How HEPA Filters and Boundary Seals Help Protect Us During Pandemics

Boundary seals that help keep a certain environment sealed in while keeping the world out are everywhere.

If you look around your home, you may be surprised to see there are seals surrounding every door — and not just at the bottom. Your oven, microwave, and of course refrigerator door all have seals around them.

All these seals are different, yet they perform the same function. Your microwave is especially interesting, as its primary purpose is to keep microwaves from escaping the chamber that’s cooking your food. Your refrigerator seal has a magnet built into it, which keeps the door sealed shut.

Boundary seals are also found in many cell phones and electronic devices, keeping them water-resistant or water-proof (depending on the manufacturer). And in the industrial world, we have seals to create explosion-proof boxes in hazardous environments. The simple O-ring is found at the end of every cylinder cap to keep fluids in and the environment out.

We all go through great expenses to seal our houses from the outside with sturdy doors, only to find that we need fresh air here and there. Our windows have a series of seals around them keep the heat or the cold outside, but can be opened to allow fresh air when we want it.

In the same way that boundary seals work, the pandemic has many of us thinking about how to keep hazardous germs from entering into our homes. And if we have to fly, we may wonder how fresh the air is in the cabin, and if viruses have an easier time spreading inside of an airplane.

Boundary Seals in Aviation

Let’s begin with general aviation aircraft with pressurized cabins. The door’s seal is in the form of a bladder, which you pump up with the same type of bulb often found on a blood pressure cup.

Doors are especially difficult to seal, as they’re required to open and close. A rubber seal that would compress and seal the door completely would make the door too difficult to open and close.

After the door is closed, the pilot pumps up the bladder to seal the door. As the engines are wound up, the flight deck begins the process of pressurizing the aircraft. A pressure system from the engine maintains the pressure within the cabin around 8000 feet, allowing the pilot to breathe without the use of supplemental oxygen.

While these seals are not dynamic in the true sense of the word, they are constantly changing based on the altitude of the aircraft.

Most of the pressurization seals on our modern jets are static. But every door, including the luggage compartment, has seals that must be pressurized in order for the aircraft to maintain a safe level of oxygen in the cabin.

picture of HEPA filter by GoreDo Jet Planes Blow Clean Air?

Many travelers worry about getting sick on airplanes. With tight quarters and no ability to open a window and get some air, travelers may wonder whether the air from the vents above them is blowing fresh air — or if it’s circulating stale air and germs.

A few months ago, Cliff at Eclipse Seal performed a non-scientific study on a flight by asking the passengers next to him what they thought of the circulated air in modern aircraft today. Cliff was not surprised to find a wide range of answers, varying from someone envisioning a squirrel blower forcing air around the cabin, with others believing 100% of the air comes from the outside.

HEPA Filters on Airplanes

The truth lies somewhere in-between. Turns out, 50% of the air blowing through jet cabins is actually coming from the outside.

That’s one of the reasons why the air that blows through the vents is so cold — the 50% of air that comes from outside is around -30F, which is why stewardesses need to turn the heat on to keep us comfortable.

The rest of the air is recirculated air through a HEPA filter system, or “High Efficiency Particulate Air.”

This is the same air found in surgical operating theaters or clean rooms, with an efficiency that oftentimes exceeds 99% pure. In our modern-day aircraft, this filter helps stop the spread of whatever just came out of that guy’s mouth 5 rows up, cleans cigarette smoke, and even works to stop the spread of infectious viruses through the cabin.

If you’re traveling on one of the silver birds, your best option for the cleanest air is to turn that overhead jet on high and let it blow around your face. This funnel forces air that may be lingering around your nose and mouth aside, providing a fresh stream of cool, clean air.

Cliff even spoke to the pilot or driver of an A320, who has seen the process of cleaning the HEPA Filters. He claimed it was about as nasty as cleaning…well…you get the point.

