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Earlier this week, there was yet another Spray Dryer Explosion on an older dryer. No one was hurt and the safety systems worked correctly, but the issue was older nozzle lances that weren’t maintained. This event could have been prevented.
You can go back into the history of accident investigations for spray dryer fires and explosions and find one common denominator in 90 percent of all fires and explosions.
Ninety percent of spray dryer fires begin with the high pressure atomization nozzle. The issue may manifest in other areas—for instance, embers in a fluid bed—but the source and root cause is most often the nozzles.
Through diligently implementing functional and well documented procedures, continually re-enforced with effective training, these occurrences of spray dryer fires and explosions can be minimized, if not eliminated.
You can and should have all of your safety systems in place, tested and functioning properly. These will protect people and equipment in case of an event. But even though these systems will work as designed, there will still be days of lost production and hopefully, a thorough investigation of the root cause.
But we can also look at the history of the causes and learn from them to prevent future occurrences. There are several aspects of high pressure nozzles to remain vigilant about:
Meet The Engineers
- Correct Assembly before production
- Everyone must be trained to assemble the nozzle according to manufacturer’s recommendation
- Make sure that o-rings and gaskets are replaced as recommended and that adequate spares are on hand
- Leaking Nozzles during production
- There are systems that allow nozzles to be tested under pressure outside of the dryer, prior to installation in the dryer
- Cameras are often implemented to monitor spray patterns during production. An uneven spray pattern can indicate a leaking nozzle
- Check Nozzle threads regularly for damage and replace when there are signs of damage
- Check the internal nozzle parts for signs of wear or chipping
- Any signs of burned or charred liquid on the outside of a nozzle or lance should be taken with extreme seriousness
- Correct installation of the lance in the dryer
- There have been repeated instances of the lance being installed incorrectly in the spray dryer causing a fire.
- Nozzle Bearding
- The build up of powder into a small beard of charred particles on the nozzle body is a sign that dried particles are being drawn back up too high into the dryer and could create embers. This is a serious issue. If nozzle bearding is found during any dryer production run, the run should be stopped immediately and the root cause diagnosed and corrected.
Ask yourself these questions:
- Has every operator received proper training in the correct assembly of nozzles and the dangers of incorrect assembly?
- Are the procedures documented and available for everyone to re-check, if needed?
- Are the necessary o-rings and gaskets available in the adequate quantity?
- Are spare lances and nozzle bodies available?
- Do the operators know the expectations of the company and the procedures to follow if dangerous conditions arise during a production run?
If you are concerned about preventing spray dryer fires and/or need assistance making corrections to any of the above issues, contact us. Call 410-822-6900 or send email to problem.solved@caloris.com.
