EVALUATION OF ANTIWEAR PROPERTIES OF HYDRAULIC FLUIDS IN PUMP O. P. Lapotko, V. M. Shkol'nikov, Sh. K. Bogdanov, N. G. Zagorodnii, and V. V. Arsanov
UDC 621.892.86.001.4
The four-ball friction tester [i] is the apparatus most generally used to evaluate the antiwear properties of hydraulic fluids. However, data obtained in laboratory or physicochemical tests may deviate considerably from data obtained in actual servie, and hence can be ~ used only for preliminary screening of oils. Today, more and more use is being made of qualification test methods; this is one of the most promising trends in chen~mtology. The distinctive features of such tests are, first, the possibility of a more accurate and thorough evaluation of the service properties of petroleum products than can be obtained by physicochemical methods, and, second and most important, the possibility of evaluating these properties much more rapidly and economically (by orders of magnitude) than can be done by the use of long-term service tests. Among the qualification test methods for the antiwear properties of hydraulic oils, the greatest recognition has been given to the test method in a Vickers V-I04C plate pump (ASTM D 2882-74T Test Method Standard, USA). This method is also used in Western Europe, and is covered in Great Britain by the standard BS-5096 and in West Germany by the proposed standard DIN-51389 [5]. The MP-I qualification test method that has been proposed for use in the USSR for approval of hydraulic fluids is free of certain shortcomings of the test methods using the V-104C pump [5], such as the extended test time and the large volume of fluid required for test. Comparative characteristics of the test methods are listed in Table I [3, 5]. The antiwear properties of hydraulic fluids are rated quantitatively by the amount of wear (either weight loss or linear wear) of the elements of the rubbing pairs in the plate pump, under specific test conditions, The test section of the MP-I unit (Fig. i) consists of the plate pump 2 driven by an electric motor, filter 6, heat exchanger 5, hydraulic accumulator 7, and adjustable throttle i. The volume of fluid required for test is kept down by the system of internal passages in
TABLE I
Parameter
=%
MP-1
e~
V-104C Pump type 14 Pressure, MPa Test fluid , ' volume, liters Test time, h
100
68
68
0,7
250
25O
50 (10")
$tator and plates
Parts inspected Accuracy of meast~ernent, mg
GI2-31A 7
•
-+-I .I +1
Ptates _0,1
*When surface activation method is used.
Belorussian Polytechnic Institute. Masel, No. 4, pp. 51-53, April, 1981.
Translated from Khimiya i Teckhnologiya Topliv i
0009-3092/81/0304-0231507.50
9 1981 Plenum Publishing Corporation
231
3 z
Test section of MP-I unit: I) a d throttle; 2) plate pump; 3) plate; 4) passage; 5) heat exchanger; 6) filter with replaceable elements; 7) hydraulic accumulator; 8) central pipe; 9) fitting for cooling fluid; I0) suction passages. Fig. I. justable
TABLE 2 4'
ITems in Working flu/d (oil)
T e ~ m MP, i :
C~sh~q: scar
plate wear, mg
diameter, mm 1-20A 1-45A Tp-22 AMG-10 Hydzaulic fluids A R M-10V MGE-32V MG-30 Hy&aulic fluids Unios-58 IGSp-18
testl
[ test2 i
0,92 0,84 0,76 1,18
43,8 11,8 28,4 53,9
61,8 16,3 30,4 68,4
0,57 0,62 0,46 0,42 0,96
13,5 17,6 6,2 12,1 18,9
19,0 9,6 14,2
36,6 13,9
121,9 18,7
t~s on trac~
withOGP
9,30 . 0,45
TABLE 3 oGP
t~ ~
evaluations 9
s=vice
]. I
. ~
.
"
Cycle2
t oo, 0 330 647 I000 1210 1420 1570 1800 2000
.
