Research on Increasing Passing Rate

Key words: Characteristic of material, passing rate, bounce balls cleaning device, ultrasonic cleaning system, anti-blocking, material motion track, tensioning coefficient.

∆ Passing rate means the rate that materials pass through wire sieve.

Sieving, sorting, de-dust, impurity-removing and filtration, as an essential procedure to improve the quality level of finished products, have been applied in all of industries. In this whole procedure, the sieving precision and capacity is the core parameters to measure the efficiency of sieving machine. And the key factor affecting sieving precision and capacity is passing rate.

YONGQING MACHINER as a professional designer and manufacturer of fine screening machine, strives to research and development of fine screening machine since 1986. Based on our more than 30 years industry experience and research, the mainly factors affecting passing rate are summarized and listed for YONGQING MACHINER esteemed user reference.  

A. Characteristics of material.

Please check the characteristics of the materials by referring to the following table:

Characteristics
Shape	particles	powder	crystal	Liquid
Flowability	□Very	□Middle	□Poor
Caking	□Very	□Middle	□None
Hygroscopic	□Very	□Middle	□None
Electrostatic	□Yes		□NO
Corrosiveness	□Very	□Middle	□None
Stickiness	□Very	□Middle	□None
Abrasiveness	□Very	□Middle	□None
Fragility	□Very	□Middle	□None
Explosiveness	□Yes		□NO
Moisture regain	□Very	□Middle	□None
Magnetic	□Very	□Middle	□None

The different sieving solution could be specially customized based on characteristics of the materials.

B. Anti-blocking structure

Nowadays, the commonly used Anti-blocking structure has two kinds: Bounce balls self-cleaning device and ultrasonic cleaning system;

a. Bounce balls self-cleaning device (See picture 2) is an additional device aiming to prevent the wire sieve from being blocked. During the running, the bounce balls and ball-holder ring will be thrown to hit the wire sieve continuously at a high frequency, which could be very helpful to solve the problem that materials are stuck in the wire sieve, and increase the passing rate. The structure is mainly applicable to ordinary powder or particle material (0.2mm~1mm).

picture 2

b. Ultrasonic cleaning system (See picture 3) is another special anti-blocking device, integrated under wire sieve against easy-caking, hygroscopic, and electrostatic ultra-micron powder (0.3mm~0.02 mm). The ultrasonic system is equipped on the net frame directly. The ultrasonic high frequency vibration wave is transmitted to the wire sieve directly. It is a special cleaning device to solve the adhesion, friction, and static of ultra-micron powder. The precision and efficiency of screening could be improved a lot.  

        picture 3

C. Discharging speed;

The sieving precision could be affected if the discharging speed is too fast, then the material is not sorted well, and the passing rate will be also low. Suggested effective solution:

a. Keep evenly feeding, the mass feeding is not permitted.

b. Controlling the thickness of materials on the sieve (See picture 4).

c. Adjust the motion track of materials to make the sieving time is longer (See picture 5-1,5-2).

d. Add an additional valve at outlet (See picture 6).  

D. Tensioning of the wire sieve

Picture 6

The installation of wire sieve is also a key factor. The wire sieve is required to be tensioned tightly on net frame. The tensioning of wire sieve will affect passing rate directly. Loose tensioning will be easy to absorb the vibration force, which will result in that the wire sieve surface is lack of enough vibration to make the materials pass the sieve. The following tensioning coefficient could be a standard to check if the wire sieve is tensioned tightly or not.

Type	Mesh size (microns)	Tensioning Force (N/CM)
Stainless steel wire sieve	10 000~3 000	12~16
Stainless steel wire sieve	3 000 ~ 300	16~20
Stainless steel wire sieve	300 ~ 20	20~30

On our sieving machine, all of the wire sieve must be detected before next installation to ensure the tensioning is qualified.

Picture 7, 8