Stainless Steel Flexible Hoses
Keyser Stainless Steel Flexible Hoses
Keyser Technologies leads the region in advanced flexible hose engineering. Keyser has an unrivalled reputation in the design, manufacture and supply of wide range of metal hoses in the region to suit various industries. The series of stringent tests and quality control ensures a product of the highest possible quality that meets the stringent demands of the industry today. Keyser's metal hoses are used throughout the region for use in automotive, petrol chemical plants, power generator plants and other industrial applications.
Selection of Metal Hoses
A number of factors affect the selection of the right metal hose for the right application.
|
1. Pressure
a. Maximum Working Pressure
This is the maximum operating pressure the hose will be subjected to. It is usually at 25% of the Nominal Design Burst Pressure.
b. Maximum Proof Pressure
This is the maximum test pressure the hose will be subjected to. It is usually at 150% of the Maximum Working Pressure with the hose installed straight.
c. Nominal Design Burst Pressure
This is the pressure point where the hose can be expected to rupture. Based on the minimum annealed tensile strength of the braid wire and corrugated hose alloys at 21…C with the hose installed straight.
d. Shock Pressures
When this occur possibly due to fast closing valves, the peak pressure shall not exceed 50% of the Maximum Working Pressure.
e. Pressure Relative to Unbraided Hose
At Maximum Working Pressure, 1 to 2.5% elastic elongation might take place in unbraided hose assembly. The unbraided hose should be unrestrained at one end or installed in a manner to allow free axial expansion due to pressure. This is to avoid squirm from occurring.
f. Pressure Relative to Braided Hose
Elongation occurs when internal pressure is applied to a corrugated metal hose. To avoid this, a wire braid sheath over the hose is applied. The braid has minimal effects on the bending and flexibility.
g. Pressure Relative to Temperature
For operating temperatures in excess of 21…C, the tabulated pressures must be decreased in accordance with the table below.
|
|
|
2. Maximum Service Temperatures Of Materials
3. Flow Velocity
a. Use of a fully interlocked flexible metal hose
Where flow velocity exceeds 30.5m/sec (gas) / 15.25m/sec (liquid) in unbraided hose, or in 45.75m/sec (gas) / 22.84m/sec (liquid). In conditions where there are bends, these flow conditions should be reduced by 50% for a 90… bend and 25% for a 45… bend.
b. Use of corrugated metal hose
When the amount of pressure drop through longer lengths of hose is a significant factor, a larger diameter hose may be required. Generally, pressure drop through a corrugated metal hose is approximately three times that in comparable size standard steel pipe.
|
4. Motion
a. Offset Motion
Offset motion is the parallel motion that occurs in a tube with flanges at both ends, while the distance between the flanges remain the same.
b. Radial Motion
When a tube is bent and attached, radial motion is the horizontal or vertical motion at the beginning of the circular arc. Generally called a moving loop, the amount of motion is expressed as the horizontal or vertical distance moved.
c. Axial Motion
Axial motion refers to the dimensional variation of a flexible tube along its longitudinal axis, and displacement is expressed as the amount of extension/contraction.
d. Permanent Bend
Permanent Bends are used in place of ordinary bent pipe to simplify the connection of two piping systems.
e. Random Motion
This is the last mode of motion. A good example will be the garden hose. When it is freely handled, it moves randomly
| |
|
|
5. Motion Frequency
A flexible metal hose may be subjected to repeated flexing or bending. Generally, these are separated into basic categories, vibration, intermittent, continuous and static bend.
a. Vibration
Vibration is shown as the un-shaded area of the chart in the diagram. When the expected combination of double amplitude and frequency falls into the shaded area, consult our engineers.
b. Intermittent Motion
This refers to the motion that occurs on a regular or irregular cyclic basis due to thermal expansion and contraction.
c. Continuous Motion
This refers to the motion that occurs on a regular cyclic basis normally at a slow cyclic rate and constant travel.
d. Static Bend
This refers to the minimum center line bend radius which a flexible metal hose may be bent for installation.
| |
|
6. Cycle Life
The cycle life is affected by several factors such as operating pressure, operating temperature, bend radius, materials used etc. The cycle life is also proportional to the sum of the pressure stress range and deflection stress range.
Please note that all these information serves as a general guide only.
