Category Archives: PTFE

PTFE in Motorsports

PTFE and its many applications

Polytetrafluoroethylene (PTFE) has an interesting history and has been used in a number of ways over the years. There is, of course, the best-known PTFE brand Teflon® – the miracle cookware coating. But PTFE is also used in aerospace and computer wiring, and it’s even coated the fiberglass dome of the Hubert H. Humphrey Metrodome in Minneapolis. But the Metrodome isn’t the only sports-related application for PTFE. Because it’s so slippery and resistant to extreme temperature changes and chemical reactions, PTFE is an excellent component for many parts such as: bearings, gears, and of course, seals – like those used in so many motorsport vehicles. So, what role does PTFE play in the exciting world of motorsports?

PTFE in racing cars and trucks

TRITEC Seal’s PTFE rotary lip seals can be found in the race cars of nearly every NASCAR team, ensuring reliability for the chassis, drive train, and accessory drive systems. In addition to these high pressure seals, PTFE is now part of fuel hoses of many high performance vehicles. Relatively recent changes in fuel additives have shortened the life span of rubber fuel hoses, and PTFE, with its extreme temperature durability and chemical inertness, has been an ideal addition to fuel hoses.

picture of motorcycle ptfePTFE in motorcycles

Because of its ability to withstand high vibrations and temperature extremes, PTFE is an important component of a motorcycle’s piston seals. It can also be found in chain lubricant and some motorcycle oil.

PTFE in boats

High performance boats such as MasterCraft use PTFE seals to improve the output of their inboard shaft drive systems. PWC’s such as SeaDoo’s also take advantage of engineered sealing solutions by using PTFE rotary lip seals as well as wear sleeves in all of their PWC models. PTFE is often part of boat wax because of its ability to repel dirt and stains, and offer a high-sheen finish.

PTFE in riding mowers

Believe it or not, PTFE can even be found in the specialized sport of lawnmower racing. It is sometimes a part of the lubricant for belt pulleys. And PTFE rotary oil seals are used extensively in John Deere riding lawn motors to seal the crankshaft.

PTFE in go-karts

Go-kart racers may use a lubricant that includes PTFE, or it may also be part of the seal on a kart’s ceramic bearings, although there are a number of healthy debates about whether ceramic bearings make any significant difference in performance over standard bearings. (But that’s another story!).


For more information about PTFE and to see if it’s the right application for you, contact the Gallagher Fluid Seals engineering department.

This original article was originally featured on Tritec Performance Solution’s website.

How AMS3678 Ensures Consistency in Sealing Materials

When it comes to designing and developing seals, the aerospace and industrial industries need a basis to allow production anywhere in the world.

One of the first PTFE (Teflon) standards, AMS3678, describes Teflon and the addition of fillers. This was used in conjunction with Mil-R-8791, which is one of the Mil specs describing a backup ring device.

The origin of all these specs dates back to the creation of the O-ring.

AMS3678The Origin of the O-Ring Patent

In 1939, Niels A. Christensen was granted a U.S. Patent for “new and useful improvements in packings and the like for power cylinders.” These referred to improved packing rings made of “solid rubber or rubber composition very dense and yet possessive of great liveliness and compressibility.” These products were suitable for use as packings for fluid medium pistons (liquid or air). The improved packing ring is the modern O-ring.

There was a progression of standards for the O-rings created by individual countries, such as AS568, BS 1806, DIN 3771, JIS B2401, NF T47-501, and SMS 1586. Eventually, AS568 became more accepted in the industry.

The backup ring was originally created to help improve the O-ring’s ability to resist extrusion. Teflon was widely used as one of the materials for backup ring devices. Standards were created to unify the production of this Teflon device.

The Progression of Mil Specs

The progression of standard changes has led to AMS3678/1 for Virgin PTFE through AMS3678/16. These standards describe a group of Virgin- and filled-PTFE materials accepted by the industry for manufacturing seals and back-up ring devices.

Mil-R-8791 was canceled in February 1982. This spec was superseded with AS8791, which eventually evolved into AMS3678.

AMS3678 is a tool used by customers and Teflon suppliers to create uniformity in the manufacturing and processing of seal and bearing materials. The standard is inclusive of most of the compounds upon which the industry was built.

When customers approach with an old “mil spec”, they are pushed to the new AMS spec which is currently active. Eclipse manufactures to the spec so their customers will have the confidence that they manufacture to a known standard.

