ASTM G88-90(1997)e1
(Guide)Standard Guide for Designing Systems for Oxygen Service
Standard Guide for Designing Systems for Oxygen Service
SCOPE
1.1 This guide applies to the design of systems for oxygen or oxygen-enriched service but is not a comprehensive document. Specifically, this guide addresses system factors that affect the avoidance of ignition and fire. It does not thoroughly address the selection of materials of construction for which Guides G 63 and G 94 are available, nor does it cover mechanical, economic or other design considerations for which well-known practices are available. This guide also does not address issues concerning the toxicity of nonmetals in breathing gas or medical gas systems.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.
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 requirements prior to use.
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e1
Designation:G88–90(Reapproved 1997)
Standard Guide for
Designing Systems for Oxygen Service
ThisstandardisissuedunderthefixeddesignationG 88;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Keywords were added editorially in March 1998.
1. Scope Oxygen Safety Video
1.1 This guide applies to the design of systems for oxygen
3. Terminology
or oxygen-enriched service but is not a comprehensive docu-
3.1 Definitions of Terms Specific to This Standard:
ment. Specifically, this guide addresses system factors that
3.1.1 direct oxygen service—service in contact with oxygen
affect the avoidance of ignition and fire. It does not address the
during normal operations. Examples: oxygen compressor pis-
selection of materials of construction for which Guides G 63
ton rings, control valve seats.
and G 94 are available, nor does it concern mechanical,
3.1.2 indirect oxygen service—service in which oxygen is
economic or other design considerations for which well-known
not normally contacted but in which it might be as a result of
practices are available.
a reasonably foreseeable malfunction, operator error, or pro-
NOTE 1—The American Society for Testing and Materials takes no
cess disturbance. Examples: liquid oxygen tank insulation,
position respecting the validity of any evaluation methods asserted in
liquid oxygen pump motor bearings.
connection with any item mentioned in this guide. Users of this guide are
3.1.3 oxygen-enriched atmosphere—a fluid mixture (gas or
expressly advised that determination of the validity of any such evaluation
liquid) that contains more than 25 mol % oxygen.
methods and data and the risk of use of such evaluation methods and data
3.1.4 qualified technical personnel—persons such as engi-
are entirely their own responsibility.
neers and chemists who, by virtue of education, training, or
1.2 This standard does not purport to address all of the
experience, know how to apply physical and chemical prin-
safety concerns, if any, associated with its use. It is the
ciples involved in the reactions between oxygen and other
responsibility of the user of this standard to establish appro-
materials.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4. Significance and Use
4.1 The purpose of this guide is to furnish qualified techni-
2. Referenced Documents
cal personnel with pertinent information to use in designing
2.1 ASTM Standards:
oxygen systems. It emphasizes factors that cause ignition and
G 63 Guide for Evaluating Nonmetallic Materials for Oxy-
enhance propagation throughout a system’s service life so that
gen Service
the occurrence of these conditions may be avoided or mini-
G 72 Test Method for Autogenous Ignition Temperature of
mized. It is not intended as a specification for the design of
Liquids and Solids in a High-Pressure Oxygen-Enriched
oxygen systems.
Environment
G 74 Test Method for Ignition Sensitivity of Materials to
5. Factors Affecting the Design for an Oxygen or
Gaseous Fluid Impact
Oxygen-Enriched System
G 93 Practice for Cleaning Methods for Material and
5.1 General—An oxygen system designer should under-
Equipment Used in Oxygen-Enriched Environments
stand that oxygen, fuel, and heat (source of ignition) must be
G 94 Guide for Evaluating Metals for Oxygen Service
present to start and propagate a fire. Since combustible
2.2 ASTM Adjuncts:
materials and oxygen are usually present, the design of a
system for oxygen or oxygen enriched service is primarily a
matter of understanding the factors that are potential sources of
This guide is under the jurisdiction ofASTM Committee G-4 on Compatibility
ignition or which aggravate consequential propagation. The
and Sensitivity of Materials in Oxygen Enriched Atmospheres and is the direct
responsibility of Subcommittee G04.02 on Recommended Practices. goal is to eliminate these factors or compensate for their
Current edition approved June 29, 1990. Published August 1990. Originally
published as G 88 – 84. Last previous edition G 88 – 84e .
