Bacteria Control Plan
It is imperative that for the aqueous storage of diamond products that Warren Amplex Superabrasives have a plan in place to eliminate bacterial infestation at their facility and at customers” facilities where products are sold.
In the short-term (6 to 12 months) implement clean-in-place (CIP) methodology that does not involve the additional use of chemicals or processes that may present the opportunity to:
* Provide a vector for bacterial growth.
* Provide a vehicle for particle contamination.
Long-term (more than 12 months) establish Good Management Practices (GMPs) with regard to sanitation, equipment, processes, and handling. Warren will strive to follow the FDA regulations for the food industry specifically (21 CFR 110).
When a surprise bacteria outbreak infests a microfiltration process at a storage disc manufacturing facility in Asia, Warren/Amplex Superabrasives finds itself scrambling for a solution before production lines come to a halt.
I arrived at work [Warren/Amplex Superabrasives (www.warrendiamond.com)] early one morning before anyone else only to find the word “HELP!” ominously waiting for me in the subject line of several of my e-mails. I opened the messages, and it quickly became apparent that this was going to be a long day.
There was a potentially disastrous filtering issue metamorphosing at one of our client sites, an Asia-based storage disc manufacturer. Our polycrystalline diamond slurry was clogging the filtering process, and a film of unknown origin was forming after the cleaning step following texturing.
I made a beeline for our chemist, and we immediately pulled our quality control team together. We followed a structured line of questioning and review procedures to re-examine the slurry process in question. In doing this, we attempted to determine:
- When was the problem first noted?
- What was the lot number?
- What shift?
- Were the operators new or experienced?
- Had the filters been analyzed?
- Could we have a bottle of slurry back for analysis?
- Was anything added to the slurry?
As the day progressed, we were able to piece together some answers. Apparently the problem was with the last slurry shipment. The disc manufacturer provided the lot number, but said there was no time to send samples back for analysis.
The client had three days of texturing slurry left, and more slurry was needed or production lines would go down, resulting in missed shipments. The client was in panic mode.
Enter the Slurry
In the electronics world, delivery schedules are tighter than deadlines in the daily newspaper business. Any delays — chronic or acute — in the production and delivery process inevitably create disastrous bottlenecks and poor results.
Critical components — like data storage discs — are on a scheduled component completion date for delivery to the end-user. There is no wiggle room, and usually a dollar penalty is assessed for late deliveries. With ever-tightening margins and reputation on the line, maintaining a strict schedule is of critical importance.
“Everyone is pushing dates so they can get ahead of the delivery curve,” says Nick Tumavitch, manufacturing and development chemist at Warren/Amplex.
Texturing the discs involves placing a texturing pattern on a nickel phosphate-coated aluminum disc in a uniform pattern in width and depth. These texture patterns can then be encoded so the read-write head can both deposit and retrieve information in binary code. After the texturing operation, the discs are cleaned and moved to the next operation, which is to test the lot of discs for compatibility to the corresponding read-write head.
As our QC and management team delved deeper into the problem, some light began to appear. Initially we were unaware the disc manufacturer was running our slurry through their filters. Upon finding this information out, I instructed Nick to determine the particle size distribution (PSD) in the slurry, which is a data sheet listing all the particles in the supplied distribution both in tabular and graphical form. I was trying to determine if there was any possibility that coarse pieces were clogging their filters. I wanted to know what the pH and Zeta potential were, among other issues.
Enter the Bug
Our sister company, Innovative Organics, stepped in and offered their expertise.
|From left to right, the first bug stick is free of any bacterial contamination, while the remaining three reveal various stages of contamination. Each dot representes a colony count of 10,000 bugs.|
“I”ve been on both sides of the fence, texturing and the abrasive portion. The more I reviewed the information, the more convinced I became that our problem was ‘bugs,”” says Bob Futrell, general manager of Innovative Organics.
“Bugs” is shoptalk for bacteria — a four-letter word in manufacturing environments that require sanitary, contaminant-free processes.
The solution to the problem was found in the guise of bug sticks. Paddle testers — or bug sticks — allow fast, easy screening of water samples, solid surfaces, and nonviscous liquids where unsanitary conditions may exist. Each paddle is a double-sided test pad sealed with a cap. Each side of the pad is used for testing purposes and has a molded-in grid for easy colony counting without opening the vial after the initial sample. The paddle tester is coated on one side with tryptic soy agar for total Aerobic bacteria while the other side is coated with Violet red bile agar for total coliform bacteria. Innovative Organics (www.innovativeorganics.com), a provider of environmentally friendly process coolants, lubricants, slurries, and cleaners, uses bug sticks regularly. It overnighted some to the Warren facility.
|A Warren/Amplex technician sizes submicron diamond with sterilized equipment.|
At the beginning of day two of the crisis, things were getting pretty dicey at the disc manufacturing plant with roughly a day and half left for us to solve the problem and prepare and deliver new slurry.
Our scanning electron microscope (SEM) technician was called in. Placing slurry on a dried sample peg, the SEM technician began to look for 0.5 um bacteria. After about 15 minutes of looking at different magnifications and scans, he didn”t find one amoeba-type, single-cell bacteria on the surface of our abrasive pieces.
