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MIL-PRF-6083 Hydraulic Fluid, Petroleum Base, For Preservation And OperationThis specification describes the characteristics and provides the requirements for one grade of petroleum base hydraulic fluid for use in the -54??C to +135??C temperature range \(see 6.1\). This fluid is rust inhibited and used both as a preservative for hydraulic systems and components as well as being an operational fluid. This hydraulic fluid will not be used for aircraft systems, aircraft ground support equipment, or the preservation of aircraft components. The hydraulic fluid is identified by Military Symbol OHT and NATO Symbol C-635.

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MIL-PRF-6083G

TABLE I. Hydraulic Fluid Properties and Test Methods.

Test Method

FED-

Property

Test Limits

ASTM

STD-

Method

791

Acid Number, mgKOH/g (max)

0.20

D664

API Gravity @ 15.6C/15.6C

See 3.4.1

D1298

Color, ASTM Color Scale (max)

See 3.4.2

D1500

Compatibility

See 3.4.3

See 4.5.1

Copper Strip Corrosion (72 hours at 100 � 1C), ASTM Standard

D130

(max)

See 3.4.4

D1748

Corrosion Protection (Humidity Cabinet)

Sand-blasted (3 panels) and Polished Panels (3 panels)

(100 � 1 hours at 48.9 � 1.1C air temperature)

Corrosiveness (Bimetallic Couple)

See 3.4.5

D6547

Corrosiveness and Oxidation Stability

(168 hrs at 121 � 0.5�C)

Metal specimen weight change, mg/cm2 (max)(1)

Cadmium Anod(2)

�0.2

D4636

�0.2

Proc 2

Steel Grade 1010

�0.2

Aluminum Alloy

�0.2

Magnesium

Copper(3)

�0.6

-5 to +20

Percent change in viscosity at 40�C

0.20

Change in acid number (max)

None

Separation of insoluble materials or gumming of the fluid

Evaporation Loss (22 hours at 100 �0.5C), % by weight (max)

D972

Flash Point, C (min)

D93

Foaming Characteristics

Foaming Tendency

Foam volume (mL) at end of 5 minute blowing period (max)

At 24�C

At 94�C

At 24�C after test at 94�C

D892

Foam Stability

Foam volume (mL) at end of 10 minute setting period (max)

At 24�C

At 94�C

At 24�C after test at 94�C

Isothermal secant bulk modulus @ 40C and 27.6 MPa (4000 psig),

1379

D6793

(200,000)

MPa (psi) (minimum)

Low Temperature Stability (-54 � 1�C for 72 hrs)

See 3.4.6

3458

Particulate Contamination(4)

See 3.4.7

3012(5)

D4898

Particle Count

See Table II

Gravimetric method, mg/100 mL (max)

0.5

Pour Point (�C) max

-59

D97

Rubber Swell, Standard Synthetic Rubber(6), NBR-L, %

19.0 to 31.0

D4289

(168 � 0.5 hours at 70 � 2.5C)