In a gravity flow situation, a diverter valve is used to change the direction of the material to direct it to a new destination. There are several types of diverter valves that can accomplish this task. The most simple diverter is a single blade diverter. In an A style diverter, as the material moves through the inlet, a blade directs the material either to one side of a diverter or the other. In an offset style, the material either passes straight through the diverter, or the blade intercepts the flow and diverts it to one side. These diverters are typically square or rectangular, and can be manufactured of carbon steel, stainless steel or various alloy steels.
A basket diverter is an alternative to a single blade diverter with the advantage of zero leakage to the closed leg as the basket has an underlapping lip with the inlet. On powdery materials, there can be some dusting that goes into the closed leg, but the basket does not require any type of elastomer or wearable seal and is quite reliable. These diverters are also designed in square and rectangular configurations, and with air, electric or manual actuators.
Rock Box Diverter
When handling very abrasive materials, a rock box diverter is a reliable design when cross-contamination is not an issue. Basically, the diverter consists of two shut off gates located in the chute below the crotch of the diverter. When one gate is closed and the other open, the material diverts into both legs, but builds up in the closed leg, causing the material to impact on itself forming the diverter surface. By the material impacting on itself, the wear to the diverter is minimal and the gates don’t see any impact from the material flow. This diverter style can be used in square, round or rectangular chutes.
There are several types of shut off gates available to control or stop the flow of dry bulk solids. A rolling slide gate is a blade that is manually or automatically actuated to slide on slide rails or roller wheels to pass through the flow to shut off the material flow. These gates can be designed to cut through a solid column of material by incorporating a displacement pocket at the sealing end of gate travel allowing the material a place to go. These gates can be provided with packing gland seals and full dust enclosures to minimize any dust escaping the system.
Rolling Blade Gate
A rollerblade gate is another technology available to control and shut off the flow of a dry bulk solid. A roller blade gate incorporates a curved blade that rotates through the flow and then cams forward into the seal at the end of the stroke. This cam action avoids wear on the seal during the opening and closing of the rollerblade. This rollerblade action can also be used to meter material onto belt conveyors, as well as on large systems, used to control the flow for railcar loadout systems
A Dome valve, also known as a segmented ball valve, offers a unique means to shut off and isolate a material flow for a dry bulk solid. The dome rotates approximately 90° out of the flow to allow for an unrestricted flow through the inlet orifice of the gate. When the material needs to be throttled or metered, the dome can rotate partially back through the material to a variable position. The valve can be rotated completely closed to stop the material flow. If a pressure differential needs to be maintained, and inflatable seal can seat down on the dome from the underside of the inlet to form an airtight seal, up to pressures of 100 psig. An advantage of this valve, due to the clearances between the dome and the inside housing, is the ability to handle sticky or adhesive materials. This valve can be manufactured in cast-iron or cast stainless steel, and can use air or electric actuators to rotate the valve.