ASTM G134-95(2006)
(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 G 32. 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.
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
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:G134–95 (Reapproved 2006)
Standard Test Method for
Erosion of Solid Materials by a Cavitating Liquid Jet
This standard is issued under the fixed designation G134; 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 (´) indicates an editorial change since the last revision or reapproval.
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
A276 Specification for Stainless Steel Bars and Shapes
conditions in a specified liquid, usually water.This test method
B160 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
D1193 Specification for Reagent Water
shape and size, the specimen size and its method of mounting,
E691 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 Terminology G40 – 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
3.1.1.2 Discussion—In order to erode a solid surface by
only.
cavitation, it is necessary for the cavitation bubbles to collapse
1.6 This standard does not purport to address all of the
on or close to that surface.
safety concerns, if any, associated with its use. It is the
1 2
This test method is under the jurisdiction of ASTM Committee G02 on Wear For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Erosion and is the direct responsibility of Subcommittee G02.10 on Erosion by contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Solids and Liquids. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Dec. 1, 2006. Published January 2007. Originally the ASTM website.
´1 3
approved in 1995. Last previous edition approved in 2001 as G134 – 95 (2001) . Available from ASTM International Headquarters. Order Adjunct No.
DOI: 10.1520/G0134-95R06. ADJG0134.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G134–95 (2006)
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
value. This occurs in some, but not all, cavitation and liquid
3.1.3 cumulative erosion—the total amount of material lost
impingement tests.
from a solid surface during all exposure periods since it was
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
thesamethroughoutallexposureperiods,withnointermediate
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
s5 (1)
3.1.5 cumulative erosion-time curve—a plot of cumulative
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,
d
erosion rate, terminal erosion rate, and erosion ratetime curve,
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
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
stages. Also, the exposure duration associated with this stage.
s5 (3)
p 2 p
u v
(Quantitatively it is sometimes defined as the intercept on the
time or exposure axis, of a straight line extension of the which for many liquids and at many temperatures can be
maximum-slopeportionofthecumulativeerosion-timecurve).
approximated by:
3.1.8 maximum erosion rate—the maximum instantaneous
p
d
s5 (4)
erosionrateinatestthatexhibitssuchamaximumfollowedby
p
u
decreasing erosion rates. (Occurrence of such a maximum is
since
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
time.)
3.2.3 jet cavitation—the cavitation generated in the vortices
3.1.9 normalized erosion resistance, N —the volume loss which travel in sequence singly or in clouds in the shear layer
e
rate of a test material, divided into the rate of volume loss of a around a submerged jet. It can be amplified by the nozzle
specified reference material similarly tested and similarly design so that vortices form in the vena contracta region inside
the nozzle.
analyzed. Similarly analyzed means that the two erosion rates
must be determined for corresponding portions of the erosion
3.2.4 stand-off distance—in this test method, the distance
rate-timepattern;forinstance,themaximumerosionrateorthe
between the inlet edge of the nozzle and the target face of the
terminal erosion rate.
specimen. It is thus defined because the location and shape of
3.1.9.1 Discussion—Arecommendedcompletewordinghas the inlet edge determine the location of the vena contracta and
the form, “The normalized erosion resistance of (test material) the initiation of cavitation.
relative to (reference material) based on (criterion of data
3.2.5 tangent erosion rate—the slope of a straight line
analysis) is (numerical value).”
drawn through the origin and tangent to the knee of the
3.1.10 normalized incubation resistance, N —the incuba- cumulative erosion-time curve, when the shape of that curve
o
tion period of a test material, divided by the incubation period has the characteristic S-shape pattern that permits this. In such
of a specified reference material similarly tested and similarly cases, the tangent erosion rate also represents the maximum
analyzed. cumulative erosion rate exhibited during the test.
G134–95 (2006)
3.2.6 vena contracta—the smallest locally occurring diam- corrosion or solid particle impingement plays a major role.
eter of the main flow of a fluid after it enters into a nozzle or However, it could be adapted to evaluate erosion-corrosion
orifice from a larger conduit or a reservoir. At this point the
effects if the appropriate liquid and cavitation number, for the
main or primary flow is detached from the solid boundaries,
service conditions of interest, are used (see 11.1).
and vortices or recirculating secondary flow patterns are
5.4 For metallic materials, this test method could also be
formed in the intervening space.
used as a screening test for applications subjected to highspeed
liquid drop impingement, if the use of Practice G73 is not
4. Summary of Test Method
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.
Cavitation bubbles collapse on the specimen, thus causing test.
erosion. Both the upstream and the downstream chamber
5.6 Because of the nonlinear nature of the erosion-time
pressuresandthetemperatureofthedischargingliquidmustbe
curve in cavitation erosion, the shape of that curve must be
controlled and monitored. The test specimen is weighed
considered in making comparisons and drawing conclusions.
accurately before testing begins and again during periodic
Simply comparing the cumulative mass loss at the same
interruptions of the test, in order to obtain a history of mass
cumulative test time for all materials will not give a reliable
loss versus time (which is not linear). Appropriate interpreta-
comparison.
tion of the cumulative erosion-time curve derived from these
measurements permits comparisons to be drawn between
6. Apparatus
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
capable of producing 21-MPa pressure. The standard nozzle 6.1.1 Fig. 1 shows an arrangement of the test chamber. A
bore diameter is 0.4 mm, but this may be changed if required cavitating jet supplied from a constant pressure source (p )
u
for specialized tests.
discharges, through a long-orifice nozzle (Fig. 2), into a
chamber held at specified constant pressure (p ). A flat-ended
d
5. Significance and Use
cylindrical specimen (Fig. 3) is mounted coaxially with the
5.1 This test method may be used to estimate the relative
nozzle so that the stand-off distance between the nozzle inlet
resistances of materials to cavitation erosion, as may be
edge and the specimen face can be set at any required value.A
encountered for instance in pumps, hydraulic turbines, valves,
movable jet deflector (Fig. 1, Item 11) may be provided to
hydraulicdynamometersandcouplings,bearings,dieselengine
protect the specimen while test conditions are being set up.
cylinder liners, ship propellers, h
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.