Another pilot friend of Cliff’s even suggested that if you have to travel during the coronavirus outbreak, you should turn the air on and allow the HEPA filters the opportunity to blow clean, fresh air over your nasal cavities, promoting a safer ride and reducing the probability of infection.

So, bundle up, turn on the jets, and sit back and enjoy the ride. The door seals will keep you breathing, and the HEPA filters could keep you safe.


The original article was written by Cliff Golstein, CEO at Eclipse Seal and can be found on their website.

Gallagher Fluid Seals is an authorized distributor of Eclipse Seal. For more information about how Gallagher and Eclipse can help for your custom application, contact Gallagher.

Braided Packing Materials: From Flexible Graphite To Fiberglass Rope

picture of braided packingIt’s highly likely that, at some point or another, you have seen braided packing in or out of its “natural environment.” Braided packing looks like rope and is cut into rings that wrap around a rod. While packing used to be available in fairly limited styles, the mechanical packing industry has expanded over time, resulting in braided packing that is available in everything from flexible graphite to fiberglass yarn. Let’s dive into this topic, and discuss the different materials from which braided packing is made in this day and age.

Fiberglass Rope

One of the reasons why fiberglass ropes are favored for braided is that it does not burn. It can be used in continuous temperatures, up to 1,000 degrees Fahrenheit. This makes it perfect for products that are going to exist in high pressure, high-temperature environments. Furthermore, E glass in particular consists of more than 50% SiO2. SiO2, as well as B2O3, are prominent network formers, further emphasizing the usefulness of this product.

Flexible Graphite

Flexible graphite is another product used for braided packing, in part because it is made up of 95% to 99% carbon. It is the softest material, and has a score of 1 out of 10 on the Mohs hardness scale, but can resist high temperatures, and has high levels of chemical resistance. While some favor fiberglass rope over flexible graphite, it remains a classic material associated with braided packing.

Ceramic Fiber Cloth

A product known for its ability to withstand high temperatures is ceramic fiber cloth. This particular material is known to withstand temperatures up to 2,300 degrees Fahrenheit — making it even more durable than fiberglass rope. The strength of this particular product means that it shouldn’t be discounted, even when compared to flexible graphite and fiberglass rope.

Ultimately, the types of materials used for braided packing can depend on exactly what the braided packing will be used for, as well as the costs associated with the order and the long-term needs of the buyer. However, when choosing a material, one will not receive poor results when relying upon the materials like fiberglass rope, flexible graphite, and ceramic fiber cloth. There is a reason why these materials have long been valued in the braided packing industry.


The original article was featured on Mineral Seal Corporation’s website and can be found here.

For more information about compression packing and braided packing, contact Gallagher Fluid Seals today.

Kalrez® Bonded Door Seals

picture of kalrez bonded door seals

Bonded door seals for gate valves and slit valve door seal applications provide improved sealing performance versus conventional O-rings by reducing particle generation, extending seal life, and minimizing replacement time during preventive maintenance.

DuPont Kalrez® bonded door seals are designed for easy installation and low particle generation. They combine a custom seal design and proprietary adhesion technology along with the excellent plasma resistance of Kalrez® perfluoroelastomer seal materials developed for semiconductor applications. The seal is held in a “fixed” position versus conventional O-rings, thereby eliminating “rolling/twisting” and abrasion during door actuation. In addition, the seal design has been optimized using finite element analysis (FEA) to minimize high concentrations of localized stresses. As a result, both particle generation and sealing performance are significantly improved versus conventional O-rings.

Typical Applications

Bonded door seals replace O-ring seals currently used in gate valve, and slit valve dovetail grooves in particle sensitive semiconductor etch, ash, strip and/or deposition processes.