When crossing custom materials from well-known sources, customers are driven to an accepted spec that is equivalent to the original source of the material. This helps customers sell their products with internationally-known materials rather than custom, home-grown compounds that are often intended to single source those materials.

There are several qualifications of the spec that suppliers must observe. This includes dimensional stability tests. This test ensures the material has been properly annealed, and that the seal or backup ring will fit and function as it was originally intended.

Eclipse is uniquely qualified to supply parts to the latest AMS3678 specification. They understand the scope of the specification which allows us to ship parts with fully traceable certification.

AMS3678 helps validate a material to a customer to ensure they get the same material processed the same way with each order. Beyond this, there are other ways to determine what makes a part process-capable.

Continue reading How AMS3678 Ensures Consistency in Sealing Materials

Freudenberg Announces New Seals and Materials for the Aerospace Industry

Freudenberg Sealing Technologies introduced several new material and sealing innovations at the 2019 International Paris Air Show.

These new products are designed to help aerospace customers address ever increasing safety and performance requirements in the industry.

During the June 17-23 event in Paris, Freudenberg showcased a new high temperature, fireproof material; an Omegat OMS-CS cap seal; and new ethylene propylene diene monomer (EPDM) and a fluoroelastomer (FKM) developmental material.

“Our aerospace customers strive continuously to be faster, safer and more efficient, which in turn requires us to innovate to help them reach those goals – a challenge we enthusiastically embrace,” said Vinay Nilkanth, vice president, Global Mobility Sector, Freudenberg Sealing Technologies. “The launch of several new products aimed at improved performance underscores Freudenberg’s commitment to being a global leader and development partner to the industry.”

Freudenberg’s new proprietary fireproof sealing fabric is made to withstand the extremes. Tested on standard aerospace bulb seals and passing AC20-135 fireproof requirements, the fabric acts as a barrier, providing up to 15 minutes for necessary corrective action. The fabric performs as well as other industry standard solutions but is much more cost effective.

Omegat Cap Seal

For use in dynamic, reciprocating applications where low friction is required, the new Omegat OMS-CS cap seal is a two-piece rod seal set consisting of an engineered polytetrafluoroethylene (PTFE) ring and an O-ring energizer. The seal offers low breakaway and running friction, and is chemically compatible with aerospace fluids and greases. It also provides excellent wear and extrusion characteristics, and has angled blow-by notches and lubrication grooves.

Freudenberg’s new EPDM LM426288 material is for use in low pressure static sealing to -77°C (-106°F) and has excellent resistance to, and swell behavior in, AS1241 phosphate ester hydraulic fluids. The material offers high temperature compression set resistance and short term resistance to 150 °C (302°F) for high temperature hydraulic systems such as hydraulic braking.

The FKM LM426776 material for use in low pressure static sealing to -67°C (-88°F) shows excellent resistance to several aerospace media, including jet turbine and gearbox lubricants, high and low aromatic content jet fuels, and fire resistant hydrocarbon hydraulic fluids. The material offers short-term high temperature resistance to 270°C (518°F) and long-term compression set resistance at 200°C (392°F).


The original article can be found on Freudenberg’s website.

Gallagher Fluid Seals is a preferred distributor of Freudenberg Sealing Technologies. To learn more about Freudenberg products, speak to a Gallagher representative today by calling 1-800-822-4063

Case Study: Balancing Extrusion Gap and Wear Ring Exposure in a High-Pressure C02 Extraction Application

Seal designers often feel caught in the constant struggle to balance the demands of a sealing application with physical and material constraints.

picture of piston

At Eclipse, it’s an engineer’s job to understand and weigh these limitations with the goals of the application. For example, when a customer needs an extremely low friction seal that also has very high sealability, there’s always a compromise that needs to happen.

A magical seal material that has the pliability and excellent seal characteristics of rubber, and the low-friction, high-wear resistance and temperature range of PTFE simply doesn’t exist.

Another frequent scenario is a customer needing a seal to accommodate loose or poor hardware tolerances, yet has a very small physical envelope to incorporate a seal. The smaller the seal, the smaller the effective deflection range due to the physical limits or an O-Ring or spring.

While the application might need to cover the range of a 400-series spring or O-Ring, there may only be room for a seal the size of a zero series, which presents a problem. Similarly, a customer might have the desire for a seal with very long wear life, yet the hardware assembly may be severely limited in the area meant for the seal.

