Bultmann's Roll Compaction-site
on Dry Granulation

Characterization checklist for Roller Compaction equipment selection
(taken and adapted from: Walzenkompaktierung, M. Bultmann; ISBN 3-xxxxxxxx-x in preparation)
Property / feature units explanation value / data
Vendor / model specify n/a  
Roll diameter [mm]    
Roll width [mm]    
different roll surfaces available smooth polished
smooth satinated
other (please specify)
to accommodate different draw in properties  
variable gap system yes / no variable gap systems are prerequisite for constant porosity = high quality  
all unit sizes available (from lab size to production size yes / no to cover all steps without major equipment change  
all unit sizes use same roll diameter yes / no ease of scale up  
all unit sizes use same design yes / no ease of scale up: no change in design related parameters  
max. throughput1 [kg/h]    
min amount of powder [g] for development porposes: the less the better  
quasi contained production zone by default while area still visible (e.g. perspex door) yes / no health and safety issues, facilitate cleaning but still allowing observation of process  
flanges /ports easily attachable to inlet and outlet yes / no allow switch to contained operation or from small scale development to full production easily  
contained version available (containment has to be proven by data !) genuine by vendor
third party working with vendor
not at all
total solution from vendor provides best overall performance  
relative roll position inclined
horizontal: might cause issues with material flowing through the gap by itself: poor
vertical: different draw in angles at the rolls: poor
designed for reduced surfaces (pay attention to nuts, covers, sealings, welding seams) yes / no sophisticated design implies reduction of welding seams (milled from solid block preferred), avoidance of nuts and bolts, covering of them wherever possible, tight sealings between drive shafts and housing  
WIP available yes / no facilitates cleaning (under contained conditions); health and safety  
CIP available yes / no provides cleaning (under contained conditions); health and safety  
number of augers 2 / 1 two auger systems provide high flexibility from predensification to aeration of powder. Widens range of processable material  
predensifying augers no / yes predensification should not be forced by default by auger design  
cooling of rolls available yes / no widens range of processable materials to products with low melting point / low degradation temp.  
working2(!) rim roll sealing available yes / no rim rolls provide more uniform porosity distribution across ribbon; but must be a real working rim principle. Ribbons must show plain sharp edges  
adjustable speed ratio between augers yes / no allow high flexibility from predensification to aeration of powder. Widens range of processable material  
torque control for feed auger yes / no allows to provide material of constant predensification to tamping screw  
recycling of fines necessary no / yes uncompacted) fines should not occur right after compaction (optimization of formulation necessary or machine not working properly).Fines will occur after milling of course, but recycling them is not suggested for several reasons  
automatic gap control with adjustable(!) PID parameters yes / no automatic mode provides constant gap at constant force. PID parameters must be adjustable to offer potential for adaption to product if necessary  
Granulation unit attached yes / no reduces processing steps, facilitates containment  
low speed3 granulation plus granulator speed plus angle of rotation plus direction adjustable yes / no high milling speeds produce lots of fines. Granulator movement should be adjustable to match individual needs / throughput  
ease of rotor sieve distance adjustment (reproducibility !) fool proof … hard to adjust, not adjustable rotor sieve distance becomes important under certain circumstances. distance adjustment should be made easy and reproducible  
mesh sizes available please specify    
conidur sieves available as standard option yes / no conidur sieves provide more cutting action and can help to reduce fines. On the other hand through put is limited  
Sample theif/chute for ribbons yes / no necessary for drawing ribbons  
sample thief/chute for granules yes / no necessary for drawing granule samples  
Different agitator shapes available yes / no widen range of processable material (aeration or just movement instead of predensification in feeding hopper)  
creeping mode with(!) ramp yes / no saves material (especially relevant for development); fast steady state  
tip mode for each drive individually selectable yes / no relevant for cleaning  
rolls and tamping auger reverse tip mode available yes / no required in case of clogging  
full instrumentation of all(!) drives (speed, torque, temperature); similar for hydraulic pump yes / no better process understanding, ease of trackin process, usable for QbD, PAT  
Data export function yes / no tracability and evaluation of process and parameters; necessary for development  
dynamic (!) force calibration (force exerted on powder) yes / no truly displays the actual force on the powder leaving all other influencing factors beside (oil leakage, bear friction, lever bending…)  
dynamic (!) gap calibration yes / no assure that gap display is accurate for all force settings  
(proven!) spare time delivery instant .. the faster the better, of course  
CFR 21 / 11 compliant yes / no self explaining  
through the wall assembly available yes / no save lab space, facilitate cleaning and maintenance in high potent production zones  
experience available within own company yes / no roll er compaction is a complex topic. advantage of inhouse experience is self explaining  
machine displays the actual force exerted on the powder (rather than hydraulic pressure or a force measured somewhere in the machine) yes / no anything else doesn't make much sense. actual force on the powder facilitates scale up  
consistent with internal equipment and process of choice documents) yes / no self explaining  

[1] using Avicel PH101 + 0.5% MgSt; ribbon porosity ~20%
[2] ribbons must not be pressed through/over rims
[3] to give an impression: Quadro Comil(TM) for example is high speed; oscillating granulators are usually low speed