ASTM D4174-89(1999)

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An American National Standard
Designation: D 4174 – 89 (Reapproved 1999)
Standard Practice for
Cleaning, Flushing, and Purification of Petroleum Fluid
Hydraulic Systems
This standard is issued under the fixed designation D 4174; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
Section
Storage 7
1.1 This practice is intended to aid the equipment manufac-
General 7.1
turer, the installer, the oil supplier and the operator in coordi-
Inspection 8
General 8.1
nating their efforts towards obtaining and maintaining clean
System Components 8.2
petroleum fluid hydraulic systems. Of necessity, this practice is
Valves, Strainers and Coolers 8.2.1
generalized due to variations in the type of equipment, build-
Sumps and Tanks 8.2.2
Control Devices 8.2.3
er’s practices, and operating conditions. Constant vigilance is
Pumps 8.2.4
required throughout all phases of design, fabrication, installa-
Flushing Program 9
tion, flushing, testing, and operation of hydraulic systems to General 9.1
Preparation of System for Flushing 9.2
minimize and reduce the presence of contaminants and to
Oil Heating Prior to Flushing 9.3
obtain optimum system reliability.
Selection of Flushing Oil 9.4
1.2 This practice is presented in the following sequence: System Operation Oil 9.4.1
Special Flushing Oil 9.4.2
Section
Flushing Oil Selection Guide 9.4.3
Scope 1
Flushing Procedure for New Systems 9.5
Referenced Documents 2
Flushing Oil Charge 9.5.1
Significance and Use 3
Cleaning of Filtration Devices 9.5.2
Definitions 4
Cleaning of System Components 9.5.3
Types of Contamination 5
System Flushing 9.5.4
General 5.1
Draining of Flushing Oil 9.5.5
Water 5.2
Displacement Oil 9.5.6
Soluble Contaminants 5.3
Interim Corrosion Protection 9.5.7
Insoluble Contaminants 5.4
New Fluid Charge 9.5.8
Lodged Contamination 5.4.2.1
Flushing of Used Systems 9.6
Suspended Contamination 5.4.2.2
General Guidelines 9.6.1
Contamination Control 6
Procedure 9.6.2
General 6.1
System Maintenance 10
Initial Filling 6.1.1
Shipping 10.1
In-Service Units 6.1.2
Preinstallation 10.2
Connection of Contamination Control System 6.1.3
In-Service Units 10.3
Piping to Contamination Control System 6.1.4
Decision to Flush In-Service Hydraulic Systems 10.4
Contamination Control Procedures 6.2
Fluid Condition Monitoring 11
Full Flow Contamination Control 6.2.1
Fluid Sampling Techniques 11.2
Bypass Contamination Control 6.2.2
Visual Inspection 11.3
Batch Contamination Control 6.2.3
Laboratory Analysis 11.4
Contamination Control Processes 6.3
Fluid Cleanliness Criteria 11.5
Gravity 6.3.1
General Information 12
Mechanical 6.3.2
Filter Ratings 12.2
Centrifuge 6.3.2.1
Centrifuge Ratings 12.3
Filters 6.3.2.2
Coalescence 12.4
Supplementary Methods 6.3.3
Vacuum Dehydration 12.5
Limitations of Contamination Control Devices 6.3.4
Adsorption 12.6
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
This practice is under the jurisdiction of ASTM Committee D-2 on Petroleum
Products and Lubricants and is the direct responsibility of D02.N0.02 on Industrial
responsibility of the user of this standard to establish appro-
Applications.
priate safety and health practices and determine the applica-
Current edition approved Oct. 27, 1989. Published December 1989. Originally
bility of regulatory limitations prior to use.
published as D 4174 – 82. Last previous edition D 4174 – 82.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 4174
2. Referenced Documents and installation. In used systems, the emphasis is on the
removal of contaminants that are generated during operations,
2.1 ASTM Standards:
from failures that occur during operation; or contaminants
D 445 Test Method for Kinematic Viscosity of Transparent
introduced during overhaul.
and Opaque Liquids (the Calculation of Dynamic Viscos-
2 4.3 While the flushing and cleaning philosophies stated in
ity)
this practice are applicable to all primary and servo hydraulic
D 664 Test Method forAcid Number of Petroleum Products
systems, the equipment specified herein does not apply to
by Potentiometric Titration
compact systems that use relatively small volumes of fluid
D 974 Test Method for Acid and Base Number by Color-
unless they are servo systems where it is economically justi-
Indicator Titration
fied.