Lower Particle Generation and Extended Seal Life versus Conventional O-rings

  • Sealing element held in a “fixed” position, i.e., eliminates “rolling/twisting” in service
  • Design eliminates O-ring abrasion against edge of dovetail groove during actuation/compression
  • Kalrez® semicon product grades used to minimize particle generation in reactive plasmas
  • Kalrez® Ultrapure post-cleaning and packaging reduces unwanted contamination
  • Improved sealing performance—optimal design minimizes high concentrations of localized stresses

Less Replacement Time Versus O-ring Seals During Preventive Maintenance

  • Quick and easy assembly/disassembly to mounting hardware
  • Reduces installation problems commonly experienced with O-ring seals
  • Eliminates need to clean the seal gland during preventive maintenance
  • Barcode on packaging plus bonded door seal part number and Kalrez® product number engraved on back of commercially available bonded door seals enables traceability and identification providing assurance that it is a Kalrez® perfluoroelastomer part (FFKM).

Availability

DuPont Kalrez® bonded door seals are available for a number of valve types used in semiconductor OEM equipment platforms.  In addition, a custom Kalrez® bonded door seal can be developed for most gate valve and slit valve door applications if not currently available.  Kalrez® UltraPure post cleaning and packaging is standard for all bonded door seals.


The original article was featured on Dupont Kalrez® website and can be found here.

Gallagher Fluid Seals is an authorized Kalrez® distributor. For more information about Kalrez products or to obtain a quote, please contact Gallagher Fluid Seals today.

Case Study: Water Treatment Style 206 Expansion Joint

picture of style 206 expansion jointFacility Issue:

In a brine concentrator, an original competitor’s expansion joint failed upon start up.

Industry:

Water Treatment

Background of the Facility:

This facility is a Zero Liquid Discharge (ZLD) power plant. Water is initially pumped from a well, pre-treated, used as process water, then reclaimed and retreated with a Brine Concentrator for use in their cooling towers. No city water is used and no waste water is disposed of from the site.

Brine concentrators use thermal energy to evaporate water, which is subsequently condensed and discharged as clean distilled water.

Brine Concentrators are also used in water treatment facilities in desalination plants, mining operations and well drilling operations in the oil & gas industry.

  1. Size: 24 “x 10” FF
  2. Temperature: 221° F
  3. Media: Brine Slurry
  4. Pressure: 30 psi

Observation:

The original expansion joint unfortunately failed catastrophically without warning on start up. After consultation with the OEM of the Brine Concentrator, the recommendation was that only Garlock Expansion Joints be used for this aggressive application. The original expansion joints were replaced with Style 206 expansion joints which are built with a 4 to 1 safety factor.

Value Proposition:

Upon start up, Garlock Style 206 expansion joints offered superior performance, reliability and service life. This in turn improved plant safety, increased the mechanical integrity of equipment, and allowed Garlock’s customer to gain a competitive advantage in the market place.


The original article was featured on Garlock’s website and can be found here.

Gallagher Fluid Seals is an authorized distributor of Garlock gaskets, packing, expansion joints, and more.

For more information, contact Gallagher Fluid Seals today.

 

Reduce Downtime and Costly Seal Replacements: Seal Failure Diagnosis Part 2

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.

Original content can be found on Parker’s Website and was written by William Pomeroy, applications engineer, Parker O-Ring & Engineered Seals Division.


As mentioned in part one of Parker’s seal failure blog series, O-ring and seal failures are often due to a combination of failure modes, making root cause difficult to uncover. It’s important to gather hardware information, how the seal is installed, application conditions, and how long a seal was in service before starting the failure analysis process. In part 1, compression set, extrusion and nibbling, and spiral failure were discussed. In part 2 of Parker’s series, they will review four other common failure modes to familiarize yourself with before diagnosing a potential seal failure in your application.

Rapid gas decompressionRapid Gas Decompression

Rapid gas decompression (commonly called RGD, or sometimes explosive decompression (ED)) is a failure mode that is the result of gas that has permeated into a seal that quickly exits the seal cross section, causing damage.