There have been several times where Eclipse has been approached with applications where a space for a seal was never considered in the original design. Without a properly sized seal, wear life has the potential to be restricted due to the fact there is less seal material available to be worn away before the structural integrity and sealability is compromised.

Another common problem in sealing applications where bearings are needed is the balance between having enough exposure for the wear rings and not creating too large of an extrusion gap, which can lead to complications for the seal. Eclipse was approached by a customer facing this issue in their high-pressure, supercritical CO2 extraction equipment.

The Client’s Issue

With the growing popularity of cannabis-derived products such as CBD oil, extraction processes are being examined for increased productivity and durability.

A customer was looking to redesign the piston seals used in their CO2 SFE extraction equipment. The ideal seal would have improved wear life and longevity as well as improved lead-time and availability of the seals once they needed to be replaced.

The customer’s increased production volumes and run-rates where quickly wearing out the OEM seals, and they were unhappy with the lead-time and service of the original seal supplier.

With some of the best lead-times in the industry for custom PTFE seals, Eclipse knew it could deliver if an improved seal design could be implemented.

Operating Conditions:

  • Reciprocating Piston Seal
  • Bore Diameter: Ø3.250”
  • Stroke: 6”
  • Cycle Rate: 35 cycles per minute
  • Media: CO2
  • Pressure: 800–5,000 PSI
  • Temperature: 65° to 175°F

The customer was willing to redesign the piston seal gland configuration, but the overall length of the piston couldn’t be changed to ensure correct functionality in the original equipment.

Since there was significant side-loading of the piston, wear rings would be necessary for both proper piston guidance and to safeguard against any potential metal-to-metal contact between the piston and bore.

If metal-to-metal contact occurred and the bore was scratched or galled, the customer would face extensive down-time while they waited for a replacement part. This would cost them a significant amount of money from lost productivity, not to mention the cost of the replacement bore.

To mitigate this potential risk, the customer didn’t want to eliminate wear rings or reduce their width. Eclipse needed to find a solution that worked with this specific design constraint, and with the amount of axial space available on the piston for the seal.

This space constraint presented a challenge. With the importance of proper wear ring exposure in the system, the extrusion gap needed to be sizable. And with limited space to either substantially extend the heel of the seal or incorporate a back-up ring, Eclipse needed to utilize special design techniques and features to present a high wear life seal.

The Eclipse Solution

Balancing extrusion gap and wear ring exposure is a very typical problem in the seal industry. In systems where operating pressures are relatively low, this might not be a problem. But when pressures increase, seal integrity can quickly become compromised.

In a piston application, wear-ring exposure and seal extrusion gap become the same entity. In most cases, once tolerance stack-ups are performed with both the bearing and hardware dimensions, the resulting necessary exposure dimension will be far beyond the typical maximum extrusion gap recommendation for the seal.

If not given enough exposure on the piston, the wear ring has the potential to be loose in the groove, making it ineffective as a bearing. This would place undue side loading on the seal, leading to premature failure and/or the piston contacting the bore.

In almost every case, this metal-to-metal contact will likely gall or score the bore enough to destroy a proper sealing surface finish, if not more extensive damage.

On the other hand, if the extrusion gap that results from the need for bearing exposure is too large, the seal will eventually be pushed into the gap by the pressure and ultimately cause a failure. The higher the pressure of a system, the smaller a recommended extrusion gap will be.

Without any other considerations, extrusion gaps are typically suggested to be made as small as possible. This fact is obviously diametrically opposed to the need for bearing exposure.

To combat large extrusion gaps, spring energized seals can be made with an extended heel design. This physically puts more sealing material behind the seal, which can be deformed into the gap without affecting the critical area of the seal.

The other common solution is to incorporate a back-up ring behind the seal. A back-up ring can be designed to reduce the size of the extrusion gap that the seal is exposed to.

Both of these solutions require additional axial space on the piston, which Eclipse didn’t have the luxury of working with.

The first step: using a smaller spring series than the hardware cross-section would typically call for. The smaller spring would effectively allow the heel of the seal to be extended, aiding in the extrusion resistance of the seal. This also means the sealing lips would be thicker than normal.

Eclipse utilized this extra material in the lips to modify the seal geometry to further fortify against high pressure failure. The ultimate failure mode of a spring energized seal due to extrusion is usually when deformation of seal reaches the hinge point of the spring cavity. To guard against this, Eclipse offset the location of the spring groove to thicken this vulnerable hinge point.