D 1774 TestMethodforElasticPropertiesofTextileFibers
4.4 It should be emphasized that the established procedures
D 2709 Test Method for Water and Sediment in Distillate
to be followed for flushing and cleaning the hydraulic systems
Fuels by Centrifuge
should be accomplished through the cooperative efforts and
D 4006 Test Method for Water in Crude Oil by Distillation
agreement of the equipment manufacturer, the installer, the
F 311 PracticeforProcessingAerospaceLiquidSamplesfor
operator, and the fluid supplier. No phase of these procedures
Particulate Contamination Analysis Using Membrane Fil-
5 should be undertaken without a thorough understanding of the
ters
possible effects of improper system preparation. The installa-
F 312 Methods for Microscopical Sizing and Counting
5 tion and cleaning and flushing of the equipment should not be
Particles from Aerospace Fluids on Membrane Filters
entrusted to persons lacking in experience.
F 313 Test Method for Insoluble Contamination of Hydrau-
lic Fluids by Gravimetric Analysis
5. Types of Contamination
2.2 ANSI Standards:
5.1 General—Hydraulic systems can become contaminated
B93.2 Glossary of Terms for Fluid Power
fromavarietyofsources.Generally,therearefivecategoriesof
B93.19 Method for Extracting Fluid Samples from the
contamination: (1) water, ( 2) fluid soluble material, (3) fluid
Lines of an Operating Hydraulic Fluid Power System (for
insoluble material, (4) erroneous fluid additions, and (5)
Particulate Contamination Analysis)
hydraulic fluid deterioration. Properly designed systems can
normally control water and insoluble contaminants; however,
3. Terminology
when it is necessary to remove soluble contaminants, a fluid
3.1 Definitions:
change and flush are required.
3.1.1 absolute filtration rating—the diameter of the largest
5.2 Water—Water is almost always present in hydraulic
hard spherical particle that will pass through a filter under
fluids. It may be present in solution or in a free or emulsified
specified test conditions. This is an indication of the largest
form. Water can exist in solution at varying concentrations
opening in the filter element.
depending on the nature of the fluid, the temperature, etc. For
3.1.2 nominal filtration rating—an arbitrary micrometre
example, hydraulic fluid may hold 50 ppm of water at 21°C
value indicated by a filter manufacturer. Due to lack of
(70°F)and250ppmat71°C(160°F).Thewaterinsolutionhas
reproducibility this rating is deprecated. (ANSI B93.2)
no adverse effect on lubricating properties of the fluid and
causes no corrosion; however, when fluid passes through a
4. Significance and Use
cooler some water may come out of solution and become free
4.1 Proper fluid condition is essential for the satisfactory
water in the form of finely dispersed droplets. Many contami-
performance and long life of the equipment. Prerequisites for
nants hinder the separation of this free water from the fluid by
proper lubrication and component performance are: (1)a
settling and may cause an emulsion. In hydraulic fluids, the
well-designedhydraulicsystem,(2)theuseofagoodfluid,and
emulsion impairs circulation, interfere with lubrication and
(3) a maintenance program including proper filtration methods
adversely affect contamination control equipment.
to ensure that the fluid is free of contaminants. These prereq-
5.2.1 Water contamination can be classified as either fresh
uisites are meaningless unless the hydraulic system is initially
or sea water, as encountered in land or marine systems. Fresh
cleaned to a level that will prevent component damage on
water enters the hydraulic system from moist air as condensa-
initial start up or when debris may be dislodged by any system
tion, through improperly located vents, leaks in coolers, and
upset.
steamheaters,andbecauseofimproperoperation.Seawater,in
4.2 The cleaning and flushing of both new and used systems
marine hydraulic systems, enters through leaks in coolers,
are accomplished by essentially the same procedure. In new
faulty manhole gaskets, faulty sump tank seals and improperly
systems, the emphasis is on the removal of contaminants
located vents. Sea and brackish water can also present a
introduced during the manufacture, storage, field fabrication,
problem when used as a coolant in land-based units. Water
contamination in hydraulic fluids can:
2 5.2.1.1 Promote fluid oxidation.
Annual Book of ASTM Standards, Vol 05.01.
5.2.1.2 Reduce fluid stability.
Annual Book of ASTM Standards, Vol 07.01.
Annual Book of ASTM Standards, Vol 05.02.
5.2.1.3 Promote sludge.
Annual Book of ASTM Standards, Vol 14.02.
5.2.1.4 Promote foaming.
Annual Book of ASTM Standards, Vol 15.03.
5.2.1.5 Form emulsions.
Available from American National Standards Institute, 11 W. 42nd St., 13th
Floor, New York, NY 10036. 5.2.1.6 Promote rusting and corrosion.
