are a number of Health and Safety Regulations and Guidance
Notes regarding Finishing Plant.
ENGINEERING, recommends that you obtain, as a minimum,
a copy of the booklet HSG 178 available from the
Health and Safety Executive.
will be very pleased to advise
on your specific requirements.
Please find below a 'synopsis' of our understanding of the
main hazards from the use of flammable liquids are fire and
explosion, involving either the liquid or the vapour given
off from the liquid. Fires or explosions are likely to occur
when vapours or liquids are released into areas where there
may be an ignition source, or when an ignition source is introduced
into an area where flammable liquids are being used.
liquids can pose a health hazard if they are ingested, come
into contact with skin or eyes, or if their vapours are inhaled.
Highly Flammable Liquids and Liquefied Petroleum Gases Regulations
1972,16,17 require precautions to reduce the risk of fires
and explosions. These precautions include measures to prevent
a flammable athmosphere from being formed and to control ignition
the Management of Health and Safety at Work Regulations 1992,
18,19 every employer has a duty to carry out an assessment
of the risks to the health and safety of employees and of
anyone who may be affected by the work activity.
usual way to control the flammable vapours arising from spraying
processes is to use a ventilated spray booth or enclosure.
Its purpose is to:
the escape of vapours into the Workplace
Prevent contamination of the workplace by overspray
Protect the health of workers
Provide separation from sources of ignition and to prevent
the spread of fire:
Prevent contamination of the workpiece by dust and grease
and from the work environment.
Draw overspray away from the operator.
Control flammable and hazardous vapours.
Collect vapours, droplets and solid particles: and
Filter or wash the air before it is discharged.
are many different designs of spray booth. The design of the
booth will depend on the articles to be sprayed.
spray booth or enclosure should be of half-hour fire resisting
construction. If spraying is carried out in a partial enclosure,
a work area or a spray space, then it should be fire separated
from adjoining rooms.
ventilation should be sufficient to prevent the formation
of dangerous concentrations of flammable vapours.
basic parameter used to specify ventilation requirements is
the control velocity. This is the air velocity at the operative's
position. The control velocity required depends on the spraying
conditions. It should be sufficient to overcome turbulent
air movements generated by hoth the process and random air
currents. It should also be sufficient to draw polluted air
away frorn the operator.
minimum average air velocity of 0.7 m/s at the front of open-fronted
booths and enclosures is recommended. If the sprayer works
inside a side-draught booth or enclosure, the minimum average
air velocity where the sprayer stands should be not less than
0.5 m/s vhith a minimum measured value of 0.4 m/s. Where a
sprayer works inside a down-draught booth or enclosure, air
velocity (measured at points around a typical article to be
sprayed) should average 0.4 m/s with a minimum measured value
of 0.3 m/s.
of proprietary equipment should advise on the appropriate
flow rates for the proposed purpose.
is advisable to leave the fan running for several minutes
after spraying has finished in order to remove vapours from
the system effectively. This can be done with a time delay
in the control circuit of the fan motor. Wet items should
not be left in a booth or enclosure when the ventilation is
switched off, such as during lunch or tea breaks or at the
end of the working day as a flammable atmosphere may develop.
is impossible to avoid flammable atmospheres during spraying
of flammable liquids and so control of ignition sources is
essential. Ignition sources include:
Welding and other similar hot work activities;
Sparks generated by the discharge of static electricity;
Iinternal combustion engines.
sources should be kept out of spraying areas at all times.
Even when spraying is not taking place, flammable residues,
contaminated materials, drying and cleaning operations may
still present a fire risk.
area classification is the method used to identify areas where
flammable concentrations of gases or vapours are likely to
be present. The aim is to reduce to a minimum acceptable level
the probability of a flammable atmosphere coinciding with
an electrical or other source of ignition. It is normally
used to select fixed electrical equipment but it can also
be used in the control of other potential ignition sources
such as portable electrical equipment. hot surfaces and vehicles.
are three classes of hazardous area or zone: zone 0, zone
1 and zone 2. A zone is an area around a process or activity
where a flammable atmosphere may be present.
