MPMS 5.5-82             0732290 0054999 4                                                                            F-5-7...
MPMS 5.5-82   0732270 0 0 5 5 0 0 0 5                    Manual of Petroleum                    Measurement Standards     ...
MPMS 5.5-82                            Nothing contained in any API publication is to be construed as granting any right, ...
MPMS 5 - 5 - 8 2                                                              FOREWORD                            This pub...
CONTENTS                                                                                                                  ...
MPMS 5.5-82                 I 0732290           0 0 5 5 0 0 4 21-                                                         ...
MPMS 5.5-82                               0732290 0055005 41-         2                                                   ...
MPMS 5.5-82                   I 0732290                  0055006 b      r                                                 ...
MPMS 5.5-82                       I 0732240 0 0 5 5 0 0 7 w        4                                                      ...
MPMS 5 - 5 - 8 2                   0 7 3 2 2 9 0 0055008         o                                                        ...
MPMS 5-5-82                             07312290 0055009 l                                                                ...
MPMS 5 - 5 - 8 2              I 0732270            O055010                                                           SECTI...
A            Alarm .........                                   .........................                                 3...
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Api mpms 5.5

  1. 1. MPMS 5.5-82 0732290 0054999 4 F-5-7-a3 Manual of Petroleum Measurement Standards Chapter 5-Metering Section 5-Fidelity and Security of Flow Measurement PuIsed-Data Transmission Systems FIRST EDITION, JUNE 1982 American Petroleum Institute 2101 L Street, Northwest 1’ 1 Washington, D.C. 20037COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  2. 2. MPMS 5.5-82 0732270 0 0 5 5 0 0 0 5 Manual of Petroleum Measurement Standards Chapter 5 Metering - Section !%Fidelity and Security of Flow Measurement Puked-Data Transmission Systems Measurement Coordination Department FIRST EDITION, JUNE 1982 American Petroleum InstituteCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  3. 3. MPMS 5.5-82 Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use in connection with any method, apparatus, or product covered by letters patent, nor as insuring anyone against liability for infringement of letters patent. API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with API publications and hereby expressly disclaims any liability or responsibility for loss or damage resulting from their use; for any violation of any federal, state, or municipal regulation with which an API publication may conflict; or for the infringementof any patent resulting from the use of an API publication. Copyright o 1982 American Petroleum InstituteCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  4. 4. MPMS 5 - 5 - 8 2 FOREWORD This publication is intended as a guide to the selection, operation, and maintenance of pulsed-data, cabled transmission systems for fluid metering systems to provide the desired level of fidelity and security of transmitted data. A comprehensive API Manual o Petroleum Measurement Standards is currently being f prepared. The manual will include all subject matter now found in API measurement publications-excluding evaporation loss measurement-as well as new material. Suggested revisions are invited and should be submitted to the director of the Measurement Coordination Department, American Petroleum Institute, 2101 L Street, N.W., Washington, D.C. 20037.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  5. 5. CONTENTS PAGE SECTION 5-FIDELITY AND SECURITY OF FLOW MEASUREMENT PULSED-DATA TRANSMISSION SYSTEMS 5 S . 0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5.5.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5.5.2 Field of Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5.5.3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5.5.4 Levels of Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5.5.4.1 LevelE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5.5.4.2 LevelD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5.5.4.3 LevelC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5.5.4.4 LevelB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5.5.4.5 LevelA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5.5.5 System Design Considerations ...................................... 5 5.5.5.1 General Design Criteria ....................................... 5 5.5.5.2 Totalizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.5.5.3 Typical Causes of Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.5.5.4 Signal Pre-Amplifiers ......................................... 