General Knowledge of Belt Conveyor:Prat 2

5: Transmission Principle and Characteristics of Conveyor

The traction force of the belt conveyor is transmitted by the friction force between the driving drum and the belt. Therefore, the belt must be tightened by the tension device, so that the belt has a certain initial tension at the separation point of the drum.

The belt runs on the idler together with the cargo. Belt is not only a traction mechanism, but also a bearing mechanism. There is no relative motion between the belt and the cargo, which eliminates the friction resistance between the belt and the cargo in operation. Because the roller is equipped with rolling bearings, the friction between the belt and the roller is rolling, so the running resistance is greatly reduced, thus reducing the power consumption and increasing the transportation distance. For a belt conveyor, the transmission capacity of traction depends on the tension of the belt, the enclosure angle of the belt on the driving drum and the friction coefficient between the belt and the driving drum. In order to ensure that the belt of the belt conveyor does not slip on the transmission drum and runs normally, corresponding measures should be taken according to different conditions in production practice. To improve the transmission ability of traction, we can start from the following aspects: 

    • Increase the tension (initial tension). In the operation of belt conveyor, the belt should be extended, resulting in a decrease in traction. Therefore, according to the situation, the belt should be properly tightened by the tension device to increase the belt tension, so as to improve the traction.

    • Increase the friction coefficient. The concrete measures are to protect the wood lining or rubber lining covered on the driving drum to increase the friction coefficient, on the other hand, to reduce the water and coal to prevent the reduction of the friction coefficient.

    • Increase the envelope angle. Underground belt conveyor is driven by double drums to increase enclosure angle because of poor working conditions and large traction force.

6: Conveyor Belt:

The conveyor belt is composed of reinforcing material (belt core), core material (sticker), covering glue and side glue.

    • Reinforcement material (belt core): It is the key to the carrying capacity of conveyor belt. It determines the tensile strength of conveyor belt and can absorb the impact of material on conveyor belt.

    • Core layer material (glue): It can make the fabric layer of reinforced material have good bonding strength and prevent the delamination of core in the process of using.

    • Covering glue: It can protect and strengthen materials, transfer power, transport materials, absorb the impact of materials, and resist wear and tear.

    • Side glue: Protect reinforcing material from medium erosion, absorb the extrusion force from the side of conveyor belt, prevent the phenomenon of delamination of belt core.

Conveyor belts are classified according to the performance of covering layer: ordinary conveyor belts, heat-resistant conveyor belts, flame-retardant conveyor belts, wear-resistant conveyor belts, tear-resistant conveyor belts and cold-resistant conveyor belts.

Ordinary conveyor belts are classified into three types according to the abrasion and impact properties of the conveyed materials. Their codes are H, D, L.H-strong splitting working conditions, D-strong abrasion working conditions and L-general working conditions

Type H: It is used for conveying large non-corrosive materials with density below 2.5t/m3 at room temperature.

Type D: It is used for conveying medium and small non-corrosive materials with density below 2.5t/m3 at room temperature.

Type L: It is used for conveying non-corrosive powdery materials with low density and wear resistance at room temperature.

Conveyor belts are divided into steel cord conveyor belts, fabric core conveyor belts and steel mesh conveyor belts according to the varieties of reinforcing materials. Fabric core conveyor belts are divided into cotton canvas conveyor belt CC, nylon conveyor belt NN, polyester conveyor belt EP, glass fiber conveyor belt GG and whole core conveyor belt.

Conveyor belts can be divided into whole core conveyor belts, laminated conveyor belts, annular conveyor belts, sidewall belts and pattern conveyor belts.

The core of laminated conveyor belt develops from natural fibers to synthetic fibers, from multi-layers to few layers, from low strength and low modulus to high strength and high modulus. CC of cotton canvas conveyor belt has been basically eliminated in foreign countries and gradually replaced by nylon and polyester fabric conveyor belt at home.

Conveyor belts are processed according to side glue and divided into two parts: wrapping side belt and trimming side belt.

There are three methods of conveyor belt connection: mechanical connection method, cold rubber connection method and hot vulcanization connection method. Mechanical connection method and cold rubber connection method are only suitable for fabric core conveyor belt, and hot vulcanization connection method is suitable for various rubber conveyor belts.

    • Mechanical connection method: It has the advantages of simple operation and short joint time, but the joint strength is low, generally only 40%-50% of the conveyor belt strength.

    • Cold glue connection method: It is a method of connecting conveyor belts with adhesive as raw material. It has the advantages of high joint strength, no noise, no vibration, simple operation and short time. The joint strength generally reaches 60%-70% of conveyor belt strength.

    • Thermal vulcanization connection method: the conveyor belt is connected by thermal vulcanization. It has the characteristics of high strength and long service life. The strength of the joint generally reaches 80%-90% of the conveyor belt strength, but the time of the joint is longer.

 Requirements for hot vulcanization connection of conveyor belt: 

    • The length of bonding step of vulcanized joint of conveyor belt is more than 250mm (bandwidth B > 500-600).

    • The vulcanization bonding temperature of belt is 130-150 C.

    • The heating time of belt vulcanization is 30-45 minutes.