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What to Know, Avoid, and Consider When Planning Seals for Medical Devices

Seals are one of the most important components in many medical devices. While small in cost, seals for medical devices have a profound affect on the function of said device and the outcome of a medical procedure.

Engineered sealing solutions have advanced to meet the new medical device designs due both to new materials and to new processes for producing these seals. An understanding of the fundamentals of seal design, the tools available to assist in the manufacturing process and pitfalls to avoid will help in achieving a successful seal and medical device outcome.

Classifying the three basic seal designs

When approaching a new seal design, It is important to classify the seal based on its intended function. All seals fall into one of three distinct groups. While certain applications may combine more than one group, there is always one that is dominant. The three basic seal designs are:

Static — seal applications where there is no movement.
Reciprocating — seal applications where there is linear motion.
Rotary — seal applications where there is rotation.
Static seal applications are the most common and include those that prevent fluids and drugs from escaping into or out of a medical device. The seal design can range from basic O-rings to complex shapes. Static seals can be found in the broadest range of medical devices from pumps and blood separators to oxygen concentrators.

trocar design
New advances in trocar designs incorporating specialized seals allow multiple instruments to be inserted in the single trocar.

A reciprocating seal application with linear motion would include endoscopes that require trocar seals. These trocar seals are complex in design and allow the surgeon to insert and manipulate instruments to accomplish the medical procedure. These procedures range from relatively simple hernia repairs to the most difficult cardiac procedures. All of these minimally invasive surgeries employ endoscopes with seals that rely on seal stretch, durability and ability to retain shape during lengthy and arduous procedures. This particular seal application combines both reciprocating and rotary motion with the main function being linear motion.

A rotary seal application most commonly includes O-rings used to seal rotating shafts with the turning shaft passing through the inside dimension of the O-ring. Systems utilizing motors such as various types of scanning systems require rotary seals but there are many other non-motorized applications that also require rotary seals. The most important consideration in designing a rotary seal is the frictional heat buildup, with stretch, squeeze and application temperature limits also important.

Function of a particular seal design

What is the function of the seal? It is important to identify specifically if the design must seal a fluid and be impermeable to a particular fluid. Or will the seal transmit a fluid or gas, transmit energy, absorb energy and/or provide structural support of other components in device assembly. All of these factors and combinations need to be thoroughly examined and understood to arrive at successful seal design.

A seal’s operating environment

In what environment will a seal operate? Water, chemicals and solvents can cause shrinkage and deformation of a seal. It is important therefore to identify the short and long term effects of all environmental factors including oxygen, ozone, sunlight and alternating effects of wet/dry situations. Equally important are the effects of constant pressure or changing pressure cycle and dynamic stress causing potential seal deformation.

There are temperature limits in which a seal will function properly. Depending on the seal material and design, a rotary shaft seal generally would be limited to an operating temperature range between -30° F and +225°F. To further generalize, the ideal operating temperature for most seals is at room temperature.

Expected seal life – How long must the seal perform correctly?

Continue reading What to Know, Avoid, and Consider When Planning Seals for Medical Devices

Enhanced Surface Profiles for Gaskets

How this feature can improve performance and efficiency with gaskets

Gaskets have always been part of industrial production. However, gaskets have not always been forgiving, easy to use or simple to remove. What if the sealing products were designed to optimize the work put into them? What if the design had a level of intelligence built in? What if the design could make up for equipment damage? When used properly, enhanced surface profiles for gaskets can reduce leaks, spills and other releases that can damage the environment, put people at risk, result in fines and lead to costly downtime.

Using surface profiling to reduce area and increase stress is found in everyday life, from the soles of running shoes to the treads on vehicle tires. Reducing the contact area while maintaining compressive force results in increased stress. In the case of gaskets, traction or friction between a gasket and the flange faces is critical to holding internal pressure. If the downward force created by the fasteners in a flange is diluted or spread over a larger area, the overall stress is reduced.

Compressibility

Adding raised features to the surface of a gasket to reduce contact area and increase stress also tends to impact compressibility. Compressibility represents the ability of the gasket to conform to the surfaces it is being used to seal. Flange surfaces usually show signs of wear, pitting, scratches or other defects. It is cost-prohibitive to make two mating flange faces smooth and flat enough to seal without a gasket. The more compressible a gasket is, the better chance the user has of attaining an effective seal.

picture showing different gasket views
Image 1. (clockwise left to right) Traditional material sees heavier load around the gasket bolts and lighter load farther from the bolts. Image 2. Load distributed more evenly. Image 3. More stress toward the bolts. Image 4. Stress spread evenly around the gasket. (Images courtesy of Garlock)

Pressure Resistance

Compressibility also impacts the amount of pressure exposure on the gasket. When a flange assembly is pressurized, the internal media pushes outward on the inner diameter of the gasket. The thinner a gasket becomes, the less outward force it sees from internal pressure. This is referred to as improved “blowout resistance.” Unfortunately, one common error made when a gasket blows out is to replace it with a thicker gasket. This puts more gasket surface in the pipe or vessel for the internal pressure to act on.

Sealability

To create an effective seal, there are two functions the gasket must accomplish.

First, it needs to conform to the flange face to prevent the media from passing between itself and the flange faces. This is where the compressibility is important. Continue reading Enhanced Surface Profiles for Gaskets

Measuring Metal Hose Assembly Lengths

“Which way do I measure this metal hose?”

A common question among some customers who use metal hoses is: “Which way do I measure this metal hose?” Well, there’s a few different options.

  1. The first method is to measure the overall length of the assembly.
  2. Or, the live flexible length of the hose assembly can be measured.