5 5.5.5.5 Standby Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5 S.5.6 Test Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.5.5.7 General Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.5.6 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.5.6.1 Signal Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5 S.6.2 Signal-To-Noise Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.5.6.3 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.5.7 Inspection and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.5.7.1 Need for Inspection and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 5 7 . 2 Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Index ............................................................... 9 Figures 1-Typical Functional Arrangement of a Level E Pulse Security System ........ 2 2-Typical Functional Arrangement of a Level D Pulse Security System ....... 2 3-Typical Functional Arrangement of a Level C Pulse Security System ........ 3 4-Typical Functional Arrangement of a Level B Pulse Security System ........ 4 5-Typical Functional Arrangement of a Level A Pulse Security System ....... 4COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  6. 6. MPMS 5.5-82 I 0732290 0 0 5 5 0 0 4 21- Chapter 5-Metering SECTION 5-FIDELITY AND SECURITY OF FLOW MEASUREMENT PULSED-DATA TRANSMISSION SYSTEMS 5.5.0 Introduction 5.5.4 Levels of Security Thepurpose of this publicationis to serve as a guide for the Five levels of security protection are identified and des- selection, operation, and maintenance of various types of ignated, of which Level E represents the minimum accept- pulsed-data, cabled transmission systems for fluid metering able level. Typical examples of these five levels are shown systems to provide the desired level of fidelity and security of diagrammatically in Figures 1 through 5 . A metering system transmitted data. This publication does not endorse or advo- may comprise sections having the same or different levels of cate the preferential use of any specific type of equipment or security protection, where the outputs are used for different systems, nor is it intended to restrict future development of purposes. Figures 1 through 5 show typical functional ar- such equipment. rangements of modules required to achieve the specified Acknowledgement is extended to the Institute of Pe- levels of security. These function modules may be housed troleum in the United Kingdom for their contribution to this separately or in combination. section of the Manual of Petroleum Measurement Standards. In the examples, emphasis has been placed on the trans- mission system because this is considered the most vulner- 5.5.1 Scope able area of the whole. Fidelity and security for scaler and The recommendations set forth in this publication are totalizer are not illustrated and are considered to be accept- concerned only with the fidelity and security of pulsed-dah, able to Level E for the majority of applications. It may, cabled transmission systems between a flow meter or flow however, be considered necessary in some circumstances to meter transducer and a remote totalizer. duplicate the scaler and/or totalizer section. 5.5.2 Field of Application 5.5.4.1 LEVEL E In order to achieve different levels of security that can be Error reduction at Level E is achieved solely by correctly applied to transmission systems, criteria and recommenda- installed apparatus of good quality. This is a straightforward tions for the design, installation, use, and maintenance of the totalizer system. Figure 1 illustrates a simple system with no relevant equipment are described in this publication. The built-in provisions for error monitoring. Only good quality levels of security are designated E to A from the lowest to the components and subunits, correctly installed, will lead to highest order of security, respectively. Chapter 5 Section 5 confidence in the security of the system. The use of a pre- does not define which levels of security are to be used for a amplifier transmitter to drive the transmission line is consid- particular system application. ered beneficial for the majority of applications, as is the 5.5.3 Definitions provision of signal conditioning. The system, though simple, does not differ in hardware quality from more secure systems See MPMS Chapter 1, “Vocabulary,” for additional that use the same elements’. definitions. Fidelity is defined as the exactitude with which the primary 5.5.4.2 LEVEL D indication reproduces the inherent precision of the measure- ment. A Level D system consists of manual error monitoring at Methods of comparison, as used in Levels A through D, is specified intervals by methods of comparison. This level of the determination of the fidelity of primary indication by use security is intended to give protection against functional of a redundant, alternate, or secondary source to verify the errors and failures and is a method of verification by manual desired level of security. action. The readout can be visually checked against an inde- Noise consists of unwanted signals that may affect fidelity pendent totalizing system. Figure 2 illustrates a simple sys- and which occur for periods exceeding 0.2 seconds. tem with means of making a periodic manual assessment of A scaler is an electronic device that operates a recorder security. The secondary readout may be permanent or tem- after a specified number of impulses, appearing too rapidly porary, local or remote. Manual comparison made during a for individual recording. periodic check will monitor the integrity of the transmission Transients are disturbances having a duration of 0.2 sec- and totalizer elements. It may be less convenient than provi- onds or less. sions of Level C, as the system may have to be stopped for 1COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  7. 