ASTM G134-95(2001)e1
(Test Method)Standard Test Method for Erosion of Solid Materials by a Cavitating Liquid Jet
Standard Test Method for Erosion of Solid Materials by a Cavitating Liquid Jet
SCOPE
1.1 This test method covers a test that can be used to compare the cavitation erosion resistance of solid materials. A submerged cavitating jet, issuing from a nozzle, impinges on a test specimen placed in its path so that cavities collapse on it, thereby causing erosion. The test is carried out under specified conditions in a specified liquid, usually water. This test method can also be used to compare the cavitation erosion capability of various liquids.
1.2 This test method specifies the nozzle and nozzle holder shape and size, the specimen size and its method of mounting, and the minimum test chamber size. Procedures are described for selecting the standoff distance and one of several standard test conditions. Deviation from some of these conditions is permitted where appropriate and if properly documented. Guidance is given on setting up a suitable apparatus, test and reporting procedures, and the precautions to be taken. Standard reference materials are specified; these must be used to verify the operation of the facility and to define the normalized erosion resistance of other materials.
1.3 Two types of tests are encompassed, one using test liquids which can be run to waste, for example, tap water, and the other using liquids which must be recirculated, for example, reagent water or various oils. Slightly different test circuits are required for each type.
1.4 This test method provides an alternative to Test Method G32. In that method, cavitation is induced by vibrating a submerged specimen at high frequency (20 kHz) with a specified amplitude. In the present method, cavitation is generated in a flowing system so that both the jet velocity and the downstream pressure (which causes the bubble collapse) can be varied independently.
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.6 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.
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Designation:G134–95 (Reapproved 2001)
Standard Test Method for
Erosion of Solid Materials by a Cavitating Liquid Jet
This standard is issued under the fixed designation G 134; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Editorial changes were made throughout in April 2001.
1. Scope responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
1.1 This test method covers a test that can be used to
bility of regulatory limitations prior to use.
compare the cavitation erosion resistance of solid materials.A
submerged cavitating jet, issuing from a nozzle, impinges on a
2. Referenced Documents
test specimen placed in its path so that cavities collapse on it,
2.1 ASTM Standards:
thereby causing erosion. The test is carried out under specified
A 276 Specification for Stainless Steel Bars and Shapes
conditions in a specified liquid, usually water.This test method
B 160 Specification for Nickel Rod and Bar
canalsobeusedtocomparethecavitationerosioncapabilityof
B211 Specification for Aluminum and Aluminum Alloy
various liquids.
Bar, Rod, and Wire
1.2 This test method specifies the nozzle and nozzle holder
D 1193 Specification for Reagent Water
shape and size, the specimen size and its method of mounting,
E 691 Practice for Conducting an Interlaboratory Study to
and the minimum test chamber size. Procedures are described
Determine the Precision of a Test Method
for selecting the standoff distance and one of several standard
G32 Test Method for Cavitation Erosion Using Vibratory
test conditions. Deviation from some of these conditions is
Apparatus
permitted where appropriate and if properly documented.
G40 Terminology Relating to Wear and Erosion
Guidance is given on setting up a suitable apparatus, test and
G73 Practice for Liquid Impingement Erosion Testing
reportingprocedures,andtheprecautionstobetaken.Standard
2.2 ASTM Adjuncts:
reference materials are specified; these must be used to verify
Manufacturing Drawings of the Apparatus
the operation of the facility and to define the normalized
erosion resistance of other materials.
3. Terminology
1.3 Two types of tests are encompassed, one using test
3.1 Definitions—See Terminology G40 for definitions of
liquids which can be run to waste, for example, tap water, and
terms relating to cavitation erosion. For convenience, defini-
the other using liquids which must be recirculated, for ex-
tions of some important terms used in this test method are
ample, reagent water or various oils. Slightly different test
quoted below from TerminologyG40 – 90a.
circuits are required for each type.
3.1.1 cavitation—the formation and collapse, within a liq-
1.4 This test method provides an alternative to Test Method
uid, of cavities or bubbles that contain vapor or gas, or both.
G32. In that method, cavitation is induced by vibrating a
3.1.1.1 Discussion—In general, cavitation originates from a
submerged specimen at high frequency (20 kHz) with a
decrease in static pressure in the liquid. It is distinguished in
specified amplitude. In the present method, cavitation is
this way from boiling, which originates from an increase in
generated in a flowing system so that both the jet velocity and
liquidtemperature.Therearecertainsituationswhereitmaybe
the downstream pressure (which causes the bubble collapse)
difficult to make a clear distinction between cavitation and
can be varied independently.
boiling, and the more general definition that is given here is,
1.5 The values stated in SI units are to be regarded as the
therefore, preferred.
standard. The values given in parentheses are for information
only.
1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
Annual Book of ASTM Standards, Vol 01.03.
Annual Book of ASTM Standards, Vol 02.04.
