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Environmental Conditionsfor Process Measurementand Control
Systems:
Mechanical Influences
Approved 12 January 1995
ANSI/ISAS71.031995
A M E R I C A N N A T I O N A L S T A N D A
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Copyright
1995 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 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 27709
ANSI/ISA-S71.03, Environmental Conditions for Process
Measurement and Control Systems:Mechanical Influences
ISBN: 1-55617-576-0
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ANSI/ISA-S71.03-1995 3
Preface
This preface, as well as all footnotes and annexes, is included
for informational purposes onlyand is not part of
ANSI/ISA-S71.03.
This standard has been prepared as part of the service of ISA,
the international society formeasurement and control, toward a goal
of uniformity in the field of instrumentation. To be of realvalue,
this document should not be static but should be subject to
periodic review. Toward thisend, the Society welcomes all comments
and criticisms and asks that they be addressed to theSecretary,
Standards and Practices Board; ISA; 67 Alexander Drive; P. O. Box
12277; ResearchTriangle Park, NC 27709; Telephone (919) 990-9227;
Fax (919) 549-8288; e-mail:[email protected].
The ISA Standards and Practices Department is aware of the
growing need for attention to themetric system of units in general,
and the International System of Units (SI) in particular, in
thepreparation of instrumentation standards, recommended practices,
and technical reports. TheDepartment 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 dealingswith other countries. Toward this
end, this Department will endeavor to introduce SI-acceptablemetric
units in all new and revised standards to the greatest extent
possible. The Metric PracticeGuide, which has been published by the
Institute of Electrical and Electronics Engineers asANSI/IEEE Std.
268-1992, and future revisions, will be the reference guide for
definitions,symbols, abbreviations, and conversion factors.
It is the policy of ISA to encourage and welcome the
participation of all concerned individuals andinterests in the
development of ISA standards. Participation in the ISA
standards-makingprocess by an individual in no way constitutes
endorsement by the employer of that individual, ofISA, or of any of
the standards, recommended practices, and technical reports that
ISA develops.
This document is one of several standards that address various
environmental conditions
affecting process measurement and control systems. In developing
this standard, the committeegoals included the following:
1) To provide a practical standard that can be applied with a
minimum of research andtechnical effort by the user.
2) To provide a concise method of stating environmental
classifications for convenientcommunications between all users of
the standard.
3) To cover real-world ranges of each classified parameter.
The following people served as members of ISA Committee
SP71:
NAME COMPANY
K. Gulick, Chairman Digital Equipment Corporation*M. Zielinski,
Managing Director FisherRosemountD. Boyle Consultant
*One vote per company
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4 ANSI/ISA-S71.03-1995
NAME COMPANY
*D. Brown FisherRosemountR. Calcavecchio ConsultantR. Cowles
Union Camp CorporationE. Demers Foxboro CompanyL. Falat Westvaco
Technical Center
R. Funwela U.S. SteelM. Hopkins KeyTek Instrument CorporationM.
Huza Flanders/FCP MicroenvironmentalE. Lee U.S. Nuclear Regulatory
AgencyL. Leonard ConsultantT. Mallory Power Safety InternationalC.
Muller Purafil, Inc.A. Perkins Rhorback Cosasco SystemsJ. Saine
Weyerhaeuser Company
*T. Schey Allen-Bradley CompanyT. Shelton Westvaco CorporationK.
Stickrod ABB
*R. Turk Allen-Bradley CompanyJ. Vajda Modicon, Inc.
*C. Yi FisherRosemount
This standard was approved for publication by the ISA Standards
and Practices Board onJanuary 2, 1995.
NAME COMPANY
M. Widmeyer, Vice President Washington Public Power Supply
System
H. Baumann H. D. Baumann, Inc.D. Bishop Chevron USA Production
CompanyP. Brett Honeywell, Inc.W. Calder III Calder EnterprisesH.
Dammeyer Phoenix Industries, Inc.R. Dieck Pratt & WhitneyH.
