& Design > Motion
Offset Motion Lateral
Hose Live Length
The live length of the hose assembly must be sufficient in order for
the hose to properly meet the movement requirements. A hose assembly with
a live length shorter than suggested could cause premature failure.
occurs when the hose centerline is moved in a plane perpendicular to the
longitudinal axis with the end remaining parallel. Dynamic offset motion
should never be more than 25% of the minimum centerline bend radius. See
page 25 for design information on lateral offset.
Angular movement is defined as the bending of the hose so that the ends
are no longer parallel. Amount of movement is measured in degrees from
centerline of the hose if were installed straight. See Angular
Offset Motion for design information on angular offset.
Axial movement is compression or elongation along the longitudinal axis.
Metal hose assemblies installed in line with the longitudinal axis of
the piping should not be subjected to axial movement.
Two design options are available to compensate for axial movement. The
first option is installation of the metal hose assembly perpendicular
to the longitudinal axis of the pipeline. As axial movement occurs, the
metal hose assembly will be subjected to lateral offset. See Lateral
Offset Motion for additional design information.
The second option is the use of a Class B traveling loop.
Movement for design requirements of traveling loops.
Torsion movement occurs when the hose is twisted or torqued such as when
the hose bends out of plane or during improper installation.
Twisting forces are extremely destructive and are one of the most common
causes for premature failure.
The rate of flexure that the hose is subjected to in a given time period.
Three basic types of motion
frequency include vibration, dynamic motion and continuous motion.
This is low amplitude motion occurring at high frequency. Vibration is
normally found in engine exhaust, pump and compressor applications. Hose
resonance must be avoided to prevent premature failure. Consult OmegaFlex
engineering if hose resonance is anticipated or for additional vibration
Non-continuous or intermittent motion such as the result of thermal expansion.
Dynamic bend radius is used in calculations determining the hose live
length for lateral offset, angular offset and radial motion during dynamic
or intermittent flexing.
A non-moving or fixed radius bend in a hose assembly used to compensate
Regular cyclic motion at a slow cyclic rate and constant travel. The dynamic
minimum centerline bend radius must be doubled on continuous motion applications.
The uncontrolled motion of a metal hose such as motion that occurs during
The minimum radius the hose can be bent and still maintain the integrity
of the hose. Usually expressed as dynamic or static centerline bend radius.
The bend radius is used in calculations associated with angular and lateral
The number of cycles a hose is flexed before failure. Some factors that
affect cycle life include working pressure, temperature, bend radius,
hose and braid materials. OmegaFlex uses the ISO10380 fatigue test standard
for cycle life testing. See ISO 10380
Summary for a more complete description of the ISO 10380 standard.