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So You Want to Be a Cleaning Lady, Part 2 - Wonderful Dish Soap (Not)
Barbara Kanegsberg
"We fixed the cleaning problem. The cleaning equipment didn’t work, so we changed the equipment. Then, the aerospace cleaning liquid stuff didn’t work worth jack-spit. One of the guys brought in some dishwashing soap from home. We dip the parts in; and it takes off all of the dirt that the water-based stuff and the big aqueous cleaning system missed.”
We’re not big fans of using consumer-oriented products for critical cleaning applications; and this includes both aqueous-based products like dish soap and solvents from the hardware store. With very rare exceptions, such products are not designed for manufacturing; and the vendors that supply them typically do not support manufacturing activities.
However, let’s suppose you are faced with such a situation. There you are, in a room containing an enormous bottle of dish soap, row upon row of colorful plastic tubs, and production people dunking parts by hand. There’s a lot wrong with this picture. This is supposed to be a new, high-tech cleaning process for a new aerospace client, not a row of plastic tubs. How did the process get this way? How do you get a controlled, robust process? A number of you ask how to become a “cleaning lady” (or gentleman), so here are a few approaches tofixing the problem.
Note: This is the second in a series of articles on how you can become a “cleaning lady” (or gentleman). For the first of these articles, refer to Clean Source, Vol 7, Issue 3.
Removing the soil – the wash step
You’ve established that the dish soap is successfully removing soil from the parts. Maybe the parts are visually clean; perhaps someone has taken the effort to do particle determination or non volatile residue (NVR) testing.
Why is this dubious process working? How might you optimize it? We’ll track through the process; and, for your clarification, we have also provided a summary at the end of this article.
You look closer and determine that people submerge two to three parts at a time in a plastic tub; then they agitate each part by hand. They repeat the process in three rinse tanks (in this case, in lipstick red wash tubs). When the parts are removed, they look pretty clean, visually.
“We tried putting the fancy aerospace stuff in the tubs,” the lead assembler explains. “As soon as we stopped sloshing the parts around, we got this layer of grease at the top. When we pulled the parts out, the grease settled right back on.”
The wash portion of the cleaning process has two functions. The first is to remove the soil from the surface of the part; the second is to keep the soil away from the part. This has to be accomplished without damaging the part being cleaned. In addition, it is highly desirable to keep the cleaning agent clean and to regenerate the cleaning agent. This is particularly important for high-volume production. With high soil loading, the wash bath stops removing effectively; and soil may settle back on the part. In addition, every time you have to change out the wash bath, you are probably paying good money to treat the bath as hazardous waste. After all, the cleaning agent may be acceptable for disposal; but the cleaning agent with dissolved oils and metals probably is not.
The dish soap and the aerospace cleaning agent are each behaving just as they were designed to do. Many aqueous cleaning agents designed for manufacturing have what is called an oil-splitting chemistry. The oil pops up to the top. This is a desirable feature in that, when used in a cleaning system, the oil can be removed from using a sparger. In contrast, the dish soap does not have an oil-splitting additive package; dishpans are not designed with spargers. It contains additives that hold the soil in suspension. In this example, it works well, especially for washing a few parts at a time.
Dish soap problems
You have other problems with the dish soap. In all likelihood, eventually, a “new and improved springtime rose scented” version of the dish soap is likely to appear, without details on the contents that impart the rose scent. Will this change in formulation affect the part you are cleaning? You might not know until a lot of parts have moved further up the production chain. A more immediate problem is that the contract with your aerospace customer specifies use of a few cleaning agents. You reread the specs and find that, astonishingly, dish soap (with or without the springtime rose scent) isn’t on the list of approved cleaning agents.
The dish soap is not an option, not if you need to comply with the customer contract.
Cleaning system – not quite as described in the colorful brochures
Let’s look at the cleaning system that they said wasn’t working – why did they replace it with a series of dishpans? When you ask where it is, you are pointed toward a hulking metallic object on the loading dock. What is before your eyes is not the system you had clearly specified for this new product line and thought had been ordered. Instead, you see ancient, semi-corroded cleaning equipment.
