Designing with inflatable seals for the medical industry
Seals are central parts of the design of medical equipment with moveable, interlocking parts that must be secured for sanitary, thermal, or radioactive reasons.
Designing with inflatable seals requires the inclusion of a source of compressed gas, which is used to inflate seals in the medical device industry and it is often already available on the plant floor, in a laboratory, or medical environment. It is also possible to inflate with liquids rather than gas in demanding applications, and water would be an acceptable inflation media in this sector, although not common. For some low-temperature applications, a seal may be inflated with a blend of glycerine and water.
Designing with inflatable seals
Seals used on doors and openings should be part of the early phases of product design. In some cases, contact seals may be effective, but they often require substantial force be applied to load the seal, which impacts product design and increases manufacturing cost. Inflatable seals enable more cost-effective machinery fabrication for two reasons:
Inflatable seals are more forgiving because the seal can inflate to close a gap between structural members and achieve equal sealing pressure around the flange as long if the gap falls within a broad tolerance. An inflatable seal will work whether the gap spans 3mm or 10mm, for instance. A compression seal or other contact seal will not be effective unless the seal and flange contact each other with great precision, which can be difficult to achieve on new equipment. Even a robust and precision-manufactured machine with well-designed flanges will lose some of its geometric integrity as hinges and other components deform or bend over years of use. Throughout the course of the equipment lifecycle, a contact seal may become problematic and exhibit leakage.
Inflatable seals enable lighter and more affordable methods of equipment fabrication. The force exerted on the chassis of a piece of equipment means doors and related components must be thicker, and perhaps machined instead of welded. These components are typically made of stainless steel, and inflatable seals might be attractive due to lowered material costs.
Which equipment needs inflatable seals?
Isolators — where a leak-tight enclosure can be critical for environmental health protection due to hazardous substances or processes. — can secure glove boxes, access gates, transfer systems and filtration systems that handle toxic or sterile components.
Sterilizers — which may rely on heat, chemicals, irradiation, or filtration — may be suitable for desktop autoclave sterilizers, sterilizing tabletop autoclaves and static air depyrogenation sterilizers.
Dryers and freeze dryers – used to sterilize everything from machine components to glassware.
Material handling functions – to raise, lower, or grasp objects.
Original content can be found on Parker’s Websiteand was written by members of the O-Ring & Engineered Seals Division. Jacob Ballard – research and development engineer, Jason Fairbanks – market manager, and Nathaniel Sowder – business development engineer.
The emergence of degradable and dissolvable materials is providing oilfield service companies an opportunity to increase efficiencies and cut costs in the oilfield by simplifying well completions. These materials replace their conventional metallic and polymeric counterparts in completion tools, but eventually break down and disperse when exposed to common completion fluids. This eliminates the need for well interventions to mill out or retrieve used tools. This can result in a reduction of drill time, a safer work environment, and monetary savings for the operator. Parker Hannifin produces dissolvable and degradable metal alloys, thermoplastics, and elastomeric materials that can enhance your well completions.
Parker O-Ring and Engineered Seals (OES) Division produces degradable elastomer formulations that can be used in frac plugs, liner wipers, and other sealing applications common in the completions segment. These elastomer formulas have tough physical properties and low compression set and are designed to replace materials such as Nitrile or HNBR in conventional tool designs. With proper design, tools using Parker degradable elastomer can withstand the high pressures (>8,000 psi) generated during hydraulic fracturing while still eventually deteriorating away, allowing well production without having to be drilled out. These degradable elastomers can be produced in a variety of desired forms such as O-rings, custom molded shapes, and packing elements. They can also be bonded to dissolvable metal alloys to produce completely degradable solutions. If needed, Parker offers a product engineering team to assist with the design of components and rapid prototyping services to help cut down on development timelines.
Parker Engineered Polymer Systems (EPS) Divisionmanufactures engineered degradable Thermoplastic materials which can be used in many types of completion tools that traditionally use non-degradable elastomers. Parker EPS’s high-grade thermoplastic materials have increased physical properties over conventional elastomers making it ideal for both high pressure/high temperature and wear resistant applications. The increased physical properties of EPS thermoplastics provide enhanced resistance to extrusion, temperature and wear over most degradable non-metallics in the market. These unique thermoplastic materials may be manufactured in both homogenous as well as bonded components such as Packers, Parker back-up rings, Frac Plugs and liner wipers and are ideal for hot trouble well applications.
With a wide range of wellbore temperatures and completion fluids seen across the industry, selecting the right degradable compound can be complicated. Gallagher Fluid Seals, in coordination with Parker, can help assist in recommending the proper paramaters for using degradable elastomers.
