ASTM D1092-99
(Test Method)Standard Test Method for Measuring Apparent Viscosity of Lubricating Greases
Standard Test Method for Measuring Apparent Viscosity of Lubricating Greases
SCOPE
1.1 This test method covers measurement, in poises, of the apparent viscosity of lubricating greases in the temperature range from -53 to 37.8°C (-65 to 100°F). Measurements are limited to the range from 25 to 100000 P at 0.1 s and 1 to 100 P at 15000 s . Note 1-At very low temperatures the shear rate range may be reduced because of the great force required to force grease through the smaller capillaries. Precision has not been established below 10 s .
1.2 This standard uses inch-pound units as well as SI (acceptable metric) units. The values stated first are to be regarded as standard. The values given in parentheses are for information only. The capillary dimensions in SI units in Fig. A2.1 and A2.2 are standard.
1.3 This standard does not purport to address all of the safety problems, 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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An American National Standard
Designation:D1092–99
Standard Test Method for
Measuring Apparent Viscosity of Lubricating Greases
This standard is issued under the fixed designation D1092; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This test method has been adopted for use by government agencies to replace Method 306 of Federal Test Method Standard No. 791b.
1. Scope 3.1.1 apparent viscosity, n—of a lubricating grease is the
ratio of shear stress to shear rate calculated from Poiseuille’s
1.1 This test method covers measurement, in poises, of the
equation, and is measured in poises (see 10.1).
apparent viscosity of lubricating greases in the temperature
3.1.2 capillary, n—For the purpose of this method, a capil-
range from−54 to 38°C (−65 to 100°F). Measurements are
−1
lary is any right cylindrical tube having a length to diameter
limited to the range from 25 to 100000 P at 0.1 s and1to
−1
ratio of 40 to 1.
100 P at 15000 s .
3.1.3 shear rate, n—the rate at which a series of adjacent
NOTE 1—Atverylowtemperaturestheshearraterangemaybereduced
layers of grease move with respect to each other; proportional
because of the great force required to force grease through the smaller
to the linear velocity of flow divided by the capillary radius,
−1
capillaries. Precision has not been established below 10 s .
and is thus expressed as reciprocal seconds.
1.2 This standard uses inch-pound units as well as SI
(acceptable metric) units. The values stated first are to be 4. Summary of Test Method
regarded as standard. The values given in parentheses are for
4.1 The sample is forced through a capillary by means of a
information only. The capillary dimensions in SI units in Fig.
floating piston actuated by the hydraulic system. From the
A1.1 and Fig. A1.2 are standard.
predeterminedflowrateandtheforcedevelopedinthesystem,
1.3 This standard does not purport to address all of the
the apparent viscosity is calculated by means of Poiseuille’s
safety concerns, if any, associated with its use. It is the
equation.Aseriesofeightcapillariesandtwopumpspeedsare
responsibility of the user of this standard to establish appro-
used to determine the apparent viscosity at sixteen shear rates.
priate safety and health practices and determine the applica-
Theresultsareexpressedasalog-logplotofapparentviscosity
bility of regulatory limitations prior to use.
versus shear rate.
2. Referenced Documents
5. Significance and Use
2.1 ASTM Standards:
5.1 Apparent viscosity versus shear rate information can be
D88 Test Method for Saybolt Viscosity
useful in predicting pressure drops in grease distribution
D217 Test Methods for Cone Penetration of Lubricating
systems under steady-state flow conditions at constant tem-
Grease
perature.
D3244 Practice for Utilization of Test Data to Determine
6. Apparatus
Conformance with Specifications
6.1 The assembled pressure viscometer consists of four
3. Terminology
major divisions, the power system, the hydraulic system, the
3.1 Definitions:
grease system (described in the annex and shown in Fig. 1),
andabathofoptionaldesign.Fig.2isaphotographofthefirst
three divisions as commonly used at room temperature. This
form of the apparatus can be used with a cylindrical insulated
This test method is under the jurisdiction of ASTM Committee D-2 on
tank178mm(7in.)indiameterand508mm(20in.)deep.The
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
bathmediummaybekeroseneoralcoholcooledmanuallywith
D02.G on Lubricating Grease.
Current edition approved Nov. 10, 1999. Published November 1999. Originally
dry ice. Alternatively the grease system, the grease and
published as D 1092–50T. Last previous edition D 1092–93.
hydraulic system, or all three major divisions can be built into
Annual Book of ASTM Standards, Vol 04.04.
any liquid or air bath that will cover the temperature range and
Annual Book of ASTM Standards, Vol 05.01.
Annual Book of ASTM Standards, Vol 05.02. maintain the grease at test temperature 60.25° C (60.5°F).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D1092–99
FIG. 1 Schematic Drawing of Apparatus
7.2 Generally no special preparation of the sample is nec-
essary.
NOTE 3—The apparatus works the samples to some extent as they pass
through the capillary. Somewhat better precision is obtained if they are
previously worked as described inTest Methods D217.Working of some
greases may cause aeration.
NOTE 4—Itisdesirabletofiltersomegreasesthrougha60-meshscreen
to prevent plugging the No. 8 capillary.
