A line blank can be viewed as an “isolation flange” inserted between two mating flanges to switch on or off the piping system after disassembling certain flange bolting. In many piping systems, line blanks are usually required to isolate individual pieces of equipment at shutdown and to positively blank off selected process lines at the piping unit limits. They are also needed during operation, maintenance, or inspection and testing wherever positive shutoff is required to prevent leakage of one fluid into another. Line blanks are generally manufactured in accordance with ASME B16.48. The standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for operating line blanks in sizes NPS 1/2 through NPS 24 for installation between ASME B16.5 flanges in the 150, 300, 600, 900, 1500, and 2500 pressure classes. Besides, line blanks can also be designed in accordance with ASME B31.3.


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