The conductance values for piping and openings through which air and
other gases pass can be determined with nomographic methods. It is possible
not only to determine the conductance value for piping at specified
values for diameter, length and pressure, but also the size of the pipe diameter
required when a pumping set is to achieve a certain effective pumping
speed at a given pressure and given length of the line. It is also possible to
establish the maximum permissible pipe length where the other parameters
are known. The values obtained naturally do not apply to turbulent flows. In
doubtful situations, the Reynolds number Re (see Section 1.5.) should be
estimated using the relationship which is approximated below