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This hydraulic fluid is blended with highly refined mineral based oils and modern additive technology to provide protection against rust, wear, demulsibility, and to afford greatly improved viscosity - temperature characteristics as well as enhanced oxidation – corrosion resistance.

This specification covers the requirements for one type of synthetic
hydrocarbon base hydraulic fluid.
The type of hydraulic fluid is as follows:
Type I - Undyed and Identified by Military Symbol FRH and NATO Code No. H-544.

MIL-PRF-46170 Intended use
The hydraulic fluid covered by this specification is intended for use in recoil mechanisms and hydraulic systems of military ground vehicles and equipment.
If used in other mechanisms or systems, a study should be made to determine its applicability for such usage, with particular attention given to operation at high and low temperatures and the topic of elastomer compatibility. The hydraulic fluid is rust inhibited and may be used as a preservative medium for hydraulic systems and components.
The hydraulic fluid has a wide range of operating temperatures and is thermally stable, corrosion inhibited, and fire resistant. The combination of all of these quantities is not found in commercial hydraulic fluids. This fluid is adopted for military use by NATO countries. (NOTE: TYPE II of the previous revision “C©?
is no longer available.)

Fluid handling
Owing to the difficulty of preventing contamination after the opening of a container, it is recommended that the hydraulic fluid be purchased in 1-quart and 1-gallon containers by all users. If the fluid is dispensed from larger containers, strict procedures must be employed to exclude and remove moisture, solid particles or other contaminants from the fluid.

Recommended corrosion inhibitor
It has been found that 1.75 ± 0.25% barium dinony1naphthalene sulfonate provides the required degree of rust protection. The diluent of the rust inhibitor should be the synthetic hydrocarbon base stock.

Handling and safety precautions
CAUTION: Personnel handling the product shall wear appropriate impervious clothing to prevent repeated or prolonged skin contact.
The local environmental officials will relate health and safety implications as well as to prescribe precise application of protective clothing. If skin or clothing becomes moistened with the product, personnel should promptly wash with soap or mild detergent and water. Respirators are not required unless there is a potential for inhalation exposure to misting. Personnel should wear protective clothing when using the product and when cleaning up spills.

Background (safety)
The product may contain 0.5% tricresyl phosphate, of which not more than 0.01% may be present as the ortho isomer. If this ortho isomer of tricresyl phosphate is absorbed through the skin or taken internally, it may cause paralysis. The corrosion
inhibitor contains barium. The accumulated waste liquids will have the exterior of the outer pack marked as containing barium and tricresyl phosphate to assist disposal facilities to manage the product according to regulations promulgated by the US Environmental Protection Agency under Public Law 94-580, Resource Conservation and Recovery Act of 1976.

Storage conditions
Prior to use of product in the intended equipment, the product
may be stored under conditions of covered or uncovered storage on geographic areas ranging in temperature from –57°C to 71°C (-71°F to 160°F).

Interchangeability and compatibility
MIL-PRF-46170 fluids are not interchangeable with any other fluids.
MIL-PRF-46170 fluids are not to be regarded as compatible with any other fluids except those conforming to MIL-PRF-5606, MIL-PRF-6083, MIL-PRF-83282, and MIL-PRF-87257. Dilution with MIL-PRF-5606 or MIL-PRF-6083 severely lowers the flash point.

MIL-PRF-46170 Qualification
The hydraulic fluid 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. Any change in the formulation of a qualified product will require re-qualification.

Hydraulic fluid
The hydraulic fluid shall consist of a synthetic hydrocarbon base
stock (alpha-olefin polymer). Additives shall not include resins, gums, fatty oils, oxidized hydrocarbons, chlorine or silica.

Kinematic viscosity
The kinematic viscosity of the hydraulic fluid shall be as
specified in table below, TABLE 1:TABLE I. Kinematic viscosity

1/ mm 2/s = Square millimeters per second.

MIL-PRF-46170 Trace sediment
The hydraulic fluid shall have maximum trace sediment of 0.005 milliliter (mL)

MIL-PRF-46170 Water content
The hydraulic fluid shall have maximum water weight of 0.05 percent.

MIL-PRF-46170 Acid or base number
The hydraulic fluid shall have maximum acid or base number of 0.20 milligrams (mg) of potassium hydroxide per gram of hydraulic fluid (mg KOH/gram (g).

MIL-PRF-46170 Bulk modulus
The isothermal secant bulk modulus of the hydraulic fluid shall be 1.379 x 106
kilopascals (kPa) minimum, at 40°C (104°F) at pressures between 0 and 68 950 kPa.

MIL-PRF-46170 Water sensitivity
The light transmittance of a water-treated sample of hydraulic fluid shall be a minimum of 90%.