DiamondFace is an innovative microcrystalline diamond coating for mechanical seals. It is extremely hard and offers high wear protection, excellent heat conductivity, maximum chemical resistance and low friction. The coating adhesion also exceeds all known practical requirements. This increases the service life of mechanical seals several times over, the maintenance intervals are extended accordingly and the life cycle costs are greatly reduced.
The diamond thin-layer technology was developed in 2007 by EagleBurgmann together with the Fraunhofer Institute for Surface Engineering and Thin Films (IST), the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Fraunhofer Institute for Mechanics of Materials (IWM), the Condias GmbH, and the Forschungszentrum Jülich. EagleBurgmann has established DiamondFace for mechanical seals as a series-produced product – the very first on the market.
The technology behind it is a microcrystalline diamond layer up to 15 μm thick which is applied to the seal face under vacuum at temperatures of 2,000 °C (3,632 °F) by chemical vapor deposition (CVD). The properties of this diamond layer are where you benefit. Primarily from its extreme hardness and robustness.
Increased Service Life of Mechanical Seals Mechanical seals are a factor that has a decisive effect on the cost-effectiveness of your operation because their wear determines the productivity of the entire system, whether it is a pump, agitator or compressor. What causes damage to the seal faces? One reason is dry running which is often unavoidable due to insufficient lubrication or when gas-lubricated seal faces get in contact. The resulting temperature rise causes the seal to wear. And ultimately results in system downtimes.
EagleBurgmann has solved this problem which directly affects the success of your plant. Thanks to DiamondFace, the service life of mechanical seals is increased several times over, the maintenance intervals are extended accordingly and the life cycle costs are greatly reduced. The advantages for the operator are clear: Continue reading DiamondFace by EagleBurgmann – Innovative Sealing Technology→
Recent gasket failures in flanged joints of High Density Polyethylene (HDPE) piping.
HDPE piping joints are typically thermal fusion welded joints, but flanges may also be used. When flanges are used, an HDPE flange adapter with a metal backing ring is fused to HDPE piping, as shown in Figure 1. The HDPE flange adapters are used to connect to other flanged fittings, such as valves, elbows, tees, etc., with gaskets inserted between the flanged fittings.
In 2018, two HDPE flange adapter gaskets on two different valves that were part of an underground fire suppression system at a Department of Energy (DOE) nuclear facility in Amarillo, TX failed, causing several weeks of unplanned interruptions to nuclear facility operations. Fire suppression water was isolated to two nuclear facilities, requiring nuclear operations to be paused and fire watches to be established. Both couplings were installed by the same contractor and had been in service for approximately eight years. Both flanges were correctly torqued to 160 foot-pounds with no indication of the necessary re-torque. The initial failure of the gasket caused a low flow, high-pressure leak that was not detected for some time. With the system pressure operating at approximately 150 pounds per square inch (psi), the orifice created by the failure of the gasket(s) between the two flanged faces created a water jet, which eroded the metal valve flange and bolts.
Because HDPE will relax after the flange bolts are torqued, a re-torque after 24 hours is required. Even after the bolts are re-torqued, the face stresses drop to 400–600 psi. The lower face stress reduces the friction for maintaining the gasket in between the flange faces. The challenge is finding a gasket that can handle pressures that may exceed 200 psi, gauge (psig), but also seal well at relatively low stresses.
Due to the many inquiries from customers and engineering firms for gasket applications involving HDPE piping, Garlock, a gasket manufacturer, published a memo in January 2017 recommending using either GYLON® Style 3545 or MULTI-SWELL™ Styles 3760/3760U as the best options for HDPE flanges, even though the available compressive loads are lower than recommended. The reinforced gasket material of the GYLON and MULTI-SWELL has proven to prevent the internal water pressure from damaging the gasket under low-compression loads.
Other gasket manufacturers may have similar gaskets that will work for this application. It is important for the Design Engineer to work with the gasket manufacturer to properly specify the correct gasket.
Recommendations to HPDE Piping and Flanged Joints
When using HPDE piping with flanged joints, ensure that the flange bolts are re-torqued at least 24 hours after gasket installation.
When evaluating gasket material, be sure to include any surge pressure that could be caused by opening valve and starting pumps. Also, include any additional design/safety factors in your gasket calculation. And, directly work with the gasket manufacturer in making a selection.
A Lubrication Leak Doesn’t Always Mean a Seal Failure
A well-known technique for increasing pump reliability is sealing the bearing housing with non-contacting bearing isolators rather than contact seals. Because contact seals use contact as their sealing method, they have a more limited life expectancy, since they can wear at the point of contact or groove the shaft. When this occurs, lubricant will escape to atmosphere and contaminants will enter the bearing housing, leading to bearing failure. Though more expensive, bearing isolators effectively retain lubricants and exclude contaminants while providing a virtually infinite life expectancy. This increases mean time between repair (MTBR).
