1、Environmental Conditionsfor Process Measurementand Control Systems:Temperature and HumidityApproved 15 August 1986ISAS71.011985STANDARD Copyright 1985 by the Instrument Society of America. All rights reserved. Printed in the UnitedStates of America. No part of this publication may be reproduced, sto
2、red in a retrieval 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-S71.01 Environmental Condition
3、s for Process Measurement and Control Systems: Temperature and HumidityISBN 0-87664-894-4ISA-S71.01-1985 3PrefaceThis preface is included for informational purposes and is not part of ISA-S71.01.This standard has been prepared as part of the service of ISA toward a goal of uniformity in the field of
4、 instrumentation. To be of real value, 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 1
5、2277, Research Triangle Park, NC 27709, 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 i
6、nstrumentation standards. The Department is further aware of the benefits to U.S.A. 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 introd
7、uce SI-acceptable metric units in all 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,
8、symbols, abbreviations, and conversion 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 th
9、e employer of that individual, of ISA, 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 covering various environmental conditio
10、ns affecting process measurement and control systems. In developing this standard, the committee goals included the following:1) To provide a practical standard that can be applied with a minimum of research and technical effort by the user.2) To provide a concise method of stating environmental cla
11、ssifications for convenient communication between all users of the standard.3) To cover real-world ranges of each classified parameter.In order to be compatible with international standards, the SP71 committee used the same limit values, wherever appropriate, as presented in Publication 654-1, First
12、 edition (1979), of the International Electrotechnical Commission: “Operating Conditions for Industrial-Process Measurement and Control Equipment, Part 1: Temperature, Humidity and Barometric Pressure.“For Classes B3 and B4 described in this standard, the committee specified limits of 5 to 90 percen
13、t relative humidity instead of 5 to 95 percent relative humidity as specified by the International Electrotechnical Commission. The committee concluded that for this class (Class B), relative humidity values above 90 percent should be covered in Severity Level X.4 ISA-S71.01-1985The persons listed b
14、elow served as members of ISA Committee SP71, which prepared this standard.NAME COMPANYW. Holway, Chairman The Foxboro CompanyD. Boyle (retired) National Bureau of StandardsD. Cummins Purafil, Inc.J. Duffy Fisher Controls CompanyK. Gulick Digital Equipment CorporationM. Huza Circul-Aire Inc.F. Kent
15、Fischer and Porter CompanyE. J. Laderoute The Foxboro CompanyM. Lombardi Honeywell, Inc.R. Magnuson Hewlett PackardW. T. Mitchell Dow Chemical, USAR. Prescott (Director) Moore ProductsE. Rasmussen Fluor Engineers & Constructors, Inc.W. T. Rhodes CONOCO, Inc.R. H. Walton Exxon Company, USAISA-S71.01-
16、1985 5This standard was approved for publication by the ISA Standards and Practices Board in February 1985.NAME COMPANYN. Conger, Chairman Fisher Controls CompanyP. V. Bhat Monsanto CompanyW. Calder III The Foxboro CompanyR. S. Crowder Ship Star AssociatesB. Feikle Bailey Controls CompanyH. S. Hopki
17、ns Westinghouse Electric CompanyJ. L. Howard Boeing Aerospace CompanyR. T. Jones Philadelphia Electric CompanyR. Keller The Boeing CompanyO. P. Lovett, Jr. ISIS CorporationE. C. Magison Honeywell, Inc.A. P. McCauley Chagrin Valley Controls Inc.J. W. Mock Bechtel CorporationE. M. Nesvig ERDCO Enginee
18、ring CorporationR. Prescott Moore Products CompanyD. E. Rapley ISTSC. W. Reimann National Bureau of StandardsJ. Rennie Factory Mutual Research CorporationW. C. Weidman Gilbert Commonwealth Inc.K. Whitman ConsultantP. Bliss* ConsultantB. A. Christensen* Continental Oil CompanyL. N. Combs* RetiredR. L
19、. Galley* ConsultantT. J. Harrison* IBM CorporationR. G. Marvin* Roy G. Marvin CompanyW. B. Miller* Moore Products CompanyG. Platt* RetiredJ. R. Williams* Stearns Catalytic Corporation*Director EmeritusISA-S71.01-1985 7Contents1 Purpose 92 Scope . 93 Introduction . 94 Definitions . 104.1 Normal oper
20、ating conditions, operative limits, and transportation and storage conditions . 104.2 Maintenance conditions . 114.3 Maintenance 115 Location classifications 115.1 Air-conditioned locations (class A) . 115.2 Enclosed temperature controlled locations (class B) . 115.3 Sheltered locations (class C) .
