SHINI Central Material Processing System

 

Application Scope

With development of industrial modernization and automation, central material processing system plays an irreplaceable role in production of plastics industry. The investment and operation cost is low. Drying and storing of materials takes place somewhere far away from equipment, which could save the clean workplace, perfect companys image; it may also rise the degree of automation and brings convenient management; it can save money by reducing maintenance and inventory.

 

Working Principle

Central material processing system consists of central conveying and central drying. Material conveying takes the material from packing bag to drying hopper or from drying hopper to molding machine. One dehumidifier is adopted for certain drying tanks or dehumidifying&drying system is use for drying materials altogether.

 

Central Conveying System

Material conveying system employs vacuum suction with air conveying. It takes air below barometric pressure as medium and high pressure vacuum blower to form a vacuum pipeline, in which materials are conveyed to a certain destination. It is a kind of suspending conveying device.

 

Because material conveying system mainly depends on the vacuum degree in the pipeline, there are high-vacuum device and low-vacuum device. High-vacuum device refers to vacuum degree above 7.8kPa, while low-vacuum device is below it. At present, SHINI adopt the latter.
 

 

■ Primary Conveying (Packing Bag → Drying Hopper)

When the drying hopper needs more material, the material level switch will send the message to PLC of central control station, and the feeding blower begins to add materials from the packing bag to the vacuum hopper by way of suction pipe (box) and conveying pipeline. The drying hopper dehumidifies the material until material level calculator informs PLC. The control blower stops and the first conveying is finished.

■ Secondary Conveying (Drying Hopper → Machine)

Photosensor hopper of mould machine informs PLC of central control station the need of materials, PLC sends a control signal to operate the feeding blower. After the drying process, the material is conveyed into the electric hopper and then the feed opening of machine by suction box and feeding pipeline. The material level calculator sends a message until there are enough materials. The control blower stops and the second conveying is finished.

 

Central Material Dehumidifying System

Based on hot air drying principle, hot air in the system comes into material tank from the bottom of it. The hot air blends thoroughly with the plastic granules and removes internal and external moisture of the material.

Drying and dehumidifying system owns functions of drying and dehumidifying. It is equipped with honeycomb-rotor dehumidifier and drying machine. SD-H, combined with certain SHD-U can deal with different sorts of plastic materials altogether.

 

System Planning

■ System Configuration

Central conveying system often consists of feeding device, convey pipeline, separator, dust-removing device, air supplying equipment, air pipeline and control parts. Working sequence is shown as below:

■ Feeding Device

Feeding device refers to components sucks materials such as suction pipe, suction box (shut-off), which consist basic parts of feeding device.

During long-distance ( more than 30m) or second conveying (drying hopper→mould machine) , shut-off suction is necessary for fear that material choke the pipeline or moisture regain.

 

■ Convey Pipeline

Central conveying system often uses stainless steel (SUS201). As for some particular industries such as food, medicine, stainless steel (SUS304) or glass tube is needed.

 

■ Separator

Separator is a material reception hopper used to separate material from air, which can be divided into SHR-U-S and SHR-U-ES.

SHR-U-S is usually launched on the drying tank, and SHR-U-ES is often installed at the feed opening of the mould machine.

 

■ Dust-Removing Device

In central conveying system, dust in the material or carried during long distance transportation gets into separator and then dust-removing device. The dust-removing device employs cyclone dust cleaning machine equipped with filters. Filter accuracy of SHINIs standard central filter SCSF is 90μm. According to personal conditions, customers can choose filter of high accuracy up to 5μm.

 

■ Air Supplying Machinery

As material conveying system adopts vacuum suction air convey, the air supplying equipment employs high-pressure vacuum blower or Roots blower.

High-pressure vacuum blower is allocated with safety valve (vacuum breaking valve), muffler and air outlet pipe.

 

Choices of Main Units

■ Blending Proportion

Blending proportion refers to ratio between the material and air conveyed within the same time, which indicated by m. The value of m is restricted by some factors such as blower function, material property, convey condition. It is also an important parameter relates to efficiency and reliability of conveying device. We must calculate it prudently with factors of all aspects when projecting.

 

■ Air Velocity

There is a limited air velocity for each kind of material that ensures the granules keep suspending, which is also called safe air conveying velocity or economic velocity.

Although this device can convey materials with safety if the chosen conveying velocity is much higher than economic velocity, the loss of pressure and power consumption is high. It also may aggravate the pipeline (as wear and tear between bend pipe and horizontal pipe), and the material may break. On the contrary, the pulse flow will raise the loss of pressure and block the pipeline to fail the system.

 

Pipeline Design

■ One Pipeline for One Material

According to customers requirement, the design of one pipeline for one material is adopted when different kinds of material are employed and the material contains instability. The mould machine can switch speedy while renewing materials at any time.

 

■ One Pipeline Shared by Machines

 

The design of one pipeline for certain machines is suitable for using single material. One pipeline shared can be divided into two kinds: one is three-way air tube; the other is Y-type three-way air tube equipped with pneumatic ball valve.

 

When customers need change materials frequently and the kind of material is single, this design shown in diagram above is adoptable. The pneumatic ball valve can be installed on the mould machine or the supporting frame of the tube. In order to reduce pressure loss of system and ensure smoothness of material conveying, diameter of the Y-type three-way tube should be the same.