Here’s why the dishpans happened. The new cleaning system was never ordered; the new cleaning system was not in the budget. The purchasing department vetoed it; after all they pointed out that there was a perfectly wonderful parts washer that had been languishing in a warehouse. So, the production department resurrected the old parts washer and set it up for the new process. This wash tank has no sparger and no way of agitating the parts. There is only one rinse tank. The drier seems to be blowing particles on to the parts. If there ever was an air filter, there is no longer any sign of it. The system just was not working, but something needed to be done; the customer expected completed product. It’s no wonder that the production group moved the parts washer out of the facility and resorted to dishpans with dish soap.
So what’s the short-term fix?
The older cleaning system simply does not work and should be sold as scrap or perhaps repurposed as a lovely planter. At least currently, throughput is low enough that benchtop-type batch cleaning is an option. You go back to the list of approved aerospace cleaning agents and investigate their properties. Fortunately, three of them are not oil-splitting. So, you test them, first on scrap (not on product, please). Why test? Because each production situation is different, that fact that a product is specified does not mean it is appropriate for your application. Let’s say all three of them perform effectively, but one has an unpleasant odor (at least in the opinion of your key assembler); we can rule that one out. A second product is relatively inexpensive. However, it is supplied by a distributor who provides zero product support, blocks the producers and formulators from exposure to mere mortals in industry, is secretive about planned product changes, and has been unresponsive when production support is needed. The other costs perhaps 10% more, but the distributor works closely with the formulator (and has allowed you to talk to the formulator), has been responsive, and provides great technical support. In general, you are probably wise paying for a more reliable product – and reliability includes great product support. So, you pay a friendly visit to the purchasing agent; explain that you must have the slightly more expensive cleaning agent, pronto – or the whole contract will be at risk. Then, you check back to make sure the approved cleaning agent is in place.
You may not have achieved an optimal, rugged process (the room is still full of dishpans), especially if you want to be able to ramp up production rates. However, you have at least achieved a workable process for now, one that removes the soil effectively, uses cleaning agent that is formulated for manufacturing applications, is supported by the supplier, and meets your customers’ requirements.
Timeline
The above article is an illustration of approaches to managing cleaning process problems. It is an amalgam of problems that we encounter in consulting. Art Gillman has also written an engaging, entertaining, and helpful series of such experiences and anecdotes. You can find it in Volume 2 of the new edition of “Handbook for Critical Cleaning.”
For your convenience, the following outlines the sequence of events depicted.
Your company has a new project with an aerospace client.
A new cleaning process is needed.
You determine an acceptable cleaning agent and cleaning equipment.
You hand in your report along with recommendations.
The Production Department orders the cleaning agent and the cleaning equipment.
The cleaning agent arrives.
The cleaning equipment order is cancelled by the Purchasing Department.
The Production Department is given an old, dysfunctional piece of equipment.
Production tries the new process.
The parts come out more soiled than when they started.
The offending equipment is relegated to the loading dock.
Production tries to clean the parts in plastic tubs using the aerospace-approved cleaning agent and scrubbing each part by hand.
The oil-splitting chemistry doesn’t work in dishpans. The oils redeposit on the parts.
Someone in Production brings in a big bottle of dishsoap; they change out the wash baths every two to three cycles.
The process works; but it is inefficient and doesn’t comply with the contract.
You test approved oil-splitting chemistries; and you recommend one that meets customer requirements.
A few take-home lessons
• Successful cleaning is a process, not just a chemical and not just equipment.
• While dish soap can remove manufacturing soils, it is not an optimal approach.
• You can’t assume that the process you specify is the one that will be used.
• Check to see that the process is actually working.
• Communicate. Communication is a two-way street.
• Get buy-in from the production people, or you won’t manufacture successfully.
• Specifying a process does not mean that it will happen.
Reference:
B. Kanegsberg, “The Joyful Dawn of a New Era”, Process Cleaning Magazine, Vol. 2, Number 3, May/June 2007.
A. Gillman, “Blunders, Disasters, Horror Stories, and Mistakes You Can Avoid,” in Volume 2 of “ Second Edition Handbook for Critical Cleaning: Applications, Processes and Controls” B. Kanegsberg and E. Kanegsberg editors, CRC Press, 2011.