Annual Book of ASTM Standards, Vol 02.02.
Annual Book of ASTM Standards, Vol 11.01.
1 6
This test method is under the jurisdiction of ASTM Committee G02 on Wear Annual Book of ASTM Standards, Vol 14.02.
and Erosion and is the direct responsibility of Subcommittee G02.10 on Erosion by Annual Book of ASTM Standards, Vol 03.02.
Solids and Liquids. Available from ASTM International Headquarters. Order Adjunct No.
Current edition approved Oct. 10, 1995. Published March 1996. ADJG0134.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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G134–95 (2001)
3.1.1.2 Discussion—In order to erode a solid surface by 3.1.10 normalized incubation resistance, N —the incuba-
o
cavitation, it is necessary for the cavitation bubbles to collapse tion period of a test material, divided by the incubation period
on or close to that surface. of a specified reference material similarly tested and similarly
analyzed.
3.1.2 cavitation erosion—progressive loss of original mate-
3.1.11 terminal erosion rate—the final steady-state erosion
rial from a solid surface due to continued exposure to cavita-
rate that is reached (or appears to be approached asymptoti-
tion.
cally) after the erosion rate has declined from its maximum
3.1.3 cumulative erosion—the total amount of material lost
value. This occurs in some, but not all, cavitation and liquid
from a solid surface during all exposure periods since it was
impingement tests.
first exposed to cavitation or impingement as a newly finished
3.2 Definitions of Terms Specific to This Standard:
surface.Unlessotherwiseindicatedbythecontext,itisimplied
3.2.1 cavitating jet—a continuous liquid jet (usually sub-
thattheconditionsofcavitationorimpingementhaveremained
merged) in which cavitation is induced by the nozzle design or
the same throughout all exposure periods, with no intermediate
sometimes by a center body. See also jet cavitation.
refinishing of the surface.
3.2.2 cavitation number, s—a dimensionless number that
3.1.4 cumulative erosion rate—the cumulative erosion di-
measures the tendency for cavitation to occur in a flowing
vided by the corresponding cumulative exposure duration, that
stream of liquid, and that, for the purpose of this test method,
is, the slope of a line from the origin to a specified point on the
isdefinedbythefollowingequation.Allpressuresareabsolute.
cumulative erosion-time curve.
~p 2 p !
d v
3.1.5 cumulative erosion-time curve—a plot of cumulative s5 (1)
rV
erosion versus cumulative exposure time, usually determined
by periodic interruption of the test and weighing of the
where:
specimen. This is the primary record of an erosion test. Most
p = vapor pressure,
other characteristics, such as the incubation period, maximum
v
p = static pressure in the downstream chamber,
erosion rate, terminal erosion rate, and erosion ratetime curve, d
V = jet velocity, and
are derived from it.
r = liquid density.
3.1.6 flow cavitation—cavitation caused by a decrease in
3.2.2.1 For liquid flow through any orifice
static pressure induced by changes in velocity of a flowing
liquid. Typically, this may be caused by flow around an 2
r V 5 p 2 p . (2)
u d
obstacle or through a constriction, or relative to a blade or foil.
A cavitation cloud or “cavitating wake” generally trails from
where:
some point adjacent to the obstacle or constriction to some
p = upstream pressure.
u
distance downstream, the bubbles being formed at one place
3.2.2.2 For erosion testing by this test method, the cavitat-
and collapsing at another.
ing flow in the nozzle is choked, so that the downstream
3.1.7 incubation period—in cavitation and impingement pressure, as seen by the flow, is equal to the vapor pressure.
erosion, the initial stage of the erosion rate-time pattern during
The cavitation number thus reduces to
which the erosion rate is zero or negligible compared to later
p 2 p
d v
s5 (3)
stages. Also, the exposure duration associated with this stage.
p 2 p
u v
(Quantitatively it is sometimes defined as the intercept on the
which for many liquids and at many temperatures can be
time or exposure axis, of a straight line extension of the
approximated by:
maximum-slopeportionofthecumulativeerosion-timecurve).
p
d
3.1.8 maximum erosion rate—the maximum instantaneous
s5 (4)
p
u
erosionrateinatestthatexhibitssuchamaximumfollowedby
since
decreasing erosion rates. (Occurrence of such a maximum is
typical of many cavitation and liquid impingement tests. In
p . p . p (5)
u d v
some instances it occurs as an instantaneous maximum, in
others as a steady-state maximum which persists for some
3.2.3 jet cavitation—the cavitation generated in the vortices
time.)
which travel in sequence singly or in clouds in the shear layer
3.1.9 normalized erosion resistance, N —the volume loss
around a submerged jet. It can be amplified by the nozzle
e
rate of a test material, divided into the rate of volume loss of a
design so that vortices form in the vena contracta region inside
specified reference material similarly tested and similarly
the nozzle.
