This week, especially because it’s December and so close to the Christmas holiday, I worked on an alarming application that involved a static hazard. 100% ethanol was poured from a plastic container, which held approximately 5 gallons of the liquid, into smaller or larger containers that were also made of plastic. Ethanol is a colorless, volatile liquid. Most people recognize it as the ingredient in liquor, which has an intoxicating effect on most people. However, it is also used as a solvent which can ignite under certain conditions. Static electricity is one of the three components necessary to create an event, which is a soft way of saying an arc-over, a fire or an explosion. The other two ingredients are oxygen and a volatile vapor.
There are well established protocols for handling and working with ingredients that can go “boom in the night”. The front line of defense in protecting oneself from mishaps is grounding everything that is capable of being grounded. If we take a simplistic approach and look at the world as being made of only two materials, insulators and conductors, you can get a better sense of safety procedures that will keep to us out of harm’s way. Metal is a conductor and easily grounded by clamping onto a known building ground or electrical ground or even by driving a rod deep into the earth. Hence, we call it an earth ground. A water pipe inside of a facility can also act as a good ground source. By grounding the metal, electrons can flow through the metal to ground itself. Conversely plastic cannot be grounded. This is why my static application hit a bump in the road. Static is generated on plastic materials through friction which we call Tribocharging. There are a myriad of types of plastic, but for the most part, assume that all plastics are huge static generators. Plastics are insulators and not conductive so the energy generated by simply handling plastic stays on the surface and can be a source of ignition.
In my static hazard application, an ungrounded person holding the ethanol picks up an ungrounded plastic container and pours it into another ungrounded container. This is not a good situation. During the pouring process, a potentially explosive, volatile vapor cloud forms around the pouring action in both the dumping container and the receiving container. There are three possible opportunities that can cause ignition in this scenario: a discharge from the ungrounded tech who is pouring the flammable ethanol; a discharge from static on the container which is high enough in proximity to the vapor cloud which forms in the discharging plastic container; a discharge from static to the same cloud that can form in the receiving plastic container. If a static charge is present, with enough energy behind it, there is a strong chance that any of these actions can create a safety hazard.
A Grounding Solution
Finding a solution to this problem can be a bit tricky. The basic approach is to ground everything that can be grounded or switch to materials that can be grounded. Simply switching from plastic containers to metal is a huge step in the right direction. There will be times when grounding is not possible and materials cannot be changed. In that case, ionization is the only choice. There are approved ionizing static bars and blowers that remove or greatly reduce static electricity on plastic materials. Static Clean and Fraser AntiStatic Techniques of England have formed a strategic alliance / partnership to address these dangerous scenarios. When you have concerns about your facility and the safety of workers who may be in harm’s way, please reach out to Static Clean for help. At this special time of year as with any time of year, it is important to always think “safety first”.
I was chatting with a friend/customer the other day and asking him if he was still playing hockey in a men’s no-check league. His response was that it was “time to hang it up”. It got me to thinking about all the things we do in life where we can use or connect that phrase.
The obvious meaning of hang it up is to stop doing something that you’ve done for a long time. How about hang it up as in hat, coat, phone, pictures, and decorations. The gloomier side of the phrase can mean break-up, bring to a close-like a chapter in one’s life- and cease, which has very strong connotations, but the one that I like the most is “bag it”. Many of us have used the phrase, “why don’t you bag it” on people we know. From watching detective TV shows involving criminal investigations and forensics, “bag it” refers to putting evidence in a sealed bag or container.
Plastic, All Wrapped Up?
There are many kinds of bags and containers that are produced every day in factories throughout the world. They can be either converted film, blow molded containers, injection molded boxes or cast materials, but can you imagine not having a plastic storage bag or container to keep food in the refrigerator? While we all try to be “green”, the plastics converters are working to make improvements with bio-degradable, engineered materials, but the reality is that plastic bags and containers are creature comforts that make our lives easier and will be around for a long time.
Most plastics come from petroleum based resin, that by the time it becomes a finished product on the various machines, it has been subjected to high amounts of static electricity. These unwanted static charges can cause defect in the materials, lost production because of having to run the equipment slower than possible, particle attraction which reduces quality and jamming in the process, which causes down-time and lost profits. Static Clean provides many types of ionizing air products that reduce the ill effects of static electricity. They are available in the form of static bars, blowers, nozzles, air knives and cleaning systems.