The most common perception of bearing housing seal failure on process pumps is lubricating oil leaking from the bearing housing. For most operators, the analysis is simple: no leaking oil means the seal is fine while leaking oil equates to failure. Though true for contact seals, the presence of leaking oil from a bearing isolator is most likely due to factors other than seal failure.
Following are some of the more common causes of bearing isolator lubricant leakage in process pumps.
Common Causes of Bearing Isolator Lubricant Leakage
1. Too Much Oil
It seems simple, but the greatest cause of bearing isolator leakage on process pumps is an over-filled bearing housing. It has become common practice for maintenance professionals to fill up to, if not a bit over, the maximum fill line. The thinking is that if leakage occurs, there will be extra lubricant available. This practice can inadvertently contribute to leakage. Fortunately, once returned to the proper level, bearing isolators will generally stop leaking and return to normal function. There may be some oil leakage as the seal clears itself of excess lubricant, but that should diminish over time.
Most bearing isolators have a lubricant return designed into their respective labyrinth patterns. This return needs to be installed at the bottom dead-center or six o’clock position of the bearing isolator for proper function. This allows oil to easily return to the sump. One of the most common causes of improper seal orientation is a lack of training or unclear installation instructions.
3. Obstructed Lubricant Return Path
Most modern bearing isolators are effective at collecting splash lubricant in their respective labyrinth patterns. Once they have collected the lubricant, they need a clear, unobstructed path to return collected lubricant back to sump. But the return path to the sump may be blocked by counter-bores in the housing, which were originally designed to provide a positive stop for pressed-in lip seals. The area between the bearing and the bearing housing seal may lack a drain channel. When this occurs, lubricant will accumulate in this area until the space becomes completely flooded and the seal leaks. To solve this, the area between the bearing and the bearing isolator must include an unobstructed return pathway to the sump. Relying on the lubricant to drain to sump only through the bearing will likely result in lubricant leakage.
4. Improperly Applied External Oilers
External oilers are extremely sensitive to position and must be installed on the proper side of the housing relative to the direction of shaft rotation following the manufacturer’s guidelines. Oilers must also be installed square and straight. The pipe connecting the external oiler to the bearing housing must also be sufficiently ridged to prevent vibration or shaking the oiler. Questionable installations of may result in over-filling of the bearing housing and subsequent lubricant leakage.
The forceful flow of air over a bearing housing can cause lubricant leakage by creating a pressure differential between the inside and outside of the bearing housing. Couplings and external cooling fans attached to pump bearing housings are a potential source of harmful air flow. Gapless, solid coupling guards that enclose the bearing housing seals with little or no gap around the bearing housing may induce leakage. While taking all required safety precautions, having some of the coupling and fan guarding accomplished by tight grating, rather than solid surfaces, allows for better air flow and helps prevent pressure from building.
6. Improper Non-Contact Seal Selection
Some bearing isolators are designed specifically for grease lubrication, others for oil or oil mist. There are some designs that can handle all lubrication types in a single design. In some instances, benefits can be achieved by designing bearing isolators for specific applications rather than relying on standard catalog items. For example, in pump bearing housings with a high degree of lubricant splash, designing the labyrinth pattern to communicate directly with the lubricant return path can greatly increase effectiveness. Experienced bearing isolator providers can design engineered-to-order seals quickly and economically, and ensure the seal design addresses any concerns and is applied to provide the best reliability possible. Time spent on up-front engineering tasks is well worth the effort, and assures the bearing isolators will perform as intended.
The advantage of non-wearing bearing isolators is that once properly applied, they perform essentially trouble-free for years with no degradation in performance. The challenge is that they require a bit more attention to application details. Taking the time to check a few simple parameters will go a long way towards ensuring trouble-free operation.
Rare and Ultra-Pure Resources Present Unique Challenge to Finding Appropriate Low Temp Gasket
Modern technology often requires rare or ultra-pure materials that can only be handled or obtained within extreme environmental conditions. These same conditions present unique and hazardous difficulties when transporting or utilizing these resources. Resources such as liquid oxygen, nitrogen, or argon; all of which are classified as “industrial gases” are handled well below the normal temperature ranges that every-day liquids exist; ranging as low as -195.8°C (-320.4°F). This often makes it a challenging task to find a low temp gasket to fit the specifications for the application.
As an example, let’s look at argon; an important gas used in Welding, Neon Lights, 3D Printing, and Metal Production, just to name a few. It is far more economical to house and transport argon in its liquid state. However, it must be held at an astonishingly low -185.9°C. Fitting the pipes together and maintaining a seal in a cryogenically engineered system that the liquid argon is housed presents unique difficulties. Argon gas is colorless, odorless, tasteless, and can irritate the skin and the eyes on contact. In its liquid form it can cause frostbite.
There are important considerations that should be taken into account when installing gaskets for dangerous extreme low temp materials.
