Purified water is frequently used in the pharmaceutical industry during the manufacture of medicines. This water is distributed throughout the manufacturing facility to points-of-use using high quality process pipework. The installation of a pipe tee in this pipework often creates a stagnant dead-leg zone. This dead-leg can contaminate the entire distribution network resulting in lost production, contaminated product and down time for cleaning.
The formal definition of a pipe dead-leg as given by the Food and Drug Administration (the FDA) is:Pipelines for the distribution of purified water for manufacturing or final rinse should not have an unused portion greater in length than 6 diameters (the 6D rule) of the unused portion of pipe measured from the axis of the pipe in use.
The FDA suggest the 6D rule will help prevent contamination: however industrial experts are designing systems with dead legs limited to 3D or less. Some systems and fittings claim to have zero dead legs.
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