Eclipse chose its ET040: Polyimide/MoS2 filled PTFE for the spring energized seal jacket. While this isn’t the most extrusion resistant material Eclipse has to offer, the customer’s stainless-steel bore material was limiting on how aggressive the seal material could be.

ET040 would provide a good level of toughness without wearing the bore. The added internal lubricity reduces friction, and the fine particle size of the Polyimide improves sealabilty while sealing gases such as CO2.

Eclipse chose its ET010: bronze-filled PTFE for the wear rings. This industry standard bearing material fit well within the design objectives of the project.

How the ET040 and ET010 Performed

With Eclipse’s revised seal and piston design, the customer saw increases in seal life and reliability. This allowed them to run their production processes for longer intervals between scheduled maintenance.

The reduced downtime increased plant productivity, positively affected the customer’s bottom-line, and allowed them stay on top of shipments of their high demand product.

The customer was also very pleased with Eclipse’s comparatively short lead-time and reliable delivery on replacement seals. Their moderate investment in redesigning their piston configuration to use Eclipse seals proved to be a profitable choice.

eclipse engineering seal and wear rings


Article written by Eclipse Engineering, Inc. For the original article, visit their website.

Gallagher Fluid Seals is a preferred distributor of Eclipse Engineering. Call us at 1-800-822-4063 for more information on Eclipse seals.

Reduce Maintenance Costs When Sealing Dry Running Equipment

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

Original content can be found on Parker’s Website and was written by Nathan Wells, Application Engineer, Parker Engineered Polymer Systems Division.


My grandpa used to have a rusty, old air compressor in his shop. As a child, when my siblings and I would visit him, he’d use it to power air wrenches, grinders, and inflate flat soccer balls for us. I noticed it had a port labeled “ADD OIL DAILY” that was covered in the same thick layer of greasy dust as all the other unused junk in his shop. Knowing my grandpa, if asked about adding oil he probably would have said, “Oil is expensive. That’s how the companies get ya!” The compressor’s seals leaked so badly, you could hear the hissing even over the loud motor. I was certain one day it would explode.

picture of dry running equipmentPneumatic tools are common in factories, tool shops, and DIY garages around the world. Using compressed air for power is convenient, simple, and — when maintained properly — safe and efficient. However, air treatment costs can add up fast. Traditional rubber seals used in air tools require clean, low moisture, compressed air with the proper amount of lubrication added. Good Filter/Regulator/Lubricator systems (FRLs) cost as much as the tools themselves! So, what would happen if we didn’t have to provide pristine air?

Today we have the technology to create seals for tools which don’t require daily or even yearly upkeep. You’ll find these tools labeled “maintenance-free,” which sounds great to the guy responsible for maintenance. It sounds even better to the guy paying for maintenance … and to engineers designing tools who want to keep warranty costs down.

Seal materials for dry running

Early pressure seals were made out of leather. My grandpa’s compressor probably wasn’t that old, but even since his time, we’ve come a long way.

When I’m asked for seal recommendations in totally dry-running applications, my mind clicks to a material called PTFE (chemical name polytretrafluoroethylene). Most people know PTFE by the brand name Teflon® and are familiar with its use when applied to cookware as a high temperature, slippery, non-stick coating.

PTFE is a semi-hard plastic which feels slick to the touch thanks to its low friction properties. It’s considered self-lubricating because it leaves micro deposits on the sealing surface and reduces friction after just a few strokes. Because of this, it’s good for high-speed sealing and can operate completely dry.

By adding fillers to PTFE, seal manufacturers can tailor materials for greater suitability in meeting performance requirements for a wide range of conditions. String-like additives including fiberglass and carbon fiber increase pressure rating, wear resistance and seal life. Dry lubricant-type additives such as graphite or molybdenum disulfide (MoS2) further increase a seal’s ability to run without lubrication, and at higher speeds and pressures. In pneumatic medical, pharmaceutical, and food processing systems, clean grade mineral-based strengtheners may be used as additives.

PTFE seals for dry running equipment are available in several profile configurations:

Continue reading Reduce Maintenance Costs When Sealing Dry Running Equipment

Solving High-Pressure, High Eccentricity Seal Issues

Facing challenges, head-on is what Vanseal does every day – which is why their customers trust them to deliver tested and proven, material and design solutions that improve the performance of their seals, no matter how tough the environment.

