1、Environmental Conditionsfor Process Measurementand Control Systems:PowerApproved 30 June 1991ISAS71.021991STANDARD Copyright GA4 1991 by the Instrument Society of America. All rights reserved. Printed in the UnitedStates of America. No part of this publication may be reproduced, stored in a retrieva
2、l system, ortransmitted in any form or by any means (electronic, mechanical, photocopying, recording, orotherwise), without the prior written permission of the publisher.ISA67 Alexander DriveP.O. Box 12277Research Triangle Park, North Carolina 27709ISA-S71.02 Environmental Conditions for Process Mea
3、surement and Control Systems: PowerISBN 1-55617-324-5ISA-S71.02-1991 3PrefaceThis preface is included for informational purposes and is not part of the standard.This standard has been prepared as part of the service of ISA toward a goal of uniformity in the field of instrumentation. To be of real va
4、lue, this document should not be static, but should be subject to periodic review. Toward this end, the Society welcomes all comments and criticisms, and asks that they be addressed to the Secretary, Standards and Practices Board, ISA, 67 Alexander Drive, P.O. Box 12277, Research Triangle Park, NC 2
5、7709, Telephone (919) 549-8411, e-mail: standardsisa.org.The ISA Standards and Practices Department is aware of the growing need for attention to the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrumentation standards. The Depa
6、rtment is further aware of the benefits to USA users of ISA standards of incorporating suitable references to the SI (and the metric system) in their business and professional dealings with other countries. Toward this end, this Department will endeavor to introduce SI-acceptable metric units in all
7、 new and revised standards to the greatest extent possible. The Metric Practice Guide, which has been published by the Institute of Electrical and Electronics Engineers as ANSI/IEEE Std. 268-1982, and future revisions will be the reference guide for definitions, symbols, abbreviations, and conversio
8、n factors.It is the policy of ISA to encourage and welcome the participation of all concerned individuals and interests in the development of ISA standards. Participation in the ISA standards-making process by an individual in no way constitutes endorsement by the employers of the individual, of ISA
9、, or of any of the standards that ISA develops.The information contained in the preface, footnotes, and appendices is included for information only and is not a part of the standard.This document is one of several standards that cover various environmental conditions affecting process measurement an
10、d control systems. In developing this standard the committee goals include the following:1) To provide a practical standard that can be applied with minimum research and technical effort by the user.2) To provide a concise method of stating environmental classifications for convenient communications
11、 between users of the standard.3) To cover real-world ranges of each classified parameter.This standard is limited to power considerations only, covering power considerations that affect industrial process measurement and control systems.In order to make S71.02 compatible with international standard
12、s, the SP71 committee used the same limit values, except as noted below, as presented in Publication 654-2, first edition (1979), of the International Electrotechnical Commission: Operating Conditions for Industrial Process Measurement and Control Equipment, Part 2: Power. The following exceptions w
13、ere made:AC voltage unbalanced for polyphase systems was added to bring this standard into compliance with an existing ANSI standard.4 ISA-S71.02-1991DC voltage tolerance, range 2, was adjusted to reflect tighter tolerance limits introduced since 1979.The number of pneumatic power supply levels has
14、been reorganized for instruments and control elements.The assistance of those who aided in the preparation of this standard, by their review of the draft and by offering suggestions toward its improvement, is gratefully acknowledged.The persons listed below served as members of ISA Committee SP71, w
15、hich prepared this standard.NAME COMPANYK. Gulick, Chairman Digital Equipment CorporationD. R. Boyle RetiredD. Brown* Fisher Controls CompanyR. Calcavecchio IBMM. C. Cardinal Exxon Chemical Co.R. Cowles Union CampJ. DArcy Boise Cascade Paper CompanyE. Demers The Foxboro CompanyJ. Duffy* Fisher Contr
