Solvent-cleaningmust be Safe and Ecologic.SOLUTIONS with Effective, Practical Advice
While solvents are useful and economic to use, they can cause several types of problems if they are not handled properly. Therefore it is imperative to be aware of limitations and necessary precautions. Solvent selection is largely based on the type of soil to be removed. Different contaminants have different chemical and physical properties. Therefore they must be treated by different means. Some of these soils like salts, show increased solubility in polar environments as water based solutions, while others like oil-based contamination is best removed in semi-polar organic solvents such as modified alcohols. In general wherever possible, for increased cleaning efficiency, it would be better to separate those treatments in different systems. Solvent-cleaning operations are generally more flexible and effective than aqueous-based cleaning. Applications vary depending on a lot of factors. Possible solutions that involve immersion of parts to be cleaned with or without mechanical or ultrasonic liquid agitation, manual brushing, mechanical spray in a closed system are all among practical ways of performing Solvent-cleaning. Important AnnouncementWhen you need Welding-metallurgy knowledge (Sponsored Links) For successful welding, parts must be clean from oil, grease and other contaminants. It is therefore pertinent to any welding operation to devise and implement the most suitable cleaning method without danger to workers or damage to the environment. The high and nearly complete solvent reclaiming is one of the major advantages of Solvent-cleaning systems, when compared to aqueous cleaning operations and, as most installations operate at room temperature, the energy demand for recovery by distillation is almost all power that is needed. A common strategy for reducing Solvent-cleaning material quantity, consists in adopting a two-stage system. The first stage is used to clean the dirtiest parts. Cleaner solvent in the second stage provides final cleaning and rinsing. When that in the second stage is too contaminated, it is moved to the first stage. The discarded solvent is due to reclaiming by distillation, while new or reclaimed solvent replaces that in the second stage. Normally parts dry up in air, but vapors or fumes should be vented. Depending on their flash point temperature, some solvents can pose a fire or explosion hazard. Suitable precautions must then be implemented to avoid those dangers. Other solvents can cause immediate or long-term health effects to exposed workers if used at too high concentrations when they risk to be inhaled or absorbed through the skin. Certain solvents contribute to air pollution and most of them cause environmental problems, if not properly disposed of. For the industrial companies using Solvent-cleaning, the cost of processing, including equipment, materials, energy needed to recycle and waste management, becomes the most important issue, after having satisfied quality requirements, safety precautions and environmental concerns. Maintenance in Solvent-cleaning applications is considered much easier than with aqueous-cleaning systems. Every installation however, must be constantly kept under control to avoid any possible influence likely to change the stability of the solvent, deteriorate the cleaning results or cause corrosion to equipment or to items being processed. Different, increasing cleaner stages are available with additional expenses, depending on type of parts, contamination and their further processing requirements. Only the least clean condition as required should be aimed to, for obvious economic reasons. Among the most used materials for Solvent-cleaning, the following are quite popular:
Several proprietary products are proposed for use with claimed advantages and economy of use. Chlorofluorocarbons (CFCs) and Hydrochlorofluorocarbons (HCFCs) like trichlorethylene, chloromethane, (1,1,1) thrichloroethane and others from the same families, which were in the past very popular for Solvent-cleaning, are now almost completely eliminated or still used under the most severe controls because of their demonstrated destruction of the ozone layer in the stratosphere, with its unfortunate negative influence on human health. It is claimed that a new model of Solvent-cleaning business called Chemical Leasing, is being developed, whereby performance rather than chemicals and service are sold. In fact, suppliers offer cleaning services, for supplying cleaned parts, while relieving the industry from the maintenance duties. It seems that this scheme, promoting the most complete exploitation of equipment and best use of materials, provides the least possible cost per area of cleaned parts. See Chemical Leasing Frequently Asked Questions Operators should ascertain their duties imposed by laws and regulations in their location, and obtain the required authorizations before starting production. Self-audit check forms exist, originating from several sources, corresponding to usual requirements: responsible management should make the necessary preparation work and should make sure to comply with all requirements. Any questions or comments or feedback? Write them down and send them to us by e-mail. Click on the Contact Us button in the NavBar at top left of every page.
To reach a Guide to the collection of the most important Articles from Past Issues of Practical Welding Letter, click on Welding Topics. Steel Finishing
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