MIL-PRF-46170 Corrosion protection (humidity cabinet)
The hydraulic fluid shall protect specially prepared steel test panels to the extent that no more than three corrosion dots, none of which exceed 1 mm in diameter, occur on any of the panels.

MIL-PRF-46170 Corrosiveness (bimetallic couple)
The hydraulic fluid shall not promote galvanic
corrosion, in excess of three spots, on any one of the steel test disks covered with a brass clip.

MIL-PRF-46170 Solid particle contamination
MIL-PRF-46170 Particle size
The number of solid contamination particles per 100 mL of the hydraulic fluid shall not be greater than the numbers specified in table II.

MIL-PRF-46170 Gravimetric method
The solid particle contamination of the hydraulic fluid shall not be greater than 0.5 mg/100 mL.

MIL-PRF-46170 Foaming characteristics

MIL-PRF-46170 Foaming tendency
The foam volume of the hydraulic fluid shall not exceed 65 mL (following any of the 5-minute blowing periods of the foaming characteristics test.

MIL-PRF-46170 Foam stability
There shall be no foam remaining in the hydraulic fluid, in excess of a ring of bubbles around the edge of the test container, following any of the 10-minute settling periods of the foaming characteristics test.

MIL-PRF-46170 Wear (Lubricity)
During the wear test, the hydraulic fluid shall lubricate the steel balls such that the average scar diameters on the steel balls shall not exceed 0.30 mm if the test load is 147 Newtons (N), or 0.65 mm if the test load is 392 N.

MIL-PRF-46170 High temperature - high pressure spray ignition
The hydraulic fluid, when sprayed and ignited, shall be self-extinguishing.

MIL-PRF-46170 Linear flame propagation
The linear flame propagation rate of the hydraulic fluid shall not exceed 0.30 centimeters per second (cm/s).

MIL-PRF-46170 Relative Density (specific gravity)
The relative density of transparent low-viscosity hydraulic fluid samples submitted for conformance testing shall be reproducible to no more than +/-0.0012 and repeatable to no more than +/-0.0005 (no units) between the temperature range of -2°C to +24.5°C (29°F to 76°F), and no more than +/-0.008 from the relative density of the sample approved in qualification testing. Relative density shall be expressed at 60°F/60°F or at some temperature between 29°F to 76°F. Temperatures may be the same or different, but in both cases shall be explicitly stated, for example, 65°F/65°F, or 50°F/65°F. Report the final value as relative density, with no dimensions, at the two reference temperatures, to the nearest 0.0001.

MIL-PRF-46170 Interface requirements
Corrosiveness and oxidation stability (metal protection)

MIL-PRF-46170 Weight change of test specimens
The hydraulic fluid shall not produce corrosion or oxidation effects such that the weight change of the metal specimens, except for copper specimen, exceeds a gain or loss of 0.2 milligrams per square centimeter (mg/cm2). For the copper specimen, the weight gain or loss shall not exceed 0.6 mg/cm2

MIL-PRF-46170 Appearance of test specimens
The hydraulic fluid shall not cause etching, pitting, or visible corrosion on the surface of the metal specimens, except for the copper specimen. Any corrosion produced on the surface of the copper specimen shall not be greater than No. 2 of ASTM D130 Copper Corrosion Standards.
Viscosity change
The viscosity of the oxidized hydraulic fluid at 40°C (104°F)
shall not change more than ±10% from the initial viscosity measured at 40°C (104°F).
Acid or base number change
The acid or base number of the oxidized hydraulic fluid shall not increase more than 0.30 mg KOH/g over the initial acid or base number.

MIL-PRF-46170 Insoluble material
The oxidized hydraulic fluid shall exhibit no insoluble materials or gum when examined.

MIL-PRF-46170 Swelling of synthetic rubber
Following immersion in the hydraulic fluid at a temperature of 70°C (158°F) for 168 hours, standard synthetic rubber NBR-L, in accordance with (IAW) SAE AMS 3217/2B, shall exhibit a percent volume change within the range of 15 to

MIL-PRF-46170 Compatibility
The hydraulic fluid shall be compatible, in all concentrations, with each of the fluids approved under this specification, as well as hydraulic fluids conforming to:
MIL-PRF-5606, MIL-PRF-6083, MIL-PRF-83282, and MIL-PRF-87257

MIL-PRF-46170 Fire point
The minimum fire point of the hydraulic fluid shall be 246°C (475°F)
MIL-PRF-46170 Pour point
The maximum pour point of the hydraulic fluid shall be -54°C (-65°F)

MIL-PRF-46170 Evaporation loss
The maximum mass percent evaporation loss of the hydraulic
fluid shall be 5%.

