Environmental Protection Act (PG6/23)
The Environmental Protection Act is a
Secretary of State’s guidance note for processes involving the control of
air pollution. PG6/23 relates to the coating of metal and plastic.
INTRODUCTION
This note relates to processes for
coating metal or plastic where the process is likely to use more than 5
tonnes of organic solvent in any 12 month period. This note refers to
general coating processes, for example car component coating, domestic
appliance coating, metal furniture etc. and applies in cases where there is
no specific industry user Note. This Note may also be applicable to the
coating of other substrates such as glass, where there is no Note specific
to the process.
UPGRADING
In the case of general industrial metal
and/or general industrial plastic finishing processes where the total
organic solvent consumption is between 5 and 15 tonnes per annum, only in
exceptional circumstances should upgrading completed later than 1st
April 2007. General industrial metal and/or plastic finishing processes
includes trade coaters, general engineers, industrial equipment
manufacturers, furniture manufacturers and heavy equipment manufacturers.
EMISSIONS
The following emission concentration
limits are the major areas that should apply to releases from spraybooths,
ovens, degreasers etc.
|
Emissions |
Concentration |
|
Total particulate
matter |
50 mg/m3 |
|
Isocyanates
(expressed as total NCO group (Excluding
particulate matter)
|
0.1 mg/m3 |
|
Volatile organic
compounds (expressed as total carbon excluding particulate matter) other
than from
|
50 mg/m3
where the organic solvent consumption is 15 tonnes or more per annum) or
150 mg/m3 (where organic solvent consumption is between 5 and
15 tonnes per annum) |
MONITORING
Emissions from spray booths should be
tested at lteast once a year for total particulate matter. Where
spraybooths are vented to volatile organis compounds arrestment plant (for
example, an incinerator), emission testing for particulate matter should be
undertaken on the exhaust from the volatile organic compounds arrestment
plant. However, where the operator can demonstrate that a number of
processes carry out similar operations which lead to emissions of the same
nature and volume, the local enforcing authority may approve a sampling
programme. In any case, each emission should be tested at least once every
4 years and at least 25% of all emission points should be tested each year.
Emissions from arrestment plant should be tested at least once a year.
Where coatings containing isocyanates
are used, emissions should be tested at least once a year for isocyanates.
THE SPRAYING PROCESS
Spray application of coatings should
be achieved by the use of air assisted airless, centrifugal, HVLP (High
Volume Low Pressure) where the atomisation pressure is less than 69kPa (10
psi) or any electrostatic application systems. Any other application method
should be permitted if the local enforcing authority is reasonably satisfied
that the transfer efficiency of solids is at least 65% (i.e. compliant
technology).
There will be a limited number of cases
where high-solid, heavy-duty coatings are applied to structural steel used
in civil and marine engineering (such as girders and RSJs) and to shops and
other marine vessels and where airless methods should be accepted. These
are cases where air assisted airless or other methods could only be used by
adding organic solvents to the coating.
EXHAUST DUCTING
It is no longer the case that all
ducting should terminate 3m above the apex of your building. The height of
chimneys and vents from process and arrestment plant should be assessed on
the basis of estimated ground level concentrations of the emitted residual
pollutants.
The chimney height so obtained should be
adjusted to take into account local meteorological conditions, local
topography and other local emissions.
Insofar as the scope of the document is
relevant, the calculation procedure in HMIP Technical Guidance Note D1
should be used as a basis for the assessment. Alternative dispersion models
may be used by agreement with the local enforcing authority.
A minimum discharge velocity should be
required in order to prevent the discharged plume being affected by
aerodynamic downwash (typically 15m/s). This clause should not, however,
apply to vapour degreasing operations in order to avoid solvent drag out.
Where necessary to prevent or minimise
droplet emissions, the linear velocity within the chimney should not exceed
9m/s.
Chimneys or process vents should not be
fitted with any restriction at the final opening, for example a plate, cap
or cowl. A cone fitted at the chimney exit to increase efflux velocity
should be permitted. The discharge should be vertically upwards.
Related industries and documents that
have to comply with the EPA are listed below. The legislation may well be
similar but not identical to the above.
PG6/7
Printing and Coating of Metal Packaging
PG6/13 Coil Coating Processes
PG6/14 Film Coating Processes
PG6/15 Coating in Drum Manufacturing and Reconditioning Processes
PG6/20 Paint Application in Vehicle Manufacturing
PG6/31 Powder Coating Processes
PG6/32 Adhesive Coating Processes
PG6/34 Re-spraying of Road Vehicles
PG6/40 Coating and re-coating of aircraft and aircraft
components
PG6/41 Coating and re-coating of rail vehicles
