 The
selection of flexible metal hose for a particular application is influenced
by six primary considerations:
-
Temperature
-
Pressure
-
Media
-
Size
-
End Fittings
-
Motion
To make the best choice for
a specific application, consider all the relevant operating factors against
the properties of the various types of flexible metal hoses.
Temperature
The physical properties of
any material vary with temperature. Working pressure, the type of media
being conveyed and the nature of the application are what affect the limits
for operating temperature. Flexible metal hose can be used for a wide range
of temperatures given that the material is selected carefully. The temperature
limit depends upon the hose type, metal alloy, end fittings and the method
of fitting attachment choices.
Temperature Correction
Table
|
Temp
(°F)
|
304,
316L Stainless
|
321
Stainless
|
Bronze
|
Monel
|
Hastelloy
|
Inconel
|
| Room |
1.00 |
1.00 |
1.00 |
1.00 |
1.00 |
1.00 |
| 150 |
.96 |
.97 |
.92 |
.93 |
.97 |
.99 |
| 200 |
.92 |
.94 |
.89 |
.90 |
.94 |
.98 |
| 250 |
.91 |
.92 |
.86 |
.87 |
.92 |
.97 |
| 300 |
.86 |
.88 |
.83 |
.83 |
.91 |
.97 |
| 350 |
.85 |
.86 |
.81 |
.82 |
.89 |
.96 |
| 400 |
.82 |
.83 |
.78 |
.79 |
.87 |
.95 |
| 450 |
.80 |
.81 |
.75 |
.77 |
.86 |
.94 |
| 500 |
.77 |
.78 |
- |
.73 |
.85 |
.94 |
| 600 |
.73 |
.74 |
- |
.72 |
.84 |
.92 |
| 700 |
.69 |
.70 |
- |
.71 |
.82 |
.90 |
| 800 |
.64 |
.66 |
- |
.70 |
-81 |
.89 |
| 900 |
- |
.62 |
- |
- |
.79 |
.87 |
| 1000 |
- |
.90 |
- |
- |
.78 |
.86 |
| 1100 |
- |
.58 |
- |
- |
.75 |
.84 |
| 1200 |
- |
.55 |
- |
- |
.73 |
.82 |
| 1300 |
- |
.50 |
- |
- |
.69 |
.79 |
| 1400 |
- |
.44 |
- |
- |
.65 |
.77 |
| 1500 |
- |
.40 |
- |
- |
- |
.74 |
Pressure
The nominal pressure ratings
of flexible metal hose vary according to type, material and size. Pressure
is affected by many other factors such as temperature, pulsating conditions
and bending stresses, under actual working conditions.
Media
The type of media being
conveyed through the hose is important to consider during the selection
process. Metal hose can be corroded by the material flowing through it
and the outside environment. A metal hose can be selected that is resistant
to the proposed media for almost all applications. Since metal hose has
a thin wall, it will not have the same total life as a heavier walled tube
or pipe.
Size
The size of flexible metal
hose is specified by the nominal diameter. When choosing a metal hose for
a particular application, the existing piping will normally dictate the
size needed. Flow rate, velocity and pressure drop considerations may also
influence the selection of the hose size.
End Fittings
There is an extensive range
of end fittings available for flexible metal hose. These end fittings include
male and female pipe threads, unions, flanges, flared tube fittings or
other specially designed connectors. End fittings are attached by welding,
silver brazing, soldering or other by other mechanical means, depending
on the type of hose.
Motion
Flexible metal hose is used
in four types of applications:
-
To correct misalignment
-
To provide flexibility in manual
handling operations
-
To compensate for regular or
constant movement
-
To absorb vibration
In all types, careful hose selection,
design of the assembly and installation are important for optimal service
life. Mechanical design and the flexibility of its material determine the
flexibility of a hose. |
