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Problem:A pharmaceutical company introduced a new tablet coating formulation. The application required low flow rates and consistent small- to medium-size drops in a flat fan spray pattern.
Objective:The Spraying Systems Co. nozzle being used was able to accomplish this process. However, it was necessary to characterize the nozzle and then optimize the spray parameters to help improve the coating efficiency of the proprietary tablet coating system. The pan coating system consisted of 3 spray guns across a 100 mm header which was designed to optimize total system efficiency.
Procedure: The spray distribution, drop size distribution, and velocity distribution were collected and analyzed to offer a total spray characterization. The header was then designed and optimized for the system.
Solution:The optimal flow rate, spray height, and nozzle spacing was
determined from the results of the spray characterization data.
The customer was then able to write procedures and methods to
optimize their coating process which reduced maintenance costs
and production downtime.
Optimizing Tablet Coating Drop Size
Spray Nozzles
Spray Control
Spray Analysis
Spray Fabrication
VMAU Air Atomizing Spray Nozzle
20
25
30
35
40
45
2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3
Air Pressure (bar)
Nozzle A - Flow High
Nozzle B - Flow High
Nozzle B - Flow Low
Nozzle A - Flow Low
Dv0
.5 (µ
m)
Technical Data
The drop size distribution of the anti-bearding nozzle (nozzle B) provided droplets approximately 10 to 15 µm smaller than the standard SUE15 setup (nozzle A) at similar conditions. From these results, the optimal nozzle and operating conditions were chosen to accomplish this process.
Figure 1. Drop Size vs. Air Pressure
0.000
0.002
0.004
0.006
0.008
0.010
0.012
90 70 50 30 20 10 0 -10 -20 -30 -50 -70 -900
5
10
15
20
25
30
35
40
45
50
Volume Flux at P=High
Dv0.5 at P=High
Volume Flux at P=Low
Dv0.5 at P=Low
Volume Flux at P=Medium
Dv0.5 at P=Med
Volu
me
Flux
(cc/
cm2 /
s)
Dv0
.5 (
µm)
Position Along Axis (mm)
Figure 2. Drop Size vs. Volume Flux
Tests were performed to evaluate performance at various operating conditions. Nozzle parameters were evaluated based on drop size uniformity and volume flux uniformity as a function of axial position along the flat spray. The results quantified the expected variations for low, medium and high dosing rates. The volume flux is largest at the center of the spray and decreases towards the edges of the spray with the most uniform region existing at the spray center at high air pressures. The medium dosing rate supplies the most uniform volume flux distribution and the drop size distribution does not change drastically.
SprayNozzles
SprayControl
SprayAnalysis
SprayFabrication
Case Study 104 Printed in the U.S.A. ©Spraying Systems Co. 2007
P.O. Box 7900, Wheaton, IL 60189-7900 USA
Tel: 1.800.95.SPRAY Intl. Tel: 1.630.665.5000 Fax: 1.888.95.SPRAY Intl. Fax: 1.630.260.7593 www.SprayConsultants.com
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