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Microbial Contamination Control

November 01, 2012
Dr. Fred Passman
Online Only Articles
STLE University


There was a time when metalworking fluid (MWF) system operators never had microbial contamination problems.  They simply drained, cleaned and recharged (DC&R) their systems every 8 to 12 weeks when the stench got to be so bad that the worked refused to enter the plant. Then, in the early 1980’s, thanks to the tireless educational efforts of Drs. Ed. Bennett and Harold Rossmoore, and the innovative fluid management marketing efforts of a few small MWF compounders, the folks responsible for MWF system maintenance and management began to make the connection between uncontrolled microbial contamination and fluid performance life.  Damage caused by microbes (biodeterioration) in one of several common MWF failure mechanisms; and it is at or near the top of the list.

Think of microbial contamination control as a five piece jigsaw puzzle, with effect control being the central or keystone piece that falls into place only when the other pieces are in good condition and in their proper place.  The other four pieces are design, housekeeping, monitoring and treatment.  The STLE MWF Management Certificate Program’s Microbial Contamination Control module explains each of these foundations of microbial contamination control, describes best practices and demonstrates how they unite to form a cost-effective program that is integral to successful MWF management. 

For example, under the heading of Design we review the importance of system capacity and layout to effective maintenance.  In particular, dead-legs (sections of piping that remain in place, flanged off, after the machine to which they transported MWF has been removed) are filled with stagnant MWF that isn’t touched by the DC&R process.  As soon as recirculation restarts after DC&R, the Venturi Effect vacuum created as fresh MWF flows past the intersection of the dead-leg and live line, sucks stagnant, heavily contaminated MWF from the dead-leg into the fresh MWF and recontaminates the entire line.  This can be prevented simply by removing the unused line and flanging it off as close as possible to the pipe to which it is connected.  The module is full of practical, useable ideas that go well beyond treating contaminated MWF with a microbicide once the microbial population has gotten out of control. 

Like the information in the other modules of this 2 ½ day course, Microbial Contamination Control helps participants to understand the fundamental causes of conditions they’d invariably seen in MWF systems, provides context and guidance on how to minimize the net cost of microbial contamination, using language that makes sense people whose technical background ranges from nil to highly sophisticated.

Dr. Fred Passman is the Principal of Biodeterioration Control Associations and member of STLE. He is one of the instructors for the upcoming 2013 Metalworking Fluid Management Certificate Course (for more information, click here) and he will be teaching and chairing MWF 250: Understanding and Controlling Metal Removal Fluid Failure, an education course to be held at the 2013 Annual Meeting in Detroit, MI.

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