High-Pressure, High Eccentricity Seal Solution Demonstrates 50% Improvement

– On pressure and side-load performance of a fluid application

Recently, a customer was having difficulty with a seal failure on apicture of leoader fluid power application. The high-pressure, high-eccentricity seal operates in conditions up to 200,000 pv at 3000 psi and could not exceed maximum shaft deflection of 0.005″.

Vanseal works with these types of seal applications frequently and used a Unitized Seal that uses several components to address each of the various sealing challenges.

Vanseal’s solution for its high-pressure, high-eccentricity seal incorporated these key elements:

  • Primary Seal Lip – Made from a high-modulus elastomer, to reduce lip extrusion and inversion under pressure, better distributing high-pressure forces to enhance sealing
  • Machined PTFE Backup Lip – Used to reduce the risk of extrusion and inversion of the Primary Seal Lip
  • Support Washer – Designed to close the extrusion gap between the seal ID and shaft under high, shaft-deflection conditions
  • Excluder Lip – Works to keep contaminants from entering the assembly system
  • Metal Case – Serves as a carrier for the seal components creating a single unit to install, and thus reducing instances of installation errors caused by multi-piece installations and reducing individually purchased and inventoried items.

Vanseal has been manufacturing highly specialized seal components for over 60 years

  • Sealing systems are tricky and using a stock seal manufactured for typical high-pressure applications may not be enough to absorb high-shaft deflection.
  • Our experienced engineers have in-depth knowledge on how to address these difficult sealing challenges.
  • Along with engineering, we maintain the highest standards in quality testing and manufacturing methods.

The original article can be found on Vanseal’s website.

To learn more about Vanseal’s products, speak to a Gallagher representative today by calling 1-800-822-4063

Lower Friction, Weight, and Emissions – The Freudenberg BlueSeal

Freudenberg-NOK Sealing Technologies has begun supplying innovative, lightweight radial shaft seals to a major Detroit-based vehicle manufacturer for installation on the V6 and V8 engines powering its newest pickup trucks and sport utility vehicles (SUVs).  Enter the Freudenberg BlueSeal.

The BlueSeal, part of Freudenberg’s award-winning Low Emission Sealing Solution (LESS) portfolio of engine, transmission and E-Mobility product solutions, provides significant weight, friction and installation advantages over traditional radial shaft seals. Under the contract, Freudenberg-NOK will produce more than 2 million BlueSeals annually. Production is expected to increase further to more than 4 million units annually with orders from additional customers.

40 percent lighter and 50 percent less space to install

From turbocharged engines and 10-speed transmissions topicture of blueseal electrified and electric vehicle systems, the propulsion technologies on display at the 2019 North American International Auto Show (NAIAS) offer evidence that fuel economy, emissions and performance are still top of mind with manufacturers and consumers alike. Freudenberg’s BlueSeal offers customers a way to help achieve better fuel economy and lower emissions in large displacement internal combustion and turbocharged engines. The BlueSeal is 40 percent lighter than conventional radial shaft seals and requires 50 percent less space to install.

“Vehicle manufacturers are looking at every possible way to increase fuel efficiency and reduce weight, especially in trucks, SUVs and turbo-charged performance vehicles,” said Jeff Nelson, vice president, Automotive Sales, Freudenberg-NOK. “Even the smallest components can have a dramatic impact on the function and efficiency of vehicle powertrains.”

The BlueSeal is made of a single material – a steel-reinforced Polytetrafluoroethylene (PTFE) – designed to withstand harsh engine fluids while providing an axial space reduction, which allows manufacturers to downsize the engine. The seal has a low-friction Power Optimized Polytetrafluoroethylene (POP®) lip design that insures smaller dissipation loss, reduces the temperature in the contact area between the seal and shaft and performs flawlessly under different engine conditions.

Dual product development strategy for the automotive industry

The BlueSeal increases durability through its perfect sealing behavior and has a higher resistance to pressure than traditional seal designs. Its R-Tight® technology results in near-zero air leaks during assembly tests, allowing manufacturers to isolate other potential leak paths in the system.

Freudenberg is pursuing a dual product development strategy that supports continued development of advanced materials and components for internal combustion powertrain applications while pursuing new technologies that address emerging challenges associated with alternate mobility options like lithium-ion batteries and fuel cells. The BlueSeal, like many of Freudenberg’s LESS products, offers system benefits in both arenas.