2 3
Annual Book of ASTM Standards, Vol 14.02. Available from ASTM Headquarters, Order PCN 12-700880-31.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G88
presence. Preventing fires involves both minimizing system pressure oxygen is released into a dead-ended tube or pipe,
environments that enhance fire and maximizing the use of quickly compressing the residual oxygen that was in the tube
system materials with properties that resist ignition and com- ahead of it. (Example: a downstream valve in a dead-ended
bustion. high-pressure oxygen manifold.) The elevated temperatures
produced can ignite contaminants or elevate system compo-
5.2 Factors Recognized as Causing Fires:
nents above their ignition temperature. The hazard of heat of
5.2.1 Temperature—As the temperature of a material in-
compression increases with system pressure and with pressur-
creases, the amount of energy that must be added to produce
ization rates.
ignition decreases. Operating a system at unnecessarily el-
evated temperatures, whether locally or generally elevated,
reduces this safety margin. The ignition temperature of the
TABLE 1 Theoretical Maximum Temperature Obtained when
most easily ignited material in a system is related to that
Compressing Oxygen Adiabatically from 20°C and One Standard
A
temperature measured by Test Method G 72 but is also a
Atmosphere to the Pressures Shown
function of the system pressure, configuration and operation,
Final Pressure, P Final Temperature, T
f Pressure f
and the thermal history of the material. Elevated temperature
Ratio P/P
f i
kPa PSIA °C °F
also facilitates sustained combustion of materials that might
345 50 3.4 143 289
otherwise be self-extinguishing.
690 100 6.8 234 453
1000 145 9.9 291 556
5.2.2 Pressure—As the pressure of a system increases, the
1379 200 13.6 344 653
ignition temperatures of its components typically decrease, and
2068 300 20.4 421 789
the rates of fire propagation increase. Therefore, operating a
2758 400 27.2 480 896
3447 500 34.0 530 986
system at unnecessarily elevated pressures increases the prob-
5170 750 51.0 628 1163
ability and consequences of a fire. It should be noted that pure
6895 1000 68.0 706 1303
oxygen, even at lower than atmospheric pressure, may still
10000 1450 98.6 815 1499
13790 2000 136.1 920 1688
pose a significant hazard with noncompatible materials such as
27579 4000 272.1 1181 2158
hydrocarbon pump oils.
34474 5000 340.1 1277 2330
5.2.3 Concentration—As oxygen concentration decreases
100000 14500 986.4 1828 3322
1 000 000 145000 9863.9 3785 6845
from 100 % with the balance being inert gases, there are
A
See 5.2.6.
progressive decreases in the likelihood and intensity of a
potential reaction. Greater latitude may therefore be exercised
in the design of a system for dilute oxygen service.
5.2.6.1 Equation—A formula for the theoretical maximum
5.2.4 Contamination—Contamination can be present in a
temperature that can be developed when pressurizing a gas
system because of inadequate initial cleanness, introduction
rapidly without heat dissipation from one pressure and tem-
duringassemblyorservicelife,orgenerationwithinthesystem
perature to an elevated pressure is as follows:
by abrasion, flaking, etc. Contaminants may be liquids, solids,
~n21!/n
or gases. Such contamination may be highly flammable and
T/T 5 @P/P # (1)
f i f i
readily ignitable, for example, hydrocarbon oils. Accordingly,
where:
it is likely to ignite and promote consequential system fires.
T 5 final temperature, abs,
f
However, even normally inert contaminants, such as rust, may
T 5 initial temperature, abs,
i
produce ignition through particle impact (see 5.2.5) or friction
P 5 final pressure, abs,
f
(see 5.2.7) or through augmenting of resonance heating effects
P 5 initial pressure, abs, and
i
(see 5.2.8).
C
p
5.2.5 Particle Impact—Collisions of inert or ignitable solid
n 5 5 1.40 for oxygen (2)
C
v
particles entrained in an oxidant stream are associated with
potential ignition. Such ignition may result from the particle
where:
beingflammableandignitinguponimpactand,inturn,igniting
C 5 specific heat at constant pressure, and
p
othersystemmaterials.Ignitionmayalsoresultfromheatingof
C 5 specific heat at constant volume.
v
the particle and subsequent contact with system plastics and
5.2.6.2 Table 1 gives the theoretical temperatures which
elastomers, from fine flammable particles produced during the
could be obtained by compressing oxygen adiabatically from
collision, or from the direct transfer of kinetic energy during
20°C and one standard atmosphere to the pressures shown.
the collision.Absolute removal of particles is not possible, and
5.2.7 Friction—The rubbing together of two surfaces can
systems can self-regenerate particles. Hence, a system must be
produce heating and can generate particulates. Such heating
designed to tolerate at least some particle presence.The hazard
may elevate a system component above its ignition tempera-
associated with particles increases with both the particles’ heat
ture. Particulates can participate as contaminants (see 5.2.4) or
of combustion and their kinetic energies. The quantity of
in particle impacts (see 5.2.5). The hazard associated with
particles in a system will tend to increase with the age of the
friction generally increases with the loading and rubbing rates.
system.