MIL-PRF-46170 Autoignition temperature
The minimum autoignition temperature of the hydraulic
fluid shall be 343°C (649°F).

MIL-PRF-46170 Low temperature stability
The hydraulic fluid shall show no evidence of gelling, crystallization, solidification or separation of insoluble material when subjected to a temperature of -40 ± 6°C (-40 ±11°F) for 72 hours.

MIL-PRF-46170 Packaging
For acquisition purposes, the packaging requirements shall be specified in the contract or order. When actual packaging of materiel is to be performed by DoD or in-house contractor personnel, these personnel need to contact the responsible packaging activity to ascertain packaging requirements. Packaging requirements are maintained by the Inventory Control Point's packaging activities within the Military Services or Defense Agency, or within the military service's system commands. Packaging data retrieval is available from the managing Military Department's or Defense Agency's automated packaging files, CD-ROM products, or by contacting the responsible packaging activity.

MIL-PRF-46170  covers the requirements for one type of synthetic hydrocarbon base hydraulic fluid

Status: ACTIVE
MIL-PRF-46170 Hydraulic Fluid, Rust Inhibited, Fire Resistant, Synthetic Hydrocarbon BaseIntended for use in recoil mechanisms and hydraulic systems of military ground vehicles and equipment. If used in other mechanisms or systems, a study should be made to determine its applicability for such usage

MIL-SPEC, military specification, military standard (MIL-STD) is a United States Defense standard used to describe a product that meets specific performance and manufacturing standards for equipment and chemicals.

Other non-defense government organizations, technical organizations and industry may also use military specifications are not just limited to The Department of Defense, as other government organizations and Industry use them as well.

Here is a Q&A from the Department of Defense:

What is a performance spec?
A. A performance specification states requirements in terms of the required results with criteria for verifying compliance, but without stating the methods for achieving the required results. A performance specification defines the functional requirements for the item, the environment in which it must operate, and interface and interchangeability characteristics.

Q. What guidance have we given on how to write a performance specification?
A. Writing performance specifications is not a new concept. We have been teaching how to write performance requirements for years at our specification training course. It has received extra emphasis in our training on how to write Commercial Item Descriptions. What is new is that we are now designating documents as "performance specifications."

Q. If you have a performance spec that is MILSPEC, is a waiver needed?
A. No.

Q. Is it possible for a general specification to be designated as performance and its associated specification sheets to be designated as detail?
A. No. Since a general specification must be used together with a specification sheet, the fact that the specification sheet is detail requires the general specification also to be designated as detail.

Q. Within the same family of specification sheets, is it possible for some to be designated as detail and others to be performance?
A. Generally, no. The decision whether to convert a family of specification sheets to performance specifications must be consistent across-the-board. In some cases, however, the number of specification sheets that must be converted to performance specifications may be very large, making it difficult to convert all of them at one time. In this situation, there may be a temporary blend of detail and performance specification sheets within the same document number series. This situation is acceptable as long as the goal is to convert all of them to performance specifications.

Q. Can a performance spec ever cite a detail spec as a requirement?
A. The citing of a detail spec as a requirement does not automatically mean that a spec is not performance, but it is a strong indicator that as spec may not be performance. Performance specs should not cite any detail spec as a requirement if it demands a specific design solution. But performance specs may cite a detail spec if it relates to a physical or operational interface requirement.
For example, it would be permissible to have a requirement in a performance engine specification that required the engine to operate with specific substances, such as lubricating oil or fuel, which conform to detail specs. The requirement that the engine be able to operate on a specific type of fuel is an operational interface requirement and does not dictate the specific design of the engine. However, it would not be permissible in a performance spec to require the engine be made of certain materials or that the various engine components conform to detail specs since such requirements would dictate specific design solutions instead of stating the performance expected.

Q. I'm writing a spec that describes a "kit."
Should it be a detail (MIL-DTL-) or a performance (MIL-PRF-) specification?
A. In general, the answer is that it will likely be a detail specification; however, there can be exceptions. A spec for a kit describes a collection of related items, such as adapters, couplings, bags, tools, attachments, or accessories. A kit may contain items for installing, testing, or starting up a system or piece of equipment; it may be provided to equip an existing system for specific functions; or it may be used to adapt equipment to meet new or specialized conditions. If the spec writer were careful to write all of the requirements for the kit's contents in terms of form, fit, function, and interfaces, and to cite only performance-type documents, the resulting spec would support a MIL-PRF designation. As is frequently the case, however, if one or more of the kit's components are described using a specific design solution, Technical Data Package, MIL-DTL type spec, or a non-government standard that contains detail design requirements, the kit spec must be designated as a MIL-DTL. The spec writer needs to keep in mind that all of the requirements for all of the kits' components must be stated in performance terms in order to produce a MIL-PRF.