The Effect of Abrasive Powders on Rotary Valves

The Effect of Abrasive Powders on Rotary Valves

The Effect of Abrasive Powders on Rotary Valves

Abrasion occurs when two materials rub against each other, if one product is harder than the other, the hard product wears away the softer product.

Generally these type of products tend to flow well because they are heavy which can be an advantage in providing a high filling efficiency.

A positive pressure differential below a rotary valve will greatly speed up the wear process. If suitable wear resistant options are not considered it will shorten the valve life substantially.

For lighter abrasive products excess leakage air can aerate the product which reduces the bulk density and therefore the throughput. In extreme cases it could cause the product to bridge.

The Solution - Choose the right valve

In many cases drop through style rotary valves are better suited to abrasive products than blow through style rotary valves, mainly because the rotor on a drop through rotary valve sits up higher within the valve body. Rotors on blow through style valves are located directly in the pneumatic conveying line where, depending on the profile of the conveying pipe connection of the selected valve, product can be conveyed against the end cover face.

When there is no positive pressure present (often referred to as a gravity application) the mechanical wear properties of abrasive products as far less dominant.

There are wear resistant features that will significantly extend the life of your valves such as:

  • Hardened steel replaceable rotor blades

  • Tungsten carbide or hard chrome coated bore, end covers & rotor journals

  • Plasma nitride coating

  • Ni-hard rotors or end discs

  • Extra Heavy Duty style with replaceable internal components

In most cases these features will help extend the life of a rotary valve being used in harsh conditions, but there are some system and design parameters that can also greatly impact wear and valve life.