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Selecting
Metal Hose
Consider these selections factors for a particular
application:
1.
Size of Connection Pipe.
The
size of metal hose for a given application is
usually determined by the size of the existing
piping and matting fittings. However, other considerations
such as pressure drop, rate of flow and velocity
also influence your selection of the proper size
of hose.
2. Temperature of Operation in Relation to Pressure
and Material.
Temperature, of course, affects the physical
properties of any material. This factor must be
taken into account, as well as the working pressure
and specific application, Hose type, metal alloy,
fittings, and attachments determine the temperature
limit.
3.
Media in Relation to Corrosion of Hose Material.
A
primary consideration in specifying metal hose
is to select a material which is resistant to
the media to be conveyed through the hose; this
is possible in most applications. Remember to
consider the corrosive effects of the outside
environment, as well as the media covered within.
Both factors are significant. Remember also the
metal hose, a thin walled material, will not have
the same total length of usage as pipe or tube
that is heavy-walled material, even though both
are of the same material.
4.
Pressure - Operating, Test and Burst Needed for
the Application.
The pressure rating for each type of
flexible metal hose is affected by the conditions
of actual use, such as, shock or pulsating conditions,
temperature, and bending stresses. The maximum
operating pressure is 25% of the Nominal Burst
Pressure, while the maximum test pressure is 150%
of the Maximum Operating Pressure. The Nominal
Burst Pressure is the pressure at which the hose
can be expected to rupture. When pulsating, surge
or shock pressures exist, from conditions such
as fast closing valves, the peak pressure should
not exceed 50% of the Maximum Operating Pressure.
Refer to Catalog, page 3, that specifies the pressure
ratings for each of these conditions, as it relates
to both braided and unbraided hose. In addition,
you should refer to the Definitions
Page for the pressure ratings as affected
by temperatures in excess of 70° Fahrenheit.
5.
Motion Type Affecting Hose and Amount of Motion.
Flexible
metal hose is specified for several different
applications:
- whenever there is excessive vibration;
- whenever misaligned pipe or tube is encountered;
- whenever flexibility is needed for manual handling
situations.
To select the proper hose for any of these applications
requires, careful consideration of the inherent
flexibility of the material in regards to the
design of the assembly, installation, and versatility
expected of the hose.
6.
Length of Hose Needed to Absorb Motion in Relation
to Space Available.
The type of motion, the offset motion, vibration,
as well as live length required, are all factors
to consider in determining the proper hose selection.
Refer to Definitions and
Offset Chart pages for
exact specifications of these conditions.
7.
Fittings Needed to Connect to Existing Connections
Compatible
with Media, Temperature, and
Pressure.
End Fittings may have male or female threads.
In addition to conventional unions - flanges,
flared tube fittings - special designs or custom
connectors are available. The attachment method:
welding, soldering, silver brazing, or mechanical,
is determined by the appropriate type of hose,
alloy, and temperature Contact American Boa for
custom fitting information.
8.
Flow Velocity
High flow velocities in metal hose can cause vibration
resulting in noise and premature failure. See
Definitions Page for liner
recommendations.
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