7. MPMS 5.5-82 0732290 0055005 41- 2 CHAPTER 5-METERING FLOW TRANSDUCER TRANSMISSION Ø PULSE SIGNAL TRANSMITTER CONDITIONER + SCALER - - - ) TOTALIZER O 1 ! ! I PREAMPLIFIER I FLOW SUPPLIES LOW TRANS- AMPLIFICATION CONVERSION OF MEASURE- IMPEDANCE SIGNAL MISSION AND FREQUENCY PULSE COUNTS READOUT MENT OVER FULL OF SIGNAL RANGE LIMITING, TO READOUT OPERATING PULSE SHAPING, UNITS FREQUENCY COMMON MODE INTERFERENCE REJECTION I 1 I--------- I rALARMTF- I FREQUENCY IS --- 1 I I OUTSIDE THE SET I I PREAMPLIFIER I ------ LIMITS I I RATEREADOUT I L--- - --- -J NOTE: modules and functions shown in full are essential. Those shown dotted are optional. The Figure 1-Typical Functional Arrangement for a Level E Pulse Security System TRANSMISSION TRANSDUCER PULSE SIGNAL SCALER W - 3 I TRANSMITTER CONDITIONER --------- I I HIGH/LOW FLOW I 1 I 0 O I L---,,,-J I GATE -------- i ALARM I W OUT (PERMANENT 1INDICATION ! OR TEMPORARY, LOCAL OR REMOTE) U ~ ~~~~ FLOW SUPPLIES LOW TRANS- AMPLIFICATION MEASURE- IMPEDANCE SIG- MISSION AND FREQUENCY OF PULSE COUNTS READOUT MENT NALS OVER FULL OF SIGNAL RANGE LIMITING, TO READOUT UNITS OPERATING FRE- PULSE SHAPING, QUENCY COMMON MODE r------ INTERFERENCE r------- 7 I ALARM IF FRE- I QUENCY IS I 1 REJECTION I I OUTSIDE THE SET INTERVALS U &-------- I LIMITS 1 RATE READOUT NOTEThe modules and functions shown in full are essential. Those shown dotted are optional. The modules and functions boxed in double lines indicate the difference from Level E. Figure 2-Typical Functional Arrangement for a Level D Pulse Security SystemCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  8. 8. MPMS 5.5-82 I 0732290 0055006 b r SECTION 5-FIDELITY AND SECURITY 3 O readings to be taken. Overall security is mainly inferred from the performance during the error monitoring period. tion, and alarm signaling by methods of comparison. This level of security is intended to give warning of transients and other spurious influences, in addition to functional errors and 5.5.4.3 LEVEL C failures. Figure 4 illustrates a dual transmission system with a dual pulse comparator in which the pulse trains are continu- A Level C system consists of automatic error monitoring ously monitored for number, frequency, phase, and sequence and error indication at specified intervals by methods of and any irregularity is indicated. Simultaneous interfering comparison. This level of security is intended to give protec- pulses must be detected and indicated. Alarm is given if tion against functional errors and failures and may be pulses are lost or gained on either channel. - achieved by design methods. The time intervals for error monitoring may be subject to revision in the light of experi- ence gained. Figure 3 illustrates a dual transmission system with a dual pulse comparator of simple design. If the pulses 5.5.4.5 LEVEL A delivered become numerically out of step, warning will be Level A consists of continous verification and correction given by the comparator (differential counter). Level C se- by methods of comparison. This level of security is intended curity will be defeated by other disturbances dealt with by to give protection against transients and other spurious influ- higher level security systems, for example, simultaneous ences, in addition to functional errors and failures. Figure. 5 interference superimposed on both channels will not be de- illustrates a dual transmission system protected against both tected because a numerical difference between channels is dynamic faults arising from monitoring the duplicated not caused. It is intended that this form of error monitoring be pulses and by static testing the electrical integrity of the carried out periodically; the monitoring equipment may thus transmission circuits. The system should still operate as a be shared with other metering systems. Level C security is Level E system if one of the transmission channels fails. An inferred from the results obtained during the monitoring incidental advantage of Level A is its ability to detect some period. mechanical faults in the transducer, Simultaneous pulses caused by symmetrical interference are automatically re- 5.5.4.4 LEVEL B jected and do not influence the system. Alarm will be given in Level B consists of continuous monitoring, error indica- all circumstances when impaired pulses are received by the FLOW TRANSDUCER TRANSMISSION CHANNEL A LINES TRANSMITTER CONDITIONER w r------ 1 If r-------,I I HIGH/LOW I PREAMPLIFIER I - 2 O O I L ------- 1 ------- I FLOW ALARM GATE z ------- JI I INDICATION il...