At 10 a.m., EST, the bug sticks arrived. I immediately got the package, read the instructions, and got our chemist. We put on lab coats, latex gloves, and hairnets. We opened the vessel and the stick, which has agar medium on it — a standard nutrient base that is used to grow bacteria — and dipped it into the slurry.
|A Warren/Amplex technician measures out sterilized diamond for a customer sample.|
Once the agar covered bug stick was dipped into the polycrystalline diamond slurry, it was then placed in Warren”s hot room. It was maintained at 85 F, a perfect temperature for growing bacteria. The bug sticks required a 24-hour incubation period.
At this point, we had roughly one business day left to fix the problem and send new material to the disc manufacturer before they were forced to shut down and put 3,200 hourly workers on the street with no pay.
After the bug sticks had been incubating only eight hours — one-third the time required for complete incubation — we could already see a few black spots forming. Each black spot represented a bacterial colony count of 10,000. We definitely had a problem on our hands. Since we were not familiar with the procedure for scanning for live organisms, the voltages we were using (25 kv) — we were literally vaporizing the bacteria before we could spot them.
Proceeding on the basis that the end-user had a bacterial infestation in their slurry products, the next piece of the puzzle was determining how to eliminate the bugs from infecting new and existing slurry production runs.
Some suggested remedies were:
- Dry the material and send it through our fusion cleaning process. This was too time consuming.
- Use technical grade hydrogen peroxide at 30 percent concentration to oxidize the bugs. Good idea, but we were not equipped to handle this type of oxidizer safely. Another problem was how much to use, and how would we get rid of all the excess liquid. Using the peroxide would unbalance the percent solids since the slurry product was consistent to four decimal places in abrasive content.
- Another suggestion was a bactericide. Not a bad suggestion, but this would require a waiver from the data disc manufacturer since Warren slurries are manufactured chemical-free.
As we were mulling through our options, we determined that anything short of a complete solution was unacceptable. “Then it came to us as an epiphany. Pasteurization, just like they process milk,” says Jamie Montano, QC manager at Warren/Amplex.
|A Warren/Amplex technician programs a diamond autograder. the program will consistently extract only the required PSD core from a diamond feed.|
We decided to heat the entire vessel containing the polycrystalline diamond slurry to a certain temperature to kill the bacteria. This process would not involve any additional liquids, which meant if it worked Warren could send the next slurry shipment in time to prevent a shutdown at the disc manufacturing plant.
Fortunately, it is not necessary to boil water to pasteurize it. Heating water to 65 C for six minutes will kill all bacteria, viruses, and parasites. As such, the vessels containing the bug-infested slurry were heated to 80 C for 10 minutes.
We did another bug-stick test after we followed the plan and waited. By the time we put the treated slurry bug stick in the hot room for incubation, the first one was completely covered. It looked like black cotton candy. But the second stick, tested after the pasteurization, remained bacteria-free. The process worked, and the customer was satisfied with the results.
|PSD measurement diamond in the size range from 0.12 to 1.0 micron is measured by laser light scattering.|
A 400-bottle order of new pasteurized polycrystalline diamond slurry was produced and shipped overseas special delivery. The shipment arrived at the customer site and was immediately put into service. Soon the disc manufacturer was running full steam ahead on all texturing lines.
When our distributor first reported the problem, there was a clear lack of understanding of the fundamental issues involved in this scenario.
In the final analysis — which the ISO QMS requires — the following was discovered and reported to the disc manufacturer at a follow-up meeting.
|ION chromatography preparation where samples are boiled under reflux to ensure all surface soluble ions.|
Warren/Amplex had been supplying diamond slurries to this disc maker for three years on a make-to-demand basis. Warren would submit samples to the manufacturers, and they would approve the particle size that best matched the technical requirements of the hard disc. Scratch patterns, texturing tome, and magnetics were the criteria. Once a particle size distribution was approved, Warren duplicated the PSD throughout the program”s life. So the lead-time between making the product and shipping was literally within days and sometimes for just-in-time delivery.
With the advent of the higher density drives (120 megabyte and higher), the requirement changed. Warren was now required to produce and enter lot of product , sample from the entire lot, and upon approval ship the entire contents.
|The Coulter PSD machine measures diamond sizes with an extended range up to 120 microns. The Coulter PSD machine is primarily used for customized product requests.|
“This was a change that we did not fully appreciate at the time,” says Jamie.
Warren was now required to have diamond in deionized water sitting in a stainless steel vessel for a week or longer until the lot was approved. The manufacturing team did not foresee that this change in operations could, and did, have an effect in the customer”s operations. Bacteria!
We were not apprised of the change in operations at the customer”s facility. Their filtering of our product with the use of 0.5 um filters was a requirement of their Asian customer. Had we known of this, we could have filtered some of our product through the same filter to see if there was any change in particle size distribution, not to mention clogging due to bacteria.
About the Author
Ron Abramshe, Ph.D., is the plant and product manager at Warren/Amplex Superabrasives. He earned a Ph.D. in Engineering Management from Kennedy-Western University, a master”s degree in Engineering from Polytechnic University of New York, and a bachelor”s degree in Industrial Engineering from the University of Dayton . Dr. Abramshe was the lead technician and general crisis manager as detailed in this article. He can be reached at firstname.lastname@example.org or 508 795-5908.
For More Information: www.warrendiamond.com