Production Machining

NOV 2018

Production Machining - Your access to the precision machining industrial buyer.

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CLENING TECH BRIEF 38 PRODUCTION MCHINING :: NOVEMBER 2018 Choosing the Right Vapor Degreasing Method L ike any equipment purchasing decision, a precision machine shop's choice about the type of parts cleaning unit to implement comes with deliberation by the company management about its needs. Considerations include the type of contaminant to be removed, the construction of the parts being cleaned and the time limitations for the cleaning process. A properly designed, operated and maintained vapor degreaser is a reliable and cost-eective cleaning choice for many applications. However, before investing in a vapor degreasing system, a shop must understand the three types of solvent degreasing processes available: mono-solvent cleaning, azeotrope cleaning and co-solvent /bi-solvent cleaning. Determining which method is best for an appli- cation requires knowing the ins and outs of each chemistry and, of course, understanding the shop's individual needs. Even before that, however, it is helpful to understand how vapor degreasing works. Vapor Degreasing's Functionality Vapor degreasing uses solvent immersion combined with vapor rinsing and drying to remove all types of oil, grease, wax, €ux and particulate. It is a closed-loop system consisting of a top-loading steel vessel composed of two chambers, both ƒlled with solvent. In one chamber, the solvent is heated to a boil, and this then generates a vapor cloud that rises to meet two sets of cooling coils. „ese cooling coils cause the vapors to condense and return to their liquid state. „is liquid is then channeled to the second chamber—the rinse chamber. A hoist lowers a basket containing the contaminated parts through the vapors and into the boil sump ƒrst. „e basket is then lowered into the rinse sump containing the clean solvent that has been condensed from the vapors. „is process is easily programmable and allows for excel- lent process control and repeatability. „e parts come out clean, dry and ready for packaging or further processing. In the past decade or so, companies have commercialized environmentally acceptable cleaning chemicals suitable for vapor degreasing. „is means that the speed, convenience and energy savings of this technology now is easily available to engineers everywhere. „e following describes the three types of vapor degreasing options and their chemistries. Note that each has its advantages as well as its drawbacks, but they all can be beneƒcial if used in the right application. Mono-Solvent Degreasing „is type of vapor degreasing, as its name suggests, contains only one component and is usually the most cost-eective option because it is easier to manufacture. „e operator also does not need to monitor solvent concentrations or worry about what solution to add into the one-component degreaser. And because the composition remains consis- tent, it can clean in both liquid and vapor phases, making it a practical option. However, the mono-solvent's cleaning abilities are limited, and some of the most common mono- solvents today can have €ammability or toxicity issues. N-Propyl bromide (nPB), trichloroethylene (TCE) and perchloroethylene (PERC) are some of the most popular mono-solvents, and they can all contribute to safety and environmental problems. Although mono-solvents can be relatively aggressive in cleaning strength, they are best used to remove machining oils and lubricants consisting of hydrocarbon components. High-boiling mono-solvents can be used to melt waxes and remove high-boiling contaminants. „ey also work well on metals, although it is important to monitor the process for acid acceptance if using one of the less stable (chlorinated) mono-solvents. By Venesia Hurtubise • • • • •

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