Fluid Dynamics – Laminar Flow – Turbulent Flow – Transitional Flow & Particle Reduction

Fluid Dynamics – Laminar Flow – Turbulent Flow – Transitional Flow & Particle Reduction

In physics and engineering, fluid dynamics is used to describe the flow of fluids – liquids and gases. For the sake of this discussion, it includes the subset of aerodynamics, which is the study of air and other gases in motion. Many clean room consultants chagrin at the idea of using compressed air movement inside of a clean room that was developed using Laminar Flow techniques. Laminar air flow by design is intended to be slow, smooth regular paths of an air pattern traveling from entrance to exit. The air then travels back through the pre-filters, to the laminar flow filters and back into the room as part of the air change rate per hour. Laminar air low patterns are important to keeping particulate moving out of the clean room, but what if products being process inside of the clean room are already contaminated with particles that could come from people, other items that were brought into the space or that were created by the process itself.

In order to clean particulate from a device, component or packaging material, compressed air devices are necessary. The air devices are typically in the form of ionizing air guns, blowers, nozzles or air knives. These air tools cause turbulent flow, which is fluid motion that agitates the parts and creates eddies, which are violent swirling motions caused by the position and direction of turbulent flow. Eddies can transport mass, momentum and energy across different regions of the flow, with a result being clean, static-free parts. Heat transfer also happens in turbulent flow. So why is heat important? With heat, the flow resistance decreases, making it easier to clean parts. The process of laminar flow becoming turbulent is known as laminar-turbulent transition. It is also known as transitional flow.

Is there a happy medium between using compressed air and maintain an acceptable level of laminar flow? Can we agree that compressed air is a requirement and that compressed air is turbulent? Static Clean believes in the idea of “Controlled Turbulence”. The placement of Static Clean Particle Trap® Systems, in conjunction with compressed ionizing air devices means that the turbulence is localized, particles are captured and removed from the process and the products and parts are clean. By using an ionizing air gun or similar device in front of a Particle Trap®, the debris is directed into the flow of these source capture systems and delivered into the filter media and not back into the clean room to re-contaminate cleaned parts.

Particle Size, Particle Retention & Process Practicality

Particle Size, Particle Retention & Process Practicality

Particle collection efficiency by a filtration device usually brings a common question. What is the ISO number that is associated with HEPA filters used in the Static Clean Particle Trap® series products? A recent request from a customer asked this exact question. Our answer in response was that the ISO rating on our HEPA Filter is ISO 40E-99.99% at MPPS. Obviously, the customer with the questions knew what to ask and was technically astute, but to a novice it may seem confusing, so first let’s establish what MPPS mean. It is the Most Penetrating Particle Size. Larger particles are unable to avoid the special filter media in a HEPA filter and they become embedded in the filter material. The smaller particles become the MPPS, which gives the HEPA their rating. For more critical filtration needs, ULPA filters are available and could have an efficiency of 99.99995% at MPPS.

For the world of static control, and filter efficiency of the Static Clean Particle Trap® Systems, we are mostly talking about HEPA filtration. But filtration only tells a part of the story. Although you can perform tests to validate HEPA filters and modern particle counters can provide information on airborne particulate, it doesn’t tell the story on how clean a medical injection molded plastic part may be or how many particles are on a catheter or the tray or package that is going to house the medical device. Yes, there are liquid particle counters that can verify all particle sizes, but real time production of high-volume parts means that, at best a visual inspection on the fly is the standard.

Most of the Medical Device Manufacturing is done in an ISO Class 7 or ISO Class 8 cleanroom, with an emphasis on ISO Class 8. Federal Standards FS 209E and ISO 14644-1 require specific particle measurements to verify the cleanliness of the clean room or clean area. When talking about an ISO Class 8 environment, it does mean that the maximum/particles/m3 allows for almost 30,000 particles in the 5 micron or smaller range. It also means two other things as well. There will be particles greater than 5 microns in an ISO 8 space and that total reliance on a cleanroom is not the complete answer. The use of additional filtration methods at key points in the manufacturing process will improve yields by reducing particles on products and in single use packaging that may finds its way to the hospital or clinic. The fact that ionization is used to control static on medical devices, optics and industrial environments is common knowledge, but, source capturing debris at critical stages in the process is less understood but becoming more accepted as the right tool at the right time.

