8 BULKDISTRIBUTOR Components
Sanitiser and
grounding –
May/June 2020
beware of sparks
The metal cages containing the plastic IBC should be grounded (as it appears to be here)
As many companies reconfigure
production lines to produce hand
sanitisers, consideration needs to be
given to incendive electrostatic
discharges, says Mike O’Brien, managing
director of Newson Gale
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Manlid Assemblies
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Many companies are reconfiguring production lines, or
starting up new ones, to increase the supply of hand
sanitiser in response to the COVID-19 pandemic.
However, industry groups like the Solvents Industry Association are
concerned with reports of inappropriate packaging of solvents and
an incident of a static discharge igniting vapours present on an
operator’s hand after the application of hand sanitiser.
This note outlines what approaches can be taken in terms of
managing the risk of solvents (including alcohols) being ignited by
uncontrolled discharges of electrostatic sparks.
The importance of grounding people
Managers of facilities where operators have exposure to potentially
flammable or combustible atmospheres need to ensure the
operators are grounded. This is because people isolated from a
ground source (eg, flooring capable of dissipating static charge to
earth) can accumulate large electrical potentials (voltages) beyond
20,000 volts without even realising it until they discharge a spark.
In addition, if operators are regularly applying hand sanitisers,
either inside or outside a designated hazardous area, it is important
to ensure that they do not have the potential to accumulate
electrostatic charge on their bodies.
Ignition of vapours emanating from the hand can occur if the
person approaches or touches a grounded object (eg, door handle,
stair railing) resulting in a static spark discharge with enough energy
to ignite the vapour.
The most effective means of grounding personnel is to ensure that
they are provided with safety footwear that meets the static
dissipative criteria specified in standards like EN ISO 20345 or ASTM
F2413-18. Testing all footwear prior to entry into the facility is
recommended. Easy to use footwear testers can be installed at
designated entry points to hazardous areas in the facility, (or to the
overall facility if required).
Such testers use a simple plate on which an individual stands, with
their safety shoes on, and presses a button with their index finger to
initiate the test. If the resistance threshold of the shoes is below the
required level, as specified in EN ISO 20345 or ASTM F2413-18, the
test will indicate a positive output with a green LED indicator which
provides the operator with a ‘Good-to-Go’ message that he/she can
enter the hazardous area.
If the shoes fail the test the indicator will stay red and the tester’s
buzzer alarm will activate. At this point the operator should not
enter the hazardous area and should report the failed shoe test to
the most relevant authority in the facility. An inter-lockable output
contact can be specified to control the door entry system and
prevent access to the hazardous area.
Containers
In relation to the use of containers, particularly IBCs, they should,
ideally, be of an all metal construction so that when they are
grounded, electrostatic charge cannot accumulate on the surface of
the container. If the supply or use of fully metal IBCs is not possible,
then the metal cages that contain the plastic container should be
grounded.
Splash filling should be avoided as this increases the rate of charge
generation.
If electrostatic charge is permitted to accumulate the voltage of
the IBC will rise very rapidly and result in this energy being
discharged in the form of an electrostatic spark onto a grounded
object like an operator. If the spark energy is sufficiently high it will
ignite the surrounding vapours with little effort. A discharge at
20,000 volts would be up to 60 mJ of energy via the static spark.
Best practice information
It is not possible here to discuss every potential process involving the
use of solvents. However, a more comprehensive summary of the
various processes at risk of static discharges in solvent processing
and handling operations can be viewed on the European Solvents
Industry Group website.
www.esig.org/solvents-and-static-electricity