ASTM G94-05(2014)
(Guide)Standard Guide for Evaluating Metals for Oxygen Service
Standard Guide for Evaluating Metals for Oxygen Service
SIGNIFICANCE AND USE
4.1 The purpose of this guide is to furnish qualified technical personnel with pertinent information for use in selecting metals for oxygen service in order to minimize the probability of ignition and the risk of explosion or fire. It is intended for use in selecting materials for applications in connection with the production, storage, transportation, distribution, or use of oxygen. It is not intended as a specification for approving materials for oxygen service.
SCOPE
1.1 This guide applies to metallic materials under consideration for oxygen or oxygen-enriched fluid service, direct or indirect, as defined in Section 3. It is concerned primarily with the properties of a metallic material associated with its relative susceptibility to ignition and propagation of combustion. It does not involve mechanical properties, potential toxicity, outgassing, reactions between various materials in the system, functional reliability, or performance characteristics such as aging, shredding, or sloughing of particles, except when these might contribute to an ignition.
1.2 This document applies only to metals; nonmetals are covered in Guide G63.Note 1—The American Society for Testing and Materials takes no position respecting the validity of any evaluation methods asserted in connection with any item mentioned in this guide. Users of this guide are expressly advised that determination of the validity of any such evaluation methods and data and the risk of use of such evaluation methods and data are entirely their own responsibility.Note 2—In evaluating materials, any mixture with oxygen exceeding atmospheric concentration at pressures higher than atmospheric should be evaluated from the hazard point of view for possible significant increase in material combustibility.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: G94 − 05 (Reapproved 2014)
Standard Guide for
Evaluating Metals for Oxygen Service
ThisstandardisissuedunderthefixeddesignationG94;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Liquid Oxygen (Impact Sensitivity Threshold and Pass-
Fail Techniques)
1.1 This guide applies to metallic materials under consider-
D2863Test Method for Measuring the Minimum Oxygen
ation for oxygen or oxygen-enriched fluid service, direct or
Concentration to Support Candle-Like Combustion of
indirect, as defined in Section 3. It is concerned primarily with
Plastics (Oxygen Index)
the properties of a metallic material associated with its relative
D4809Test Method for Heat of Combustion of Liquid
susceptibility to ignition and propagation of combustion. It
Hydrocarbon Fuels by Bomb Calorimeter (Precision
does not involve mechanical properties, potential toxicity,
Method)
outgassing, reactions between various materials in the system,
G63Guide for Evaluating Nonmetallic Materials for Oxy-
functional reliability, or performance characteristics such as
gen Service
aging, shredding, or sloughing of particles, except when these
G72Test Method for Autogenous Ignition Temperature of
might contribute to an ignition.
Liquids and Solids in a High-Pressure Oxygen-Enriched
1.2 This document applies only to metals; nonmetals are
Environment
covered in Guide G63.
G86Test Method for Determining Ignition Sensitivity of
NOTE 1—The American Society for Testing and Materials takes no
Materials to Mechanical Impact in Ambient Liquid Oxy-
position respecting the validity of any evaluation methods asserted in
gen and Pressurized Liquid and Gaseous Oxygen Envi-
connection with any item mentioned in this guide. Users of this guide are
ronments
expresslyadvisedthatdeterminationofthevalidityofanysuchevaluation
methods and data and the risk of use of such evaluation methods and data
G88Guide for Designing Systems for Oxygen Service
are entirely their own responsibility.
G93Practice for Cleaning Methods and Cleanliness Levels
NOTE 2—In evaluating materials, any mixture with oxygen exceeding
for Material and Equipment Used in Oxygen-Enriched
atmospheric concentration at pressures higher than atmospheric should be
Environments
evaluated from the hazard point of view for possible significant increase
G124Test Method for Determining the Combustion Behav-
in material combustibility.
ior of Metallic Materials in Oxygen-Enriched Atmo-
1.3 The values stated in SI units are to be regarded as the
spheres
standard.
G126Terminology Relating to the Compatibility and Sensi-
1.4 This standard does not purport to address all of the
tivity of Materials in Oxygen Enriched Atmospheres
safety concerns, if any, associated with its use. It is the
G128Guide for Control of Hazards and Risks in Oxygen
responsibility of the user of this standard to establish appro-
Enriched Systems
priate safety and health practices and determine the applica-
2.2 ASTM Special Technical Publications (STPs) on the
bility of regulatory limitations prior to use.
Flammability and Sensitivity of Materials in Oxygen-Enriched
Atmospheres:
2. Referenced Documents
ASTM STPs in this category are listed as:812, 910, 986,
2.1 ASTM Standards:
1040, 1111, 1167, 1197, 1319, 1395, and 1454
D2512Test Method for Compatibility of Materials with
2.3 Compressed Gas Association Documents:
Pamphlet G-4.4-2003 (EIGA Doc. 13/02)Oxygen Pipeline
Systems
ThisguideisunderthejurisdictionofASTMCommitteeG04onCompatibility
Pamphlet G-4.8Safe Use of Aluminum Structured Packing
and Sensitivity of Materials in Oxygen Enriched Atmospheres and is the direct
for Oxygen Distillation
responsibility of Subcommittee G04.02 on Recommended Practices.
