A: Ricky Patel, Lorenz Conveying Products, says:
Valve and gate wear can be a problem in a pneumatic conveying system. For gravity-fed systems, several options are available to reduce component wear, including abrasion-resistant steels and material pockets. However, material pockets aren’t usually suitable for a high-velocity pneumatic conveying system because the air-entrained material’s velocity can cause material degradation as the material in the airstream deflects off of the collected material in the pocket.
For pneumatic conveying systems, choose valves and gates that provide little to no obstruction in the material’s path in the conveying line (when the valve or gate is open) because any obstruction, such as the plate in a butterfly valve, will wear while in the material stream. Knife-type or slide-gate valves are often the most suitable in pneumatic conveying since they offer no obstruction to the material flow, which minimizes wear.
Using a diverter valve in a pneumatic conveying system can cause additional wear since the act of diverting a moving material stream will subject the valve to wear. Many diverter valves used in pneumatic conveying systems consist of either a tube or pipe wye fitting where one leg of two is opened to allow material to flow through. Since this diverter relies on the wye fitting to divert material, the fitting itself is extremely susceptible to wear. Strategies to combat this wear are similar to those used for elbows, including using a thicker tube or pipe material or adding an open-cavity or ceramic backing.
A diverter valve that uses a flexible hose to divert material will handle wear better. The hose can be made from a wide range of materials depending on the application, but the hose is typically either rubber or polyurethane, which is soft enough to be abrasion-resistant. A flexible hose type diverter valve is highly recommended if the system is conveying a variety of materials and cross-contamination needs to be avoided.
Lorenz Conveying Products, Cobourg, ON, manufactures couplings, tubes and pipe bends, fittings, diverter valves, slide gates, cyclones, and custom accessories for pneumatic conveying and bulk material handling systems.