16、ols CompanyL. Falat Westvaco Technical CenterW. G. Holway RetiredM. Huza FCP MicroenvironmentalR. L. JonesG. Koepke National Institute of Standards the maximum deviation from the average is 7 volts, and the average unbalance = 100 x (7/231) = 3.03 percent.12 ISA-S71.02-1991Table 1 AC power classific
17、ationsNotes: All parameters must be measured at the process measurement and control equipment input terminals.T.B.S. = To Be SpecifiedN.A. = Not Applicable is defined as “less than or equal to”5.3 DC power classificationsThe following classes, as shown in Table 2 and 5.3.3, should be used to specify
18、 a DC power source.5.3.1 Class F voltage tolerance is specified as the percent deviation from nominal voltage.5.3.2 Class G ripple is specified in percent as the ratio of the peak-to-peak value of the AC component to the nominal voltage.Table 2 DC power classifications5.3.3 Class H ground reference
19、is specified as polarity of the terminal of a DC power source, if any, that is connected to a ground reference.H1. Positive if the positive terminal is connected to a ground reference.H2. Negative if the negative terminal is connected to a ground reference.H3. Floating if neither terminal is connect
20、ed to a ground reference.Parameter Class Range12345Voltage toleranceA 1% 10% 15%to 10%20%to+15%T.B.S.FrequencydeviationB 0.2% 1.0% 5.0% T.B.S. N.A.HarmoniccontentC 2% 5% 10% 20% T.B.S.Phase angledepartureD 1 2 5 T.B.S. N.A.VoltageunbalanceE 1% 2% 5% T.B.S. N.A.Parameter Class Range12345Voltage toler
21、anceF 1% 10% 15% 25% T.B.S.Ripple G 0.2% 1.0% 5.0% 15% T.B.S.ISA-S71.02-1991 136 Pneumatic power classification6.1 GeneralPneumatic power is required for pneumatic elements of process control systems. These elements include transmitters, controllers, displays, final control elements, and auxiliary f
22、unctions.6.2 Pneumatic energy sourcesPneumatic energy for operation of systems may be provided by direct connection to a single power source or connection to a power supply device. Other energy sources include auxiliary, standby, or backup pneumatic power sources that provide for operation of the pn
23、eumatic system in case of failure of the primary pneumatic power source.6.3 Instrument air qualityInstrument air must be supplied in accordance with quality air standards specified in ISA-S7.3-1981, Quality Standard for Instrument Air.6.3.1 Instrument air contaminants shall be specified in accordanc
24、e with ISA-S71.04-1985, Envi-ronmental Conditions for Process Measurement and Control Systems: Airborne Contaminants.6.4 Pneumatic power supply classificationThe following classifications, as shown in Table 3, should be used to specify a pneumatic power source.6.4.1 Class J instrument pressure is sp
25、ecified as the operating pressure range used by transmitters and controllers.6.4.2 Class K control element pressure is specified as the operating pressure range used by pneumatic actuators and positioner-actuators.6.4.3 Class L pneumatic power supply dew point is specified as the dew point temperatu
26、re of the gas supplied at the lowest ambient temperature and maximum operating pressure of the pneumatic system.Table 3 Pneumatic power source classificationsParameter Class Range123Instrumentpressure, kP(lb/in.2)J130 to 150(18.9 to 21.8)217 to 265(31.5 to 38.4)T.B.S.Control elementpressure, kP(lb/i
27、n.2)K130 to 30(18.9 to 43.5)550 to 1050(79.8 to 152.3)T.B.S.Dew point L 10C less than minimum ambient temperatureT.B.S. N.A.Developing and promulgating technically sound consensus standards, recommended practices, and technical reports is one of ISAs primary goals. To achieve this goal the Standards
28、 and Practices Department relies on the technical expertise and efforts of volunteer committee members, chairmen, and reviewers.ISA is an American National Standards Institute (ANSI) accredited organization. ISA administers United States Technical Advisory Groups (USTAGs) and provides secretariat su
29、pport for International Electrotechnical Commission (IEC) and International Organization for Standardization (ISO) committees that develop process measurement and control standards. To obtain additional information on the Societys standards program, please write:ISAAttn: Standards Department67 Alexander DriveP.O. Box 12277Research Triangle Park, NC 27709ISBN: 1-55617-324-5
