| Alert Listing |
These and similar fuel gases may damage
some grades or types of welding hose:
APACHI, FLAMEX, MAPP, PROPANE, PROPYLENE.
Use of the indicated or similar fuel
gases at regulator settings above 40 psi
may be particularly hazardous.
Users are also alerted against the use
of ACETYLENE at any pressure above 15
psi.
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The user is first cautioned to shut off
the gas at the torch and then at the regulator
or supply source when the torch will not
be used for periods in excess of 30 minutes,
in order to limit permeation of gas through
the hose wall.
The user is further cautioned not to
shut off the fuel gas at the regulator
or supply source first as a flashback
may result and thereby damage the hose.
Adequate ventilation must be provided
in confined areas where fuel gas is being
used to prevent the accumulation or concentration
of gas that could be explosive or otherwise
harmful to personnel.
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| The RMA/CGA specification
for welding hose, as originally promulgated,
considered welding hose that would be used
to convey the then common fuel gas, acetylene,
at the recommended low pressure (15 psi).
Several grades were described, the variance
between grades relating to a difference
in their resistance to deterioration in
the presence of oil, or to their resistance
to destruction by flame, or both. No differentiation
was made for a variance in performance resulting
from exposure to the fuel gas itself. It
had been determined that acetylene, when
conveyed under low pressures common to its
recommended use, had little effect on the
hose, regardless of its composition or construction.
In recent years, there have been developed
or adopted a number of fuel gases based
on specific hydrocarbons or mixtures of
hydrocarbons. It is known that these special
fuel gases have a different effect on
rubber compounds than does acetylene.
The precise effect on all the many and
varying hose compounds and constructions
of the many manufacturers has not been
determined for all the known special fuel
gases.
The effect of any material being conveyed
in a hose on the rubber compounds used
in the hose can be measured by one or
several test procedures. In the case of
fuel gases, the test procedures most applicable
would be designed to measure a change
of the physical properties after exposure
to the fuel gas including tensile, elongation,
hardness and volume.
A characteristic of rubber hose that
is significant in its use as welding hose
is a phenomenon know as permeation. Any
gas confined in the bore of a hose exhibits
a tendency to pass through the tube wall
and subsequently through the reinforcement
and cover to the environment. Each gas
has its own specific characteristic tendency
to permeate. Each rubber compound exhibits
specific resistance to permeation. The
rate of permeation increases with higher
temperature. To minimize the permeation
of fuel gas through the hose wall it is
logical to design the tube compound for
the lowest possible permeation rate. The
problem in the case of welding hose results
from the variety of gases now encountered,
the varying pressures used in service,
and the varying temperatures to be found
in the work place. The need to ventilate
the work place is evident, both for maintaining
the lowest practical temperature and to
dissipate the permeating gas, however
slight, to prevent buildup to concentrations
that are either explosive or dangerous
for breathing by workmen.
Some rubber compounds are known to have
low permeation rates with several fuel
gases but no specific rule can be laid
down to predict overall performance. Thus,
it becomes advisable to check the characteristic
of each hose construction with each gas
under actual or simulated service conditions
to qualify it for use.
CAUTION:
Users of welding hose are urged to communicate
their service conditions to the hose manufacturer
and obtain the best recommendation of
the manufacturer for a hose suitable for
those conditions.
Thank you to Goodyear Tire & Rubber company. Source material
Goodyear Catalog #99-130. Any errors in the transcription of this data are solely
the responsibility of JGB Enterprises, Inc. No warranty, including implied warranty
of merchantablility, fitness for a particular purpose, or other warranty of quality
is either expressed or implied of this product. |
