Tablet coating spray system: air-atomizing gun manifold

01

Pick the nozzle set-up: fluid tip, air cap and orifice

Spraying Systems Co.'s tablet coating catalogue describes each air-atomizing spray set-up as a fluid tip (or fluid cap) plus an air cap, interchangeable on the nozzle body but each needing its own needle size. Its VMAU set-ups come with fluid orifices of 0.035 in (0.89 mm), 0.040 in (1.02 mm) and 0.060 in (1.52 mm); its JAU and JAUSF set-ups with 0.028 in (0.71 mm), 0.035 in (0.89 mm) and 0.040 in (1.02 mm). [1]

The part numbers encode the geometry: an air cap such as VMAAB113289-60 has a 0.113 in centre orifice, two side orifices of 0.089 in and a 60° side-orifice angle, which shape the fan pattern. The catalogue lists coverage and flow-rate data with water and drop-size and spray-velocity data with OPADRY and EUDRAGIT coatings for these set-ups, so ask for the curves measured with a coating close to yours rather than water alone. [1]

Wetted parts in that catalogue are 316 or 316L stainless steel with needle seals in FDA-grade Viton or EPDM, and the sanitary bodies have no internal threads in the liquid chamber. [1] Editorial note: list the solvent or aqueous system and cleaning agents in the enquiry, because the seal elastomer has to suit both.

Give the supplier the coater model and pan diameter, number and spacing of guns, coating type (aqueous film, solvent, sugar, functional), solids content and viscosity, target spray rate per gun, atomizing and pattern air supply, pump type, the bodies' connection standard (NPT or BSPT, sanitary), seal elastomer and cleaning method, and the documentation package required.

02

Count the guns and set the atomizing and pattern air

Freund's Multi HI-COATER specification ties the number of guns to the pan: a 991 mm pan of 115 L (9.2–92 kg batch) carries 4 guns, a 1,524 mm pan of 820 L carries 8, and a 1,676 mm pan of 1,070 L (85.6–856 kg) carries 8, with batch weights based on an assumed 0.8 g/cc bulk density. Its guns are anti-bearding designs with a needle valve and separate control of pattern and atomization air, mounted on an in-process adjustable, removable manifold spray bar. [2]

Editorial calculation: at full brim volume the 115 L pan gives 92 / 4 = 23 kg of tablets per gun and the 1,070 L pan 856 / 8 = 107 kg per gun — about 4.7 times the tablet mass per gun on the largest pan. [2]

A study in AAPS PharmSciTech measured tablet-bed humidity with data loggers during pan coating and found bed relative humidity rose with higher spray rate and higher atomization air pressure, and with lower gun-to-bed distance and lower pattern air pressure; higher bed humidity correlated with more logo bridging. [4] Spraying Systems' 54000 modular manifolds hold 2 to 12 nozzles: up to 6 on the standard manifold for batch coaters, up to 12 on the large-capacity and individually fed versions for large batch or continuous coaters, with an adjustable sanitary clamp to set the spray angle. [1]

03

Keep the guns clean: anti-bearding and losses

Spraying Systems describes bearding, coating build-up on the air cap, as a cause of shutdowns to clean the guns, and says its P-Series anti-bearding set-ups ran for up to twice as long as its standard anti-bearding set-ups with minimal build-up when spraying OPADRY. [1]

Gansons describes the spray system of its GansCoater as using anti-bearding nozzles with no elastomeric contact parts, claims spray losses below 5% for its baffle and spray design, and offers ultrasonic nozzle-to-bed distance sensors to monitor suspension use. Among coating defects it lists logo bridging linked to improper atomization pressure and uneven colour linked to an uneven spray pattern. [3] Editorial note: spray loss and bearding figures are maker claims for their own systems; ask for the test conditions behind them.

04

A nozzle maker serving tablet coating: set-up drawings, orifices and flow data to request

The linked listing comes from an industrial nozzle maker that names tablet coating among its pharmaceutical applications. Ask for set-up drawings, orifice sizes, flow data with your coating and material certificates for wetted parts.

05

Fluid tip, air cap, needle and seal, manifold bar, solution pump and air controls

06

Orifice size, flow per gun, atomizing air, fan width and wetted materials for a coating gun manifold

Atomizing air is not only a spray setting: in the AAPS study higher atomization air raised bed humidity, so give the pressure range together with your drying conditions. [4]

07

Send the coater, coating and gun layout together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Coater: [model; pan diameter and volume; batch size]
Coating: [type; solids; viscosity; solvent or aqueous]
Guns: [number; spacing; gun-to-bed distance; spray rate per gun]
Nozzle: [set-up; orifice; anti-bearding]
Air: [atomizing and pattern air supply; regulators]
Pump: [type; flow range]
Materials: [wetted metals; seal elastomer; certificates]

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