Particle Trap® products are small, benchtop or floor level source-capture systems, that incorporate both pre-filters and HEPA-filters in series, whereby the pre-filter catch the larger particle and the HEPA, (the same used in the clean room construction), captures the smallest debris. What this means for the customer is that particles are taken out of the room at the source and by source, I mean either where they are created or where they can do the most harm and end up inside of a finished package. Regardless of what ionizing blow off device is used in your process, you can rely on Static Clean to make things cleaner and your customer smile.

Where do the particles go?

Where do the particles go?

Did you ever rub a balloon on your hair and stick it to the ceiling? The balloon sticks because you’ve created static electricity on the surface of the balloon. This energy is non-moving static charge. Every material is made up of atoms and they are the basic building blocks of ordinary matter and they can join to form molecules, which is a basic ingredient of most of the objects around us. An atom can hold a positive charge that is called a proton or a negative charge that is called an electron. Atoms with the same charge or polarity repel each other, while those with the opposite charge are attracted to each other. Just like the balloon scenario, static is created by the contact and separation of two materials. The same is true of when you walk across a carpet and touch the metal door knob and get a shock. We call these electrostatic forces, tribo-charging, which renders a plastic material in a state where it can attract dust and other particulates.

Let’s face it, we are using more plastic in our every day lives, from cars to single use medical devices that may end up inside of the human body. Plastic, being highly insulative, can store huge amounts of static electricity. If we just look at the medical device sector, one of the biggest reasons for rejects, rework and potential device failure, is from foreign particles that end up in the finished device. These particles could be in the form of airborne contaminants, plastic flash, skin flake, human hair and other debris that is found in the manufacturing process. Static eliminators in the form of ionizing air guns, nozzles and blowers are used to negate the ill effects of electrostatic forces that pull particles right out of the air and hold them to a device or components. The use of ionized air is absolutely a good practice, but the problem is “where do the particle go”? Typically, they hang around and end up on the worksurface to be a source of re-contamination or the particles end up downstream on already cleaned products.

Enter the Particle Trap® 6000. The Particle Trap® 6000 (PT6000) is the solution to getting rid of particles in the assembly and packaging areas of the medical device manufacturing process. The PT6000 is a source capturing system with a HEPA filter on the exhaust. You can still use the conventional ionizing air blow-off devices, but when working in front of the opening of the PT6000, dislodged particles now are delivered through a pre-filter and then through the HEPA filter, ensuring only clean air is let back into the room. The PT6000 is used not only to clean medical components, but it is especially helpful when used at the packaging level, just prior to the heat sealing of a lid stock to the thermoformed tray. The same would be true for pouching of products such as a catheter on a die cut card being slid into a long plastic bag and then sealed at the end. Normally, most medical device manufacturers do a 100% inspection for foreign matter/particles inside of the seal trays. If a particle is discovered, the lid is ripped off, the product taken out, recleaned and then repackaged. This reject rate is also called the tear down rate, which translates into poor yields, time and money along with customer dissatisfaction, when a product gets through that is not totally cleaned.

Who would benefit from the Particle Trap® 6000? The Particle Trap® 6000 and its sister products, the PT Mini, Particle Trap® CUBE and Medical Cleaning Systems. While the medical device sector has endorsed these products, they also have application in the optics, food and electronics industries for the same reason why all companies are looking to lower their tear down rates, which translates to higher profits. If you want to learn more about how Particle Trap® products can help improve your process, please visit the Static Clean Website, www.staticclean.com or call us direct for expert technical advice.

It’s That Shocking Time of the Year

It’s That Shocking Time of the Year

Ethanol; Intoxicating or Explosive?

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.

Static Hazard

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 will be introducing a new line of ionizers in partnership with Fraser Antistatics of the UK 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”.

How Static Affects the Summer Olympics

How Static Affects the Summer Olympics

Achieving Peak Performance

The Summer Olympics are in full swing and the elite athletes are always trying to find ways to achieve peak performance.  Sometimes the difference between winning a gold or silver medal is decided on a tiny margin and can depend on achieving the smallest advantage.  This year the 2016 Summer Olympics are being held in Brazil and temperatures are slated to be in the mid 80’s during the day with high humidity.   Manufacturers of sporting apparel spend huge sums of money on the research and development of clothing and other products that work with the human body.  Athletic shoes have been engineered to be lighter with better foot protection, and clothing has been made to feel so minimal it’s like wearing nothing at all. The integration of Lycra® fabric is one of the most common innovations in achieving comfort, fit and performance.

