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Hydraulic hose to SAE/DIN/EN > Recommended Practices - page 1


  Hydraulic hose to SAE/DIN/EN
Recommended Practices - page 1
 

1. Scope
SAE J1273 provides guidelines for selection, routing, fabrication, installation, replacement, maintenance, and storage of hose and hose assemblies for fluid-power systems. Many of these SAE Recommended Practices also may be suitable for other hoses and systems.

2. References
2.1 Applicable documents
The following publications form a part of this specification to the extent specified herein. Unless otherwise specified, the latest issue of SAE publications shall apply.

2.1.1 SAE publications
Available from SAE, 400 Commonwealth, Drive, Warrendale, PA 15096-0001.
SAE J343 - test and procedures for SAE 100 R Series Hydraulic Hose and Hose Assemblies.
SAE J514 - Hydraulic Tube Fittings.
SAE J517 - Hydraulic Hose
SAE J 1927 - Cumulative Damage Analysis for Hydraulic Hose Assemblies

2.1.2 ISO Publications
Available from ANSI, 11 West 42nd Street, New York, NY 10036-8002.
ISO 3457-Earth moving machinery - Guards and shields-Definitions and specifications

3. Explanation of terms
These explanations serve only to clarify this documents and are not intended to stand alone. They are presented sequentially, with the former helping to explain the latter.

3.1 Fluid power
Energy transmitted and controlled using pressurized hydraulic fluids or compressed air.

3.2 Hose
Flexible conductor. In this document, the term hose also may refer to a hose assembly with related accessories used in fluid power applications.

3.3 Hose fitting or fitting
Connector which can be attached to the end of a hose.

3.4 Hose Assembly
Hose with hose fittings attached.

3.5 Hose Failure
Occurence in which a hose stops meeting system requirements.

3.6 Hose Service Life
Length of time a hose meets system requirements without needing replacement.

4. Safety considerations
Listed in 4.1 to 4.7 are some potential conditions and situations that may lead to personal injury and/or property damage. This list is not necessarily all inclusive. Consider reasonable and feasible means, including those described in this section, to reduce the risk of injuries or property damage. Training, including the information in this document, for operators, maintenance personnel, and other individuals working with hoses under pressure is encouraged.

4.1 Fluid Injections
Fine streams of escaping pressurized fluid can penetrate skin and enter a human body. These fluids injections may cause severe tissue damage and loss of limb. Consider various means to reduce the risk of fluid injections particularly in areas normally occupied by operators. Consider careful routing, adjacent components, warnings, guards, shields and training programs.
Relieve pressure before disconnecting hydraulic or other lines. Tighten all connections before applying pressure.
Avoid contact with escaping fluids. Treat all leaks as though pressurized and hot enough to burn skin. Never use any part of your body to check a hose for leaks. If a fluid-injection accident occurs, see a doctor immediately. DO NOT DELAY OR TREAT AS A SIMPLE CUT!. Any fluid injected into the skin must be surgically removed within a few hours or gangrene may result. Doctors unfamiliar with this type of injury should consult a knowledgeable medical source.

4.2 Whipping hose
If a pressurized hose assembly blows apart, the fittings can be thrown off a high speed, and the loose hose can fall or whip with great force. This is particularly true in compressible fluids systems. When the risk exists, consider guards and restraints to protect against injury.

4.3 Burns from conveyed fluids
Flui-power media may reach temperatures that can burn human skin. If there is risk of burns from escaping fluid, consider guards and shields to prevent injury, particularly in areas normally occupied by operators.

4.4 Fire and explosions from conveyed fluids
Most fluid power media, including fire-resistant hydraulic fluids, will burn under certain conditions. Fluids which escape from pressurizes systems may form a mist of fine spray which can flash or explode upon contact with an ignition source. Consider selecting, guarding, and routing hose to minimize the risk of combustion (see section 5 and ISO 3457).

4.5 Fire and Explosions from Static-Electric Discharge
Fluid passing through hose can generate static electricity, resulting in static electric discharge. This may create sparks that can ignite system fluids or gases in the surrounding atmosphere. When this potential exists, select hose specifically designed to carry the static-electric charge to ground.

4.6 Electrical shock
Elextrocution could occur if hose conducts electricity through a person. Most hoses are conductive. Many contain metal or have metal fittings. Even non-conductive hoses can be conduits for electricity if they carry conductive fluids. Be aware of routing or using hose near electrical soutces. When this cannot be avoided, select appropiate hose. Non-conductive hoses should be considered. SAE J517 - 100R7 and 100R8 hoses, with orange covers marked "Non-conductive" are available for applications requiring non-conductive hose.

4.7 Mechanisms Controlled by Fluid Power.
Mechanisms controlled by fluids in hoses can become hazardous when a hose fails. For example, when a hose bursts, objects supported by fluid pressure may fall, or vehicles or machines may lose their brakes or steering. If mechanisms are controlled by fluid power, consider safe modes of failure that minimize risks of injury or damage.