Detection of this failure mode can be difficult, as the damage does not always show on the exterior.  When the damage is visible, it can look like air bubbles on out the outside, or perhaps a fissure that has propagated to the surface.  The damage may also be hidden under the surface.  If the seal is cut for a cross section inspection, RGD damage will look like fissures in the seal that may or may not propagate all the way to the surface.

Parker’s guidance as to how to avoid this failure mode is: 1) Keep the depressurization rate lower than 200 psi per minute.  If this cannot be achieved, they would suggest 2) RGD resistant materials.  Parker offers these RGD resistant options from the HNBR, FKM, EPDM, and FFKM polymer families.

AbrasionAbrasion

Abrasion damage is the result of the seal rubbing against a bore or shaft, resulting in a reduction of cross sectional thickness due to wear.  As the seal wears, it has the potential to lose compression on the mating surface.  This wear is compounded by the fact that dynamic applications already have lower compression recommendations.

To reduce risk for this failure mode, it requires consideration during design and seal selection.  The surface finish and concentricity of the hardware will be very important considerations.  A smooth surface results in less friction (suggest 8 to 16 RMS), which in turn results in less wear.  Increasing the durometer of the seal material helps resist wear, and there are also internally lubricated materials that could be employed.  If the application is high temperature, one should consider the impacts of thermal expansion on the elastomer being used.  The thermal expansion increases contact pressure, which would increase friction / wear. Continue reading Reduce Downtime and Costly Seal Replacements: Seal Failure Diagnosis Part 2

Vesconite Steps Up to Help During Coronavirus Pandemic

A message from one of Gallagher’s valued suppliers:


Vesconite Willing to Manufacture Ventilators

The Coronavirus is likely to result in a need for hundreds of thousands of ventilators worldwide: data shows 5-10 % of people infected need to be supported on ventilators for two to three weeks.

Vesconite has extensive machining capabilities. With 70 CNC lathes and machining centers, they can manufacture a wide range of mechanical components.

Though they are experts in bearings and bushings, they know nothing about making ventilators… but they stand by to help those in need.

If you have ventilator expertise or know a company that does have the expertise and would like to have Vesconite become involved, please fill out this form. Join with them so that they can help to manufacture the thousands of ventilators that are needed.

If there are any further questions, please email tanya@vesconite.com.


From the CEO of Vesconite, Dr Jean-Patrick Leger:

South Africa, where Vesconite is headquartered, has a population of 58 million. If 10% of the population is infected (5.8 million), an estimate (based on Italy with 7% of cases critical) is there may be a need for 400,000 ventilators.

To listen to a report from “the front line”, here is a New York Times interview with the head of the respiratory unit of an Italian hospital:


Gallagher is an authorized distributor for Vesconite products. For more information, contact Gallagher Fluid Seals today.

ASTM International Committee Releases Latest Room Temperature Tightness Test

The American Society for Testing and Materials (ASTM) International Committee F03 on Gaskets recently released the latest standard practice to derive gasket design constants for the proper design of bolted flanged joints (BFJs): ASTM F2836-18. End users of gaskets can then use these gasket constants for proper BFJ design using calculation methods that are currently being developed by a special working group of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) Section VIII at the time of this publication. In this article, the current test procedure, the mathematical models of the test evaluation and the calculation of the characteristics are described and discussed.

IMAGE 1: Example of a servo-hydraulic test stand (Images courtesy of Amtec North America, Inc.)

Background

Most industry professionals are aware that BFJs used in fluid service are complex mechanical systems. In order to create a high-performing BFJ, a designer needs to carefully consider not only the service conditions the BFJ will encounter, but also the performance characteristics inherent to the components of the BFJ. The gasket itself is one of these critical, yet often overlooked, components, and efforts to determine and quantify the performance characteristics of gaskets have been ongoing for decades.

The newest of these efforts to be published in the United States is ASTM F2836-18: Standard Practice for Gasket Constants for Bolted Joint Design (commonly referred to as the Room Temperature Tightness Test, or ROTT). The design constants produced by this method enable a more robust design of BFJs compared to previous, antiquated design constants, such as the m and y factors.