8. Calibration and Standardization
8.1 To calibrate the hydraulic system, remove the grease
cylinder and replace it with a needle valve. Select a hydraulic
oil of about 2000 cSt (2000 mm /s) viscosity at the test
temperature.Fillthesystemwithhydraulicoilandcirculatethe
oil until it is free of air bubbles. At atmospheric pressure,
quickly place a 60-mL Saybolt receiving flask (Test Method
D88),undertheoutletandstartatimer.Determinethedelivery
timefor60mLandcalculatetheflowrateincubiccentimetres
per second assuming 1 mL equal to 1 cm . Repeat this
observation at 500, 1000, 1500 psi (3.45, 6.89, 10.4 MPa) and
at sufficient pressures above 1500 psi to develop a calibration
curve of the type as shown in Fig. 3. The developed curve of
the type is used to correct flow rates when grease is dispensed.
Repeat the calibration at intervals to determine if wear is
changing the pump flow.
8.2 An alternative procedure for the calibration of the
FIG. 2 Photograph of Apparatus
hydraulic system is the measurement of the rate of flow of the
testgrease.Tocoverthedesiredrangeofshearrates,flowrates
7. Sampling
over an approximate range of pressure are determined. Any
7.1 A single filling of the grease cylinder requires about
suitable means of measuring the rate of grease flow may be
0.223 kg ( ⁄2 lb) of grease which is the minimum size sample.
used.
NOTE 2—It is possible for an experienced operator to complete the 16
9. Procedure
single determinations with a single filling. However, some samples reach
9.1 Charge the sample so as to reduce inclusion of air to a
the equilibrium pressure slowly, making it advisable to have a sample of
several pounds available. minimum. Soft greases may be poured into the cylinder or
D1092–99
where:
p = pressure dynes/cm ,
L = capillary length, cm,
P = observed gage pressure, psi (multiply by 68944 to
convert to dynes per square centimetre),
R = radius of capillary used, cm, and
v/t = flow rate, cm /s.
10.2 Calculations may be reduced to a minimum by prepar-
ingatableof16constants,oneforeachcapillaryandshearrate
(Table 1). For example, viscosity with No. 1 capillary and the
40-tooth gear is given as follows:
h5 P~observed!68944pR /~8Lv/t! or PK (3)
~1–40!
FIG. 3 A Typical Pump Calibration Curve
where:
drawn up by vacuum; heavy samples must be hand packed. 4
K 568944 p R /~8Lv/t (4)
~1240!
When filling the cylinder by vacuum, remove the capillary end
10.3 Also calculate the shear rates as follows:
capandplacethepistonflushwiththeopenendandtheninsert
into the sample. Apply vacuum to the opposite end of the
S 5 ~4v/t!/pR (5)
cylinder until the cylinder is fully charged with grease. This
Correct the flow rate to correspond to the observed pressure
must be facilitated by tapping with a wooden block. Replace
by reference to Fig. 3. Calculate 16 shear rates for the eight
the capillary end cap and fill the upper end of the cylinder
capillaries and two flow rates. This calculation need not be
above the piston with hydraulic oil.
repeated for each run since it will remain constant until
9.2 Fill the entire hydraulic system with hydraulic oil.
recalibration of the pump indicates a revision.
Disconnect, invert and fill the gage and gage connections with
10.4 Plot a curve of apparent viscosity versus shear rate on
oil.Withtheentirehydraulicsystemconnectedandcompletely
log-log paper, as shown in Fig. 4.
filled with oil, adjust the temperature of the sample to the test
temperature 60.25°C (60.5°F) as determined by a thermo-
NOTE 6—Shear stresses also can be calculated by multiplying apparent
coupleinsertedinthecapillaryendcap.Operatethepumpuntil
viscosities by their corresponding shear rates. For solving various prob-
oil flows from the gage connection on the viscometer before lems involving the steady flow of greases, shear stress-shear rate relation-
shipsmaybeplottedonappropriatecharts.Instructionsontheuseofthese
reconnecting the gage. With the entire viscometer assembled,
charts are given in the article by Rein and McGahey, “Predicting Grease
circulate hydraulic oil with the return valve open until all trace
Flow in Large Pipes,” NLGI Spokesman, April 1965.
of air is eliminated.
9.2.1 The time to attain test temperature varies with the
11. Precision and Bias
bath. At −54°C (−65°F) the grease in an unstirred liquid bath
11.1 Due to the nature of the results, the precision of this
should be ready to test in 2 h. Air baths can take as long as 8
test method was not obtained according to RR:D02-1007
h. An ASTM Thermometer 74F in the bath serves as a
“Manual on Determining Precision Data for ASTM Methods
convenient secondary means of measuring the temperature at
on Petroleum Products and Lubricants.” The precision of this
–54°C (−65°F). In an air bath the thermometer must be within
test method as determined by statistical examination of inter-
25.4 mm of the capillary.
laboratory results is as follows:
9.3 With No. 1 capillary in place and the 40-tooth gear
11.2 The data in 11.2.1 and 11.2.2 should be used for
connected, operate the pump with the return valve closed until
judging the acceptability of results (95% confidence) accord-
equilibrium pressure is obtained. Record the pressure. Change
ing to the concept of precision as given in Practice D3244.
to the 64-tooth gear and again establish equilibrium. Record
and relieve the pressure. Replace the No. 1 capillary with 11.2.1 Repeatability—The difference between two test re-
sults, obtained by the same operator with the same apparatus
subsequent ones and repeat these operations until tests have
been run with all capillaries at both flow rates. With some soft under constant operating conditions on identical test material,
would in the long run, in the normal and correct operation of
or hard greases, it cannot be practical to use all of the
capillaries. thetestmethod,exceedthevaluesgiveninTable2onlyinone
case in twenty.
