| Hose
Products |
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| Q: |
With so many types of hoses available,
is rubber or thermoplastic a better choice? |
| A: |
It really depends on the application. Both have
advantages and disadvantages. For example:
- Thermoplastic hose typically weighs less than
rubber hoses in comparable sizes.
- Thermoplastic hoses usually have a smaller envelope
size than rubber hoses.
- Rubber hoses are usually available in larger sizes
that thermoplastic hoses are not.
- Rubber hose tends to be less prone to kinking
thus being easier to route than thermoplastic hose.
- Thermoplastic hoses can have better low temperature
ratings than rubber, where rubber can have better
high temperature ratings.
- Thermoplastic hose usually has a wider fluid compatibility
range than rubber hose.
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| Q: |
What's the difference between a hose's working and
burst pressure? |
| A: |
A hose's published working pressure is the maximum
pressure the hose should see while in service. This
includes any spikes that may occur during operation,
A hose's published burst pressure is the value at which
a brand new piece of hose will fail at during a one
time pressure test.
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| Q: |
Is it necessary to clean out a hose or tube assembly
before installing it? |
| A: |
Yes. Contamination is the leading cause of problems
in hydraulic systems. Hose and tube assemblies should
be blown out with filtered shop air or flushed and blown
out with a solvent which is chemically compatible with
the hose material. The ends of the hose and tube assembly
should be capped and/or plugged until the assembly is
installed. |
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| Q: |
If I have a hose that's rated at 3,000 psi working
pressure and has a published burst pressure of 12,000
psi, why can't I use it in a 3,500 psi system? |
| A: |
Hose manufacturers give hoses working pressures and
burst pressure. These are typically at a 4:1 ratio (not
safety factor) to each other. When choosing a hose for
a system, select a hose that is rated at or above the
maximum pressure that can occur in the system. Often
times, these values may be higher than the relief setting. |
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| Tube
Fittings |
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| Q: |
What are some guidelines I can follow when preparing
tube ends for connections? |
| A: |
Tube-end preparation is one of the most critical
processes in obtaining an optimum seal of any flanged,
brazed, flared or preset tube end onnection. To help
assure the tube to fitting connection remains leak
free, you should folow the guidelines below:
- It is critical that the tube be cut squarely within
±1° in order to assure the proper tube
to fitting connection. If the tube is not cut squarely,
it will result in the tube not resting properly
in the braze sleeve or fitting body. A tube end
which is not cut squarely may also result in a flange
or flare which is not circular.
- When cutting tube in preparation for flanging,
brazing, flaring or presetting, a saw which utilizes
a toothed blade is recommended. This type of tool
will assure that the tube end is not hardened from
excessive heat or working of material.
- Deburring the inside and outside diameter of the
tube end is necessary to assure the tube fits properly
inside the braze/flange/flare sleeve or ferrule
and fitting body. Proper deburring of the tube end
is necessary to form a flanged or flared tube end
which is free of imperfections that may create a
leak path between the tube and the fitting seal
or sealing surface.
- Debris may remain in the tube end from both the
cutting and deburring process. Debris present in
the tube end can result in system contamination
or can be formed into the flange or flare which
may result in imperfections that are potential leak
paths. It is recommended that the tube end be cleaned
properly prior to any further processing such as
flanging, flaring, brazing or presetting.
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| Q: |
Are forged tube fittings better than brazed styles? |
| A: |
Yes. Forged fittings are inherently stronger than
brazed styles. A forging is formed from a single piece
of metal. A brazed fitting is made up of two or more
separate parts. Therefore, the possibility of leakage
or failure at one of the braze joints can be a concern. |
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