The crucial gasket constants produced by this standard practice are a, Gb and Gs. These constants effectively describe the tightness behavior of the gasket material, reflective of different loading and service conditions.

In addition to their application to the ASME calculation method currently under development, the constants can also be used to compare materials so the proper one may be selected for the application.

IMAGE 2: High-pressure test sequence

Who Will Use ASTM F2836-18?

ASTM F2836-18 is a helium leakage testing and evaluation method that determines tightness-based design constants at room temperature for pressurized bolted flange connections that are designed in accordance with ASME BPVC. As such, ROTT applies mainly to all types of circular gasket products—including, but not limited to, sheet-type, spiral wound, solid metal and jacketed gaskets.

As such, these constants stand to be of interest to all parties who work with circular gaskets and have a vested interest in producing a high-performing BFJ, including end users, BFJ assembly contractors and gasket manufacturers.

Testing Procedure

The test method consists of analyzing data from multiple gasket leakage tests in order to calculate the three aforementioned design constants for a particular model and size of gasket. The testing can be performed in a pair of appropriately sized flanges, using bolts to achieve varying gasket loads, or in a servo-hydraulic test stand of adequate capacity (Image 1).

In total, the procedure consists of two high-pressure (HP) tests at 6 megapascal (MPa) (870 pounds per square inch [psi]) of helium and two low-pressure (LP) tests at 2 MPa (290 psi) of helium, for a total of four tests on four different specimens. In addition to the differences in internal pressure, the HP and LP tests are also distinct from each other in terms of the gasket loading sequences.

The HP test consists of loading and unloading sequences, continually introducing successively higher loads onto the gasket while interrupting this loading sequence with intermittent unloading ramps. The LP test consists of only a loading sequence.

In both tests, the helium leak rate is measured at these various gasket loads.

For the purposes of test evaluation and gasket constant derivation, the different loading sequences of the tests are categorized as either Part A or Part B. Part A consists of the loading sequences, while Part B consists of the unloading sequences. Therefore, the HP test contains both Part A and Part B sequences, while the LP test consists of Part A only.

IMAGE 3: LP test sequence

See Image 2 and Image 3 for details of the HP and LP testing sequences, respectively.

With its increasing gasket loads, Part A simulates assembly of the gasket in the joint, and therefore represents the gasket seating process. The data from this portion of the test is used to determine the required seating load for the gasket to create a tight seal.

Part B simulates the operating conditions by unloading the specimen to different gasket stress levels. This replicates unloading of the gasket, seen in real applications, due to various factors including internal pressure and relaxation effects of a gasket during operation. Part B test data is used to determine the required operating gasket load in order to maintain a tight seal. Continue reading ASTM International Committee Releases Latest Room Temperature Tightness Test

The Advantages and Disadvantages of the Channel Seal

The Channel Seal (or Cap Seal, as it’s often referred to), was one of the earliest forms of Polymer or Teflon sealing in the seal industry.

The product is easily applied. It didn’t replace the O-ring, but instead offered improved life while reducing drag.

In doing so, hydraulic and pneumatic systems operated cooler and quieter, while improving overall performance of the product.

picture of channel seal

Evolution of the Channel Seal

Before the Channel Seal, the Backup ring was established. The first Backup rings started out as leather, as this material was readily available and could be easily formed into any shape with simple dies to stamp the Backup ring out.

Back up rings provided support for the O-ring, allowing the O-ring to operate at higher pressures, while closing off the Extrusion or “E” gap. This stopped the O-ring from being nibbled in the extrusion gap, therefore extending the life of the O-ring.

Teflon Backup rings were a big improvement, as they would better fill the gap and would stay put (as opposed to leather, which tended to shift in the groove). With the use of two Backup rings, an O-ring was well supported from pressure in both directions.

