Conveyors horsepower

For continuous applications, the primary-drive system must have adequate horsepower to handle a fully loaded conveyor. Horsepower requirements should be determined based on the specific product s density and the conveyor s maximum-capacity rating. 

Horsepowers listed are calculated for average conditions and are of the proper motor size with factors for length of conveyor, momentary overloads, etc., taken into consideration. 

Fairfield Engineering Co. data in U.S. customary system. Metric conversion is rounded off. For inclined conveyors, add lift liotnepower to center horsepower for total horsepower. For temrinals multiply horsepower hy the following factotn 0-50 ft (15.2 m), 1.20 51-100 ft (.30.5 m), 1.10 101-150 ft (45.7 m), 1.05. For countershaft drives, multiply horsepower hy 1.05 for each reduction (cut geatn). 

Two-winding motors may be built for constant torque, variable torque, or constant horsepower. Constant-horsepower motors are capable of handling the same horsepower at both speeds (i.e., higher torque at the low speed). Constant-torque motors can handle the same load torque at either speed (e.g., conveyor drives). Variable-torque motors are designed for loads in which load torque varies as the square of speed and horsepower varies as the cube of speed. Typical applications are as follows ... 

Diameter of Conveyor, Inches Diameter of Coupling, Inches Maximum Horsepower at 100 R.P.M. Maximum Torque Capacity in Inch Pounds... 

TABLE 5.7. Speed and Horsepower of Drag-Type Conveyors of Redler Design8... 

Screw conveyors No Bulk density Flow rate Diameter Drive horsepower 90 1 8 1 20... 

Choose a bucket elevator to handle 150 tons/h (136.1 tonnes/h) of abrasive material weighing 50 lb/ft3 (800.5 kg/m3) through a vertical distance of 75 ft (22.9 m) at a speed of 100 ft/min (30.5 m/min). What horsepower input is required to drive the elevator The bucket elevator discharges onto a horizontal conveyor which must transport the material 1400 ft (426.7 m). Choose the type of conveyor to use and determine the required power input needed to drive it. 

Related Calculations. This procedure is valid for conveyors using rubber belts reinforced with cotton duck, open-mesh fabric, cords, or steel wires. It is also valid for stitched-canvas belts, balata belts, and flat-steel belts. The required horsepower input includes any power absorbed by idler pulleys. 

Labor expense, almost a negligible factor with belt conveyors, may be arbitrarily set at cts. per inch of width of conveyor per hour, irrespective of the load handled. Incidental expenses for supplies to keep the equipment in good operating condition vary closely with the power requirements and may be taken at % ct. per horsepower per hour. 

Example.— Required the net operating cost per ton of a 400-ft. conveyor handling 60,000 tons of fine coal during 1,200 operating hours in the year. The conveyor to elevate the coal 24 ft. and distribute it by means of an automatic tripper over a bunker 60 ft. long. Power delivered at the conveyor drive commands a value of 3 cts. per horsepower. 

Fixed charges for screw conveyors may be taken as 8.5 per cent a year by allowing an annual renewal charge of 20 per cent of initial cost. Labor expense of about % ct. per inch diameter of screw during hours of operation and a supply expense of 1)4 cts. per horsepower constitute the other charges included in the net cost of operation. 

A peculiarity of suction conveyors is that once the necessary degree of vacuum has been created in the system, it requires practically no more power to operate a long conveyor than it does a short one—within reasonable limits. With reasonably tight intakes, the formula for horsepower is given as Formula (30) and it will he noted that the power requirement is quite independent of the load carried, being simply that required to maintain the suction necessary to handle the capacity load. 

Example of Net Operating Costs,—Required the net operating cost per ton of a 10-in. suction conveyor handling 7,500 tons of ashes per year, power commanding a value of 3 cts. per horsepower delivered at the exhaust fan drive. Ashes weigh 45 lb. per cubic foot. 

The main variables for selection and design of scraper conveyors are the capacity and the power. The capacity of horizontal scraper conveyors loaded with materials of approximately 800 kg/m bulk density, has been calculated and is presented in Table 3.8. The theoretical horsepower requirement P for flight conveyors can be determined from the following equation ... 

Constant Torque. These motors maintain constant torqne at all speeds. Horsepower varies directly with speed. This type of motor is applicable to conveyors, mills, and similar applications. 

The horsepower requirement for the conveyor-head shaft, H, for horizontal screw conveyors can be determined from the following equation ... 

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