When it comes to screw washers, wear on the protective shoes covering the flights is inevitable. However, in most sand applications, wear follows a predictable pattern—starting from day one on a brand-new machine.
In a typical sand screw application, the middle third of a shaft’s wear shoes—around the tub’s waterline—will usually wear out within three to four years. The following year, the shoes at the tub’s discharge will wear out, followed by those at the feed end, which are usually submerged, the year after that.
The most cost-effective maintenance approach is to replace one-third of the shoes annually after the initial three- to four-year period. However, many operators overlook this simple routine in an effort to reduce maintenance downtime—often at the expense of long-term efficiency.
Neglecting timely shoe replacement can lead to more extensive repairs.
When wear shoes aren’t replaced on time, the steel welded to the shaft begins to wear down. This means operators have to cut off the damaged flights, leading to longer repair times and extended downtime.
Instead of a quick shutdown to swap out a set of shoes, operators can find themselves out of commission for days, as worn flights need to be removed and replaced entirely.
Order trends also reveal a common maintenance misstep. Many times, orders come in for a full set of shoes for an entire shaft, which suggests that at least one-third of those shoes are being replaced two years later than they should be.
Selecting the correct material for wear shoes is another crucial factor in extending their lifespan. Common materials include:
Ni-Hard has a consistent wear rate per ton, regardless of the material, whereas rubber wears more slowly with natural materials but much faster when exposed to sharp particles.
Matching the right shoes to the material being processed is essential—whether on a brand-new screw washer or an existing unit.