Seals for tank roofs
Emissions from tank roofs that do not have proper seals can constitute a significant portion of total emissions from aboveground storage tanks (ASTs). Wind and other associated factors can increase volatile organic compound (VOC) emissions, particularly from roof fittings that are not properly sealed. There is a variety of methods for sealing the roofs of ASTs. The roof systems must be able to meet operational needs efficiently while also addressing safety and, increasingly, environmental regulations for the storage of petroleum and other chemicals. They have to be able to keep odours and emissions in, and also rain, wind and airborne (or other) contaminants out. Roof seals, therefore, play a very important part in the success of meeting these objectives. The type of seal depends on the type of roof that the AST has. The choice of material for a tank roof seal is also important as it has to withstand the stored product, exposure to the sun and rainwater contact. Seals can be manufactured in a wide variety of materials, including different grades of aluminium, galvanised steel, stainless steel and polymer materials.
API 650 is the accepted standard in the US and is also widely acknowledged throughout the tank storage industry, although some countries have specific national codes and standards for the design and construction of covered storage tanks.
It establishes minimum requirements for material, design, fabrication, erection and testing for vertical, cylindrical, aboveground, closed- and open-top welded carbon or stainless steel storage tanks in various sizes and capacities. The standard applies only to tanks whose entire bottom is uniformly supported and to tanks in non-refrigerated service that have a maximum design temperature of 93ÁC or less. API 650 was updated in June 2007 and is now in its 11th edition. US regulations
