Ricky Patel, engineering associate, Lorenz Conveying Products

Wear should be considered during the design phase of a dilute phase pneumatic conveying system but is often overlooked since a component designed for long wear life may not always be the most efficient or may bear a higher up-front cost. All components should be selected based on a geometry that provides the necessary efficiency, wear, and product handling characteristics. These are important aspects to consider during the design phase as changes to the system are not aways feasible after the system is in place.

Elbows in a dilute phase pneumatic conveying system are especially susceptible for wear. The easiest option to combat wear problems in an elbow is to utilize an elbow made from a thicker or more wear-resistant material. This will work only by the fact that since there is a thicker or more resilient material for the product to wear through, it will provide additional life.

Elbows can also be modified from a standard bent tube/pipe to become more wear resistant:

• Open Cavity: The outside of a standard smooth flow elbow is boxed in with heavy-gauge metal. The elbow initially will perform as a standard elbow. As product wears through the main elbow, it will fill the open cavity and provide an impact cushion.

• Filled Cavity: Is similar to the open cavity, however, the cavity created between the elbow and the outside wall, is filled with concrete or another abrasion-resistant compound.

• Lining: The inner surface of the smooth flow elbow is coated with an abrasion-resistant material such as ceramic.

• Ceramic Backing: A hard ceramic material is applied to the outside of the elbow. When the material wears through the metal of the elbow, it will encounter the ceramic material on the outside and wear on it.

Alternatively, various fabricated/cast elbow designs exist that incorporate special features intended to minimize wear or allow for easy replacement of critical wear areas.

Wear can also be a problem for the valves and gates used in the conveying system. Valves and gates that provide little to no obstruction to the material path when open should be chosen. Knife-, slide-, or ball-type valves/gates are often the most suitable.

Diverting valves is another issue. The act of diverting a moving product stream will subject the component to wear. Many diverter-type valves used in pneumatic conveying systems consist of a tube/pipe wye fitting where one leg of two is opened to allow material to flow through. The fitting itself is extremely susceptible to wear. Strategies to combat this wear can be similar to those used for elbows.

Another type of diverter well suited for wear better utilizes a flexible hose or moving chute to divert. This hose can be made or lined from a variety of materials based on the application (such as rubber or polyurethane). This is an ideal type of diverter valve if cross-contamination needs to be avoided.

Wear is inevitable. There is no perfect way to stop it. Considering the various options available can help increase life span of components and reduce downtime and product loss due to failure.

Ricky Patel is engineering associate, Lorenz Conveying Products (Cobourg, ON, Canada. For more information, call 800-263-7782 or visit lorenzproducts.com.