It was a simple matter to connect the two Backup rings with a thin membrane of Teflon, which removed the O-ring from the sealing surface. This change reduced drag and improved performance, while still maintaining an excellent mechanism for extrusion resistance.

This design was relatively simple to machine out of Teflon, but installation was a challenge, as the Backup rings were full depth. This caused the seal to become distorted during the install process. Today, we almost never see this type of design.

With CNC machining, the ability to nestle, and an O-ring design in a complex Teflon shape, it gave rise to what is referred to today as the Channel Seal, or Cap Seal.

This style seal offers an abundance of advantages over standard back-up rings and the early version of the Channel Seal, which was simply a Backup ring with the membrane of Teflon in-between. Continue reading The Advantages and Disadvantages of the Channel Seal

Reliable Sealing of Heat Exchangers

ePTFE Gasket Tapes for High Chemical Resistance

The connections to shell and tube heat exchangers pose immense challenges for the seals that are used because of both the chemically aggressive media and the frequent temperature load changes. Despite its excellent chemical resistance,polytetrafluoroethylene (PTFE) is not typically suitable as a sealing material in this case because the creep tendency of this material jeopardizes a reliable seal.

Shell and tube bundle heat exchangers generally include not only several connection pieces but also a shell cover flange with a significantly larger nominal diameter.The shell cover flange creates the seal to the tube bundle flange, which then seals the shell flange. These connections are subjected to the full operating pres-sure and test pressure of dozens of bar and seal it from the environment. Oftentimes the tube bundles are arranged in several passes that are channeled by the use of partition plates. This requires a seal at the head of the heat exchanger and between the tube passes at the partition plates where the pressure difference is considerably lower. The numerous potential different arrangement of the passes  requires specially adapted seal designs. The sealing challenges that pertain to the shell cover flange position can be attributed to a combination of different conditions:

  • chart showing 500 series gasket tape benefitsHigh temperatures/pressures
  • Temperature load changes caused by starting up and shutting down part of the process
  • Complex sealing geometries including separators, often combined with large nominal diameters
  • Chemically aggressive media
  • Damaged sealing surfaces, due to corrosion or warping
  • The economic necessity of minimizing downtime
  • The requirement to document legal compliance

“Creeping” gasket tapes made of PTFE

Gasket tapes are occasionally used to seal the static connections to shell and tube heat exchangers — sealing materials with a defined width and thickness, but an undefined length. They offer a way of functionally connecting the junction points and can be shaped as desired at the point of installation. Since the gasket circumference is completed at the time of installation, it is no longer necessary to completely dismantle the heat exchanger, removal of the tube bundle, for example. It is only important that the sealing surfaces be sufficiently accessible. Gasket tapes have been around in many different industrial fields for several decades. By introducing the Gore Joint Sealant, Gore launched the first gasket tape made of expanded PTFE (ePTFE) back in 1971. However, multiaxially expanded PTFE technology finally made it easier to use ePTFE with shell and tube heat exchangers across a broader range of application conditions.

The need for these material performance improvements by Gore is the low creep resistance of PTFE. In molecular terms, PTFE consists of a chain of carbon atoms that is saturated with fluorine atoms. The strong covalent carbon-fluorine bond is responsible for this polymer’s nearly inert chemical reaction behavior. This explains why this material is desired as a sealing material in aggressive media. However, the lack of reactivity also means that PTFE chains cannot be molecularly linked like other materials, elastomers for example, and this results in a profound cold and warm flow behavior, also known as “creeping”.

