Q. What exactly do you mean by the term “critical cleaning”?
Here at MicroCare, we define “critical cleaning” as those factory environments in which a cleaning failure could result in extraordinary costs, product failures, legal action, product recalls, or even potentially the loss of life. Critical cleaning environments permit zero failures. When it’s got to be perfect, every time, that’s critical.
Q. How does critical cleaning differ from precision cleaning?
Precision cleaning is a less-critical process. It can tolerate some proportion of cleaning failures. The many degrees of cleaning are defined by one crucial question: “What does it cost when the cleaning isn’t perfect?”
Imagine a person working in a Class 1,000 cleanroom making medical devices. An undetected cleaning problem can lead to product failures or bacterial growth. We’re talking infections, additional surgery, lawsuits, recalls, reputations tarnished. It’s major; it’s catastrophic; it’s critical.
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Q. Companies have been cleaning in controlled environments for years. So what’s driving this change?
The difference today is many of the tried-and-true cleaning answers used in those cleanrooms today soon may not work or may not be available. The processes companies have used for years even may not be obtainable at any price.
A great example is in electronics, and the continued miniaturization of new products which makes cleaning much more difficult. These smaller, denser, more complex electronics are much harder to clean, and the old techniques ain’t going to get it done. So let me put it to you straight: the old answers are going away.
Q. Is going “green” the problem? Is it also the answer?
There are huge pressures on companies to become more “green.” Many regulators want companies to minimize use of smog-producing chemicals, called “volatile organic compounds” and the most popular VOC is simply alcohol. The European REACH regulations, new toxicity research, and simple economics also are forcing vendors to reformulate or even to withdraw products altogether. For example, Asahi Glass has pulled from the market their popular cleaner, HCFC-225, to comply with the Montreal Protocol. Using alcohol in California is almost impossible today. At the same time, water-cleaning is losing its economic and environmental advantage. Water-cleaning systems generally have been getting bigger to accommodate the tougher cleaning problems. These super-sized machines have trouble fitting conveniently into the expensive floor space of a cleanroom. They also use more electricity (which contributes to global warming) and release hot, humid air into the humidity-controlled environment of the cleanroom.
In contrast, low surface tension, non-flammable cleaning fluids easily can achieve cleanroom performance standards, even in relatively small machines. They cut water consumption completely and cut electricity consumption by 70%. They reduce consumables and simplify maintenance. They don’t require a protective bubble of space, wiring, and plumbing around them. Vapor degreasers simply are very flexible. It’s a win-win for everybody.
Q. These systems sound remarkable. Why don’t we hear more about the capabilities of vapor degreasing?
When I explain vapor degreasing to young engineers — say, people under 35 — they think I’m Professor Dumbledore. The process sounds like magic. But it’s not. It’s just simple thermodynamics, and in a properly engineered system it works great. And, not too long ago, it worked everywhere. Vapor degreasing was widely used through the 1980s. Virtually every factory had a vapor degreaser; they were fast, effective, and cheap. This was a thoroughly well-proven technology and every old-timer today probably remembers one from their early years.
But there’s a catch. With vapor degreasing, you need both good hardware and good cleaning fluids to make it all work. But as late as the 1990s, the most popular fluids were all ozone-depleting substances. So when the solvents went away, the machines went with them.
Q. What do these machines look like?
In general, there are three types of vapor degreasers. The most common is the batch-style, open-top degreaser in which the parts are moved vertically in and out of the cleaning chambers. These can be as small as a 4-liter machine that fits on a desktop, and as big as a 5,000-liter system into which you could insert a jet engine. These are suitable for less critical clean rooms and the costs vary widely based on features and capacity.
For customers who require zero-emissions, there are “vacuum degreasers” that look like front-loading clothes washers. These use the same solvents but completely reclaim the solvent during use. These would be very well-suited for the most stringent cleanroom environments. These typically cost $250k or more and have longer cleaning cycles. For the highest-volume customers, there are in-line vapor degreasers. Each configuration has its drawbacks and advantages, but all of them out-perform aqueous cleaners.
Q. How are they configured?
Modern vapor degreasers are perfectly compatible with most cleanroom environments. They are generally installed in one of three places. The least expensive option is just outside the cleanroom, with a positive-pressure air system to move the cleaned parts immediately into the white room. Another popular configuration is the through-the-wall style, where the dirty parts are dropped into the machine outside the cleanroom and clean parts are removed inside the cleanroom. There also are systems that nicely fit inside cleanrooms themselves. The tiny quantity of volatile chemistry that may be emitted from the cleaner does not affect the performance of the cleanroom in any way.
Q. What is the most important consumable in these types of systems?
The big decision is the choice of cleaning solvent. There are many good chemical choices today. Each one has good features and drawbacks, so I can’t say one particular formulation is the best. But I can tell you this: the solvent selection is driven by the contamination. “Start with the dirt,” we like to say. Find the cleaning fluid that works best with your contamination, and that will drive the rest of the process decision.
Q. What is the most common hardware mistake made with vapor degreasing in a cleanroom?
The most painful mistake we see people making is they buy cheap cleaning machines. You see, there are many good makers of vapor degreasers. But there are an even larger number of companies that make junk. Those companies don’t understand the thermodynamics, materials compatibility or even the vapor cleaning process. So they cut corners on the design and never explain how those short-cuts will degrade the cleaning process.
Q. What’s involved in maintaining these cleaning systems?
Unlike water-based cleaning systems, solvent-based cleaning systems have very simple maintenance requirements, and are very easy to operate. The customer will need to maintain a proper solvent level in the machine. Allow excess moisture to drain from the machine via the drains that are designed into the degreaser. Lastly, periodically clean the sumps, clean the heater elements, and change the particulate filters. That’s about it for maintenance. There are many vapor degreasers out there that operate for decades with very minimal maintenance.
Q. Does vapor degreasing have an “Achilles heel”? What should we watch out for?
Most customers initially are surprised by the cost of the cleaning fluid. Water-based saponifiers and surfactants cost hundreds of dollars per drum; vapor degreasing solvents are thousands of dollars per drum. It’s a huge difference.
But, in use, the cost-equation swings the opposite way. People buy far less solvent with a vapor degreaser, because modern systems recycle the fluid and have very low solvent losses. In contrast, most aqueous systems are a “use and lose” design, with slower cycles and much higher energy costs. So vapor degreasing is almost always the lowest cost, per-part-cleaned.
Q. How can a company determine the cleaning system that is best for its operation?
The trick is to compute, in the greatest possible detail, the cost-per-part-cleaned. You need to collect all the cost of your cleaning operation: the cost of the equipment, the cost of installing the equipment, the consumables, the labor, electricity, waste disposal, scrap, everything. Then you divide those costs by the number of parts to be cleaned.
The system with the lowest cost-per-part-cleaned is probably the best choice for that application. While the data collection may be complex, the analysis itself is a fairly straightforward spreadsheet.
Q. What you are planning for the future?
Three significant trends are at work across most industries: the continued miniaturizing of components, the need to protect people and the environment, and the need to minimize production costs while boosting quality. To adapt to this new world, the only viable, low-risk option that meets all the critical cleaning requirements is solvent cleaning.
There’s no doubt about it: vapor degreasing is the critical cleaning answer of the future.
Mike Jones is Vice President of MicroCare Corp. in New Britain, Conn. www.microcare.com
This article appeared in the March 2015 issue of Controlled Environments.
