Metal Finishing Guide Book


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media. Rely on local outside sources for expertise. Determine if you want to spend a little extra up front to gain the benefits that better equipment, media, and product support offers: higher quality, higher yield, and an improved work environment. REFERENCES 1. By ditching the old trigger blast gun and upgrading instead to a more effective gun with a foot treadle, you'll blast faster and lessen the chance of workman's compensation squeezing that trigger for hours on end has lead to claims for carpal tunnel, tennis elbow, etc. 2. Changing nozzle size may necessitate other system changes. Consult your supplier. 3. Photo of ergonomic blast gun courtesy of Kennametal Abrasive Flow Products. 4. Dust is erosive, prevents free-flow of media, clogs filters, slows blasting, and in manual operations, reduces visibility – which is important to speed and quality results, without costly rework. 5. Photo by the author. 6. Most pressure vessels are rated for 125 PSI; some newer ones for 150 PSI. 7. Older designs of wet slurry blasting machines did not have the advantages of today's models. Be sure the one you select is designed for easy maintenance, durability, and clean operation – and is constructed with all-stainless steel (or roto-molded plastics when lower production economics are required). A glandless vortex pump will beat an older design in performance, and be sure the pump is rebuild-able, without tools, in minutes. This is one case where you get what you pay for, and good engineering counts. 8. Photo provided courtesy Wet Technologies, Inc. 9. Sizing the dust collector involves determining the total air flow (CFM) required, friction factors through the system (including ductwork), the airto-filter ratio (CFM: FT2) appropriate for the particular contaminant, and a variety of other factors. Therefore, adapting surplus collectors to blasting processes should only be done after a complete evaluation. (That would also include the risk of inheriting potentially hazardous dust shipped in with a used collector). The blaster's dust collector should be sized not just to overcome the incoming amount of compressed air, but also create several air changes, up to 10 or more per minute, depending upon the cabinet size. The blower that powers the dust collector must be matched in air flow rate with its reclaimer. 10. UltraWeb® by Donaldson-Torit is the originator, and many consider the best. This style filter prevents submicron particles from bypassing or prematurely clogging the filter media, amongst other benefits. 11. Wild changes in filter loading caused by inattention to the basic operational task of filter purging will lead to fluctuations in the operating conditions, and that can affect quality, cost, and add to the dust burden. For this reason, automating the cleaning cycle, using a narrow on/off band, is recommended. 12. A VFD, when tied in with an airflow controller, keeps air flow consistent, increases the service life of the filters, saves electricity, and ensures that your critical reclaimer system stays "in tune." 13. Photo by the author. 14. Photo of micro-blast courtesy of Vaniman Manufacturing. 19

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