analyzed. Similarly analyzed means that the two erosion rates
3.2.4 stand-off distance—in this test method, the distance
must be determined for corresponding portions of the erosion
between the inlet edge of the nozzle and the target face of the
rate-timepattern;forinstance,themaximumerosionrateorthe
specimen. It is thus defined because the location and shape of
terminal erosion rate.
the inlet edge determine the location of the vena contracta and
3.1.9.1 Discussion—Arecommendedcompletewordinghas the initiation of cavitation.
the form, “The normalized erosion resistance of (test material) 3.2.5 tangent erosion rate—the slope of a straight line
relative to (reference material) based on (criterion of data drawn through the origin and tangent to the knee of the
analysis) is (numerical value).” cumulative erosion-time curve, when the shape of that curve
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G134–95 (2001)
has the characteristic S-shape pattern that permits this. In such possible, by suitably altering the pressures, to accelerate or
cases, the tangent erosion rate also represents the maximum slow down the testing process (see 11.2 and Fig. A2.2).
cumulative erosion rate exhibited during the test.
5.3 This test method with standard conditions should not be
3.2.6 vena contracta—the smallest locally occurring diam- used to rank materials for applications where electrochemical
eter of the main flow of a fluid after it enters into a nozzle or corrosion or solid particle impingement plays a major role.
orifice from a larger conduit or a reservoir. At this point the However, it could be adapted to evaluate erosion-corrosion
main or primary flow is detached from the solid boundaries, effects if the appropriate liquid and cavitation number, for the
and vortices or recirculating secondary flow patterns are service conditions of interest, are used (see 11.1).
formed in the intervening space.
5.4 For metallic materials, this test method could also be
used as a screening test for applications subjected to highspeed
4. Summary of Test Method
liquid drop impingement, if the use of Practice G73 is not
feasible. However, this is not recommended for elastomeric
4.1 This test method produces a submerged cavitating jet
coatings,composites,orothernonmetallicaerospacematerials.
which impinges upon a stationary specimen, also submerged,
5.5 The mechanisms of cavitation erosion and liquid im-
causing cavitation bubbles to collapse on that specimen and
pingement erosion are not fully understood and may vary,
thereby to erode it. This test method generally utilizes a
depending on the detailed nature, scale, and intensity of the
commercially available positive displacement pump fitted with
liquid/solid interactions. Erosion resistance may, therefore,
a hydraulic accumulator to damp out pulsations. The pump
arisefromamixofpropertiesratherthanasingleproperty,and
deliverstestliquidthroughasmallsharp-entrycylindrical-bore
has not yet been successfully correlated with other indepen-
nozzle, which discharges a jet of liquid into a chamber at a
dently measurable material properties. For this reason, the
controlled pressure. Cavitation starts in the vena contracta
consistency of results between different test methods (for
region of the jet within the length of the nozzle; it is stabilized
example, vibratory, rotating disk, or cavitating jet) or under
by the cylindrical bore and it emerges, appearing to the eye as
different experimental conditions is not very good. Small
a cloud which is visible around the submerged liquid jet. A
differences between two materials are probably not significant,
button type specimen is placed in the path of the jet at a
and their relative ranking could well be reversed in another
specified stand-off distance from the entry edge of the nozzle.
test.
Cavitation bubbles collapse on the specimen, thus causing
5.6 Because of the nonlinear nature of the erosion-time
erosion. Both the upstream and the downstream chamber
curve in cavitation erosion, the shape of that curve must be
pressuresandthetemperatureofthedischargingliquidmustbe
considered in making comparisons and drawing conclusions.
controlled and monitored. The test specimen is weighed
Simply comparing the cumulative mass loss at the same
accurately before testing begins and again during periodic
cumulative test time for all materials will not give a reliable
interruptions of the test, in order to obtain a history of mass
comparison.
loss versus time (which is not linear). Appropriate interpreta-
tion of the cumulative erosion-time curve derived from these
6. Apparatus
measurements permits comparisons to be drawn between
different materials, different test conditions, or between differ-
6.1 General Arrangement:
ent liquids.Atypical test rig can be built using a 2.5-kWpump
6.1.1 Fig. 1 shows an arrangement of the test chamber. A
capable of producing 21-MPa pressure. The standard nozzle
cavitating jet supplied from a constant pressure source (p )
u
bore diameter is 0.4 mm, but this may be changed if required
discharges, through a long-orifice nozzle (Fig. 2), into a
for specialized tests.
chamber held at specified constant pressure (p ). A flat-ended
d
cylindrical specimen (Fig. 3) is mounted coaxially with the
5. Significance and Use
nozzle so that the stand-off distance between the nozzle inlet
edge and the specimen face can be set at any required value.A
5.1 This test method may be used to estimate the relative
movable jet deflector (Fig. 1, Item 11) may be provided to
resistances of materials to cavitati
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