^-y-........I L =,i CONDITIONER c------ - ISUPPLIES LOW I I AMPLIFICATION I II FLOW NUMERICAL QUANTITY I I I MEASURE- IMPEDANCE MISSION AND FREQUENCY COMPARISON OF PULSE COUNTS TO READOUT MENT SIGNALS OVER OF SIGNAL RANGE LIMITING, PULSE TRAINS READOUT UNITS I FULL OPERATING PULSE SHAPING. AUTOMATICALLY BUT NOT CONTINUOUSLY ALARM IF IS -----i--- I (COM PA RATOR r------- I 1 MAY BE SHARED) FREQUENCY i I I I I PREAMPLIFIER I I !OUTSIDE THE SET I I L _______ -1 NOTE modules and functions shown in full are essential. Those shown dotted are optional. The modules and The functions boxed in double lines indicate the difference from Level D. Figure 3-Typical Functional Arrangement for a Level C Pulse Security SystemCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  9. 9. MPMS 5.5-82 I 0732240 0 0 5 5 0 0 7 w 4 CHAPTER 5-METERING FLOW TRANSDUCER CHANNEL TRANSMISSION LINES - O - SIGNAL SCALER TOTALIZER TRANSMITTER r------- CONDITIONER --- -- --1 I3 O ! I PREAMPLIFIER L----,--l I I ~HIGWLOW FLOW ALARM I i O 5 CHANNEL 8 - L _______ I RATE INDICATOR I J P TRANSMITTER 1 :Low SUPPLIES LOW AMPLIFICATION CONTINUOUS CONVERSION OF QUANTITY AEASURE. IMPEDANCE SIG- MISSlOlr AND FREQUENCY COMPARISON OF ERROR PULSE COUNTS TO READOUT AENT NALS OVER FULL RANGE LIMITING. PULSE TRAINS INDICA- READOUT UNITS OPERATING FRE- SIGNAL PULSE SHAPING FOR NUMBER, TION AND COMMON MODE FREQUENCY, ALARM CHANNEL A INTERFERENCE PHASE AND 1 1 REJECTION AND E PULSES TO DIFFER IN SEQUENCE i ALARM IF FRE- I PHASE ANDIOR I I QUENCY IS OUTSIDE THE ,SET LIMITS I I r------ I PREAMPLIFIER L- -- - - - - NOTE The modules and functions shown in full are essential. Those shown dotted are optional. The modules and functions boxed in double lines indicate the difference from Level C . Figure 4-Typical Functional Arrangement for a Level B Pulse Security System TRANSMISSION FLOW CHANNEL A LINES TRANSDUCER PULSE TRANSMITTER SCALER TOTALIZER r----- I PREAMPLIFIER I L-----J COMPARATOR AND O SIGNAL ANALYZER CHANNEL E I SUPPLIES LOW TRANS- AMPLIFICATION CONTINUOUS INDICATION IMPEDANCE SIG- MISSION AND FREQUENCL COMPARISON OF OF ERROR PULSE COUNTS TO NALS OVER FULL OF RANGE LIMITING PULSE TRAINS FOR AND SIGNAL READOUT UNITS OPERATING FRE- SIGNAL PULSE SHAPING, NUMBER IRREGU- QUENCY COMMON MODE FREQUENCY, LARITY CHANNEL A INTERFERENCE PHASE AND I I AND E PULSES TO DIFFER IN PHASE AND/OR lEE9 REJECTION SEQUENCE ANALYSIS OF PULSE VALIDITY, AND ALARM Ä Ã RIFFFET LRM -1 I QUENCY IS I OUTSIDE THE SET I I - SELECTION AND PROCESSING OF I LIMITS I r----- PREAMPLIFIER 1 I VALID PULSES I I RATE READOUT J- , , , , ,L I NOTEThe modules and functions shown in full are essential. Those shown dotted are optional. The modules and functions boxed in double lines indicate the difference from Level B. Figure 5-Typical Functional Arrangement for a Level A Pulse Security SystemCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  10. 10. MPMS 5 - 5 - 8 2 0 7 3 2 2 9 0 0055008 o r SECTION 5-FIDELITY AND SECURITY 5 - comparator. It may be desirable to provide redundancy in one 5. Common-mode noise induced in cabling. or ali of the elements shown. 6. Series-mode noise induced in cabling. 7. Noise introduced from ground loop problems. 5.5.5 System Design Considerations 8 . Excessive gain and frequency response of the system elements. 5.5.5.1 GENERAL DESIGN CRITERIA 9. Spurious signals induced from other meters sharing the The most important consideration is to prevent the occur- same multicore cable. rence of spurious pulses rather than rely upon the provision of 10. Short circuit or open circuit of conductor pair or short verification circuitry to provide protection against the results circuit of either conductor to ground or shield. of false measurement. The design approach shall, therefore, 11. Bad connections, temperature variations and extremes, take into account the noise environment. Poorly designed vibration shock, and adverse environmental conditions. units and inadequate regard for noise pick-up can seriously influence the performance of the equipment. Low-level 5.5.5.4 SIGNAL PRE-AMPLIFIERS high-impedance signais become attenuated by line loses, and A signal pre-amplifier should be introduced into the the overall signal-to-noise ratio can further be impaired by transmission system at the transducer, if transmission dis- the greater probability of noise in longer lines. A secure and tance or manufacturers ’ requirements so dictate. reliable pulsed-data transmission system will be achieved most readily by concentrating on the elimination of error sensitive elements. Addition of dual circuits or other 5.5.5.5 STANDBY POWER SUPPLY techniques aimed at increasing security will guard against Where a power interruption could result in a significant influences that are beyond the control of the designer. error in measurement, provision for an uninterruptible power As a precaution, suppliers of signai processing equipment supply should be considered. should be advised of radio frequencies used in close prox- imity so radio frequency interference immunity can be in- 5.5.5.6 TEST REQUIREMENTS vestigated. Careful consideration should be given to the form of tests 5.5.5.2 TOTALIZERS to be applied to the electronic system for fidelity and secu- rity purposes. The tests should take into account