used downstream each meter of foreignmaterial that has accumulated. Based on this infor- to balance flow when one or more meters taken off line are mation, major problems caused by foreign materials can be or when proving takes place. it isneceSSaty to prevent the If avoided. flow of liquid from reversing direction, valve that allows a If the flow cannot stopped for strainer maintenance, be flow in only one direction should used. be dual strainersmay be used. Strainersare also available that A minimum back pressure must maintained to prevent be are cleaned through periodic back washing ato sump or liquid from vaporizing or flashing(seeA P I MPMS Chapters other disposal facility. 5.2 and 53. This may require the use a back-pressure .) of controller and conml valve that can maintain the required a 5.4.1 1.2 AIR OR VAPOR ELIMINATORS back pressure under line pressure. any Air or vapor in a flowing stream will be measured as If a meter is equipped with counter that can be preset for a liquid andwill result in an error in the indicated volume. delivering a particular volume, the odoff valve is usually Large volumes of air, such as those that may exist in an so controlled by the counter that the flow can stopped at be empty piping system, can result in overspeeding and damage the proper time.The preset countermay be linked to the to a meter. or valve by mechanical, electrical, other means. Lines to and from tanks are normally keptfull of liquid; Pressure-reducing valves are commonly employed in however, if the same line used to pump liquid into and outpipelines to reduce presswe to a level thatis suitableto meter is o station manifolding. r Care must be exercised to ensure that of a tank air may enter after a delivery is completed. Like- pressure is not reduced enough for vaporizationoccur. It to wise, operating at unusually lowtank levels may allow or air is not good practice to throttle immediately upstream a of vapor to be drawn into the system. Under these conditions, flow meter since may mate flow disturbances and this cause air elimination equipment required; additional shutdowns is measurement error. and alarms may also be required. High vapor pressure liquids, suchas liquefied petroleum 5.4.1 2 Monitors gas, are handled under pressure conditionsare intended that Some conditions and properties of liquid hydrocarbons to maintain the product in the liquid phase. If adequate pres- have a greater effect on measurement accuracy than do sure is not maintained, the liquids may flash orv p r z .In aoie others; monitors may thereforebe desirable to assess the such cases,a vapor separatoror condensing tank must be temperature, pressure, density, and viscosity of the flowing installed in the system the problem cannot corrected by if be liquid. For example, l0C change in gasoline temperature a another means. can produce a volume change of 0.12percent (a1°F change Air eliminators are normally not required pipeline on can produce a volume change of percent), and change 0.07 a installations where flow does not originate from nearby in pressure of 7 kilopascals (1 pound per square inch) in the tanks; however, a means of manual venting should be same product affects volume by only percent. Inthis O.OOO8 so provided at strategic locations that air or vapor can be case, the equivalency relationship between pressure and released during starbup and after maintenance. temperature is 960 kilopascals to1°C (80 pounds per square Selecting the and t p of air separator for an installa- inch to 1OF). size ye tion requires that careful consideration be given to piping When the temperam of a metered stream is determined and other equipment and to the operating details of the for correcting the thermal effects on the stream or meter, system. These details should include the quantityr, thea of i obtaining the stream temperature inside the meter body is type of liquid being handled (with particular reference its to most desirable. Some meters provide for a temperature- size viscosity and foaming characteristics), the and length of measuring device installed in the meter body; however, this piping, thetype and locationof the pumps, and the rate of is impractical with many meters because of theway they are flow. The piping downstream of the separator/eliminator constructed o the type of temperam-measuringdevice that r must remain filled with liquid to prevent or vapor from air is selected. being measured along with the liquid. If it is impractical to mount the temperature-measuringCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 14. device in the meter, the device should installed either be 5.4.12.5PRESSURE RECORDERS immediately downstream or immediately upstream the of The range ofa pressure. recorder should suited to the be meter. In liquid turbine meters, the temperature-measuring expected range of the metering operation and should not be device should be located immediately downstream theof wider than required. The instrument’s indicator and its downstream flow-conditioning tube. Where several meters sensing device shouldbe checked frequently with master a temperam sensor located in are manifolded in parallel, one gauge or a deadweight tester, and necessary adjustments is the total liquid stream acceptable if the temperatures at should be made. each meter and at the temperature-sensor location in are accordance with Table 1in API MPMS Chapter 7.2. 5.4.12.6 HYDROMETERS are Floating bulb-type hydrometers used to determine the 5.4.12.1 THERMOMETERS relative density or API gravity required for the volume The accuracy and resolution ofthermometer used in a a correction calculations described in MPMS Chapter API measurement system should appropriate for the meter’s be 12.2. Referto M I MPMS Chapters 9 and 11for instructions needs and scale of operation. Since metering requires the to be followed and tables be used in converting readings to to highest accuracy possible, the equipment should allow for standard reference conditions. precisereadingandshouldbechecked or calibrated frequently. 5.4.1 3 Security API MPMS Chapter 7.2 discusses in greater detail the Consideration should be givento sealing the meter requirements for temperature measurements associated with systems to prevent or identify unauthorized attempts at meters. tampering with or manipulating system components. The of accuracy, usefulness, and output a measurement system 5.4.12.2 TEMPERATUREPRESSURE- can be compromised in many ways, resulting the lossof in AVERAGING INSTRUMENTS credit for hydrocarbon liquids that pass through the meter. Temperature/pressure-averaging instruments determine Meter systemsare often equipped with security seals made the temperature and pressure a metered quantity ona of of we plastic, or paste that when broken i, r o disturbed indi- r volumetric o time-paced basis. The devices accurately r also cate possible tampering. Electronic systems can bealso determine average conditionsinstantaneous line conditions if so secured with key locks, access codes, and forth. Each are changing. system shouldbe reviewed to define exposure risk and to its identify appropriate locations and techniques. seal 5.4.12.3 TEMPERATURE RECORDERS Recording liquid temperatures on chart facilitates the a 5.4.13.1 SECURITY FOR DISPLACEMENT averaging of temperatures over period of time. The accu- a METERS racy of the remrded temperames cannot greater than that be Common seal points for displacement meter installations of the temperature-sensing device. Recorded temperatures are meter cover and accessory stack flange bolts, meter are often less accurate. The sensing, recording, and chart- counter mountingbolts, calibrator and compensator adjust- integration partsof a temperature recorder should be Cali- ments, right angle drive covers, and covers for electrical brated periodically. conduits and control boxes. 5.4.12.4PRESSURE GAUGES 5.4.13.2SECURITY FOR TURBINEMETERS Pressure gauges must be selected to suit the rangeof Common seal points for turbine meter installations are the expected operating pressures. They should be checked mechanical counter enclosures, pickup mounting fittings, frequently against master gauger a deadweighttester,and a o preamplifier housings, electrical conduit covers, and control necessary adjustments should m d . be a e box covers. Sealing electrically operated systems that haveCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 15. ~~ API MPMS*5*4 95 W 0 7 3 2 2 9 0 0548975 5 2 8 1-01 102-9/95”4C (3E)COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 16. ~~ ~ API MPMS*5.4 95 0732290 0 5 4 8 9 7 b 4 6 4 m American PetroleumInstitute 1220 L Street, Northwest Order No. H05043COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services