The HMA Materials Handling flow control gate is used wherever bulk solids have to be discharged from stockpiles, silos and bins in a metered and controlled manner. The sliding gates can be modulated to match the required flow rate, either via a setpoint or from feedback by a downstream device such a belt scale.

HMA Materials Handling Undercut Gates are generally used to control the flow of large (+4″”) material. They are generally of very robust construction in order to be able to withstand high-impact loads and wear. Undercut gates can be designed to easily close through a column of large material without jamming. This is because the tolerances can be made large and the pinch point at the closed position easily eliminated. Undercut gates are not applicable for metering flow, are difficult to seal, and require more headroom that some other gate designs.

The typical undercut gate application is loading rock and raw ore from loading hoppers in to haul trucks. For some undercut gates it is necessary to determine when they are open and closed.
Some of the devices available to determine the gate blade position are:

• A limit switch can be used to detect the closed or open position
• A proximity switch can be used to detect the closed or open position
• Position indication devices are available from the actuator manufacturers to indicate the actuator and therefore the gate blade position

The actuators available for use on undercut gates are:

• Hydraulic cylinder
• Air cylinder
• Electric linear actuator