UNDERSTANDING LOW-PRESSURE CAVITY AIR PURGE

"Remember, you don't have to brush ALL your teeth... just brush the ones you want to keep."

• Anonymous Mother’s Wisdom

Much like the early age fear of cavities instilled by mothers around the world, in the realm of pneumatics, we face our own cavity concerns, not in our mouths, but in our rotary valves (usually – though some may have a few extra holes in their heads).

The primary adversary of rotary valves is abrasive material on wear surfaces. Silicates and other abrasives can erode the clearances necessary for rotary valves to maintain tight seals and minimize air leakage when functioning as airlocks. To counter this erosion, manufacturers often recommend the use of closed end rotors, where a flat plate, referred to as a shroud, is welded on the end to protect against excessive wear on end plates, seals, and bearings.

However, to ensure the valve spins freely, these shrouds must be machined with clearances, creating a cavity between the shroud and the end plate. This cavity needs to be kept clear, or "purged," for the valve to continue rotating freely and maximize its lifespan.

Typically, manufacturers use compressed air tapped into the end plates, regulated slightly above convey pressure, to blow out the cavity. While effective for moderately abrasive materials and smaller valves, this method has limitations, especially for larger valves where the air consumption required can be significant and may not always suffice.

In response to this challenge, Blowvac Systems introduced the "Low-Pressure Cavity Air Purge." This method utilizes a small amount of the conveying air stream below, vented through an orifice plate to induce slightly greater pressure, handling the purge without the need for high-pressure compressed air. This approach proves more efficient for larger valves, reducing costs and extending the valve's lifespan.

Over the years, this low-pressure method has proven to be a cost-effective way to maintain the valve's health.

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Do you have questions about the "Low-Pressure Cavity Air Purge"? Would you like an in-depth service or repair completed?