Pamphlet G-4.9Safe Use of Brazed Aluminum Heat Ex-
Current edition approved Jan. 1, 2014. Published January 2014. Originally
approved in 1987. Last previous edition approved in 2005 as G94–05. DOI:
changers for Producing Pressurized Oxygen
10.1520/G0094-05R14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from Compressed Gas Association (CGA), 4221 Walney Rd., 5th
the ASTM website. Floor, Chantilly, VA 20151-2923, http://www.cganet.com.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G94 − 05 (2014)
Pamphlet P-8.4 (EIGA Doc. 65/99)Safe Operation of Re- 3.1.14 threshold pressure—there are several different defi-
boilers Condensers in Air Separation Plants nitions of threshold pressure that are pertinent to the technical
literature.Itisimportantthattheuserofthetechnicalliterature
2.4 ASTM Adjuncts:
fully understand those definitions of threshold pressure which
Test Program Report on the Ignition and Combustion of
apply to specific investigations being reviewed. Two defini-
Materials in High-Pressure Oxygen
tions for threshold pressure, based on interpretations of the
bulk of the current literature, appear below.
3. Terminology
3.1.14.1 threshold pressure—in a promoted ignition-
3.1 Definitions:
combustiontestseriesconductedoverarangeofpressures,this
3.1.1 autoignition temperature—the lowest temperature at
is the maximum pressure at which no burns, per the test
which a material will spontaneously ignite in oxygen under
criteria, were observed and above which burns were experi-
specific test conditions (see Guide G126).
enced or tests were not conducted.
3.1.2 direct oxygen service—in contact with oxygen during
3.1.14.2 threshold pressure—the minimum gas pressure (at
normaloperations.Examples:oxygencompressorpistonrings,
aspecifiedoxygenconcentrationandambienttemperature)that
control valve seats (see Guide G126).
supports self-sustained combustion of the entire standard
3.1.3 exemption pressure—the maximum pressure for an
sample (see Guide G124).
engineering alloy at which there are no oxygen velocity
restrictions (from CGA 4.4 and EIGA doc 13/02). 4. Significance and Use
3.1.4 impact-ignition resistance—the resistance of a mate-
4.1 The purpose of this guide is to furnish qualified techni-
rial to ignition when struck by an object in an oxygen
cal personnel with pertinent information for use in selecting
atmosphere under a specific test procedure (see Guide G126).
metals for oxygen service in order to minimize the probability
of ignition and the risk of explosion or fire. It is intended for
3.1.5 indirect oxygen service—not normally in contact with
use in selecting materials for applications in connection with
oxygen, but which might be as a result of a reasonably
the production, storage, transportation, distribution, or use of
foreseeable malfunction, operator error, or process upset.
oxygen. It is not intended as a specification for approving
Examples: liquid oxygen tank insulation, liquid oxygen pump
materials for oxygen service.
motor bearings (see Guide G126).
3.1.6 maximum use pressure—the maximum pressure to
5. Factors Affecting Selection of Materials
which a material can be subjected due to a reasonably
5.1 General:
foreseeable malfunction, operator error, or process upset (see
5.1.1 The selection of a material for use with oxygen or
Guide G63).
oxygen-enriched atmospheres is primarily a matter of under-
3.1.7 maximum use temperature—the maximum tempera-
standing the circumstances that cause oxygen to react with the
ture to which a material can be subjected due to a reasonably
material. Most materials in contact with oxygen will not ignite
foreseeable malfunction, operator error, or process upset (see
without a source of ignition energy. When an energy-input
Guide G126).
exceeds the configuration-dependent threshold, then ignition
3.1.8 nonmetallic—any material, other than a metal, or any
and combustion may occur. Thus, the material’s flammability
composite in which the metal is not the most easily ignited propertiesandtheignitionenergysourceswithinasystemmust
componentandforwhichtheindividualconstituentscannotbe
be considered. These should be viewed in the context of the
evaluated independently (see Guide G126). entire system design so that the specific factors listed in this
guidewillassumetheproperrelativesignificance.Insummary,
3.1.9 operating pressure—the pressure expected under nor-
it depends on the application.
mal operating conditions (see Guide G126).
5.2 Relative Amount of Data Available for Metals and
3.1.10 operating temperature—the temperature expected
Nonmetals:
under normal operating conditions (see Guide G126).