the major 5.5.5.2.1 Primary Totalizer environmental hazards that experience shows are likely to be It is basic to security requirements that the value of the encountered on site. totalizer count cannot be impaired during delivery. The use of a nonresettable counter is mandatory for revenue ac- 5.5.5.7 GENERAL PRECAUTIONS counting systems and is recommended for all other primary systems. The gain and frequency response of the system elements should be restricted to that required by the application. Sen- 5.5.5.2.2 Secondary Indication sitivity controls on pre-amplifiers, scalers, and others shall not be capable of unauthorized adjustment. The totalized Where it is acceptable to the parties concerned in a trans- pulse counts existing at the time of any power failure shall be action, ancillary devices need not have as high a degree of retained. Cable pairs and the instrument input circuit shall be securiq protection as the primary indication. However, such protected from excessive transient voltages or currents as devices should be given basic approval as part of an overall well as electrical storms. approval and should be compatible with it. Representative secondary indicators include a counter directly driven by a flow meter, an electromechanical counter, or an electronic 5.5.6 Installation counter equipped with a standby battery. 5.5.6.1 SIGNAL AMPLITUDE 5.5.5.3 TYPICAL CAUSES OF ERROR The following points shall be observed so that the signal amplitude from the transducer to the receiver can be main- Typical causes of error which should be taken into con- tained at a high level. The installation recommendations sideration are as follows: specified by the manufacturers shall be carefully followed, 1. Electromagnetic interference. while complying fully with statutory requirements and/or 2. Transients. safety codes. The length of transmission lines from the 3 . Power supply variations and/or interruption. meter to the readout equipment shall be held to a minimum. 4. Inadequate signal level as a result of line loss. Proper impedance matching shall be ensured. The appropri-COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  11. 11. MPMS 5-5-82 07312290 0055009 l r 6 CHAPTER 5-METERING ate technically compatible signal transmission cables shall 5.5.6.3 COMMISSIONING be used. The supply voltages to pre-amplifiers and constant amplitude pulse generating systems shall be checked to 5.5.6.3.1 General ensure that they are of proper magnitude and do not exceed Before commissioning an installation, the commissioning noise or ripple maximums as specified by the equipment engineer shall ensure: manufacturer. 1. Correct mechanical installation of the equipment. 5.5.6.2 SIGNAL-TO-NOISE RATIO 2. A satisfactory electrical installation, with particular at- The following points should be observed so that the tention to weatherproofing of the electrical devices, espe- signal-to-noise ratio can be optimized. Only shielded trans- cially the field junction boxes. mission cable of the proper material, size, and number of 3 . Satisfactory wiring, in compliance with applicable stan- conductors shall be used. dards and electrical safety codes. Individual twisted shielded pairs afford the maximum protection against noise. Helical lay cables are accept- 5.5.6.3.2 Testing able for many installations. Parallel lay cables should be The commissioning of different types of systems will avoided. The shield of a transmission cable should be demand different procedures, which shall be clearly de- grounded at one point only, to prevent formation of fined by the manufacturers. Many manufacturers are able to ground loops, provide relatively simple equipment for testing individual A continuous run of transmission cables should be used parts of a system after installation, and the initial testing and whenever possible. Wherejoints are unavoidable, continuity calibration of the equipment can often and conveniently be of the shield shall be assured. Joints should be encapsulated carried out before an attempt is made to check the whole to maintain the electrical specification and security of the system. All necessary electrical test apparatus, including an cable. oscilloscope and pulse generator, should be provided for When multireadout devices are used and wired in paral- those personnel responsible for the inspection and mainte- lel, shielded cables should be used for connecting wiring. nance of the system. The pulse generator used should be The data transmission lines should not share a conduit with capable of emulating the pulse form of the particular type of anything other than shielded cables or cables from direct transducer being substituted. Such equipment must be of a current temperature sensors. If the maximum electrical type which is electrically safe for the environment in which power carried by any one transmission cable is ten or more it is to be used. times greater than the minimum power carried by any A typical test method which may be used is to inject a train flowmeter signal data transmission cable, separate conduits of test pulses into a transmission system at the transmitter should be provided. In the event