Hose (also includes hose assemblies) has a finite
life and there are a number of factors which will reduce
This recommended practice is intended as a guide to
assist system designers and/or users in the selection,
installation, and maintenance of hose. The designers
and users must make a systematic review of each
application and then select, install, and maintain the
hose to fulfill the requirements of the application. The
following are general guidelines and are not necessarily
a complete list.
The following is a list of factors which must be considered
before final hose selection can be made.
2.1 Pressure - After determining the system pressure,
hose selection must be made so that the recommended
maximum operating pressure is equal to or
greater than the system pressure. Surge pressures
higher than the maximum operating pressure will
shorten hose life and must be taken into account by
the hydraulic designer.
2.2 Suction - Hoses used for suction applications must
be selected to insure the hose will withstand the
negative pressure of the system.
2.3 Temperature - Care must be taken to insure that
fluid and ambient temperatures, both static and
transient, do not exceed the limitations of the hose.
Special care must be taken when routing near hot
2.4 Fluid Compatibility - Hose selection must assure
compatibility of the hose tube, cover, and fittings
with fluid used. Additional caution must be observed
in hose selection for gaseous applications.
2.5 Size - Transmission of power by means of pressurized
fluid varies with pressure and rate of flow. The
size of the components must be adequate to keep
pressure losses to a minimum and avoid damage
to the hose due to heat generation or excessive
2.6 Routing - Attention must be given to optimum
routing to minimize inherent problems.
2.7 Environment - Care must be taken to insure that
the hose and fittings are either compatible with or
protected from the environment to which they are
exposed. Environmental conditions such as
ultraviolet light, ozone, salt water, chemicals, and
air pollutants can cause degradation and premature
failure and, therefore, must be considered.
2.8 Mechanical Loads - External forces can significantly
reduce hose life. Mechanical loads which
must be considered include excessive flexing,
twist, kinking, tensile or side loads, bend radius,
and vibration. Use of swivel type fittings or adapters
may be required to insure no twist is put in the
hose. Unusual applications may require special
testing prior to hose selection.
2.9 Abrasion - While a hose is designed with a reasonable
level of abrasion resistance, care must be
taken to protect the hose from excessive abrasion
which can result in erosion, snagging and cutting of
the hose cover. Exposure of the reinforcement will
significantly accelerate hose failure.
2.10 Proper End Fitting - Care must be taken to insure
proper compatibility exists between the hose and
coupling selected based on the manufacturer s
recommendations substantiated by testing to
industry standards such as SAE J517d.
2.11 Length - When establishing proper hose length,
motion absorption, hose length changes due to
pressure, as well as hose and machine tolerances
must be considered.
2.12 Specifications and Standards - When selecting
hose, government, industry, and manufacturer s
specifications and recommendations must be
reviewed and applicable.
2.13 Hose Cleanliness - Hose components vary in
cleanliness levels. Care must be taken to insure
that the assemblies selected have an adequate
level of cleanliness for the application.
2.14 Electrical Conductivity - Certain applications
require that the hose be non-conductive to prevent
electrical current flow. Other applications require
the hose to be sufficiently conductive to drain off
static electricity. Hose and fittings must be chosen
with these needs in mind.
After selection of proper hose, the following factors must
be considered by the installer.
3.1 Pre-Installation Inspection - Prior to installation, a
careful examination of the hose must be performed.
All components must be checked for correct style,
size, and length. In addition, the hose must be
examined for cleanliness, I.D. obstructions, blisters,
loose cover, or any other visual defects.
3.2 Follow Manufacturers Assembly Instructions.
3.3 Minimum Bend Radius - Installation at less than
minimum bend radius may significantly reduce hose
life. Particular attention must be given to preclude
sharp bending at the hose/fitting juncture.
3.4 Twist Angle and Orientation - Hose installations
must be such that relative motion of machine
components produces bending of the hose rather
3.5 Securement - In many applications, it may be
necessary to restrain, protect, or guide the hose to
protect it from damage by unnecessary flexing,
pressure surges, and contact with other mechanical
components. Care must be taken to insure such
restraints do not produce additional stress or wear
3.6 Proper Condition of Ports - Proper physical installation
of the hose requires a correctly installed port
connection while insuring that no twist or torque is
put into the hose.
3.7 Avoid External Damage - Proper installation is not
complete without insuring tensile loads, side loads,
kinking, flattening, potential abrasion, thread
damage, or damage to sealing surfaces are corrected
3.8 System Check Out - After completing the installation,
all air entrapment must be eliminated and the
system pressurized to the maximum system pressure
and checked for proper function and freedom
Note: Avoid potential hazardous area while testing.
Even with proper selection and installation, hose life
may be significantly reduced without a continuing
maintenance program. Frequency should be determined
by the severity of the application and risk potential.
A maintenance program should include the following as
4.1 Hose Storage - Hose products in storage can be
affected adversely by temperature, humidity,
ozone, sunlight, oils, solvents, corrosive liquids and
fumes, insects, rodents and radioactive material.
Storage areas should be relatively cool and dark,
and free of dust, dirt, dampness and mildew.
4.2 Visual Inspection - Any of the following conditions
requires replacement of the hose:
a. Leaks at fitting or in hose.
(Leaking fluid is a fire hazard).
b. Damaged, cut or abraded cover.
(Any reinforcement exposed).
c. Kinked, crushed, flattened or twisted hose.
d. Hard, stiff, heat cracked or charred hose.
e. Blistered, soft degraded or loose cover.
f. Cracked, damaged, or badly corroded fittings.
g. Fitting Slippage on hose.
4.3 Visual Inspection - The following items must be
tightened, repaired, or replaced as required:
a. Leaking port conditions.
b. Clamps, guards, shields.
c. Remove excessive dirt buildup.
d. System fluid level, fluid type, and any air
4.4 Functional Test - Operate the system at maximum
operating pressure and check for possible malfunctions
and freedom from leaks.
Note: Avoid potential hazardous areas
4.5 Replacement Intervals - Specific replacement
intervals must be considered based on previous
service life, government or industry recommendations,
or when failures could result in unacceptable
down time, damage, or injury risk.