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Sandblasting/Blast Cleaning

Interblast first became involved in sandblasting in the early 1970's, undertaking the repairs on an old wrought iron toll bridge over the River Wyre. It soon became apparent that, prior to any welding repairs, layers of old paint would need to be removed. Hand tools and needle guns were not sufficient for this and it was decided sandblasting would be the only method to remove the paint successfully.

Applications

From those early beginnings, we have now built up the experience and facilities to handle items for various applications and industries:

blasting
  • Aerospace
  • Off-shore
  • Power
  • Rail
  • Pulp & Paper
  • Chemical
  • Domestic
  • Hobbies

Capabilities

We have the capacity to handle steel fabrications, tanks, vessels and pipework assemblies.

Sandblasting types we use include:

  • Grit Blasting
  • Steel and Shot Blasting
  • Aluminium Oxide Blasting
  • Garnet Blasting
  • Glass Bead Blasting

Sandblasting

Sandblasting is a generic term for the process of smoothing, shaping and cleaning a hard surface by forcing solid particles across that surface at high speeds; the effect is similar to that of using sandpaper, but provides a more even finish with no problems at corners or crannies.

Sandblasting can occur naturally, usually as a result of the particle blown by the wind causing eolian erosion, or artificially, using compressed air. An artificial sandblasting process was patented by Benjamin Chew Tilghman on October 18, 1870.

Historically, the material used for artificial sandblasting was sand that had been sieved to a uniform size. The silica dust produced in the sandblasting process caused silicosis after sustained inhalation of dust.

Sandblasting may now only be performed in a controlled environment using ventilation, protective clothing and breathing air supply.

Other materials for sandblasting have been developed to be used instead of sand; for example, steel grit, steel shots, copper slag, glass beads (bead blasting), metal pellets, dry ice, garnet, powdered abrasives of various grades, powdered slag.

Even ground coconut shells or corncobs have been used for specific applications and produce distinct surface finishes.

British Standards

The preparation of steel substrates before the application of paints and related products is imperative. Therefore, the visual assessment of surface cleanliness needs to be carried out to appropriate standards.

Also, the performance of protective coatings of paint and related products applied to steel is significantly affected by the state of the steel surface immediately prior to painting.

The principal factors that are known to influence this performance are:

  • the presence of rust and mill scale
  • the presence of surface contaminants (including salts, dust, oils and greases)
  • the surface profile

The preparation grades are designated by the appropriate letters: Sa – Denotes the surface preparation by blast cleaning.

ISO logo

Interblast is a BS EN ISO 9001: 2000 Registered company – our certificate (560kB PDF) is available
for download

Sa 1 – Light Blast Cleaning

When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter.

Sa 2 – Thorough Blast Cleaning

When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from most of the mill scale, rust, paint coatings and foreign matter. Any residual contamination shall be firmly adhering.

Sa 2½ – Very Thorough Blast Cleaning

When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from mill scale, rust, paint coatings and foreign matter. Any remaining traces of contamination shall show only as slight stains in the form of spots or stripes.

Sa 3 – Blast Cleaning to Visually Clean Steel

When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and shall be free from mill scale, rust, paint coatings and foreign matter and have a uniform metallic colour.

Permission to reproduce extracts from BS ISO 8501-1 1998 (Supplement) is granted by the British Standards Institution. British Standards can be obtained from BSI Customer Services, 389 Chiswick High Road, London W4 4AL, UK. Tel: 020 8996 9001 (email)