that separate conduits are not connections. This test signal should have a strength of not feasible, additional cable shielding should be incorporated more than 50 percent at the normal transmitter signal. The and circuits tested to verify necessary fidelity of signals. Data test signal shall be monitored by the installed receiving ap- transmission cables should not be run in parallel with power paratus, and the signal received shall conform with the test cables, When this is not possible the cables should be signal to within two pulses in one hundred thousand. sufficiently spaced to prevent interference or be adequately The test should be pedormed at two conditions that repre- shielded. sent the maximum and minimum flows between which the If it is necessary for transmission cables and power cables meter normally operates, except during startup and shut- to cross, this should be at right angles whenever possible. down. When transmission cables are run in ducts or inside control cabinets, every attempt should be made to keep the shielded 5.5.7 Inspection and Maintenance cable bundle intact and separate from other conductors. All 5.5.7.1 NEED FOR INSPECTION AND spare transmission cable and conductors that are run in a conduit with an active transmission line should have the MAINTENANCE shield and conductors grounded at the same single point as It is essential that regular inspection and maintenance of all the active line. apparatus, systems, and installations (including cable con- The grouping of cables to intrinsically safe devices with duit and the like) is carried out with competent personnel other current-carrying cables requires special consideration according to a schedule that has been agreed upon after in hazardous areas, and governing regulations must be fol- lowed. Typical references are NFPA 493, Instrinsically National Fire Protection Association, Batterymarch Park, Quincy, Mas- Safe Apparatus in Division I Hazardous Locations, and ISA2 sachusetts 02269. RP 12.6, Installation of Instrinsically Safe Instrument Sys- %stmment Society of America, 67 Alexander Drive, Box 12277, Re- tems in Class I Hazardous Locations. search Triangle Park, North Carolina 27709.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  12. 12. MPMS 5 - 5 - 8 2 I 0732270 O055010 SECTION 5-FIDELITY A N D SECURITY 7 consultation between the manufacturers, their agents, and the very low current level involved, no indication can be given at users. It should be noted that an apparently correct functional the current carrying capacity of the circuit under test. Fur- operation of a system does not necessarily ensure compliance thermore, the tests can be adversely affected by stray current. with the selected level or levels of security. Grounding continuity does not guarantee the effectiveness of cable shielding. 5.5.7.2 GUIDELINES 5.5.7.2.3 Protective Devices 5.5.7.2.1 General At intervals determined by the engineer responsible for the All normal precautions relating to safety must be taken into system, all protective devices (such as alarms, trips, and account, especially those pertaining to work in-hazardous standby equipment) shall be examined and, if considered atmospheres. Although production or other operational re- necessary, tested to ensure that equipment is operating at quirements should be considered, these should not result in design settings. the postponement of essential inspection, maintenance, or repairs. Following any repairs, adjustments, or modifica- tions, those parts of the installation that have been disturbed 5.5.7.2.4 Outside Interference should be checked for compliance with the system specifica- Checks should be made to ensure that no additional extra tion. Thepulseintegrity testdescribedin 5.5.6.3.2 should be apparatus has been installed in the vicinity of the system. If performed at intervals specified by the engineer. other apparatus has been installed since the last inspection, then the system shall be tested to ensure that no signal is 5.5.7.2.2 Ground Continuity induced into the system by the adjacent apparatus. Unless special ground fault protection is employed, the The transmission system shqll be tested for continuity, ground path impedance of each circuit should be low enough insulation, and signal impedance. to permit the passage of a current at least three times the current rating of the circuit fuse or protective device. 5.5.7.2.5 Records All grounding connections (including those of any A system shall be established to record the results of supplementary grounàing conductors) shall be checked to inspections and tests for all apparatus, systems, and instalia- ensure that they are clean and tight, and the ground path tions and the details of corrective actions taken. The records impedance associated with each item of apparatus shall be shall include details of all modifications, additions, or measured at intervals determined by the engineer responsible deletions, none of which are to be made without prior for the system. Ground path impedance measurements shall permission. The signal strength produced during normal be made as follows, depending upon the area classification operation should be measured at the receiver and compared and the results of any necessary certification testing by the with the values obtained when the system was installed or responsible authority. If there is no likelihood of a flammable most recently modified. atmosphere being present, impedance measurements shall be made at a current of not less than 15 amperes. 