+o+.o
5,9 6,0 6,4 8,1 7,6 8,2 9,1 8,7 I0, I
0 24 400 526 727
960
6,2 8,8 10,3 8, I 11,2 12,8
6,2 8,1 13,2 9,5 8,8
the pump body and cover [4]. Since the test elements used to rate the antiwear properties of fluids are the plates 3 of the pump, high oil pressure is maintained only in the pump body. The needlevalve throttle 1 is mounted in the pressure cavity of the pump. After passing through the throttle, the fluid passes through the passage 4 and tube coil of the heat exchanger and then enters the chamber with filter elements 6. The suction line consists of
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the central pipe 8 and the passages i0 in the pump cover. Leakage and temperature fluctuations of the fluid in the closed hydraulic system are compensated by the hydraulic accumulator, made in the form of a subpiston chamber, piston, and load. In the operation of the MP-I unit, the fluid pressure can be adjusted up to I0 MPa, the temperature from 30 to 95~ and the fineness of filtration to 16, 40, and 80 ~m [3]. The length of the test period for a single sample of fluid is determined by the length of operating time required to obtain a statistically reliable value for the wear of the rubbing-pair elements of the pump. There are two possible ways in Which the test time can be reduced -- by increasing the wear rate by operating under severe conditions, and by the use of highly accurate methods for rating the wear [5]. In tests on hydraulic fluids in the V!04C plate pump, the unit operates at twice the rated pressure, so that the antiwear properties of the oils can be evaluated in 100-250 h. In the M P~I unit, when we adopt as a criterion for rating the antiwear properties of fluids the weight loss of plates that have previously been run in, the weight loss being determined to within • 0.I mg, reliable results are obtained in 50 h of operation. Before a test on a new type of fluid, the unit must be flushed with the test oil; then the weight of the plate set is determined, they are installed in a predetermined position on the pump rotor, and new filter elements are installed. It is recommended that a new type of fluid should be tested at least twice. The test in which a lower amount of plate wear is obtained is considered to be the more reliable. From the results of five parallel tests, we were able to define the following metrological characteristics of the MP-I method. With an average weight loss of the plates (criterion of antiwear properties of the fluid) of 14.4 mg, the standard deviation was • 2.65 mg and the coefficient of variation 0.18. In order to compare the ratings obtained in the basis of physicoehemical methods and qualification test methods, the antiwear properties of a number of working fluids for hydraulic drives were investigated in a ChShM-I four-ball friction tester (GOST 9490-75) and in the MP-I unit (Table 2). The operating conditions for the ChShM-I friction tester were: axial load 200 N, oil temperature 20 • 2~ test time 4 h. Conditions for the Mp-i unit were: pressure 7 • 0.i MPa, oil temperature 52 • 2~ fineness of filtration 40 Bm. The coefficient of correlation between the test results in the ChShM-I friction tester and the MP-I unit (Test i) is 0.56, indicating a low degree of comparability of the physicochemical and qualification test methods. The results obtained on the antiwear evaluations in the plate pump should be considered as the more reliable [2, 3, 5]. By the use of surface activation in evaluating the linear wear of the upper edge of preirradiated plates of the MP-1 unit, the accuracy in evaluating the criterion of fluid antiwear properties could be improved to • 0.i Bm, and the test time could be reduced to i0 h. The plates were activated in a series U-20 cyclotron in a stream of deuterons with an energy of 12.5 MeV, in vacuum. The linear wear of the plates was rated without dismantling the MPi unit, by means of a spectrometric device [3]. The short length of the fluid test period in the MP-I unit and the small volume of oil required for test are factors that make it possible to investigate the change in antiwear properties of M-10V oil, which is used as the working fluid in the volumetric hydraulic transmission of the MTZ-80B Belarus' tractor, during the course of test-stand and service evaluations. Samples of the fluid were drawn from the operating hydraulic transmission at specified intervals of time during service, and these samples were tested at a pressure of 8 • 0.I MPa, temperature 70 • 3~ and test time i0 h. These test results (Table 3) provided a basis for defining the rate of deteioration of M-10V oil quality and the service life of this oil. The qualification test method for rating the antiwear properties of hydraulic fluids by tests in a plate pump can be used in developing optimal requirements for oil quality, classification of oils, and studies of the processes of change in hydraulic fluid properties in actual hydraulic systems in machinery.
233
LITERATURE CITED i. 2. 3. 4. 5.
234
GOST [All-Union State Standard] 9490-75, Materials, Lubricant, Liquids and GreasesMethod for Determination of Lubricating Properties in Four-Ball Tester [in Russian]. K.K. Papok, Chemmotology of Fuels and Lubricants [in Russian], Voenizdat, Moscow (1980). O.P. Lapotko and V. V. Arsenov, Procedure for Rating Antiwear Properties of Working Fluids of Volumetric Hydraulic Drives of Machinery [in Russian], Izd. Akad. Nauk BSSR, Minsk (1978). USSR Inventor's Certificate 567,118. O. Langosch, Oelhydraul. Pneumat., 1__6, No. 12, 498-501 (1972).