Hopkins Utility Products of ArizonaA. Iverson Lyondell
Petrochemical CompanyK. Lindner Endress + Hauser GmbH + CompanyT.
McAvinew Metro Wastewater Reclamation DistrictA. McCauley, Jr.
Chagrin Valley Controls, Inc.G. McFarland Honeywell Industrial
Automation & Control
J. Mock ConsultantE. Montgomery Fluor Daniel, Inc.D. Rapley
Rapley Engineering ServicesR. Reimer Allen-Bradley CompanyR. Webb
Pacific Gas & Electric CompanyW. Weidman ConsultantJ. Weiss
Electric Power Research Institute
*One vote per company
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ANSI/ISA-S71.03-1995 5
NAME COMPANY
J. Whetstone National Institute of Standards & TechnologyC.
Williams Eastman Kodak CompanyG. Wood Graeme Wood ConsultingM.
Zielinski FisherRosemount
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ANSI/ISA-S71.03-1995 7
Contents
1 Purpose
...................................................................................................................................
9
2 Scope
......................................................................................................................................
9
3 Introduction
............................................................................................................................
9
4 Definitions
............................................................................................................................
10
5 Location classification
........................................................................................................
10
5.1 Explanation of instrument locations and mechanical influence
classes ..................... 105.2 Instrument locations
...................................................................................................
115.3 Class of mechanical influence
....................................................................................
11
6 Example of intended usage
................................................................................................
13
Annex
A Vibration test
program........................................................................................................
15
Tables
1 Vibration
.............................................................................................................................
122 Shock
.................................................................................................................................
12
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ANSI/ISA-S71.03-1995 9
1 Purpose
The purpose of this standard is to classify mechanical
influences that may affect processmeasurement and control
instruments, in order to provide users and manufacturers of the
instruments with a means of specifying the class of mechanical
influences to which a specifiedinstrument may be exposed.
This document is one of a series of standards on environmental
conditions for processmeasurement and control systems.
2 Scope
2.1 This standard encompasses mechanical influences,
specifically shock and vibration, forindustrial process measurement
and control systems. Specifications for other environmental
con-ditions, including seismic and transportation, are beyond the
scope of this standard.
2.2 This standard establishes mechanical influence classes for
non-mobile installations, andincludes storage.
2.3 The classes of environmental conditions that are specified
in this standard are suitable forprocess instrumentation. The
classes, which include design, manufacturing, sales,
installation,test, use, and maintenance, serve as a guide to
establish requirements for environmental controlof buildings or
other protective housings for industrial process measurements and
control systems.
2.4 These classifications pertain only to the environment
external to the instrument that may affectthe instrument externally
or internally.
2.5 The effects of environmental conditions on the safety,
comfort, and performance of operatingand maintenance personnel are
not considered in this standard.
This standard is limited to vibration and shock only, covering
mechanical influences that affectindustrial measurement and control
systems.
3 Introduction
3.1 Normal operating conditions for vibration have been
established according to the type oflocation. Within each
classification, severity levels have been established. Parameter
limit valuesare tabulated for each classification and severity
level of the location. These values are shown inTable 1of this
standard. The classification consists of a class location letter,
followed by a severityidentification numeral.
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10 ANSI/ISA-S71.03-1995
Example:
Normal operating conditions, vibration classification A2, would
represent a class A location and level 2
severity.
3.2 Normal operating conditions for shock have been established
according to the type of equip-ment location. Within each
classification, severity levels have been established based on
equip-ment weight. Parameter limit values are tabulated for each
classification and severity level of the
location. These values are shown in Table 2of this standard. The
classification consists of a classlocation letter, followed by a
severity identification numeral.
Example:
Normal operating conditions, shock classification B1, would
represent a class B location and level 1severity.
3.3 Storage and handling conditions are specified with the
equipment not powered, but storedand handled outside of its normal
operating environment. Vibration and shock can be specifiedby using
the classifications as described.
