8/21/2019 Ball Indenter Irhd
Chellappa Chandrasekaran, in Anticorrosive Rubber Lining, 2017
Some Typical Process Conditions in Chemical IndustriesRoad Tanker for Phosphoric Acid Transportation
Indentation hardness tests are used in mechanical engineering to determine the hardness of a material to deformation. Several such tests exist, wherein the examined material is indented until an impression is formed; these tests can be performed on a macroscopic or microscopic scale.
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An autoclave curable semiebonite lining of shore hardness 60 degrees D and 5 mm thickness will be quite suitable for this application. However, large storage tanks in terminals cannot be cured in an autoclave because of size limitations if lined with semiebonite lining. In this case a soft natural rubber of 55 degrees A hardness is suited, which is made by the cold bonding technique. The static and dynamic loading of the storage tank as well as the road tanker, respectively, should be borne in mind in the selection of the type of lining. Road tankers are provided with baffle plates inside to reduce knocking and spilling of acids during transportation.
Generally, engineers in the chemical industry do not mention the working conditions in a process for fear of disclosure to competitors. Nor do they mention the additives given at low proportion to the main chemicals because these are normally proprietary techniques of a particular chemical industry, for example, the fertilizer industry. In the case of handling phosphoric acid the clients do not disclose the deforming agent added to the bulk acid stored in huge storage tanks. During such situations, suggesting a suitable rubber lining is a challenging task for the rubber technologist.
In the case of phosphoric acid storage tanks at harbor terminals or inside the plant, the choice between butyl, neoprene, or natural rubber lining will be decided according to the defoamers that are used. A neoprene lining will show better resistance to the defoaming fatty acid than butyl rubber or natural rubber. Where no defoaming agent is added, as in the case of some fertilizer plants, a soft natural rubber or butyl lining is sufficient for phosphoric acid storage tanks. Here again the choice depends on cost considerations.
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Phosphoric acid is considerably weaker than hydrochloric and sulfuric acids, but it is much stronger than acetic and boric acids. Phosphoric acid is used chiefly in the form of its salts. The acid is used to make various phosphatic fertilizers, as a replacement for organic acid in foods and soft drinks, and in engraving and lithography.
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