Analysis of Irregular Material Metering of SGB

A company in Foshan, Guangdong, is a large automotive manufacturer. It uses Shini ‘s gravimetric blender SGB-600-4 which is equipped with 4 discharging valves and maximum throughput of 600KG/H. 

The user requires metering of 3 kinds of materials whose respective ratio is 64.4%、35% and 0.6% (Hopper 3 serves as a backup.). There are 2 failures during operation. One is about getting stuck of material or failing to discharge occurring in hopper 2. The other one is that the metering precision of hopper 4 doesn’t reach the standard. On site Information:  The hopper whose discharging is abnormal meters glass fiber with diameter of 3mm and length of 15-20mm. The hopper whose metering precision is not up to the standard meters master batch with ratio of 0.6%. 

The reason for getting stuck of material or failing to discharge is that the glass fiber is long and thin as well as irregular. The diameter of standard vertical discharging valve is too small that it’s easily to get the material blocked. Besides, the ratio of hopper 4 is 0.6%; the discharging speed of the vertical valve with standard diameter is about 600g/s while the discharging weight of each time is only 24g with batch weight of 4000g. The discharging speed is high while the required discharging quantity is low. To solve these problems, the discharging port diameter of hopper 2 is enlarged to 52mm to enable the glass fiber to be discharged normally. Hopper 4 is changed to be equipped with a vertical valve whose diameter is 32mm to decrease the discharging speed. After all this be done, the machine is in normal condition and can meet clients’ all requirements, like throughput precision. 

SGB is able to meter raw materials and recycled materials of different natures. However, the dimensions and forms of materials are different and some materials which are irregular or are carrying static charges will bridge or get stuck when being metered. Basing on the controllable precision, appropriately enlarge the diameter of the discharge valve or add anti-bridging device. Metering 0.1% or low ratio of master batch and additive, the required quantity in one cycle is little. However, the discharging speed of standard vertical valve is high and the metering precision is hard to control. It should be replaced with a small metering valve or use the vertical dosing screw. Materials of mixing ratio not higher than 1% requires vertical dosing screw for best precision of metering.