Example:Storage and handling conditions, vibration class C3,
would represent a class C location and a level 3severity; shock
class C1 would represent a class C location and a level 1
severity.
4 Definitions
4.1 operating conditions, normal:The range of operating
conditions within which an instrument
is designed to operate and for which operating influences are
stated.
4.2 storage conditions: The conditions to which an instrument
may be subjected prior toinstallation. Also included are the
conditions that may exist during shutdown. No permanentphysical
damage or impairment of operating characteristics shall take place
under these conditions.
5 Location classification
5.1 Explanation of instrument locations and mechanical influence
classes
A broad distribution of shock and vibration levels exists within
industries that use processmeasurement and control equipment. Each
of these levels may produce an effect that rangesbetween
insignificant and catastrophic. The effects of shock and vibration
depend on the type ofequipment, method of application, and
frequency of occurrence. They are also influencedby external
factors such as temperature and corrosion. See ANSI/ISA-S71.01
andANSI/ISA-S71.04 standards for Environmental Conditions for
Process Measurement andControl Systems.
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ANSI/ISA-S71.03-1995 11
Table 1is set up in such a way as to classify exposures by
environment type and frequency-acceleration response, as described
in Annex A.
5.2 Instrument locations
5.2.1 Environment "A" locations, defined as controlled
mechanical influence environments, are
those areas usually provided for sensitive process measurement
and control systems that requirea controlled environment.
5.2.2 Environment "B" locations, defined as uncontrolled
mechanical influence environments, areprocess measurement and
control system areas outside the controlled environment but not
affecteddirectly by the process.
5.2.3 Environment "C" locations, defined as uncontrolled
mechanical influence environments, areprocess measurement and
control system areas outside of the controlled area that are
directlyaffected by the process.
5.3 Class of mechanical influence
5.3.1 Class 1, low severity
This designation applies to an environment that is within the
90th percentile of the data recorded,as described inAnnex A.
5.3.2 Class 2, moderate severity
This designation applies to an environment that is within the
95th percentile of the data recorded,as described inAnnex A.
5.3.3 Class 3, harsh severity
This designation applies to an environment that is within the
99th percentile of the data recorded,as described in Annex A.
5.3.4 Class X, severe
This designation applies to an environment in which the
mechanical influence causes total andunrecoverable loss of the use
of an essential function. In this environment, the limit exceeds
the99th percentile of the data recorded and described in AnnexAor
is subject to negotiationbetween user and supplier.
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12 ANSI/ISA-S71.03-1995
Table 1 Vibration
1Refer to Annex A.2See 5.2 for definition of operating
environment.3See 5.3 for definition of mechanical influence.4See
5.3 for percentile occurrence classification.5Constant acceleration
measured in meters m/sec2. Divide by 9.81 to get acceleration in
g's (based on value of g
at sea level: g=9.81 m/sec2.)6Peak displacement measured in
millimeters (mm).7Use peak displacement (s) below 8 Hz to 9 Hz. Use
constant acceleration (a) above 8 Hz to 9 Hz.8TBS = To Be
Specified.
Table 2 Shock
1TBS = To Be Specified2Not to exceed values listed
Operation vibration classes, percentiles, and environment(1, 3,
7)
Environment2Class3/Percentile4
1/90th 2/95th 3/99th X/Special
Constant acceleration5/Peak displacement6
VA 1.0/0.35 2.0/0.75 5.0/1.6 TBS8
VB 2.0/0.75 5.0/1.6 10.0/3.5 TBS
VC 10.0/3.5 20.0/7.5 50.0/16.0 TBS
Weight (kg) Environment ClassFree fallHeight(cm)
1/2 sineacceleration2
(m/sec2)
< 100 SA1
x
60
TBS1
250
TBS
100 - 200 SB1
x
45
TBS
70
TBS
> 200 SC1
x
30
TBS
20
TBS
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ANSI/ISA-S71.03-1995 13
6 Example of intended usage
6.1 The manufacturer and/or user should specify the system
performance in a stated environ-mental class. The following example
shows how a manufacturer or user might specify several sets
of environmental classes for operating or maintaining the same
system.
