Valves, Gates & Airlocks

Valves have become an integral part of the bulk material handling process because of their intensive usage and can be used to shut off, meter, or divert material. Hence, selecting the correct valve for bulk material handling is crucial, as the wrong valve could hamper the flow of the material.

Valves for bulk material handling are primarily used to control the flow by the gravity of materials from storage vessels or through mechanical conveying systems and direct the flow through pneumatic conveying systems.

Valves for bulk material handling also apply in dense phase pneumatic conveying systems to release pressurized materials from the blow pots that provide the motive power.

The actuation of valves can range from manual, pneumatic, electric to hydraulic. Each type offers particular benefits or is designed for a specific application. Slide valves are perhaps the most widely recognized, but a butterfly, disc, dome, diverter, iris, and rotary valves are widely used too.

Powder valves have an application in varying industries, primarily the pharmaceutical and chemical industries, and are designed to handle solid materials. Powder valves rotate 180 degrees (counter)clockwise to break up and disseminate material through the valve to the following processing stage. Depending on the application of powder valves, a specific actuator is required that facilitates the rotation. The most common valves used in powder handling applications are butterfly valves, diverter valves, and rotary valves.

Butterfly valves: Butterfly valves regulate flow by starting, slowing, or stopping a fluid. A rotating disk is a mechanism used to control the flow by allowing the disk to close the valve intermittently. Butterfly valves are among the most desirable valve types because of their low cost and lighter weight.

Diverter valves: Diverter valves are employed to convey powder amongst other materials to multiple destinations with care. Diverter valves are often required in dairy, food, and pharmaceutical application and therefore need hygienic standards for safe powder handling.

Rotary valves: Rotary valves find their primary usage in bulk material handling, dust collection, and pneumatic conveying. Rotary valves regulate the flow of material and create consistency to prevent leakage, damage to the valve, and jamming.

Many people think selecting a valve for dry material handling is relatively simple. But in reality, valve manufacturers need more information to choose the suitable valve for the application accurately.

The vast range of valve types reflects the challenges of controlling and directing the flow of dry bulk solids. Installation criteria determine which valve line is appropriate. The most critical question is, “what is the valve intended to do?” After establishing the intended usage of the valve, more concrete attributes of the valve could be evaluated, such as the shape and size of the opening, the temperature requirements, and the material of which the valve should be crafted. After this, the material characteristics need to be considered for optimal valve selection.

Selecting the suitable valve could be time-consuming but is always worthwhile as it could prevent future hindrances.

There are several basic types of solids valves:

• Ball valves: valves that control the flow of a liquid or gas utilizing a hollow, perforated, and pivoting ball.
• Butterfly valves (see powder valves)
• Control valves: Control valves are critical in controlling processes by manipulating flowing fluids.
• Diverter valves (see powder valves)
• Flap valves: Valves that allow the flow of gases or fluids in one direction while preventing flow in the opposite direction.
• Iris valves: Valves that control flowing powders, granules, and pallets.
• Pinch valves: Valves that control the flow of corrosive, abrasive, or granular material. The valve opens and closes using pressurized air.
• Knife gate valves: Valves that chop up material to allow this material to flow with no interference freely.