Conveyor controls

Bin apron feeder for controlled conveyor loading linked to belt weigher for accurate control... 

Automatic storage and retrieval systems—Storage racks linked through automatically controlled conveyors and an automatic storage and retrieval machine or machines that ride on floor-mounted guide rails and power-driven wheels. 

No contact with the material, no moving parts to wear out or corrode Unaffected by changes in the tension or stiffness of the conveyor belt Direct readout and adaptabiUty to modem controls... 

Belt-conveyor scales determine the amount of material being conveyed on a belt. A section of belt is weighed by placing the belt support rollers on a scale the belt speed is also measured. Weight and speed data are suppHed to a controller which integrates them to arrive at a material flow rate, often stated in tons per hour. The controller may display a flow rate, shut the conveyor down when a predeterrnined amount of material has passed, or it may be used to maintain a specified flow rate. Accuracy is limited because of the number of detrimental influences involved, eg, variable belt tension. 

Process industries frequently need to weigh and control the flow rate of bulk material for optimum performance of such devices as grinders or pulverizers, or for controlling additives, eg, to water suppHes. A scale can be installed in a belt conveyor, or a short belt feeder can be mounted on a platform scale. Either can be equipped with controls to maintain the feed rate within limits by controlling the operation of the device feeding the material to the conveyor. Direct mass measurement with a nuclear scale can also be used to measure and control such a continuous stream of material. 

In paste drying the leather is spread on glass or porcelain plates and held in place with a low strength water-soluble paste. The plates are on a conveyor and the drying is done in a drying tunnel. The dryer usually has several temperature- and humidity-controUed zones to control the rate of drying and to prevent overdrying. 

Kutrieb Corporation (Chetek, Wisconsin) operates a pyrolator process for converting tires into oil, pyrolytic filler, gas, and steel. Nu-Tech (Bensenvike, Illinois) employs the Pyro-Matic resource recovery system for tire pyrolysis, which consists of a shredding operation, storage hopper, char-coUection chambers, furnace box with a 61-cm reactor chamber, material-feed conveyor, control-feed inlet, and oil collection system. It is rated to produce 272.5 L oil and 363 kg carbon black from 907 kg of shredded tires. TecSon Corporation (Janesville, Wisconsin) has a Pyro-Mass recovery system that pyroly2es chopped tire particles into char, oil, and gas. The system can process up to 1000 kg/h and produce 1.25 MW/h (16). 

Several plants employ cooled-belt flakers. These consist of flexible steel belts, ca 1-m wide and up to 50-m long, that have short mbber skirting at the edges. Molten pitch flows from a thermostatically controlled tank over a weir to give a flat thin sheet on the belt, which is cooled from below by water sprays. At the end of the belt, the solid pitch is broken up by rotating tines. The pitch flakes are drained and transported to a covered storage silo by belt conveyor, during which time the surface moisture evaporates. 

Manually adjusted screw or ratchet take-ups that adjust the position of the tail pulley to control belt tension can be used on relatively short, light duty conveyors. Automatic take-ups are used on conveyors over about 25 to 30 m long. The most common is the weighted automatic gravity take-up (see Fig. la). Other types of automatic take-ups have hydrauHc or pneumatic powered devices to adjust a snub pulley position and maintain a constant belt tension. The requited take-up movement varies according to the characteristics of the belt constmction and the belt length. Typically, take-up movements for pHed belts are 2% to 3% of the center distance between head and tail pulley, and about 0.5% for steel cable belts. The take-up movements requited for soHd woven belts are usually shorter because of the lower elastic stretch. Take-up requirements for a particular situation should be confirmed by the belt manufacturer. 

---