Example 1
Conditions Shock and vibration classNormal operating conditions,
vibrations VA2Normal operating conditions, shock SB1Storage and
handling VC3
SC1
This example might be used by an instrument manufacturer to
indicate the following:
a) The system is designed to operate within a control room type
of environment with a
maximum indicated vibration mechanical influence class 2.b) The
system is designed to operate at shock levels normally experienced
by equipment
located on the shop floor with a maximum indicated limit
mechanical influence class 1.
c) The system can be stored and handled with a vibration maximum
indicated limit listedas class 3 and a shock maximum indicated
limit listed as class 1.
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ANSI/ISA-S71.03-1995 15
Annex A Vibration test program
A.1 Introduction
In the preparation of this series of standards that deal with
environmental conditions for processmeasurement and control
systems, it was determined that insufficient data were available
todescribe the vibration levels of operating instrumentation.
Therefore, in conjunction with thepreparation of this standard, a
study was conducted to gather vibration information through
theprocess industry in the United States and Canada. The data
gathered were used to establish thevibration tables of this
standard.
NOTE All raw test data used in the preparation of this standard
are the property of ISA.
The vibration analyzer that was purchased for this study is
normally used on rotating machinery.After each series of tests, the
analyzer was recalibrated to assure repeatability.
A.2 Testing procedure
A.2.1 Test equipment
The accelerometer of the vibration analyzer was mounted to a
magnet and was sensitive in thedirection perpendicular to the force
of the magnet. Measurements were taken on three planes foreach
location where equipment would normally be mounted. Peak
acceleration was recorded forfrequency ranges of 0-100 Hz and
0-2000 Hz.
The field data were then processed to generate
frequency-acceleration graphs and show the99th, 95th, and 90th
percentiles for all the data collected in this program.
A.2.2 Surfaces to be tested
A device measurement requires that the vibration levels be
recorded in three different directions.
The accelerometer was mounted:
a) perpendicular to the mounting surface;
b) parallel to the mounting surface; and
c) perpendicular to the first two positions.
A.2.3 Testing procedure
After mounting the accelerometer, the test chart was placed in
the platen, the battery level waschecked, the range switch was set
to 2000 Hz, and the test was started. The test was completedin
about one minute. If any information existed in the 0-200 Hz range,
the pen color waschanged, the range switched to 200 Hz, and the
test run again.
The test was repeated with the accelerometer placed in each of
the positions listed in 2.2 above.
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A.2.4 Documentation of data
In addition to specific test technician, date, and other
relevant information, the following datawere collected for each
test.
A.2.4.1 Process description: Identify industry and process as
petroleum, pulp and paper, steel,mining, etc.
A.2.4.2 Type: Identify application and instrument as
temperature, pressure, flow, level, computer,etc.
A.2.4.3 Type of mounting: State type and description such as
pipe, floor, panel, rack, etc.
A.2.4.4 Location Environmental: Specify exposed, sheltered,
control room.
A.2.4.5 Remarks:Describe anything that may have significantly
influenced the test or the analysisof its results (e.g., truck
passing during test).
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Developing and promulgating technically sound consensus
standards,
recommended practices, and technical reports is one of ISA's
primarygoals. To achieve this goal the Standards and Practices
Departmentrelies on the technical expertise and efforts of
volunteer committeemembers, chairmen, and reviewers.
ISA is an American National Standards Institute (ANSI)
accreditedorganization. ISA administers United States Technical
AdvisoryGroups (USTAGs) and provides secretariat support for
InternationalElectrotechnical Commission (IEC) and International
Organization forStandardization (ISO) committees that develop
process measurementand control standards. To obtain additional
information on theSociety's standards program, please write:
ISAAttn: Standards Department67 Alexander DriveP.O. Box
12277Research Triangle Park, NC 27709
ISBN: 1-55617-576-0