“The automotive industry is undergoing profound transmission and driveline changes,” Nelson said. “It is our job to provide customers with exceptional component solutions that address the needs of all mobility platforms regardless of the fuel they use. The need to harness energy effectively and efficiently is a common denominator across our development efforts.”


The original article can be found on Freudenberg’s website.

To learn more about Freudenberg products, speak to a Gallagher representative today by calling 1-800-822-4063

EagleBurgmann’s Patented SeccoLip

A patented lip design and the patented combination of PTFE sealing lip and sliding bearing in the lip seal element provide the new dry running seal “SeccoLip” from EagleBurgmann with particularly high flexibility. These technical features help the lip seal compensate directly and safely radial deflections of the shafts in agitators, mixers and reactors.

The sliding bearing tracks the complete lip seal element to the shaft movements. Since the lip and bearing are in one element, the sealing gap between the rotating shaft and the sealing lip remains virtually constant and the seal remains tight over the long term. Compensating elements such as O-ring, expansion washer or metal bellows are not required for reliable operation.

The modular seal was specifically designed for the operating conditions in the chemical, pharmaceutical, food industry as well as in water and wastewater technology. One or more sealing elements are combined in different possible arrangements to comply with the requirements.

Connections for a supply system are available. Due to the design features, a rolling bearing is not necessary but is optionally available.

The cartridge design makes the SeccoLip easy to install and safe to use. It is particularly suitable for a sliding velocity of up to 2 m/s (6 ft/s) and a pressure range of -1 to 6 barg.

The seal complies to ATEX, FDA and TA-Luft.

Watch the SeccoLip video here:


If you have questions about using any of EagleBurgmann’s products, visit their website: EagleBurgmann.  Or call +1 (713) 939 9515

Compression Packing: A Look Beyond the Standard Stuffing Box

Compression Packing

How this application fits as a versatile solution.

Stem packing is a familiar product. The most common type is braided compression packing. Braided packing is used in a wide range of applications. Depending on the service, construction materials can be as diverse as plants or animal derivatives, mineral fibers or synthetic plastics and even metal. The process of cutting rings from rope packing, inserting them into a stuffing box and torquing them to the right density is common, but it is not always the best choice.

Another widely used manufacturing method is die-molding. It is the process of wrapping a material around a mandrel, placing it in a die and preforming it to make a seal. Using these and other manufacturing technologies, packing is found to work in applications as different as aerospace, heavy trucking and power generation. A review of some unusual applications demonstrates the versatility of compression packing as a sealing solution.

The Origin of Packing

Compression packing is an ancient technology dating back more than 5,000 years. Boats and ships used a rudder as a steering mechanism. The rudder shaft penetrates the hull of the vessel below the water line, so water can leak into the bilge. Ancient sailors, using the top technology of the day, would take pieces of clothing, sail cloth and rope, cover it with animal fat or wax and stuff it into the gap around the shaft. Eventually, a box was secured around the shaft and a gland, which could be tightened to compress the packing material, was created to improve sealing and longevity. The terms compression packing, stuffing box and gland come from these early sailors.

Compression Packing

Over time, many improvements in packing construction and materials were made. Packing today can be made of flax, Kevlar, polytetrafluoroethylene (PTFE), graphite or metal. It typically has a square cross-section and is sold in precut rings or in large coils, as shown in Image 1. Synthetic aramid fibers are abrasionresistant and can handle higher temperatures and shaft speeds. PTFE has excellent lubricity and chemical resistance. Graphite coupled with mica or an aramid fiber can stave off the heat generated by a rotating shaft and provide long life in challenging applications.

Die-Formed Packing

Die-formed compression packings are excellent in terms of sealing Picture of a die formed ringperformance and reliability and offer a wide range of long-term, low-emission and low maintenance products. See Image 2.

Not only are die formed rings easier and quicker to install, but the  pre-compression increases the density of each ring and reduces the gland loads necessary to seat and compress multiple rings in the stuffing box. The result is lower friction on the shaft or the spindle, with improved sealing performance and a longer life.

