Absauge- Abgas und Förderschläuche

Allgemeine Hinweise
General Information
Electrostatic charges in
conveying and extraction plants
1. When materials are conveyed
through plastic tubing, an electrostatic
charge arises because of the
friction of the product conveyed
against the tubing wall. At the
same time, continuous charging
processes take place between the
individual particles when there is a
flow of finely distributed materials.
This applies in particular for
chip and dust extraction plants, etc.
Electrostatic charging is
comparable with stored electrical
energy, the so-called capacitor
effect. The stored energy is
released again on discharge, so
that at a sufficient charge density,
sudden discharge can take place.
The discharge can also be
triggered by contact of charged
particles to earthed objects. Here
the discharge can have the
following effects:
a)Interference with electronic
components and thus faulty
operation of machines and
systems.
b)Heat can be generated by the
discharge leading in the
presence of combustible gases
or vapours to increased risk of
ignition and explosion.
Objects made from conductive
materials whose leakage resistance
is not greater than 10 6 ohms are
considered to be electrostatically
earthed.
2. A differentiated assessment of
ignition risks as well as of the
protective measures to be taken
requires accurate knowledge of
the materials and processes
involved as well as taking into
account the relevant regulations
and must therefore be made
separately from case to case.
When conveying and extraction
tubing with supporting helix is
used, not only parts of the conveyed
product being deposited or
clogging of the tubing can be
largely decreased but the risk of
ignition can be reduced by
earthing the supporting helix.
The specific resistance of the
tubing material can be reduced by
the incorporation of conductive
pigments so that plastic with a
leakage resistance of no more
than 10 6 ohms can be used.
3.These statements are to be viewed
only as for guidance. It is therefore
advisable to assess conveying
and extraction tubing under the
local conditions of use and their
application.
Instructions for Application
Spirally rolled metal hoses to be
used as suction, blower and silo
hoses
When using spirally rolled metal
hoses with polygonal cross section
with engaged angular profile and
without sealing, leakage must be
expected. No leakage is admissible if
the flow medium is dangerous to
health or explosive.
Spirally rolled metal hoses are particularly
produced for suction conveying
and can be used for pressure
conveying with slight overpressure
only.
Waste Gas Metal Hoses with
sealing free of harmless
substance
In many cases environmental protection
requires compromises concerning
the use of e. g. substitutes
free of harmless substance. Concerning
the substitution for asbestos,
there is presently no material
matching the positive characteristics
of asbestos, in view of the mechanical-dynamical
stress, especially in
application as metal hose sealing.
The glas fibre sealing is an alternative
of harmless substance with the
limiting characteristic that the
duration of life of the dynamically
strained metal hose sealing is
substantially reduced. At the same
time a higher leakage rate must be
expected due to the fact that the
brittle material is expanding faster
than asbestos.
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