MIL-PRF-27601C
3. REQUIREMENTS
3.1 Qualification. The hydraulic fluids furnished under this specification shall be products that are authorized by
the qualifying activity for listing on the applicable qualified products list before contract award (see 4.2 and 6.3).
3.2 Materials. The materials used in formulating this hydraulic fluid shall consist of synthetic hydrocarbon base
and shall contain additives as specified in 3.2.1. A 4 cSt hydrogenated polyalphaolefin based fluid may be used but
is not mandatory. The hydraulic fluid shall contain no admixture of resins, soaps, gums, fatty oils, or oxidized
hydrocarbons. The contractor shall certify that no carcinogenic constituents are present as defined under OSHA 29
CFR 1910.1200. Certification to this effect shall be made available to the contracting officer or the contracting
officer's representative.
3.2.1 Additives. There shall be no restriction on the types of materials used as additives in the fluid except for
those listed and those imposed by technical requirements of this specification. No pour point depressant materials
or viscosity index improvers may be used.
3.2.1.1 Oxidation inhibitors. Oxidation inhibitors of the phenolic type shall not exceed a concentration of 1.5
percent by weight.
3.2.1.2 Anti-wear agent. Anti-wear agents, such as tricresyl phosphate (TCP) conforming to TT-T-656, shall be
blended in sufficient quantity, not to exceed 2.0 weight percent, to permit the finished oil to meet the lubricity
requirements specified in 3.3.9. If TCP is used, the finished fluid shall contain less than 0.02 weight percent of the
ortho-isomer.
3.3 Finished fluid. The properties of the finished fluid shall be as specified in table I and 3.3.1 through 3.3.12
TABLE I. Properties of finished fluid.
Unit
Requirement
Property
Kinematic viscosity
-40°C, maximum
3000
cSt
40°C, minimum
15.0
cSt
100°C, minimum
3.5
cSt
Pour point, maximum
-54
°C
Flash point, minimum
200
°C
Fire point, minimum
230
°C
Neutralization number, maximum
0.20
mg KOH/gm
Bulk modulus (isothermal secant) 0 to
4
6
6.9 x 10 kPa at 40°C, min
kPa
1.379 x 10
(10,000 psi at 100°F, min)
psi
(200,000)
3.3.1 Specific gravity. The specific gravity of the hydraulic fluid shall be determined but shall not be limiting.
Samples of the hydraulic fluid submitted for quality conformance tests shall not vary more than ± 0.008 at
15°C/15°C from the sample originally approved for qualification.
3.3.2 Corrosiveness and oxidation stability. When tested as specified in 4.4.2, the change in weight of steel,
aluminum alloy, magnesium alloy and cadmium-plated steel subjected to the action of the hydraulic fluid shall not
2
be greater than ± 0.2 milligrams per square centimeter (mg/cm ) of surface. The change in weight of copper under
2
the same conditions shall be no greater than ± 0.6 mg/cm of surface. There shall be no pitting, etching, nor
visible corrosion on the surface of the metals when viewed under magnification of 20 diameters. Any corrosion
4