Factor in STAMPS

As mentioned in an article previously published by the Fluid Sealing Association, (Sealing Sense, Pumps & Systems, March 2005), there are several key factors to consider when choosing the right packing. They include:

  • size or stuffing box bore
  • temperature inside the stuffing box application: whether it’s a pump, valve, mixer, refiner, process, characteristics such as pH level and chemical compatibility
  • motion: rotary, helical or reciprocal
  • pressure inside the stuffing box
  • surface speed expressed in feet per minute or meters per second

Keeping this in mind, here are some applications to consider when you are going way beyond the typical stuffing box: Continue reading Compression Packing: A Look Beyond the Standard Stuffing Box

How to Investigate Compression Packing Failure Modes

Over-tightening, excessive speed and improper installation can cause a system to falter.

In many respects, troubleshooting and failure analysis of compression packing materials is similar to the investigation of a crime scene. A good investigator knows how to gather clues from many different sources and put them together to understand what has happened. A good troubleshooter uses the same information gathering method, familiarizing themselves with the sealing materials, the process equipment and the systems where they are used.

Start by Interviewing Witnesses

The troubleshooter should seek information from the people who work with the equipment on a regular basis. Seal installers, maintenance personnel, operators, process engineers and others can all shed light on potential causes of failure. Some key questions should be:

  • How is failure defined? Some examples include excessive leakage, overheating, high rate of flush water consumption, excessive friction load and blowout.
  • Is this application the source of chronic seal failures, or was this an unexpected event?
  • Were there any changes to the seal material, the equipment or the overall process that preceded the failure?
  • Were there any system upsets or cleaning cycles that preceded the failure?
  • Can you describe the installation procedure?

Gather Information About the Victim

Knowing the limitations of the sealing product is a key step. The acronym “STAMPS” will help remember the key elements to ensure the right packing is selected for the application.

  • S: Size. Is the correct packing cross-section being used? Are the rings cut or formed to the correct length?
  • T: Temperature. Check the system temperature against the packing manufacturer’s established temperature ratings for the product.
  • A: Application. Some packings are made specifically for rotary equipment while others are intended for valves or static seals. Check to make sure the packing is suitable for the equipment where it is being used.
  • M: Media. This refers to the fluid being sealed. Check with the manufacturer or with compatibility charts to be sure the seal material is compatible with the media. If the media is slurry, abrasion-resistant materials may need to be specified. If the media is toxic, explosive or required to be contained within certain maximum allowable leakage requirements, then a packing must also be selected on the basis of its ability to seal at low leakage levels.
  • P: Pressure. Check the system pressure against the packing manufacturer’s established pressure ratings for the product.
  • S: Speed. Check the equipment speed against the packing manufacturer’s established surface speed ratings for the product. Surface speed is expressed in feet per minute or meters per second and not revolutions per minute.

Investigate the Crime Scene

When possible, observe the equipment while it is running. Can you see, hear, feel, smell or use a sensor to make observations? Smoke, vibration, grinding noises, the scent of burning fibers and system pressure fluctuations are only a few of the clues that can be noticed or measured while the equipment is up and running.

Examine the condition of the equipment. Most packings are robust seals that can handle less than perfect equipment condition, but there are limits to the amount of degradation they can withstand.

Valve stems and pump shafts or sleeves should be checked for scratches, corrosion pitting and general surface roughness. Rough surfaces can damage the sealing surface and result in excessive leakage and quick wear of the seal.

Extrusion of the seal material
Image 1. Extrusion of the seal material

Excessive clearances at the top or bottom of the stuffing box can lead to extrusion of the seal material and intrusion of large solid particle into the seal area (see image 1).

In severe cases, excessive clearance may result in a seal blowout.

Most packings are not meant to function as both a seal and a bearing. In rotating equipment, poor bearing condition may result in shaft runout that “wallows out” the inside diameter of the seal. Misalignment may result in shaft/stuffing box offset that causes one side of the packing set to be heavily compressed while the other side is compressed much more lightly. A similar side loading of a packing set can occur in large horizontally oriented valves where the packing is forced to bear the weight of the stem.

Check to make sure all the parts are in place. During the breakdown, repair and reassembly of equipment it is possible to misplace parts. Equipment might be put back into service without seat rings, bushings, lantern rings, O-rings and other parts that are essential to proper equipment operation.

Look at the seal and the equipment as a part of a big picture.

Consider how this piece of equipment is affected by other equipment and control devices in the system. For example, is there a downstream valve that creates pressure spikes in an upstream pump seal when the valve closes and the pump is still operating?

Continue reading How to Investigate Compression Packing Failure Modes