Patent GB-830962-A (GB)
Title: A new or improved method of and equipment for cleansing surfaces of oily deposits
Inventor: HARTOG HUIB WILLEM
IPC: B08B9/093
Filed: 1954-12-14
Abstract: A liquid for cleaning the internal surfaces of fuel tanks, in particular a cleansing liquid comprising a 0.5% by weight solution of a long chain secondary alkyl sulphate and 10% by weight of sodium chloride, is maintained at a pH lower than 7. The detergent compound may, however, be any detergent stable in acid solutions, and may be anionic, cationic or non-ionic.  The liquid may also include acid sodium phosphates, sodium sulphate, sodium nitrate and sodium nitrite.  Equivalent potassium or ammonium compounds may also be used.  If the liquid is not sufficiently acid, an organic acid, e.g. formic, acetic or lactic acid, or an inorganic acid, e.g. hydrochloric, sulphuric or nitric acid, is added.  Specifications 696,631, 742,844, 808,901 and 808,902 are referred to.ALSO:A mixture of cleansing or detergent liquid and removed oily deposits to be separated by gravity is caused to separate more rapidly by maintaining the cleansing liquid, at least during the separating stage, at a pH lower than 7.  The cleansing operation may be performed by the apparatus described in Specification 696,361, such apparatus including a pH reducing tank for containing cleansing liquid with extra acid, and means for introducing the latter into the system as and where desired to maintain the pH at the required level, for example, by pH indicators at various points associated with regulators coupled to the pH reducing tank.  The cleansing liquid may contain a buffer to automatically maintain the pH of this liquid at the required level.  The gravitational separating means may be as described in Specifications 808,902 and 808,901.  Specification 742,844 also is referred to.ALSO:A method of cleaning the interior surfaces of metal tanks comprises the use of one or more nozzles to project a cleansing liquid against said surfaces, the removal of the resulting liquid mixture to a separating means, the recirculation of the separated cleansing liquid to said nozzle or nozzles, and the maintenance of the cleansing liquid, at least during the separation stage, at a pH lower than 7.  The cleaning operation may be performed by the apparatus described in Specification 696,361, such apparatus including a pH reducing tank for containing cleansing liquid with extra acid, and means for introducing the latter into the system as and where desired to maintain the pH at the required level, for example, by pH indicators at various points associated with regulators coupled to the pH reducing tank.  The cleansing liquid may contain a buffer to maintain the pH of this liquid at the required level.  Cleansing liquid.  This may be a solution in water of a detergent compound or a mixture comprising a wetting agent stable in acid solutions and one or more water soluble additional compounds also stable in acid solution, for example, acid sodium phosphates, sodium sulphate, sodium nitrate, sodium chloride or sodium nitrite. In one example the cleansing liquid comprises 0.5% by weight of a wetting agent comprising a long chain secondary alkyl sulphate and 10% by weight of sodium chloride.  After cleansing, the tank is washed down with a passivating solution. The cleansing liquid may also be projected against the tank walls by the equipment described in Specifications 742,844, 808,901 or 808,902.