D 4174
5.2.1.7 Affect additive and concentration. 5.4.2.2 Suspended Contamination:
5.2.1.8 Adversely affect lubricating properties. 5.4.2.3 (a) Contaminants suspended in the fluid can be
generated by particles coming loose from pipe, hose, hydraulic
5.2.1.9 Promote bacteria growth.
components,tankwallsgenerallycausedbyhighfluidvelocity,
5.2.1.10 Alter fluid viscosity.
wear debris, and vibration. Suspended contaminant can be
5.2.1.11 Adversely affect fine filtration.
measured, as described in 11.3. To prevent the level of
5.2.2 In the case of severe salt water contamination, it is
suspended contaminant from getting beyond acceptable limits,
necessary to remove the operating fluid and clean and flush the
all units should be provided at least with a bypass contamina-
hydraulic systems.
tion control system (fluid filter or centrifuge). Preferably a full
5.3 Soluble Contaminants:
flow filter or a full flow filter plus bypass purification is
5.3.1 Soluble contaminants in hydraulic systems include
provided. When a full flow filter is used, a bypass purification
cleaning chemicals, solvents, rust preventives, incompatible
system may not be required.
lubricants, flushing oils, extraneous oils, oxidation products,
5.4.2.4 (b) The bypass or full flow system, or both, are in
gasket sealants, and assembly lubricants. These contaminants
operation during the flush operation as well as on a continuous
cannotberemovedbyconventionalfluidcontaminationcontrol
basis during hydraulic system operation. The rated flow capac-
equipment. Normally, a new charge of fluid is required to
ity per hour of a bypass system should be 10 to 20 % of the
correct the problem. Fluid soluble contaminants can:
total system fluid volume.
5.3.1.1 Change the fluid viscosity.
5.3.1.2 Alter the flash point.
6. Contamination Control
5.3.1.3 Change the color.
6.1 General—Contamination control in a hydraulic system
5.3.1.4 Result in sludge deposits.
is the complete program of monitoring and maintaining a clean
5.3.1.5 Attack elastomeric seals.
fluid. Contamination control must begin with the design,
5.3.1.6 Initiate additive-water interaction that can cause
manufacture, and installation of the hydraulic system and
emulsification, possible additive loss, instability, impaired
continue throughout the life of the system. When making
purification equipment performance, foaming, and air entrain-
inspections or working in or around a unit, care must be taken
ment.
to prevent contaminants from entering the system. When work
5.3.1.7 Accelerate oxidation.
that generates contaminants is being performed in the vicinity
5.3.2 When a soluble contaminant is present, the fluid
of the hydraulic system, the system components must be
supplier and consult the equipment manufacturer should be
protected even to the extent of suspending operations, and
consulted regarding the advisability of continued use of the
requiring system components to be sealed until the contami-
fluid or replacing it with a new charge.
nating activity has ceased. The contamination control system
5.4 Insoluble Contaminants:
must be capable of removing water and particulate matter
5.4.1 Insoluble contaminants normally encountered are
consistent with contamination tolerance and system cleanliness
metal particles of all types and sizes, fibers, airborne solids,
requirements.
sand, and other nonmetallic particles. These contaminants are
6.1.1 Initial Filling—When initially filling the hydraulic
often the result of improper manufacturing techniques, im-
system, all fluids are filtered through 3 to 10-µm absolute (see
proper shipping and storage practices, and careless installation
4.1) filters as they are being transferred into the reservoir. The
of hydraulic systems. Some of the effects of solid contamina-
contaminationcontrolsystemisreadyforoperationpriortothe
tion are:
hydraulic system fill and is operating throughout flushing. See
5.4.1.1 Abrasive wear or sticking of components such as:
Section 9.5.
control valve poppets, cylinders, piston rods, and seals.
6.1.2 In-Service Units—The contamination control system
5.4.1.2 Faulty control functioning, particularly plugged
is in operation as long as the hydraulic system is in service. Its
fluid lines/filter plugging.
operation is frequently and regularly monitored to assure that it
5.4.1.3 Reduced fluid stability.
is performing adequately and to determine the need for its
5.4.1.4 Sludge formation.
maintenance.
5.4.1.5 Increased foaming tendency.
6.1.3 Connection of Contamination Control System—The
5.4.1.6 Stabilized water-oil emulsions/accelerated oxidation external fluid take-off from the circulating system to the
by catalytic effect of metal particles.
contamination control system is from the lowest point of the
5.4.2 Harmful contamination can exist in the hydraulic fluid sump or reservoir, to facilitate removal of solid contami-
system in two forms:
nants and water.
5.4.2.1 Lodged Contamination—These contaminants may 6.1.3.1 Piping between the reservoir and the contamination
become dislodged by high fluid flows and temperature differ- control system is designed to minimize the potential for the
entials or by induced vibration during flushing. Contamination loss of fluid that results from piping or equipment failure. This
can be lodged in unflushed pockets or settled on
...