5.2.1 Studies of the flammability of gaseous fuels were
3.1.11 oxygen-enriched—applies to a fluid (gas or liquid)
begun more than 150 years ago.Awide variety of applications
that contains more than 25 mol% oxygen (see Guide G126).
have been studied and documented, including a wide range of
3.1.12 qualified technical personnel—persons such as engi-
importantsubtletiessuchasquenchingphenomena,turbulence,
neers and chemists who, by virtue of education, training, or
cool flames, influence of initial temperature, etc., all of which
experience, know how to apply physical and chemical prin-
have been used effectively for safety and loss prevention. A
ciples involved in the reactions between oxygen and other
smaller, yet still substantial, background exists for nonmetallic
materials (see Guide G126).
solids. In contrast to this, the study of the flammability of
3.1.13 reaction effect—the personnel injury, facility
metals dates only to the 1950s, and even though it has
damage, product loss, downtime, or mission loss that could
accelerated rapidly, the uncovering and understanding of
occur as the result of an ignition (see Guide G126).
subtleties have not yet matured. In addition, the heterogeneity
of the metal and oxidizer systems and the heat transfer
properties of metals, as well as the known, complex ignition
energy and ignition/burning mechanisms, clearly dictate that
Available from ASTM International Headquarters. Order Adjunct No.
ADJG0094. Original adjunct produced in 1986. cautionisrequiredwhenapplyinglaboratoryfindingstoactual
G94 − 05 (2014)
applications.Inmanycases,laboratorymetalsburningtestsare ignition many times over. Hence, while the selection of
designedonwhatisbelievedtobeaworst-casebasis,butcould nonmetalsbyGuideG63andthecarefuldesignofcomponents
the particular actual application be worse? Further, because so by Guide G88 are the first line of defense, optimum metal
many subtleties exist, accumulation of favorable experience selection is an important second-line of defense.
(no metal fires) in some particular application may not be as 5.3.4 Contaminants and residues that are left in oxygen
fully relevant to another application as might be the case for systems may contribute to incidents via ignition mechanisms
gaseous or nonmetallic solids where the relevance may be such as particle impact and promoted ignition-combustion
more thoroughly understood. (kindling chain). Therefore, oxygen system cleanliness is
5.2.1.1 ASTM Symposia and Special Technical Publica- essential. Guide G93 describes in detail the essential elements
tions on these symposia have contributed significantly to the for cleaning oxygen systems.
study of the flammability and sensitivity of materials in
5.4 Differences in Oxygen Compatibility of Metals and
oxygen-enriched atmospheres. See section 2.2 for listing of
Nonmetals:
STP numbers and the References Section for key papers.
5.4.1 Thereareseveralfundamentaldifferencesbetweenthe
5.3 Relationship of Guide G94 with Guides G63, G88, and oxygen compatibility of metals and nonceramic nonmetals.
G93: These principal differences are summarized in Table 1.
5.3.1 This guide addresses the evaluation of metals for use 5.4.2 Common-use metals are harder to ignite. They have
in oxygen systems and especially in major structural portions high autoignition temperatures in the range 900 to 2000°C
ofasystem.GuideG63addressestheevaluationofnonmetals. (1650 to 3600°F). In comparison, most combustible nonmetals
Guide G88 presents design and operational maxims for all have autoignition temperatures in the range 150 to 500°C (300
systems. In general, however, Guides G63 and G88 focus on to 1000°F). Metals have high thermal conductivities that help
physically small portions of an oxygen system that represent dissipate local heat inputs that might easily ignite nonmetals.
the critical sites most likely to encounter ignition. Guide G93 Manymetalsalsogrowprotectiveoxidecoatings(see5.5)that
covers a key issue pertinent to actual operating oxygen interfere with ignition and propagation.
systems; cleaning for the service. 5.4.3 Once ignited, however, metal combustion can be
5.3.2 The nonmetals in an oxygen system (valve seats and highlydestructive.Adiabaticflametemperaturesformetalsare
packing,pistonrings,gaskets,o-rings)aresmall;therefore,the much higher than for most polymers (Table X1.7).The greater
use of the most fire-resistant materials is usually a realistic, density of most metals provides greater heat release potential
practical option with regard to cost and availability. In fromcomponentsofcomparablesize.Sincemanymetaloxides
comparison, the choice of material for the major structural do not exist as oxide vapors (they largely dissociate upon
members of a system is much more limited, and the use of vaporization), combustion of these metals inherently yields
specialalloysmayhavetobeavoidedtoachieverealisticcosts coalescingliquidmetaloxideofhighheatcapacityintheflame
and delivery times. Indeed, with the exception of ceramic zoneattheoxideboilingpoint(theremaybeverylittlegaseous
materials, which have relatively few practical uses, most metal oxide). In comparison, combustion of polymers yields
nonmetals have less fire resistance than virtually all metals. gaseous combustion products (typically carbon dioxide and
Nonmetals are typically introduced into a system to provide a steam) that tend to dissipate the heat release.
physical property not achievable from metals. Nonmetals may 5.4.4 Contact with a mixture of liquid metal and oxide at
serve as “links” in a kindling chain (see 5.6.5), and since the high temperature results in a massive heat transfer relative to
locations of use are typically mechanically severe, the primary thatpossibleuponcontactwithhot,low-heat-capacity,gaseous
thrust in achieving compatible oxygen systems rests with the combustion products of polymers. As a result, metal combus-
minor components
...
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