Troubleshooting & Solutions for Tablet Coating Problems
ne of the final stages of producing any pharmaceutical or nutraceutical tablet, coating is the essential process that seals a raw tablet, often in order to protect the active ingredients in the drug, protect the stomach lining of the patient, or provide a delayed/time-sensitive release of the medication. In order to achieve these results, the coating process must run smoothly and evenly. Avoiding issues isn’t always an option, but eliminating them when they arise is possible. Here are a few troubleshooting tips to resolve three common tablet coating problems.
Problem 1: Clogging/Bearding
If the clogging is occurring at the nozzle tip, it is likely a result of the coating solution building up around the nozzle over time, commonly referred to as bearding. Look for spray nozzle tips specially designed to reduce bearding.
If the clogging is occurring elsewhere in the system, consider if your process could benefit from an automated fluid delivery system. Some advantages of automated fluid delivery systems include:
- Precise, low-pulsation peristaltic pumps eliminate “dead-leg” liquid distribution
- Nozzle liquid feed pressure sensors detect clogging
- Nozzle clearing circuit, line clearing and purge system
Problem 2: Suspended solutions settling/clogged liquid lines
Solution A: Re-circulating spray nozzles
In ordinary liquid-delivery systems, when the shut-off needle is extended, the solids in the coating solution can drop out of suspension, leading to uneven coating or nozzle clogging. In addition, temperature-sensitive solutions can harden or stagnate in a nozzle, causing blockages. Recirculating the solution inside the spray nozzle/liquid delivery system eliminates these issues, allowing the shut-off/clean-out needles to be extended for cleaning/inspection of the nozzle or to suspend the coating process.
Solution B: Re-circulating spray manifold
For larger spray systems, an integrated manifold could be one possibility. A connection hub eliminates the need for multiple connections to each nozzle, greatly simplifying setup time. Because the spray nozzles' liquid recirculation return is housed inside the nozzle body and ported through the manifold, fewer liquid lines/connections are required; this reduces the number of tubes that ultimately go inside the coating pan, reducing cleaning/changeover time.
Problem 3: Inconsistent coating thickness, inconsistent spray
Solution A: Process controls/monitoring
Achieving a consistent coating thickness within tight tolerances can be very difficult, especially with larger operations. A fluid delivery system with integrated process control software can provide precise control and monitoring over your entire process and provide real-time data for critical factors such as nozzle performance and liquid flow rate.
Solution B: Complete integration of spray and fluid delivery system with process controls.
For those with delicate, experimental or research-oriented applications, an integrated system that includes spray nozzles, nozzle connections, fluid delivery and process controls may be the solution. Working with your existing coater, these systems allow users a level of precision, monitoring, and data logging capability that can help to allievate many of the headaches of the tablet coating process, streamlining your batch operation at a fraction of the cost of a new or upgraded tablet coater.