21、115.4 Outdoor locations (class D) . 125.5 Special locations (class X) . 12Appendix A Psychrometric charts 13ISA-S71.01-1985 91 PurposeThe purpose of this standard is to establish uniform classifications of temperature and humidity conditions for industrial process measurement and control systems. Th
22、is document is one of a series of standards on environmental conditions for process measurement and control systems.2 Scope2.1 This standard covers temperature and humidity environmental conditions for industrial process measurement and control equipment. Specifications for other environmental condi
23、tions are beyond the scope of this standard.2.2 This standard establishes temperature and humidity classes for fixed (non-mobile) installations during normal operation (nonemergency conditions) or during transportation and storage.2.3 The classes of temperature and humidity conditions stated in this
24、 standard are suitable for use in activities related to process instrumentation, including design, manufacturing, sales, instal-lation, test, use, and maintenance. These classes may also be used as a guide when establishing requirements for environmental control of buildings or other protective hous
25、ings for industrial pro-cess measurement and control systems.2.4 These classifications pertain only to the environment external to the equipment which may affect the equipment externally or internally.2.5 The effects of environmental conditions on safety, comfort, and performance of operating and ma
26、intenance personnel are not considered in this standard.3 Introduction3.1 Environmental classifications have been established according to the type of location. Within each classification, severity levels have also been established. Parameter limit values are tabulated for each classification and se
27、verity level of the location. These values are shown in Table 1 of this standard. The classification consists of a class location letter followed by a severity identification numeral.EXAMPLE: Temperature and Humidity Classification A2 would represent Class A Location and Level 2 Severity.3.2 The man
28、ufacturer and/or user should specify the equipment performance in a stated environ-mental Class and Severity Level. The following example shows how a manufacturer or user might specify several sets of environmental classes for operating or maintaining the same equipment.10 ISA-S71.01-1985The above e
29、xample may also be specified as follows:NOTES: *R.H. = Relative HumidityN.A. = Not Applicable4 Definitions4.1 Normal operating conditions, operative limits, and transportation and storage conditionsThese terms are defined in the ISA-S51.1 Standard “Process Instrumentation Terminology.“ The ISA-S51.1
30、 definition of “Transportation and Storage Conditions“ includes “Shutdown.“ If the shutdown conditions are different from transportation and storage conditions, the shutdown environment shall be specified separately.EXAMPLE NO. 1Conditions Temperature and humidity classNormal operating conditions*Th
31、ese terms are defined in ISA-S51.1, “Process Instrumentation Terminology.”See Section 4, this standard, for defintion.Specified separately only when Shutdown Conditions differ from Transportation and Storage Conditions. See also Section 4.1, this standard.A2Operative limit* B2Transportation & storag
32、e conditions* C2Maintenance condtions B3Shutdown conditionsC1EXAMPLE NO. 2ConditionParametersTemperature range (C)Control tolerance (C)Max. rate of change (C/ Hour)Humidity range (% R.H.)*Control tolerance (% R.H.)Max. moisture content (Kg/Kg Dry Air)Normal operating 18 to 27 2 5 20 to 80 10 N.A.Ope
33、rative limit 5 to 40 3 10 10 to 75 N.A. 0.020Transportation and storage 40 to 85 N.A. 10 5 to 100 N.A. 0.028Maintenance 5 to 40 10 20 5 to 90 N.A. 0.028Shutdown 25 to 55 N.A. 5 5 to 100 N.A. 0.028ISA-S71.01-1985 114.2 Maintenance conditionsConditions under which maintenance is performed.4.3 Maintena
34、nceAny activity intended to keep equipment in satisfactory working condition, including tests, measurements, replacements, adjustments, and repairs. (Refer to the Scientific Apparatus Manufacturers Association Standard PMC 32.1, “Process Instrumentation Reliability Terminology.“)5 Location classific
35、ations5.1 Air-conditioned locations (class A)Class A locations are locations where both air temperature and relative humidity are controlled. These locations are usually provided for computers and other electronic equipment requiring a controlled air environment.Special consideration should be given
