You can apply wet slip enamel to metal surfaces by:

  • dipping
  • air-assisted spraying
  • wet electrostatic spraying using air-assisted and rotary atomisers
  • electrophoretic deposition.

Powder enamel is always applied using electrostatic equipment. Spray systems may be automated or manual.

What you must do

Dry application methods can create dust, especially if you pour dry, ground enamel through a vibrating screen. You may need to take measures to control dust on your premises.

Air quality

In the spraying process, you may produce waste water from slip applications, wetback spraying booths and cleaning activities.

You must not make any discharge to surface water or groundwater without consulting your environmental regulator. If you discharge without an authorisation, permit or consent from your environmental regulator you could be prosecuted and fined or imprisoned.

Preventing water pollution

You must not discharge trade effluent to a public sewer without trade effluent consent or a trade effluent agreement with your water and sewerage company or authority. If you discharge without a consent or agreement you could be prosecuted and fined or imprisoned.

Trade effluent - discharges to sewers

You must comply with your duty of care responsibilities when dealing with waste.

Duty of care - your waste responsibilities

Controls have been introduced to limit the sulphur content of fuels. You must not use gas oil with a sulphur content exceeding 0.1% by mass.

You must not use heavy fuel oil with a sulphur content exceeding 1% by mass. This is particularly relevant if you have stocks of stand-by fuel that can remain unchanged for considerable periods of time. If you operate pre-1987 combustion plant you can apply for a Sulphur Content of Liquid Fuels Permit from your local council in Northern Ireland or SEPA in Scotland.

Good practice

  • Leave extraction and abatement equipment running when you clean your application booths. This will reduce air pollution.
  • Clean up any spillages as quickly as possible. If the material is dry, use vacuum-cleaning techniques instead of washing-down techniques. This will avoid water pollution and water use.
  • Mask off empty positions on jigs to reduce the amount of cleaning required.

Jigging equipment

  • Ensure that your compressors are sited where there is a free flow of cool air. This will reduce energy consumption, condensate production and water evaporation in the slip.
  • Reduce cleaning by batching items and colours. Minimise colour changes and coat from light to dark enamels.
  • Use strippable booth coatings for easier cleaning of the spray booth.
  • Wipe your spraying equipment clean before washing.
  • Use automated gun washing machines to reduce your water consumption.
  • Carefully inspect components to avoid coating obvious rejects.
  • Rotate items when removing them from dipping baths. This helps achieve an even coating and reduces drag-out.
  • Allow sufficient drain-out time when inverting enamelled items. This improves materials efficiency and removes excess enamel.
  • With any spraying technique there will be some over-spray. Keep your spraying booths clean so that the over-spray can be recycled.
  • For manual spraying operations, ensure that your staff are trained in the correct techniques.
  • Regularly measure over-spray.
  • For automatic spraying operations, regularly evaluate spray patterns to ensure that the process is running efficiently.
  • Use electrostatic spraying techniques. These produce lower levels of over-spray as the charged particles are attracted to the item to be coated.
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