Undercut Gates from HMA Materials Handling are generally used to control the flow of large (+4″”) material. They are generally of very robust construction to withstand the 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 than some other gate designs.

Mass flow gates from HMA Materials Handling are used to modulate the flow from mass flow hoppers or bins without disturbing the mass flow characteristics of the bin or hopper. In order to accomplish this, it is necessary that, throughout the range of motion of the mass flow gate, mass flow conditions are maintained at all times.

HMA Materials Handling mass flow gates can be single flat blade design, single curved blade design, or double blade, flat or curved design. Since mass flow requires relative steep slopes, mass flow gates are bulky devices requiring considerable headroom for installation.

The adjustability of HMA Materials Handling mass flow gates is generally about 10:1. If a gate is designed to pass 6000 tph, it should be able to regulate flow to 600 tph. Horizontal slide gates usually precede mass flow gates for positive shut-off, and to allow maintenance to the mass flow gates.
Some typical applications include:

• Mass flow gates are installed on the discharge of mass flow silos, bins and hoppers to regulate the discharge without disturbing the mass flow characteristics
• Some bulk material storage stockpiles are equipped with mass flow reclaim hoppers to prevent arching and rat holing and to increase the amount of material that can be reclaimed by gravity.

These reclaim hoppers can be discharged by mass flow gates