Proper Gasket Installation
Many gasket materials can become brittle, crack, shrink, and blow out when exposed to extreme cold – not something you want to happen at any time, let alone with a liquid that can freeze you into a meatsickle. So, proper installation is also key. During installation, it is important that all parts are dry, the installation is done at ambient temperature, and then re-adjusted with changes in temperature.
Any mechanical seal that is sealing a product with a temperature below 0 degrees Celsius is given the name “Cryogenic”. Liquefied gases (LNG), such as liquid nitrogen and liquid helium, are used in many cryogenic applications, as well as hydrocarbons with low freezing points, refrigerants and coolants.
When selecting a low temp gasket or sealing material to be used in cryogenic service, it is important that the material can withstand cryogenic temperatures.
Low temperature applications are found across many industries, these include:
Garlock GYLON® and KLINGER SLS/HL
Good gasketing materials that can withstand the frigid cold and are pliable in the requirement to maintain the seal would be the Garlock GYLON family of gaskets (PTFE, capable of -450°F (-268°C)) or the Klinger SLS/HL, which is made of flexible graphite and can withstand -400°F (-240°C)
As with all gasket applications, environmental conditions should be considered in conjunction with the functional requirements of the device. Though there are limited options to solve extreme low temp gasketing challenges, Gylon and Klinger can be a good fit for your application.
Portions of the original article were written by Michael Pawlowski and Sylvia Flegg of Triangle Fluid Controls Ltd. The article can be found on Empowering Pumps website here.
A sealing system, consisting of a mechanical seal and an associated supply system that is balanced by individual applications, is the utmost guarantee for a reliable sealing point and uninterrupted pump service. The performance of the seal is greatly influenced by the environment around the seal faces, making the provision of suitable, clean fluids as well as a moderate temperature an essential topic.
This guiding booklet provides a condensed overview of all piping plans established by the API 682 4th edition guidelines. Each illustrated piping plan is briefly described, and a recommendation that considers the media characteristics in terms of the relevant application and corresponding configurations is given to help you reliably select your sealing system. Furthermore, the content of this booklet has been enriched by providing clues – so-called ‘remarks and checkpoints’ – where EagleBurgmann shares the experiences gained from multiple equipped plants.
Sealing solutions to meet any requirement
Several factors play a major role when choosing the product, the product type, the materials used and how it is operated: process conditions at the sealing location, operating conditions and the medium to be sealed.
No matter what requirements our customers have, EagleBurgmann understands how these factors affect functionality and economic viability, and they translate this expertise into outstanding long-term, reliable sealing solutions. EagleBurgmann has all the expertise needed to manage and support the entire development, life and service cycle of its sealing solutions.
EagleBurgmann and API 682
EagleBurgmann offers customers the widest product portfolio of seals and seal supply systems according to API 682 4th edition. The configurations listed for each individual piping plan are to be understood as recommendations including possible utilizations which may also be applied.
EagleBurgmann is one of the internationally leading companies for industrial sealing technology. Their products are used wherever safety and reliability are important: in the oil and gas industry, refining technology, the petrochemical, chemical and pharmaceutical industries, food processing, power, water, mining, pulp & paper and many others. More than 6,000 employees contribute their ideas, solutions and commitment towards ensuring that customers all over the world can rely on their seals and services. More than 21,000 EagleBurgmann API-seals and systems are installed world-wide.
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.
The 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.
The GYLON® Style 3504 gasket is made of PTFE with aluminosilicate microspheres. It is designed for use in many acids, some caustics, hydrocarbons, refrigerants, and more.
The Garlock 3545 style is a highly compressible microcellular PTFE with a rigid PTFE core for improved handlability. Garlock 3545, made with Gylon material, is designed to compress and conform to irregular or damaged surfaces, making it suitable for flanges that generate lower compressive stresses, such and glass-lined flanges and equipment.
Food & Beverage – Wine Production
An award-winning, family owned & operated winery in the heart of a major US wine-growing region.
The customer crushes, presses, ferments, bottles, and labels all of their wines at their winery, but having traditionally utilized EPDM gaskets, they faced ongoing issues with seal reliability. This was occurring during various stages of the winemaking process, but especially so during the sterilization procedures between each batch, with subsequent leaks creating issues in production reliability, housekeeping, and potential contamination.
Business was growing rapidly so new equipment had been installed, but at the same time the number of maintenance windows was reducing. Therefore the customer was looking for a more reliable and sanitary product to improve efficiency and help to protect the sensitive product. As well as the need to remain absolutely compliant with industry standards, the customer also placed utmost importance on prevention of any adulteration of their award-winning wine. As well as working around limited windows of opportunity for production trials the critical and expert opinion of wine tasters was therefore essential to ensure full approval of any component change in the process.
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.
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).