How Lycra® Moves Us

Lycra® is a registered brand name for a polyurethane-based synthetic fiber that’s also called spandex or elastane. The DuPont Company® first developed Lycra® in 1958 to replace latex rubber as a stretching agent in clothing.  Lycra® is prized for its strength and durability, and is almost always mixed with either cotton or polyester.  Although Lycra® accounts for only a small percentage of the final fabric, it is key in retaining the look and feel of the other fibers. An estimated 80% of clothing sold in the United States contained spandex in 2010.  Because of its ability to mold to the body, Lycra® is ideal for use in swimwear and sportswear.  It was once thought 100% cotton was best for sportswear because of its ability to breathe.  Science has actually shown us that 100% cotton can raise body temperature, making it difficult to move at a high levels of performance.

The Buzz About Lycra®

The buzz word today is to look for clothing that will wick sweat away from an athlete’s skin.  How does this help someone towards a competitive advantage, and how does it work?  For the sake of discussion, let’s focus on swimming.   According to Aqua Sport West, high performance athletes care more about reducing suit drag, skin friction and water absorption.  Lycra® along with other fabrics containing Lycra® offer the best performance and value.  It is actually hard to find any cotton in good swimwear these days.  Reducing drag is probably the most important factor.   As the material or a body moves, the lower the frictional impact of a material against air, wind or water, the more a body can lower its resistance.   This is very similar to static electricity when the lowest coefficient of friction will lower the static on a body or material.

Lycra® is a highly static material, but when intimate to the human body, the level of static is lowered.  That is why you see swimmers use bathing suits like Speedo® that are tight fitting.  The same can be said for those who wear tight clothes when racing bicycles.

The Static Eliminator

At Static Clean International we work with some of the world’s largest manufacturers of Lycra®, Polyester and other well accepted athletic materials.  During the weaving process of these materials, the static levels are very high and many of the defects found in these materials are due to static during the processing.  A little static cling can cause high defect rates, especially when running high speed clothing manufacturing equipment.  Our products eliminate static during the manufacturing process. However, once the finished product is on the human body, the static is collapsed by being intimate to the body and static is no longer an issue.  We have a keen understanding of how frictional forces during a race or a swim meet are reduced because the material of choice has a lower coefficient of friction that allows the clothing to have less resistance in motion.  From our position, we can feel good about the fact that we have helped those who compete by improving the quality of what they wear.


All That Glitters Is Not Gold


“All That Glitters Is Not Gold” Not everything that is shiny and superficially attractive is valuable.


The original form of this phrase was ‘all that glisters is not gold’. The ‘glitters’ version long ago superseded the original and is now almost universally used.

Shakespeare is the best-known writer to have expressed the idea that shiny things aren’t necessarily precious things. The original editions of The Merchant of Venice, 1596, have the line as ‘all that glisters is not gold‘. ‘Glister’ is usually replaced by ‘glitter’ in modern renditions.


Cleaner Means Safer..

Sometimes the smallest parts are the trickiest to clean.  At Static Clean our customers often bring us size challenging parts and devices to work on. Until recently no one in our industry has been able to address these challenges. Static Clean has now developed a method using our MCS and MCS-AS cleaning benches to batch clean these small part products.    Static Clean came up with a method using our MCS and MCS-AS cleaning benches to batch clean these products with small parts.  We have a Stainless Steel sieve that is fed through the upper and lower hoods that are part of our MCS line.  We had a potential customer from New Jersey who was amazed at how well it worked. Before he arrived, he went to a Michael’s store with his daughter and bought all kinds of colorful glitter that you would use for arts and crafts.  He used the glitter to contaminate the white caps that you see in the video.  It was overkill but a very good test.  The white caps that you see here go on the top of things such as suspension bottles, eye drop bottles, contact lens cleaning bottles etc.  If they have particles, plastic bits, human hair or any foreign matter, it could be the cause of a health problem.   Our batch cleaning system worked so well that he has said he is interested in purchasing not one but two MCS Systems and commented that “it worked better than I ever anticipated”.

For more information on our MCS or MCS-AS Cleaning benches visit our website or contact our technical sales department today.