Position: Solids handling equipment manufacturer Ajax Equipment has developed a variable plug length screw feeder that for the first time gives operators the ability to change the plug length to achieve a consistent flow of material into aggressive industrial processes.
The plug approach to screw feeding is commonly used when feeding material into environments where there is a significant temperature or pressure differential.
The plug is a controlled build-up of material created at the point where the screw enters the process, protecting the fed material from early exposure to high temperature and preventing ingress of vapours from the process into the screw and feed hopper.
Knowing the optimum plug length to achieve a steady flow is based on experience and often extensive trials.
The Ajax Feeder Equipment screw feeder allows the operator to adjust the length of the 'plug' to match or exceed the back pressure on the plug, thus ensuring consistent discharge from the screw feeder.
Mark Waters, director, Ajax Equipment, believes the variable plug length screw feeder will broaden the scope for screw feeders and conveyors in difficult process conditions.
"The new variable plug length screw feeder overcomes the inflexibility encountered with fixed length plugs that limits their use.
It also offers manufacturers the opportunity to use the steady feed rate possible with a screw feeder for continuous production, where previously they may have relied on batching manufacture," he said.
The variable plug length screw feeder is available in a range of screw sizes and feed rates, and the auger can be retracted for ease of cleaning.
In addition the feeder can be jacketed to allow heating or cooling of the material prior to its discharge.
Hopper and screw feeder for powder processing
Ajax Equipment is supplying Hosokawa Micron with a hopper and screw feeder as part of a turnkey powder-processing system.
The system is designed for the pre-conditioning of potassium-carbonate powder during the agrochemical manufacture.
Ajax is providing a 5m3 hopper, which will receive potassium-carbonate powder from big bags.
The batch held in the hopper will be measured by load cells, and discharged by a screw feeder into the process reactor.
Potassium-carbonate powder is a difficult-to-handle powder.
the weigh feeder can be both 'sluggish' when stored and compacted, yet light and fluffy when aerated or loosely poured.
In addition, it can be prone to caking.
Therefore, mass flow is preferred as it avoids stagnant zones and secures flow through the smallest outlets.
Based on measured flow properties of the powder, Ajax Equipment has designed the hopper for mass flow with steep walls and a long slot outlet to the screw feeder.
To serve such a long outlet, the screw feeder has a progressive pitch, Lynflow ribbon flights and stepped shaft.
This ensures the entire hopper contents move in a mass flow pattern during discharge, achieving a smooth transfer of the powder at the rate of 200kg per minute.
Both the weigh batch hopper and screw feeder are gas tight, and the equipment is designed to comply with Atex Zone 2 requirements.
For more details of the Ajax Equipment variable plug length screw feeder, please visit the website.
