“Clogging” which tends to cause problems when the powder is discharged from the container.
Discharge may take a long time or stop, resulting in uneven product quality.
In the first place, why does the phenomenon of powder clogging occur??
The main cause is the powder pressure and friction!
Ideal discharge state: mass flow
Due to the pressure of the powder in the container and the friction generated on the surface, the powder becomes difficult to slip and discharge.
Partially drained state: funnel flow
“Funnel flow” means when the powder solidifies due to the pressure of the powder and the friction on the side, and only the upper part of the discharge port flows.
“Rat hole” means when the discharge stops as the funnel flow progresses.
If the powder remains like this, the condition of the powder may become uneven and the quality may change.
Stuck and not drained: Bridge
The state in which the upper part of the discharge port is blocked like an arch by the pressure of powder and the discharge is stopped is called “Bridge”.
The bridge forms at the top of the outlet so that no powder can be ejected.
”Rat holes” (“Bridges”) and bridges occur due to various factors such as the shape of the container and the type of powder. By preventing these phenomena from occurring, the powder can be discharged smoothly.
In addition, it is necessary to take measures to quickly resolve ”Rat holes” and “Bridges”.
Then, what kind of measures we shall take?
1. Use containers suitable for powder discharge.
Hopper containers are often used to store and discharge powder,
It is important to change the size of the outlet and the specifications of the container.
1-1.Increase the diameter of discharge
Increase the diameter of the outlet to prevent clogging.
1-2.Changing the Hopper Angle
By making it an acute angle, the powder becomes slippery and easy to be discharged.
The eccentricity makes the powder more slippery than a normal hopper.
1-4.Coating with fluororesin
The inner surface of the container is coated with fluororesin to improve sliding properties.
If the powder tends to adhere to the container due to the static electricity, the antistatic coating is recommended.
There are several ways to prevent or eliminate rat holes or bridges.
For example, it is a method to give vibration to a container and a method to send air into the container.
These are commonly called “Bridge-breaker” (A.K.A arch breaker/rathole breaker).
2-1.Eliminate dust clogging by vibration
By applying vibration to the container, rat holes and bridges can be eliminated.
Knock the container
Vibration is applied by knocking the container with a hand or a hammer to break the rat hole and bridge.
This is the easiest method, but it puts a heavy burden on the operator. Also, it may cause deformation or breakage of the container.
It is often used to vibrate the tank for preventing or eliminating rat holes and bridges.
There are various mounting methods, such as the inside and outside of the tank and the outlet.
The Knocker can give a strong impact to the tank from the outside of the hopper, and eliminates the rat hole or bridge.
2-2.Eliminate dust clogging with air
By sending air into the container, rat holes and bridges can be eliminated.
2-3.Combining vibration and air to eliminate dust clogging
By combining the vibration and air-sending into the container, rat holes and bridges can be eliminated.
By vibrating a silicon disk mounted in the container with air, the bridge in the container is eliminated by the two forces of air and vibration.
2-4.Take advantage of the Breakrod
The bridge can be broken by moving the claw.
Bridge breaker breakrod
When the handle is turned, the “claw” and the “shaft” installed in the hopper rotates to clear the clogging of the powder.
This is an optional processed product that is processed when making stainless steel hoppers.
3.Combination of methods above
Multiple measures, such as a combination of a hopper and bridge breaker suitable for powder discharge, may be more effective.
NITTO KINZOKU not only manufactures stainless hoppers, but also selects peripheral devices such as bridge breakers, so please feel free to contact us if you are considering.