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What do you mean?
Barbara Kanegsberg BFK Solutions LLC
“So then, you drive off the solvent …..”
I stopped as I caught the horrified expression on the face of the woman sitting across the room. I paused, and thought: what had I said that was so terrible? I was explaining how contained, airtight and airless solvent cleaning systems keep the solvent away from workers, neighborhoods, and the environment as well as how they help achieve effective process control, cleaning, and manufacturing. The woman in question was with a group concerned with worker safety; and she obviously misinterpreted what I was saying. I’ll tell you how I diffused the issue, but let’s start with a few ideas.
• Terms used in cleaning, surface preparation, contamination control, controlled environments depend on the context.
• Our clients benefit from our experiences in developing cleaning and contamination control processes for various applications. However, to extrapolate from one area (say, medical devices) to another (perhaps aerospace applications), we have to translate the “lingo” and the underlying rationale and philosophy.
• Part of the challenge (and the joy) of editing the second edition of our “Handbook for Critical Cleaning,” is reflecting on the similarities and differences in language as used in the areas of electronics defluxing, art conservation, and pharmaceuticals. We are divided not so much by geography as we are by technical field. Sometimes, I need an English to English Dictionary.
Back to the horrified lady at the meeting. In a moment of blinding clarity,
I realized that “driving off” the solvent did not mean the same thing to her as it might to someone attempting to clean a large batch of complex widgets. To me, and perhaps to many of you, “driving off” the solvent is akin to drying. It involves removing solvent trapped in blind holes or perhaps trapped in honeycomb.
In cleaning processes using an enclosed, airless, or airtight system, the solvent is removed from (or driven off) the part and collected for re-use within the system. Depending on the cleaning system, any residual solvent may also be trapped by carbon adsorption and in some cases even the adsorbed solvent may be recovered for re-use.
Unfortunately, to the woman across the room, “driving off the solvent” conjured up an erroneous vision, probably something akin to evil, unkempt polluters tossing leaking, greasy drums of foul solvent into a rickety truck and then “driving off the solvent” to be surreptitiously dumped onto an elementary school playground in a disadvantaged neighborhood on a dark and stormy night at 1:43 A.M. Ok, so she never told me her exact thoughts, but I “read” her facial expression. I then considered how my comments might be mis-interpreted by someone who was not involved in manufacturing or precision cleaning. I clarified the technical jargon. We both relaxed and smiled; and the meeting moved forward.
Washing? Cleaning? Rinsing? Drying?
When I discuss a cleaning process, I talk about washing, rinsing, and drying. Depending on the manufacturing assembly, or rebuild/rework process, the terms cleaning, critical cleaning, and (good grief!) washing may not be commonly used, perhaps for historical reasons and perhaps because the terms are not considered sufficiently - uhm, perhaps the best word is “classy” - in the context of the application.
To review
Soil is matter out of place, dead or alive, organic (carbon based) or inorganic. Cleaning is the removal of matter out of place. A complete cleaning process consists of washing, rinsing, and drying.
Washing is removing the soil from the substrate (the product or part being cleaned).
Rinsing is removing residual cleaning agent from the substrate. Sometimes, washing continues during the rinsing step.
Drying is removing residual water or solvent from the substrate.
All three steps have to be accomplished without damaging or recontaminating the product.
What’s in a name?
Some processes, particularly in microelectronics, use the term soil removal instead of wash. Other terms include depainting or deblocking. Deblocking is used in complex instrument assembly. The concept of depainting is used in aircraft repair. The terms may be applied to the wash step or to the entire cleaning process.
Cleaning processes are often considered relative to a substrate or surface, but what is the surface? Some surfaces, including metals and composites, are porous. Because adsorbed solvent or water can interfere with product performance, a bakeout may be part of the process. In a bakeout, the component, part, or product is subjected to elevated temperature and often to reduced pressure for a long period of time. Essentially, bakeout serves to drive off the solvent. A bakeout can be considered a drying process. Alternatively, perhaps we could think of bakeout as using heat to “wash” solvent or water from the part. It’s a matter of semantics.
Cleaning versus purification
If foreign debris is removed from, say, the surfaces of or the spaces between pellets of resin, we can say that the resin is being cleaned or maybe recycled. In other instances, ionic contamination may be removed from the entire pellet – the pellet is cleaned inside and out. This is often referred to as purification or repurification. Similarly, process liquids and pharmaceuticals may also be purified. In a more encompassing sense, these could also be considered to be cleaning processes.
The customer is always right
As my dad, who ran a retail clothing store for decades, used to tell me:
The customer is always right; but remember to hear not what the customer says, but what she actually means.
I’ve always thought this to be terrific advice. Particularly with complex manufacturing processes involving people with all sorts of wonderful niche expertise, communication and active listening are essential.
Emails, blogs, and websites are invaluable but are often not sufficient. Cohesive written communication helps. So do conference calls and face to face communication. So does active listening. Active listening is an ongoing challenge for me.
Listen, ask
We can all save time and money and become more productive.
• Hear what is being said from the viewpoint of the speaker (this includes the spoken word, technical articles, blogs, and emails)
• Use instant communication – but don’t rely on that alone
• Explore the terminology of alternative technical universes
• If all else fails, ask: what do you mean?
