These two systems are primarily used for the cleaning of, and paint removal from, historic and modern masonry surfaces. The DOFF system produces a spray of high temperature water at up to 150ºC and is most suited to the removal of flexible soilings and coatings. The TORC system combines compressed air, fine abrasive and water and is best suited to the removal of brittle soilings and coatings.
When correctly used, the output of both systems can be regarded as of extremely low risk to the environment. Separate consideration must be given to what is being removed in the cleaning process and whether that contains any hazardous matter. Method Statements are available for both systems which give general guidance and precautions for use.
Provision must be made to prevent discharge of any solid waste, toxic or otherwise, into a water course. A range of abrasives are available for the TORC system, but only Calcite, Dolomite or Calcium Carbonate are recommended when cleaning is carried out adjacent to a water course. These three abrasives are from natural sources and present a negligible pollution risk. Health & Safety Data Sheets are available. Various grades of “Unil” (a synthetic abrasive) is also available but is not recommended for use near a water course due to the trace content of some metallic compounds (e.g. copper), which could present a minor ecological problem if accidentally spilled in large quantities.
The main pollution risk with the equipment is the accidental or malicious spillage of fuel. The hotbox should be located in a tray or bund. The fuel capacity of the hotbox is 13 litres. An air compressor is required for use with the TORC system. Apart from the risk of fuel spillage, the compressor will contain a significant volume of oil, loss of which could occur under certain types of mechanical failure. It is very important that only a compressor in very good condition is used. The pumps of both systems have oil filled crankcases. Whilst the content is low, less than 0.5 litres each, the pumps should be located within a tray or bund or over an oil absorbent mat as a precaution.
Descaling of the DOFF (use of an acidic ‘descaler’ to remove limescale from the hotbox and hoses) should be carried out where accidental spillage of acid or residue can be controlled. Such liquid residue, once neutralised with chalk or limestone dust, can be disposed to the foul drain.
The TORC system is fitted with two water traps, one to the air cooler and one to the pressure pot. These will remove a small but significant quantity of water from the air supply. It is possible that the compressor may also release some oil into the air flow which the water traps would remove. For this reason, the discharge from the traps should be directed into a small vessel or located over an oil absorbent mat, even though such spillage will be negligible.
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