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With Hand Tools on Process Equipment, Sterilization Alone Is Not Sufficient

An extreme example of a preventable source of contamination
In the maintenance of process equipment where contamination control is a concern, there is no longer any doubt that using Steritools™ (stainless steel Cleanroom tools) instead of ordinary carbon steel tools is the solution to the very real threat of ferrous contamination on fasteners and equipment parts. When such care and attention is paid to the regulatory standards under which such equipment is manufactured, installed, and put into service, it is difficult to believe that anything other than all-stainless steel hand tools would be considered for use during the course of its regular maintenance. Yet unwittingly, maintenance mechanics actively contribute to the loss of integrity of these well-tended and critical pieces of equipment and increase the level of risk of process contamination. The problem is a simple one, and being so simple, it very often does not command the attention it deserves. Ferrous contamination of a sterile facility can result simply from using ferrous tools on non-ferrous parts.

Ordinary plated carbon steel tools can be effectively sterilized for use in processing at least a few times before they become degraded and must be discarded. But sterilization is only part of the battle against contamination, and in fact has little effect against the long-term structural integrity of critical equipment. Even when sterilized before use, hand tools can still be a large contributing factor to the problem of contamination. Often this influence is unseen at the time it occurs, which is why it is often overlooked and poorly understood. A sterilized carbon steel tool is still a ferrous tool, and when used against stainless steel fasteners, for example, leaves an invisible trail of soon-to-be contaminants in its path. The contact of the two different materials during the course of normal use, say, using a hex key to tighten a stainless steel screw or a wrench to loosen a stainless nut, transfers iron particles to the stainless. The reaction, called oxidation, between the exposed iron particles and oxygen in an environment with even low levels of humidity results in the formation of iron oxide, or rust. This does not show itself immediately, but usually only after the offending instrument has long been put away or discarded. When rust does appear, it is often mistakenly attributed to the defective or low quality stainless of the fastener, which is not the case.

Stainless steel contains chromium and has an altogether different reaction to the surrounding environment. When chromium is exposed to oxygen it oxidizes to form a thin chromium oxide layer on the surface. This invisible layer is non-reactive, and therefore non-corrosive, giving stainless steel its "stainless" properties. In addition, this chromium oxide layer has self-repairing properties if it is scratched or damaged. As long as there is oxygen in the environment, the chromium in the stainless will "heal" itself by forming a new chromium oxide layer. Passivation, the process of forming this non-reactive, or "passive", layer, is a spontaneous result of the properties of stainless steel. Passivation can also be enhanced with the treatment of a mild oxidant, such as a citric acid solution that serves to remove the free iron from the surface as the passive layer is formed. As a standard procedure, the passivation of all Steritool tools is enhanced in this way during the manufacturing process.

Prevention is by far the most effective cure when it comes to sterile processing. Eliminating the risk of ferrous transfer by using stainless steel hand tools on process equipment has a quantifiable effect straight down the line. In any critical environment, the reduction of risk is a key factor in maintaining cGMP, with measurable financial benefits as well. Lowered risk easily equates to lowered operation costs. Since its founding in 1993, Steritool has aimed to provide sterile production industries with the tools needed not only to maintain but improve manufacturing procedures. Since then, the integration of stainless steel tools in sterile facilities has rapidly become the industry standard.

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