5. Hose Selection and Routing
A wide variety of interacting factors influence hose service life and the ability of each fluid-power system to operate satisfactorily, and the combined effects of these factors on service life are often unpredictable. Therefore, these documents should not be construed as design standards. For applications outside the specifications in SAE J517, SAE J514, r other relevant design standards, performance of hose assemblies should be determined by appropiate testing. Carefully analyze each system. Then design routings and select hose and related components to meet the system-perfomance and hose-service-life requirements, and to minimize the risks of personal injury and/or property damage. Consider the following factors:

5.1 System pressures.
Excessive pressure can accelerate hose assembly failure. Analyze the steady-state pressures, and the frequency and amplitude of pressure surges, such as pulses and spikes. These are rapid and transient rises in pressure which may not be indicated on many common pressure gauges and can be identified best on high-frequency-response electronic measuring instruments.
For maximum hose service life, hose selection should be based on a system pressure, including surges, that is less than the hose maximum working pressure. Hose may be used above its maximum working pressure where reduced life expentancy is acceptable. SAE J1927 provides one method to help predict wire-reinforced hose service life for a given hydraulic application, where the surge pressure peaks vary and/or the highest pressure peaks occur infrequently.

5.2 Suction
For suction applications, such as inlet flow to pumps, select hose to withstand both the negative and positive pressures the system imposes on the hose.

5.3 External pressure
In certain application, such as in autoclaves or under water, the external environmental pressures may exceed the fluid pressure inside the hose. In these applications, consider the external pressures, and if necessary, consult the manufacturers.

5.4 Temperature
Exceeding hose temperature ratings mau significantly reduce hose life. Select hose so the fluid and ambient temperatures, both static and transient, fall within the hose ratings. The effects of external heat sources should not raise the temperature of the hose above its maximum operating temperature. Select hose, heat shields, sleeving and other methods for these requirements, and route or shield hose to avoid hose damage from external heat sources.

5.5 Permeation
Permeation, or effusion, is seepage of fluid through the hose. Certain materials in hose construction are more permeable than others. Consider the effects of permeation when selecting hose, especially with gaseous fluids. Consult the hose and fluid manufacturers for permeability information.

5.6 Hose material compatibility
Variable that can affect compatibility of system fluids with hose materials include, but are not limited to :
a. fluid pressure
b. temperature
c. concentration
d. duration of exposure.
Because of permeation (see 5.5), consider compatibility of system fluids with the hose, tube cover, reinforcement, and fittings. Consult the fluid and hose manufacturers for compatibility information.
NOTE : many fluid/elastomer compatibility tables in manufacturers catalogs show ratings based on fluids at 21°C, room temperature. These ratings may change at other temperatures. Carefully read the notes on the compatibility tables, and if in doubt, consult the manufacturer.

5.7 Environment
Environmental conditions can cause hose and fitting degradation. Conditions to evaluate include, but are not limited to :
a. Ultraviolet light
b. salt water
c. air pollutants
d. temperature
e. ozone
f. chemicals
g. electricity
h. abrasion
if necessary, consult the manufacturers for more information.

5.8 Static-electric discharge
Fluid passing through hose can generate static electricity resulting in static-electric discharge. This may create sparks that can puncture hose. If this potential exists, select hose with sufficient conductivity to carry the static-electric charge to ground.

5.9 Sizing
The power transmitted by pressurized fluid varies with pressure and rate of flow. Select hose with adequate size to minimize pressure loss and to avoid hose damage from heat generation or excessive velocity. Conduct calculations, or consult the manufacturers for sizing at flow velocities.

5.10 Unintended uses
Hose assemblies are designed for the internal forces of conducted fluids. Do not pull hose or use it for purposes that may apply external forces for which the hose or fittings were not designed.

5.11 Specifications and standards
When selecting hose and fittings for specific applications, refer to applicable government, industry, and manufacturer's specifications and standards.

5.12 Unusual applications
Applications not addressed by the manufacturer or by industry standards may require special testing prior to selecting hose.

5.13 Hose cleanliness
The cleanliness requirements of system components, other than hose, will determine the cleanliness requirements of the applications. Consult the component manufacturer's cleanliness information for all components in the system. Hose assemblies vary in cleanliness levels, therefore, specify hose assemblies with adequate cleanliness for the system.

5.14 Hose fittings
Selection of the proper hose fittings for the hose and application is essential for proper operation and safe use of hose and related assembly equipment. Hose fittings are qualified with the hose. Therefore, select only hose fittings compatible with the hose for the applications. Improper selection of hose fittings or related assembly equipment for the application can result in
injury or damage from leaks, or from hose assemblies blowing apart (see 4.2, 6.2, 6.3, and 6.4).

5.15 Vibration
Vibration can reduce hose service life. If required, conduct tests to evaluate the frequency and amplitude of system vibration. Clamps or other means may be used to reduce the ffects of vibration. Consider the vibration requirements when selecting hose and predicting service life.