In time, the choice of materials will lean more towards environmentally friendly resins that may not cause static levels that are harmful, but until then Static Clean can help improve the process, because most of us would have to agree that it is not quite time yet to “Hang It Up” when it comes to creature comforts like plastic bags.
Tribo-Charging, Who Really Discovered Electricity?
The relationship between static electricity and particle attraction has been long known. The Ancient Greeks when polishing their jade and precious stones noticed that straw, chafe and other particles were attracted to the exact things they were trying to clean, the family jewels. This phenomena became known as “Tribo-charging“. Simply stated it was the contact and friction that generated an electrostatic field around the parts that attracted the debris.
The Plastic Attraction
In the Life Sciences Industry of today most companies use plastics in their process. Whether it is to replace body parts, catheters, injection systems, pumps, blood separators or their packing, plastics are here to stay. Not only are they here to stay, but plastic is being used in this process at an increasing rate. Most of these engineered plastics are for a specific need but the premise is the same, they generate huge amounts of static that causes Foreign Matter (FM) to be attracted to the products and the process.
Medical Device Manufacturers most often individually package each medical device and they are subjected to 100% inspection. When the inspector sees a speck of debris (FM), which could be in the form of plastic bits, fuzz balls from clothing, or even human hair, the package is then ripped open and put aside for repackaging. These units are tracked in what is generally called “the tear down rate”. In almost every case, the root cause was the forces of static electricity pulling unwanted particles onto the product and the packaging materials. In addition to the packaging level there are various stages in the assembly process where FM causes rejects. Some of those stages include Injection Molding, Coating, Ultrasonic Welding, Bonding/Gluing, Forming, and handling during the assembly processes. These are also key functions that need to be addressed. The common denominator being that contact and separation (tribo-charging) occurs, static is generated and FM comes into play to contaminate products that could end up inside the human body or blood stream. The FM could also potentially block injection or fluid systems clogging pathways designed to deliver medicine.
Gains are Being Made, Reducing FM
The front line of defense is a properly maintained clean room, but that doesn’t address process problems at the local level, aka the workstation or cell. How does static control reduce particles via ionization in the fight to reduce FM? Static Clean did a job last year for a major medical device company that was experiencing a very high tear down rate. They approached us to come up with a system where they could pass their products thru a blow-off, ionized, vacuum table. The results of this first system allowed them to run 50,000 parts without a single tear-down.
While not all medical device manufacturers have identical assembly lines, let’s take a look at the types of static controls are that implemented for specific reasons or points in the process.
Room Ionization: In this installation, ionizers are mounted in the ceilings and the preferred method is to locate the ionizer right under the Fan Filter Unit. (FFU) to take advantage of the clean air being delivered into the room.
The Increasingly popular approach has been to use source capturing methods in conjunction with ionizing air tools. Recent gains have been made in the development of customized medical cleaning workstations that meet clean room protocol and are tailor engineered to a specific product or package.
Albert Einstein once said, “The true sign of intelligence is not knowledge, but imagination” and an unknown author said, “Anyone who thinks the sky is the limit, has limited imagination. It seems like they were both “wicked smart”. A twist to being limited by one’s own imagination is being limited by someone else’s imagination. If a person can visualize something that seems impossible, there will most likely be someone who can actually make it a reality. There are times when I mix up the two words innovation and invention. Innovation refers to the use of a better device, idea or a new process, while invention is the creation of the method or the product itself.
Static Clean’s new Model TSN75E is an example of an innovation that became an invention, which is now Intellectual Property (IP). It is a high voltage line frequency 50/60 Hz transformer based AC Power Supply, with a special Resistive Output Coupler that provides optimal voltage limiting and load regulation, thus enhancing the reliability of the Static Neutralizing System.
Static Bars and Power Supplies
The number of static bars that can operate on a single power supply is dictated by the length of the static bars, the length of the high voltage cable and the construction of the high voltage cable. (Shielded or non-shielded). The load is calculated in Pico farads (pF). Customer kept asking us, can I add one more static bar to my existing power supply, so we created a matrix chart based on the new TSN75E that makes it easier for our customers to make the right choice. To learn more send an email to firstname.lastname@example.org or visit our website for a Live Chat, depending on the time of day. With that said, have a good day dream and keep using that imagination.