Risk of deformation of the sealing material

Creeping refers to the mechanical deformation of a component, in this case the seal, when subjected to loads and temperatures. One reason why seals in flange connections function is because the surface pressure caused by the bolts allows for irregularities in the sealing surfaces to be filled up and for blocking of leakage channels inside the seal. This reduces leakage (depending on the behavior of the sealing material) to an acceptable level. In this sense, leakage refers to the admissible substance flow, irrespective of the prevailing mechanism, in other words the sum of all mass flows from Fick’s law of diffusion to gross leakage.

picture of gore fibers
REM images of the Gore Gasket Tape Series 500

This sealing function is severely impaired by the creep tendency. Inside a flange connection, creep of a sealing material takes place in such a way that the load is reduced at a certain temperature until a balance between the internal strength of the seal and the external load is achieved. This behavior is called creep resistance. Deformation takes place when equilibrium is reached. With a seal, this is a reduction in the thickness that reduces the bolt elongation and thus the preload. This ultimately means a loss of strength or surface pressure that depends on the stiffness of the sealing system with respect to its extent. This surface pressure loss is called “creep relaxation” and can be so great that the bolts are loosened completely. Creep and the respective relaxation mainly occur during the heating up and cooling phases, in other words during thermal cycling. These effects occur to a significantly lower degree with a constant temperature. Creep relaxation is the main reason why simple PTFE (often brought into shape by sintering) can hardly be used in heat exchangers, which by their very nature are often subjected to significant temperature load changes.

Increasing the creep resistance through expansion

There are different ways to reduce the creep resistance of PTFE. One way is to add filler materials. This technique is only appropriate for use with gasket tapes to a limited extent due to the fact that the flexibility of filled PTFE is extremely limited. Strips of simple PTFE are also not very useful for the same reason because it is difficult to form them into the required shape at the time of installation. Expanding the PTFE material offers an effective solution. This creates a microporous structure through mechanical stretching. This structure causes a significant change in properties. On the one hand, it improves the conformability due to the higher compressibility as well as creep resistance on the other hand. Here, it is important for the expansion to take place as evenly as possible. This is crucial to ensuring that the sealing properties are and remain the same at all positions of the seal. It can still have a texture, however, although it should not extend throughout the entire seal (in other words for the entire length of a band). In fact, a controlled transverse texture (with a circular transfer radially) can have a positive effect on deployability and bending stiffness. While such a structure changes the sealing properties (the transverse strength, for example), this can be taken into consideration structurally. Expansion allows for tapes to be produced that are flexible enough to be laid in even narrow radii.

picture of gore eptfe sheet
REM images of the Gore ePTFE Sheet Material

The following properties are characteristic of gasket tapes made of ePTFE:

  • Easy and fast adaptation to suit even complex flange geometries
  • Design flexibility because of the various widths, which then allow for higher surface pressures (higher tightness classes)
  • High creep resistance compared to other PTFE-based materials
  • Excellent adaptability to flange irregularities
  • Not reusable (due to the high compression and low spring back
  • Non-biodegradable, do not age, UV-resistant
  • Resistant to all types of media (pH 0 to 14)
  • Long shelf life, limited only by the declining bonding strength of the mounting aid adhesive tape.

Mounting of ePTFE gasket tapes

ePTFE gasket tapes are mounted on one of the flat sides of the tape using adhesive tape. The adhesive only serves as a mounting aid and has little or no impact on the sealing effect. The adhesive is also considerably less temperature- and chemical-resistant than ePTFE. This means it usually decomposes during operation. This makes it easier to remove later on. When closing the seal made of an ePTFE gasket tape, one must make sure that the ends overlap and the right method is used. Basically, there are two different types of ePTFE gasket tape materials that require different overlapping methods: monoaxially and multiaxially ePTFE.

Monoaxial expansion is the older technique used to produce ePTFE gasket tapes. With this method, the PTFE is stretched to the tape only longitudinally. The texture that this creates is responsible for the weaker transverse strength. This results in greater broadening during initial compression, an aspect that must be taken into consideration in the design. Broadening of 20 % and more is quite common. The advantage that monoaxially expanded gasket tapes offer is that they can be compressed to be very thin during installation. This means they are able to adjust to micro unevenness very easily. Macro unevenness on the other hand is quite difficult to compensate for with this type of gasket tapes. Furthermore, unlike with multiaxial expansion, the ends can be overlapped. Nevertheless, monoaxially expanded gasket tapes are used only very rarely in heat exchanger applications because the lack of transverse strength results in a higher creep tendency. Although the small installation thickness compensates for this to some degree, the performance gap to multiaxially expanded PTFE gasket tapes increases as temperatures rise.

