In the U.S., hundreds of internally powered drive pulleys have been installed on portable plants since the early 1990s to handle sand and gravel, RAP, limestone and other minerals.
Thousands more have been deployed throughout the Permian Basin and other regions to handle frac sand.
Incorporating 12-in. diameter 5.5-hp and 7.5-hp motorized pulleys into plant infeed and discharge conveyors can provide safe drive systems without the need for extensive exterior mechanical equipment guarding for more than 25 years. Those drive systems can protect conveyor belts and structures by eliminating racking (i.e. twisting), especially during system start-up.
The basics
The Code of Federal Regulations 30 CFR 75.1722 – Mechanical Equipment Guards states: “(a) Gears; sprockets; chains; drive, head, tail, and takeup pulleys; flywheels; couplings, shafts; sawblades; fan inlets; and similar exposed moving machine parts which may be contacted by persons, and which may cause injury to persons shall be guarded. (b) Guards at conveyor-drive, conveyor-head and conveyor-tail pulleys shall extend a distance sufficient to prevent a person from reaching behind the guard and becoming caught between the belt and the pulley. (c) Except when testing the machinery, guards shall be securely in place while machinery is being operated.”
Internally powered conveyor drives enable manufacturers and users to be compliant with safety laws without extensive external machine guarding. This is because all potentially dangerous moving drive parts (i.e., gears and shafts) are enclosed within each pulley’s oil-filled, hermetically sealed shell. This drive technology enables a simplified machine guarding system to be installed and maintained.
The sheet steel at each side of the drive prevents personnel from placing hands between the pulley shell and the belt near the drive end. Since the motor and gearbox are enclosed within the shell and the pulley shaft is “dead” (i.e. non-rotating), no additional guarding is required at the drive to protect personnel from potential V-belt pinch points or any spinning shafts.
In the field
Fisher Industries has been incorporating Rulmeca motorized pulleys into drive infeed and discharge conveyors in the company’s 13-ft. and M76 portable air separators continuously since 1997.
In addition to minimizing the amount of machine guarding, internal drives also eliminate the need for maintenance personnel to grease external bearings because all bearings (including main support bearings) are enclosed within the pulley and automatically splash lubricated by the internal oil. Neither ladders nor manlifts are required to apply grease to main support bearings.
Since belt conveyor drive torque is transferred directly from the internally driven pulley into the conveyor support structure instead of a cantilevered external drive, conveyor structure racking, potential belt mistracking and material spillage are eliminated.
Rather than applying drive torque to the pulley with a transmission and live shaft outside of the conveyor frame, motorized pulleys apply drive torque to the pulley shell with a geared rim fixed to the shell between the two conveyor support members. Applying torque within the frame instead of outside the frame eliminates racking, especially during start-up.
Mike Gawinski is CEO of Rulmeca Corp.