5.2.8 Resonance—Acoustic oscillations within resonant
5.2.6 Heat of Compression—Heat is generated from the cavities are associated with rapid heating. The temperature
conversion of mechanical energy when a gas is compressed rises more rapidly and achieves higher values where particles
from a low to a high pressure. This can occur when high- are present or where there are high gas velocities. Resonance
G88
phenomena in oxygen systems are well documented (1), but 7.5.1 Design a system that is easy to clean and easy to
there are few design criteria. maintain clean (3). The system should be capable of disassem-
5.2.9 Static Electric Discharge—Electrical discharge from bly into elements capable of thorough cleaning. Cleaning is
static electricity, possibly generated by high fluid flow under discussed in Practice G 93.
certain conditions, may occur, especially where particulate
7.5.2 Avoid the presence of unnecessary sumps, dead-ends
matter is present. Example: arcing in poorly cleaned, inad-
and cavities likely to accumulate debris.
equately ground piping.
7.5.3 Filters should be used to limit the introduction of
5.2.10 Electrical Arc—Electrical arcing may occur from
particles and to capture particles generated in service.
motor brushes, electrical control equipment, instrumentation,
7.5.3.1 Filter use should be considered at oxygen entry
lighting, etc. Example: defective pressure switch.
points into a system, at points where particles are likely to be
generated and at critical points where particle presence pro-
6. Test Methods
duces the greatest risk, such as at the suction side of compres-
6.1 Gaseous Impact, Test Method G 74—This is a material sors or inlets to throttling valves.
test, but it can also be used with modification to stress whole
7.5.3.2 Filters should not be fragile or prone to breakage. If
components and system designs. The test repeatedly exposes
complete blockage is possible, the filter should be able to
the system to rapid cyclic pressurization with gaseous oxygen,
withstand full differential pressure.
and any combustion is noted.
7.5.3.3 Preventivemaintenanceoffiltersshouldbeadequate
to limit the hazard associated with flammable debris collected
7. System Design Method
on the filter element.
7.1 Overview—To design a system for oxygen service, the 7.5.3.4 Provision should be made for preventive mainte-
designer observes good mechanical design principles and nance of filters. Such provision may include pressure gages to
incorporates the factors below to a degree consistent with the indicate excessive pressure drop and a bypass line to allow
severity of the application. Mechanical failures are undesirable cleaning. When bypass lines are used, they should not tend to
since rupture, friction, etc. can produce heating, particulates, accumulate debris.
etc. which in turn are associated with ignition as discussed in
7.5.3.5 Since many filters have high surface-area/volume
the following sections. ratios, a highly fire resistant material is desirable (see Guides
7.2 Final Design (2)—In the final analysis, the system
G 63 and G 94).
design involves a complex interplay of the various factors that
7.5.3.6 Consider dual filters if the system cannot be shut
promote ignition and of the ability of the materials of construc-
down to change elements.
tion to resist such ignition. There are many subjective judge-
7.6 Avoid particle impacts.
ments, external influences, and compromises involved. While
7.6.1 Filters should be used to limit particle presence as
each case must be ultimately decided on its own merits, the
described in 7.5.3.
generalizations below apply. In applying these principles, the
7.6.2 Limit gas velocities to limit particle kinetic energies.
designer should consider the system’s normal operating con-
7.6.2.1 For carbon steel or stainless steel pipelines, CGA
ditions and, in addition, indirect oxygen exposure that may
Pamphlet G-4.4 (4) may be consulted for an industry approach
result from system upsets and failure modes. The system
to the limiting of oxygen velocities.
should be designed to fail safely. To this end, failure effect
7.6.3 Use highly fire resistant materials (see Guide G 94)
studies are recommended to identify components subject to
where velocities cannot be minimized, such as in throttling
indirect oxygen exposure or for which an oxygen exposure
valves.
moreseverethannormalispossible.Noteveryprinciplecanbe
7.6.4 Use highly fire resistant materials at particle impinge-
applied in the design of every system. However, the fire
ment points, such as gas streams into the side ports of tees.
resistance of a system will improve with the number of
Localimpingementplatesofhighlyfireresistantalloysarealso
principles that are followed.
acceptable.
7.3 Avoid unnecessarily elevated temperatures.
7.6.5 Minimize pressurization rates.
7.3.1 Locate systems a safe distance from heat or radiation
7.6.6 Do not impinge gas streams onto seats, seals, or other
sources (such as furnaces).
plastics or elastomers.
7.3.2 Design for efficient dissi
...
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