The multiaxial expansion of the material takes place in the direction of two vectors that stand at right angles to each other. This results in a multiaxial structure, in other words an orientation of the emerging fibrils in all directions. The transverse texture can be produced by varying the intensity of the expansion. Among other things, it helps to keep the nodes small because this non-oriented material contributes to creeping. Multiaxial expansion is of particular advantage in that it offers high transverse strength and allows for gasket tapes that are particularly resistant to creep.

Multiaxially expanded PTFE gasket tapes seal reliably

picture of notes in gore
Nodes in expanded material contribute to creep tendency

The process of expansion compensates for the disadvantage of the PTFE material, its high creep tendency, and results in a chemically stable, creep-resistant sealing material. If expansion takes place multiaxially, the creep tendency of the material will be reduced to such an extent that it can then be used as a sealing material under extreme conditions of both chemically aggressive media and frequent major temperature load


The original article was written by Christian Wimmer, Product Specialist at W. L. Gore & Associates and was featured in PROCESS Worldwide.

Gallagher Fluid Seals is an authorized distributor of Gore products.  For questions about which Gore product is right for your application, contact our engineering department today.

Sealing Solutions for Large Diameter Rotating Shafts: ZAVA V-Rings

First, What is a V-Ring?

The function of a V-Ring seal, or V-Ring, is to act as a centrifugal seal acting against the bearing face, pushing dirt and contaminants away from the bearing area.  V-Rings are not designed to seal against fluids or pressure differentials. However, as stated above, they are excellent at excluding all sorts of contaminants. They provide effective protection against loss and maintenance, reduce wear, increase the life of the retainer and bearings, and also work well in dry running applications.

V-Ring Applications

picture of zava seal v-ring
The most innovative V-Ring on the market: The Zava Seal with a quick-lock mechanism.

V-Rings are suitable for a whole range of sealing applications as well as rotary shaft applications such as electric motors, pumps, and agricultural machinery. This type of seal has proved to be reliable and effective against penetrating impurities such as dirt, sand, dust, greases, and splashes of water & oil in a variety of industries:

  • Pulp and paper
  • Steel mills
  • Cement mills
  • Mining
  • Rolling mills
  • Power generation
  • Fluid power
  • Chemicals
  • Food & Drink

How Do V-Rings Work?

V-Rings are flexible rubber seals that work by stretching and fitting onto a shaft and then rotating with the shaft against a counter face. They are designed to give the lips an automatic sealing action. They help to increase the sealing area by providing secondary sealing as pressure acting on the platform ring.

The Split V-Ring with ZAVA Quick-Lock

The V-Ring from ZAVA® Seal has a unique patented quick-lock that can be assembled quickly and easily, and in some cases can be installed without shutting down the filter. Because it’s mounted without vulcanizing, machinery downtime is significantly reduced. When “snapped in place,” the locking technology makes it impossible to detach. The quick-lock mechanism is made of acid-proof steel (SS 2343).  The split V-Ring from Zava can be made in many different lengths and cross sections and also in several different types of materials, specifications, and profiles.

Advantages of the Split V-Ring With ZAVA Quick-Lock

  1. Split and lockable
  2. Fast and easy to assemble
  3. Unique and patented quick-lock
  4. Elastic and workable
  5. Reduction in fiber loss
  6. Maximum leakage reduction
  7. No wear of the shaft
  8. A variety of different sizes

How Does the Quick-Lock Work?


For more information about the Zava Seal and to see if it might be the right fit for your application, contact Gallagher’s Engineering Department today.

Gallagher Fluid Seals is an authorized distributor of Zava Seal.