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Belt conveyors have been used for over 150 years. The concept of conveying bulk solid materials by belt, however, has not really changed. Most research has been focused on the improvement of conveyor components and on the optimization of the belt’s reinforcement material and rubber compounds. Today however, one can differentiate between open and closed conveyor systems. In conventional open belt conveyor systems the belt is troughed and the bulk solid material is in direct contact with the air, (although the total conveyor may be enclosed). In closed conveyor systems, the belt contains the bulk material, thus eliminating the risk of dust contamination.9587
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New pipe conveyor system incorporating triangular gantry concept
This paper will discuss the state-of-the-art in closed belt conveyor system design, and will highlight the most important differences between open and closed belt conveyor systems. The following topics will be discussed:
• conveyor belt design and construction requirements,
• conveyor suitability,
• conveyor loading and unloading procedures and systems,
• conveyor geometry in particular the design of horizontal and vertical curves,
• conveyor structure design,
• conveyor drive systems, in particular the energy consumption,
• environmental impact of belt conveyors.
CONVEYOR BELT DESIGN AND CONSTRUCTION REQUIREMENTS
The main difference between the three belt concepts mentioned in the introduction is the construction of the belt. This section discusses typical belt constructions.
Conventional Conveyor Belt
Conventional conveyor belting has developed over the years and today operates at tensions as high as 1000 kN/m (or N/mm) width. Their construction can be full fabric, steel cable or steel matrix, a combination of the steel and fabric, or even a monoply fabric construction. Typical carcass sections are shown in figures.
Pouch Type Conveyor Belt
The two pouch belt options differ in their appearance by the construction of the tension number, with the Sicon using a steel cable tension member offering a typical rope tension of 10 kN and the Enerka-Becker System (EBS) being a total fabric/rubber construction having a maximum operating tension of about 10 N/mm.
The basic difference between the two systems are:
• The axial profiles of the EBS belt have no reinforcement, the axial profiles of the SICON belt have a steel cord inside.
• The main body of the SICON belt has no reinforcement whereas the main body of the EBS belt includes fabric reinforcement.
• The axial profiles of the EBS belt and the belt’s rubber cover form one piece. The axial profiles of the SICON belt and the main body of the belt are two pieces (warm) vulcanized together.
Pipe Conveyor Belt
The pipe conveyor belt is based on the construction of the conventional belt conveyor. Both fabric and as well as steel reinforcing can be used. However there are subtle differences between the two concepts.
The cross section of the pipe conveyor belt through the pipe indicating that the belt must be capable of forming a complete circle or oval and have an overlap / seal. Figures show that the belt construction is such that the bending stiffness at the overlap sections, which are the two edge sections, is lower than the bending stiffness of the center of the belt.
CONVEYOR LOADING AND UNLOADING PROCEDURES
Conventional belt and pipe conveyors are loaded and unloaded in exactly the same way; being opened for a conventional belt feed system from the tail pulley and again opening out at the head pulley for discharging.
The pouch belt however uses a much more restrictive type of loading arrangement but may have a similar discharge to the other systems. All the disadvantages of a conventional loading point have been eliminated in the pouch belt where spillage and off center loading should not occur. However overloading now becomes a major concern and this problem is also carried through to the pipe conveyor. It is essential that both the pouch and pipe conveyor have a controlled feeding point to ensure that no overloading occurs. This is often achieved using controlled feeders and overload limit switches. This makes the pipe and pouch belt unsatisfactory for installations such as at crusher discharge points where surges are very common. Another point of concern with pouch conveyors is the moisture content of the bulk material. Where conventional troughed belt conveyors allow water to run off the belt at the head or the tail pulley, a pouch conveyor is completely closed at the loading point. If the head pulley is located higher than the loading point than the belt may fill itself with water, which can create major problems.