IMPROVEMENT OF SERVICE PROPERTIES OF HYDRAULIC OILS UDC 665.767:621.22.004
A~ A. Bratkov, A. P. Firsov, and Ya. A. Mymrin
Hydraulic oil quality is a major factor in obtaining reliable operation of hydraulic systems in land and marine transportation equipment. The hydraulic oils currently being used, AMG-10, AU, RMTs, LZ-MG-2, and RM, do not have the protective properties that are needed, since they do not contain rust or corrosion inhibitors. Oils that were used previously, MGE-10A (TU 38-i-307--59), AUP (TU 38~001234--75), and MGE-3A (TU 38-101-172--71), had good protective properties as a result of the use of the additive MNI-5, but they had one serious shortcoming. As shown by experience in operation with these oils and storage in various climatic zones, part of the MNI-5 additive would precipitate out of the oil at subfreezing temperatures. For this reason, there were instances of failures of hydraulic systems in land vehicles. IR spectroscopic studies of the precipitate showed that it consisted mainly of high-molecular-weight hydroxy-acids (the active part of the MNI-5 additive) and paraffinic hydrocarbons~ When the requirements on oil quality were tightened up with respect to the index "Stability of solution of additives in oil," both the consumers and the manufacturers of the hydraulic oils began to reject large amounts of the MGE-10A oil. In order to eliminate the precipitation of sludge in hydraulic oils at subfreezing temperatures, we have investigated new formulations of protective additives, with the aim of replacing the MNI-5 additive. Examination of a large number of compounds that have been used in recent years as protective additives has shown that most of them are quite unsuitable for use in hydraulic oils. In order to protect ferrous and nonferrous metals simultaneously from electrochemical corrosion, at least two additives with different types of action must be incorporated in the hydraulic oil. The most effective additives were found to he KAP-25 (a mixture of alkenylsuccinic acids) and VSP (aderivative of succinimide). Tests on the ability of these additives to displace a corrosive electrolyte from metal surfaces showed (Table i) that the KAP-25 has a high level of water-displacing capability, giving reliable protection of the surface. The VSP additive does not protect steel under these conditions. The molecule of alkenylsuccinic acid contains highly polar COOH groups and a nonpolar hydrocarbon radical, giving the molecule a high affinity for metal and a unique capability for displacing water and corrosive electrolytes from the surface being protected. If the additive content is adequate, the alkenylsuccinic acid molecules, being adsorbed on the cathodic sections, form an oriented monomolecular layer and, as a consequence, a strong chemisorbed film.
TABLE i "Content of additive in o i l base stock, wt. %
VSP 0 028 0,16 0,24 0,32 0,4
KAP-25 0,4 0,32 0,24 0,16 0,08. 0
Area of corydon
Rating
damage, % * 0 0 O,l 0,3 I0--15 9
09
09 l 4 8
lO
*Test on St3 low-carbon steel with hydrobromic acid (GOST 9.054--75, Method 5).
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. Ii, pp. 35-37, November, 1981.