NOTE 5—It may be necessary to refill the cylinder with fresh grease
11.2.2 Reproducibility—The difference between two single
when all 16 determinations are to be made.
and independent results obtained by different operators work-
10. Calculation
ing in different laboratories on identical test material would, in
10.1 Calculate apparent viscosity of the grease as follows:
the long run, in the normal and correct operation of the test
method, exceed the values given inTable 2 only in one case in
h~apparentviscosity! 5 F/S (1)
twenty.
where Fistheshearstress,and Sistheshearrate.Therefore:
ppR /2pRL
4 4
h5 F/S 5 5 ppR /~8Lv/t! 5 P68944pR /~8Lv/t!
~4v/t!/pR
(2) Annual Book of ASTM Standards, Vol 05.03.
D1092–99
TABLE 1 Suggested Data Sheet for Recording Test Results (With Illustrative Test Values)
Sample . . No. 2 Grease Temperature . . 25°C
..
Date. . Nov. 1, 1948 Operator. . R.S.
A B A C
12 3 4 5 6 7
Apparent
Observed Shear Rate, Shear Stress,
K = 68944 Viscosity,
−1
Capillary Gear Pressure, S,s = dynes per sq
pR /(8Lv/t) n poises,
P, psi (4v/t)/pR cm = n 3 S
= P 3 K
1 40 25.5 28.10 716 15 10 740
2 40 38.3 6.83 267 61 16 300
3 40 48.8 3.61 176 120 21 100
4 40 63.5 1.90 120 230 27 800
5 40 96.5 0.89 86 480 41 300
6 40 125 0.58 72.6 755 54 800
7 40 286 0.139 39.8 3 140 125 000
8 40 546 0.0464 25.3 9 320 235 500
1 64 29.5 17.60 520 24 12 470
2 64 45.8 4.27 195 98 19 100
3 64 60 2.26 135.5 195 26 400
4 64 82.3 1.19 97.9 370 36 250
5 64 130 0.556 72.4 770 55 800
6 64 165 0.363 59.9 1 220 73 200
7 64 384 0.087 33.4 5 020 167 500
8 64 720 0.029 20.9 14 900 311 000
A
Values in this column are predetermined.
B
Column 3 times Column 4.
C
Column 5 times Column 6.
FIG. 4 Typical Chart for Apparent Viscosity versus Shear Rate
11.2.3 Reproducibility of the curve drawing operation var- upon curve values of apparent viscosity at the six shear rates.
ies from 5 to 8 % for the above samples. These data are based A separate curve was drawn for each run.
D1092–99
TABLE 2 Precision
11.3 Bias—Since there is no accepted reference material
Repeat- Repro- suitable for determining the bias for the procedure in Test
Temp,
ability ducibility
Sample Method D1092, bias has not yet been determined.
°F
% of mean
11.4 There is no research report on Test Method D1092
Smooth, NLGI 2, Diester Oil −65 7 12 because this test method was developed before research report
Smooth, NLGI 2, SAE 20 Oil 77 6 19
guidelines were instituted, and are no longer available.
Fibrous, NLGI 1, SAE 20 Oil 77 6 23
Viscous, NLGI 1, SAE 90 Oil 77 7 30
12. Keywords
12.1 apparent viscosity; capillary; lubricating grease; shear
rate; viscosity
ANNEX
(Mandatory Information)
A1. APPARATUS FOR GREASE SYSTEM
A1.1 Apparatus—Assembled pressure viscometer appara- A1.5 Grease Cylinder Assembly, consisting of cylinder,
tus consists of four major parts: the power system, the
floating piston, and caps constructed to conform to the toler-
hydraulicsystem,thegreasesystemasshowninFig.1andFig.
ances shown in Fig. A1.1 with the piston moving the entire
2 and constructed as described in A1.2-A1.6, and a bath of
length of the cylinder without appreciable friction. The cylin-
optional design.
der shall be constructed to withstand a working pressure of
4000 psi (27.5 MPa). The exterior features and method of
A1.2 Power System, consisting of a ⁄3-hp, 1750-rpm induc-
fastening may be modified.
tionmotorcoupledtoa200to1speedreducer.Interchangeable
40 and 64-tooth gears are used to drive the hydraulic pump.
A1.6 Capillaries—Capillaries, eight of stainless steel and
conforming to dimensions shown in Fig.A1.2, shall comprise
A1.3 Hydraulic System, consisting of a gear pump fitted
a set. Critical dimensions are the interior radius and length. It
with saddle
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