standard&d by using a drum with specified dimensions, in which 500 g of sieved
pellets are inserted. After tumbling for 10 min at 50 rpm, the pellets are subsequently
sieved and the amount of fines passing a sieve with a grid size “just smaller than the
nominal pellet diameter” (Pfost, 1963) is determined. In practice, grid-sizes are used of
0.8 X pellet diameter. Durability is then expressed as the ratio of the weight after
tumbling over the weight before tumbling, multiplied by 10. The resultant figure
(between 0 and IO) should be rounded off to two significant digits. Nowadays, however,
durability is normally expressed as a percentage which gives the amount of fines
returned or the amount of pellets recovered. In the original description, a subscript is
added depicting the time of physical analysis of pellets after their manufacturing in
hours. Subscript + 24 indicates durability results from pellets out of the cooler for more
than 1 day, - 1 indicates results from warm pellets. In scientific publications, however,
the subscript (an important indication for comparison reasons) is not always given.
Nowadays, automated devices exist to monitor on-line the durability of pellets during
their manufacture (Anonymous, 1984). Often these devices incorporate a fast cooling
procedure to quickly obtain physical quality figures that can be used to optimise process
parameters of that specific batch.
standard&d by using a drum with specified dimensions, in which 500 g of sievedpellets are inserted. After tumbling for 10 min at 50 rpm, the pellets are subsequentlysieved and the amount of fines passing a sieve with a grid size “just smaller than thenominal pellet diameter” (Pfost, 1963) is determined. In practice, grid-sizes are used of0.8 X pellet diameter. Durability is then expressed as the ratio of the weight aftertumbling over the weight before tumbling, multiplied by 10. The resultant figure(between 0 and IO) should be rounded off to two significant digits. Nowadays, however,durability is normally expressed as a percentage which gives the amount of finesreturned or the amount of pellets recovered. In the original description, a subscript isadded depicting the time of physical analysis of pellets after their manufacturing inhours. Subscript + 24 indicates durability results from pellets out of the cooler for morethan 1 day, - 1 indicates results from warm pellets. In scientific publications, however,the subscript (an important indication for comparison reasons) is not always given.Nowadays, automated devices exist to monitor on-line the durability of pellets duringtheir manufacture (Anonymous, 1984). Often these devices incorporate a fast coolingprocedure to quickly obtain physical quality figures that can be used to optimise processparameters of that specific batch.
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