0009-3092/81/1112-0639507.50
9 1982 Plenum Publishing Corporation
639
0
Quality index
~
Immersion method with ~o sea water steel oppe~ ras$ Foaming Foam volume, cm s Foam collapse time, see
brass
Oxidation stability (30 h, 120~ oxygen 12 liters/h) Appearance of oil afl:e~ oxidation Change. in acid numbe~, mg KOH/g 2Viscoai~, m m / s e c at 50uC at -50~ Presence of sludge Corrosion of specimens, g / m z . steel (St3) copper fiVl-l) low-stability temperattze (-60~ 100 h, in cycles) , :Appearance . Viscosity, mm2/sec at 50~ at-50~ at 20~ Acid number, mg KOH/g . Colroslon ratings InstG,~ cabifiet ~opper rass In U-10 cabinet steel copper
TABLE 2
0,0 0,0
o:o 0,0 0,0
0,45 1,0 0,5 0,0 1,5 1,0 0,5
0,20 1,5 1~0 0,5 2,0' 2,5 1,0
40,0 25
50,4 25
0~
35,0 '~20 40,0 20
"
O,O 0,0 0,0 O,O O,O 0,0 ,:
0,0
3,0 0,0
0,0 0,0 0,0
948,5 ,0,73
No change
0,0 0,0
None
12,3
0,5 '
7,0 9 O,O 0,0
0,0 0,3 1,0
46,5 0,3
m
@
Sli~htiy daikened --0,09
1,5 5,0 6,0
0,0
10,3 1260
No change turbid with sediment
10,2 1420
Turbid wit: sediment
0,0
Present
12,0
11,2 1470 None
10,2 1520 None
+0,12
Slightly . No change darl~ened --0,02 -~0,03
40,0 21
6,0
42,0 21
1,5 l,O' 0,0
1,0 0,5 0,0
0,0 0,5 0,5
'
0,52
3,70 220
No change
4,0
i,5
1,5 1,0 O,O
1,0 0,0
2,'0
0,18
3,18 280
Turbid
0,0 0,0
0,0 0,0
4,2 299 None
3,4. 325 None
-~0,02
Sli~htiv darRen4d --0,09
MGE-4A
No change
~xperimenta] MGE-3A
AUP
No change
. MGE-10A regular expcrimcnta I .regular
f
o,5 ~ ~ o,3
0
.--5
,/
j
~E o,7 .1_~//
i
j
0
10
15
5
>6
j j,. ZO Z5 ~0 J5 Oxidation time, h
4O ~5
5O
55
60
Fig. i. Kinetics of oxidation of polymer-compound oil base stock MGE-10A at 150~ with antioxidant additives: i) no additive; 2) with KAP-25 and VSP; 3) with Ionol; 4) with phenyl-~-naphthylamine; 5) with Ionol and phenyl-~-naphthylamine; 6) MGE-10A oil.* *The MGE-10A designation, used elsewhere in this article to denote an obsolete product, apparently refers here to the new formulation with the KAP-25 and VSP additives plUs an antioxidant, presumably Ionol -- Translator.
As a result of an investigation of the intermolecular interaction of the additives KAP-25 and VSP by the isomolar series method, it was established that hydrogen bonds are formed between the additive molecules, involving the NH group of the VSP and the C---O groups of the KAP-25. On the basis of these studies, we selected the optimal additive package, consisting of a mixture of KAP-25 (TU 6-114-93--75) and VSP (TU 38-40183-74) in a 2.5/1 ratio. Oxidation tests on hydraulic oils with the KAP-25 and VSP additives showed that when an antioxidant of the lonol type was present, these additives gave a considerable increase in the oil oxidation stability; i.e., in this particular instance, the protective and antioxidant additives manifested as synergistic effect (Fig. i). On the basis of these studies to have been developed for the hydraulic and MGE-4A (TU 38-101573-75) with the Test results on these oils, using the are presented in Table 2.
select protective and antioxidant additives, formulations oils MGE-10A (TU 38-101572--75), AUP (TU 38-101719-78), new additive package and with improved service properties. set of qualification test methods for working fluids,
It can be seen that on the basis of the properties investigated, the new hydraulic 0ils are comparable to the oils with the MNI-5 additive, and with respect to the stability of the additive solution at subfreezing temperature s and with respect to the protective properties (particularly in the tests with 5% sea water), the new oils are considerably better. Teststand evaluations and full-scale plant tests on the oils with the new additive package have shown that they give reliable operation of the stands and hydraulic systems under the required conditions, throughout the entire test period. On the basis of the favorable results obtained in laboratory, test-stand, and full-scale plant evaluations, the hydraulic oils MGE-IOA, AUP, and MGE-4A with the new additivepackage have been approved for use in the appropriate equipmen t to replace the corresponding oils with the MNI-5 additive. The new oils are comparable to oils of the same grade produced in other countries, and are better in protective properties. The MGE-10A and MGE-4A are consolidations of grades; the MGE-4A can replace the oils LZ-MG-2 and RM, and the MGE'IOA has already replaced six grades of hydraulic oils used previously in land and marine hydraulic systems. The total economic advantage from the introduction of the hydraulic 0ils MGE-IOA, AUP, and MGE-4A with the new additive package was more than 7 million rubles in the period of the 10th Five-Year Plan.
641