5.5.7.2.6 Spares When there is any risk of a flammable atmosphere being present, impedance measurements shall be made with an Vital spares according to the manufacturers recommen- intrinsically safe continuity tester. It must be appreciated, dations should be readily available for the correct mainte- however, that in the case of these instruments, because of the nance of equipment.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  13. 13. A Alarm ......... ......................... 3,7 National Fire Protection Association ...................... 6 Amplifier transmitter ............................... . I Noise ..................... ............................ 5 definitionof ............................................. 1 environment ........................................ C Commissioning ............................................ 6 P Comparator ................................................ 3 Power supply Continuity tester .............. ......................... 7 interruption .......................... ..... 5 Counter .......................... . . . . . . . . . . .5 standby ................................................. 5 variations ............................................... 5 electronic .... ............................... 5 Pre-amplifier .............................................. 5 Precautions .................................... D Protective devices .......................................... 7 Pulse comparator . . . . . . . . . . . . . . . . . . ...................... 3 Designofsystem ........................................... 5 Pulsed-data cable transmission system .......................... 1 Pulsed security system E LevelA .............................. . Fig. 5 Electromagnetic interference ............................ LevelB .............................. . Fig. 4 Error ................................ Fig.3 ...... ...................... . Fig. 2 indication ........................... LevelE ............................................. Fig. 1 ............................... 1 .................................... 7 .................. R manual .................................. reduction ................................................ 1 Radio frequency interference . . . . . . . . . . ............ 5 Records ............................ ............ 7 Revenue accounting system .................................. 5 a t Fidelity ................................................... 1 definitionof ............................................. 1 Scaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Flammabie atmosphere ...................................... 7 Security . . . . . . . . . . . . . . . . Flow meter ................................................ 1 LevelA .................................... Fluid metering system ....................................... 1 LevelB . . . . . . . . . . . . . . LevelC ................................................. 3 LevelD ............................ .............. 1 LevelE ............................ Groundcontinuity .......................................... 7 Signal Grounding connection ....................................... 7 amplitude ............................................... 5 Ground loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 conditioning ............................................. 1 level . . . . . . . . . . . . . . . . . . . ....................... 5 H Signal-to-noise ratio .............................. Hazardous atmosphere ....................................... 7 Spares .......................................... Spurious pulses . . . ................................... 5 Standby equipment ......................... .7 I Inspection ..... ................................ 6 Installation ................................ Testing ................................. Test requirements ......................... Interference . . . . . ...................................... 1 electromagnetic ............. ...................................... 5 system .................................................. 1 ............................... 5 L Lay cables helical ............... ............... 6 definition of . . . . . Transmission parallel .............. line .................................................... 1 Levels of security . . . . . . . . . system ..... Trip ................................................ Twisted shielded pair ........................................ 6 Maintenance ............................................... 6 Methodsofcomparison ...................................... 3 definitionof ............................................. 1 Verification ............................................. 1,3 9COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services

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