36、 where hygroscopic materials, such as punched cards and chart paper, will be used. These materials, depending on the manufacturers recommendation, may require a relative humidity less than the maximum given in Table 1. The special requirements shall be described by use of Severity Level “X“ of Table
37、 1.5.2 Enclosed temperature controlled locations (class B)Class B locations are locations where air temperature is controlled but relative humidity is not controlled. These locations are usually provided where continuous operator surveillance is required. This class may also represent storage and oc
38、casionally transportation conditions.5.3 Sheltered locations (class C)Class C locations are locations protected from direct exposure to the climatic elements, such as sunlight, rain and other precipitation, and full wind pressure.Neither heating nor cooling is normally provided. Ventilation, if any,
39、 may be either natural or forced. Minimum air temperature inside the enclosure may be as low as the outdoor air temperature. Maximum air temperature inside the enclosure may be considerably greater than the outdoor air temperature due to solar radiation heating of the shelter surfaces. The air insid
40、e the shelter is the environment for the equipment. Condensation may occur on surfaces within the shelter or within the equipment enclosure due to temporary excursions below the local dew point.Sheltered locations are provided where minimum protection is required for operators, maintenance personnel
41、, or equipment. Examples of equipment shelters range from box enclosures to equipment “shacks.“12 ISA-S71.01-19855.4 Outdoor locations (class D)Class D locations are locations where there is no specific protection from the environment.Equipment in these locations may be subjected to sudden and sever
42、e changes of environment due to weather or other factors. Minimum temperature of the equipment may be as low as the outdoor air temperature. Maximum temperature of the equipment may be considerably greater than the outdoor air temperature due to solar radiation heating. Differential temperature cond
43、itions may also exist in the equipment when part of the equipment is exposed to direct heat radiation with the remaining surface shaded, or by other circumstances of this type. Condensation may occur due to temporary excursions below the local dew point. In addition to the effect of ambient air temp
44、erature, the effect of radiated heat from the sun or other sources should be considered for selecting severity levels in Table 1.5.5 Special locations (class X)It is recognized that extreme or special service conditions exist in which the excursions of temperature or humidity differ from the previou
45、sly mentioned classes. To accommodate this situation, a special Class “X“ is included in Table 1. Specifications for equipment in Class X are a matter of negotiation between user and supplier.Table 1a,b,c Location, class, and severity levelsNOTES: aThis table applies for atmospheric pressures betwee
46、n 86 kPa and 108 kPabN.A. = Not ApplicablecT.B.S. = To Be SpecifieddOperating temperature/humidity to be selected from within temperature/humidity limitseAllowable variation from the selected operating temperature/humidity control pointfMaximum rate of change within the control toleranceLocation Cla
47、ssSeverity levelTemperature limits (C)Control point tolerance (C)Maximum rate of change (C/ Hour)Humidity limits (% Relative Humidity)Control point tolerance(% Relative Humidity)Maximum moisture content (Kg/Kg dry air)Air ConditionedA1 18 to 27d2e5f35 to 75d5eN.A.2 18 to 27d2e5f20 to 80d10eN.A.X T.B
48、.S.dT.B.S.eT.B.S.fT.B.S.dT.B.S.eT.B.S.Enclosed Temperature ControlledB1 15 to 30d2e5f10 to 75dN.A. N.A.25 to 40d3e10f10 to 75dN.A. 0.02035 to 40d10e20f5 to 90dN.A. 0.02845 to 50d10e20f5 to 90dN.A. 0.028X T.B.S.dT.B.S.eT.B.S.fT.B.S.dN.A. T.B.S.Sheltered C1 25 to 55 N.A. 5 5 to 100 N.A. 0.0282 40 to 8
49、5 N.A. 10 5 to 100 N.A. 0.028X T.B.S. N.A. T.B.S. 5 to 100 N.A. T.B.S.Outdoor D1 25 to 70 N.A. 10 5 to 100 N.A. N.A.2 40 to 85 N.A. 20 5 to 100 N.A. N.A.3 55 to 65 N.A. 20 5 to 100 N.A. N.A.X T.B.S. N.A. T.B.S. T.B.S. N.A. N.A.ISA-S71.01-1985 13Appendix A Psychrometric chartsFigure 1 Air-conditioned locations, class A114 ISA-S71.01-1985Figure 2 Air-conditioned locations, class A2ISA-S71.01-1985 15Figure 3 Enclosed temperature-controlled locations, class B116 ISA-S71.01-1985Figure 4 Enclosed temperature-controlled location
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