Shot
Peening Success Stories for Processing Applications
Shot
peening has proved its effectiveness in extending the
service life and enhancing the performance of metal
components by protecting them against fatigue, fretting
fatigue, stress corrosion cracking and a variety of
other failure mechanisms. Following are some of these
success stories for processing applications:
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Food Industry Cheese Molds
The cheese/dairy industry has found that uniform dimples provide a surface that can advantageously replace other surface treatments. The textured surface from shot peening often has a lower coefficient of sliding friction that is necessary for cheese release properties on some food contact surfaces. The dimples act as lubricant reservoirs for fat or other substances allowing the cheese product to slide easier through the mold on the peaks of the shot peening dimples.
Testing has shown that shot peened finishes meet or exceed necessary requirements for cleaning in terms of microbial counts. This is due to the rounded dimples that do not allow bacteria to collect and reproduce. Sharp impressions left from grit blasting, sand blasting or broken media have proven to be less cleanable and have a much greater tendency for bacteria to collect and reproduce. Both glass beaded and stainless steel media have been used successfully in this application.
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Pneumatic Conveyor Tubing
Pneumatic
conveyor tubing can be up to 10 inches in diameter and
is usually made of a stainless or aluminum alloy. It
is used to transport plastic pellets at the facilities
of molding companies or at various production, blending
and distribution sites. Transported pellets degrade
when contact is made with internal piping surfaces.
The velocity of the pellets results in friction, heat
and lost production. Using a variation of its Peentexsm
process that produces directional dimpling, Metal Improvement
Company can achieve a directionally textured surface
that significantly reduces the formation of fines, fluff
and streamers that can account for millions of pounds
of lost and/or contaminated production each year. Directional
shot peening has been found to be much superior to other
internal treatments of the tubing, is often more economical
and can be applied on-site. The directional surface
finish has the added benefit of work hardening (when
stainless or aluminum piping is used), thus extending
the life of the surface treatment. The table shows test
results from six different internal pipe treatments.
A lower value of fines per 100,000 lbs conveyed is desirable.
The directional shot peening resulted in one third of
the fines of the next closest finish.
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