It is advisable to exclude electrical equipment from the spray
electrical equipment that has to be inside the spray area
should be designed and constructed for use in a zone 1 or
zone 2 according to the hazardous area classification. All
other sources of ignition should be removed from the hazardous
0 An area in which an explosive gas mixture is continuously
present or present for long periods.
Zone 1 An area in which an explosive gas mixture is likely
to occur in normal operation.
Zone 2 An area in which an explosive gas mixture is not
likely to occur in normal operation, and, if it does occur,
is likely to do so only infrequently and will exist for
a short period only.
spray areas, the zones depend on where spray gun may be used,
the level of ventilation, the output of the spray gun, the
flashpoint the spray and its vapour density.
many cases a qualitative or 'common-sense' assessment will
be sufficient. For example. everywhere in range of the spray
gun should be considered as zone 1. For spray booths, the
simplest approach is to regard the whole booth interior as
zone 1, and to exclude all electrical equipment and other
sources of ignition. Adequate lighting of the interior of
the booth may be achieved either by using protected lighting,
or by allowing light from an overhead fitting to shine through
half-hour fire-resistant glass panels sealed into the top
of the booth.
ductwork should be at least half-hour fire resisting. It should
be as short as practicable and have no sharp bends, as this
tends to decrease the air flow and allow the deposition of
residues. Access points for inspection and cleaning inside
the ducts may be needed. Dampers should not be fitted in exhaust
ducts unless they are essential for balancing the ventilation
motors for fans should not be situated in the path of flammable
vapours. This may be achieved using bifurcated, centrifugal-type
or belt-driven axial fans. Motors (even if they are of flameproof
construction) should not be sited within the ducts.
a relatively high volume of air will be exhausted, it is important
that the room containing the spray process is provided with
adequately sized fresh air inlets.
vapours are also released during the drying process and may
present a serious fire hazard. The drying conditions will
depend on the type of coating, some will dry at room temperature,
others may need curing or baking at higher temperatures. For
drying at room temperature, the spray booth or a designated
drying or 'flash-off ' area may be used. Ventilation should
be provided to prevent the build-up of flammable vapours.
are used for drying or curing at higher temperature. They
may be separate or combined with a spray booth (combi-booth).
They should be ventilated to prevent the build up of flammable
vapours. Some are designed to recirculate a proportion of
the warm (solvent laden) air. It is important to ensure that
the dampers are positioned to maintain an adequate exhaust
flow rate. The vapour concentration may be monitored with
gas detectors which trigger an alarm, emergency ventilation
and shutdown, if the concentration exceeds a specified level.
relief should be properly maintained: it should be covered,
obstructed or nailed down. It should vent to a safe place.
the advice on this webpage will help to reduce the risk of
a fire occurring. Unfortunately, the possibility of fire always
remains. It is important to have a pre-planned response to
such emergencies, including the appropriate actions to be
taken in the event of a fire. The main aim is to ensure people
can escape to a place of safety.
Fire Precautions Act 1971 requires the following as a minimum:
A system of giving warning in the case of fire;
Management procedures to ensure that all of the above are
available and maintained, and that there is adequate training
in their use.
Means of escape
in spray booths or workshops tend to develop extremely rapidly.
There should be adequate means of escape from enclosed, walk-in
booths. Operatives should never be more than 6 m from an exit
the booth is located within a workshop or the workshop is
a spray area, then there should be adequate means of escape
from the workshop. Again, operatives should never be more
than 6 m from an exit door. At least one exit door from the
workshop should open either directly into open air, or into
another part of the building from which there is an exit direct
to open air, separated from the spraying area by a fire-resisting
construction having at least 30 minutes fire resistance. All
exit doors, either emergency or normal use doors, from spray
booths or workshops should open outwards.
is advisable to discuss the installation of a sprinkler system
with the fire authority and with the fire insurance company.
The fire authority will also need to discuss their requirements
for fire fighting such as water supplies and access for appliances.
above is intended as an introduction and is not a comprehensive
document please contact a specialist
at RDM ENGINEERING for more information.
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