the pipediameter of the processingline or fromthe pipediameter of the
processingline to a unitoperationmachine that comesfromthe equipment
manufacture witha differentinletor outletpipediameter). At firstglance,
choosing a concentricor an eccentricexpansion is a matterof availability,
spatial requirements and, in the caseof draining againstproduct flow, a caseof
draining (eccentric is the most drain-friendly of the two ± Anon, 1993).
However, studyingthe flowin concentricand eccentric expansions froma small
pipediameterto a largerpipediameter revealsinterestingresults in relationto
the potentialcleaning effectof the flow.
The example given hereis expansionfroma 1 inchto a 2 inch(25±50mm)
pipe(Fig. 11.4).The expansion angles(8.6Îand 16.8Î)are basedon product
Fig. 11.4 Recirculationzonesin eccentricexpansionswithtwo differentslopes(a) 16.8Î
and (b) 8.6Î and a concentricexpansionwitha slopeof 8.6Î at two differenttimes(c) and
(d). The solidgreyareasillustratethe recirculationzones.Expansionsare from1 inch to 2
inch(25±50mm)pipesizes.Lengthand volumeof the recirculationzonesare: 331 mm
and 71 300 mm^3 for the eccentricexpansionwithslope16.8Î,213 mm and 18 200 mm^3 for
the eccentricexpansionwithslope8.6Î and the size is timedependentfor the concentric
expansion.
204 Handbookof hygiene controlin the foodindustry