May 16, 2012

Sulphuric acid safety

NorFalco have published a good guide to sulphuric acid manufacture, handling and storage. Many explosions have recently taken place in sulphuric acid tanks due to generation of hydrogen. The guide mentions the following:
"Storage tanks for sulfuric acid in strengths of 93% through 99% are usually fabricated from carbon steel. At normal temperatures there is usually some gradual corrosion on carbon steel that results in the evolution of hydrogen gas and the formation of an iron sulfate precipitate, most of which settles to the bottom of the tank. Wall thickness should be carefully calculated to provide corrosion allowances and for the high specific gravity of the acid. Smaller storage tanks (under 10,000 gallons) are sometimes constructed from stainless steel or a type of HDPE (High Density Polyethylene) made especially for sulfuric acid service. Such materials reduce or eliminate hydrogen and iron-sulfate generation. Regardless of the material your tank is constructed from, always ensure that it has been designed and manufactured specifically for sulfuric acid. Many storage tanks use anodic protection systems to minimize corrosion. Storage tank cleaning and inspection procedures are available on request from NorFalco .
HYDROGEN GAS: Hydrogen gas is potentially explosive and special care must be taken when working near tanks or performing maintenance on tanks. A hydrogen meter and spark proof tools and lights should be used, and open flames and welding should be avoided. 

CORROSION, INSPECTION AND CLEANING: A program of routine internal inspection should be established to ensure early detection of excessive corrosion. It is necessary to clean out the tanks at regular intervals to allow for inspection. A suggested minimum frequency is every 3 years for tanks containing hot acid and every 5 years for tanks containing cold acid".
Read the complete guide in this link.
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