Live Length vs Overall Length

Traditionally, the live length – or the amount picture showing live length versus overall lengthof flexible hose between the fitting – is used to determine whether there is sufficient hose length to accommodate a certain offset or movement, whereas the overall length of the assembly would be used to determine if the hose is going to fit in an application.

When measuring the overall length of the hose assembly, make sure to measure the overall length via end-of-fitting to end-of-fitting and if it has floating flanges on it, remember to measure to the face of the stub end on that floating flange.

JIC Swivel Fitting

If it’s a female JIC swivel fitting, however, it’s not necessary to measure the overall length to the end of the nut. Measure to the seat of the JIC inside the female swivel fitting. This is the standard for the metal hose industry.

Some customers may measure the overall diagram showing measurements with centerlinelength to the end of the JIC nut because some standards are measured differently by hydraulic manufacturers. If there are elbow fittings on the ends of the hose, metal hose industry standards dictate that measurements should be taken to the centerline of those elbow fittings rather than measuring the outside of the radius of the bend on those elbow fittings.

Laid flat with no kinks or bends

When measuring the length of a hose assembly, make sure it’s laid flat without any kinks or bends in the assembly. If it’s a strip wound hose assembly, ensure that strip wound hose is in its relaxed length, midway point between fully compressed and fully extended. Then, take the measurements on the length of that assembly.

For a great visual representation of measuring metal hose assembly lengths, watch this informative video below from Hose Master:


This video was produced by Hose Master and can be found on their Youtube channel or on their website.

For more information, contact Gallagher Fluid Seals or call 1-800-822-4063.

The Advantages of Crimped Can Seals

A combination of crimped can seals will handle a variety of applications when a rubber lip seal is not your solution.

Rotary seals are often secured in sealing hardware by crimping the sealing element in a metal can. One of the most common rotary seals is a molded rubber lip seal in a can. 

While not crimped, the can retains the sealing element, and stops the seal from rotating in the gland. Rotary sealing elements for low pressure (under 15 psi), are often nitrile or Viton rubber sealing elements.

This style of seal comes in many cross sections, and may include garter springs to help the seal stay engaged with the shaft. These seals are typically low in cost, and produced in high volume.

These seals are found in many low-pressure applications. However, as the pressures begin to climb over 10 psi and speeds run over 500 ft/min, friction generates heat, which accelerates wear on the rubber element and in turn begins to wear the mating shaft material.crimped can seal

Overcoming Friction

Friction or the resultant heat is the largest concern in rotary service.

The crimped can seal with PTFE (Teflon) elements can run with pressures in excess of 500 Psi and PV (pressure- velocity) reaching over 350,000psi-ft/ min. The crimped can allows these elements to remain secure.

The crimped case seal causes all the relative motion to remain at the sealing lip interface. With the crimped can, we have the opportunity to install multiple lips or seal cross sections to handle a variety of loads. This allows us to control leakage, and keep friction to a minimum.

We can seal most any fluid or run dry sealing gases with little or no lubrication. With widely varying temperatures, we can include springs to maintain seal contact, offset some eccentricity of shafts, keep dirt out or keep very light loads.

Continue reading The Advantages of Crimped Can Seals

Water Regulations and NSF 61 Compliant Elastomers

Replacing Aging Water Infrastructure With NSF Compliant Materials

There are over 155,000 public water systems in the United States and more than 286 million Americans who rely on community water systems daily.  Since most of the infrastructure was built between the early 1900’s and 1960 using outdated technology/products and capabilities, nearly everything is approaching the natural end of it’s lifespan.

Some estimates put the repairs and replacement of thePicture of NSF Compliant Gaskets infrastructure between $250B and $500B over the next 20-30 years. Several applications will need to be updated or fully replaced for the safety of consumers and quality of delivery, including:

  • Joining and sealing materials
  • Mechanical devices
  • Pipes or related products
  • Process media
  • Plumbing devices
  • Non-metallic potable water materials
  • Hydrants
  • and Public drinking water distribution (tanks and reservoirs, maters, individual components)

Joining and Sealing Materials

When these systems were being constructed and assembled decades ago, there were limited regulations and requirements that needed to be met. Gaskets, at least the traditional ones, were often made in two different ways: (1) Red Rubber (ASTM D1330 Grade 1 &2) with compressed non-asbestos or (2) cloth-inserted rubber with compressed asbestos.

However, today’s acceptable gasket requirements for the potable water industry differ greatly from those in the past. Gaskets have strict guidelines to abide by and must be:

  • Chemically resistant
  • NSF compliant
  • Food grade compliant
  • Electrically isolating

Because of the need for health and safety, the National Sanitation Foundation (NSF) was created in order to establish minimum requirements for the control of potential adverse human health effects from products that contact drinking water. In addition to gaskets, the NSF covers a variety of products and parts relevant to the water industry, including: pipes, hoses, fittings, cements, coatings, gaskets, adhesives, lubricants, media, water meters, valves, filters, faucets, fountains, and more.

So you might ask – why does the NSF require different materials and regulations for gaskets compared to years ago?

First things first – leaks are a major issue with the aging infrastructure. Improperly placed gaskets & seals or faulty products can cause leaks. This in turn could pose health risks to people drinking potable water or using products processed with potable water.

Additionally, the treatment process and chemicals utilized are Picture of NSF 61 Compliant Sealsdifferent from previous “standard” products. For example, research and testing over many years has concluded that traditional gaskets, which were used many years ago, could pose a safety threat to those drinking water processed with specific materials. This led to updated regulations for NSF 61’s drinking water system components.

Lastly, engineered sealing solutions are more important than ever. There’s a wide variety of custom engineered water systems throughout the U.S. – climate, geographic terrain, and the needs of the community are all reasons for why water infrastructure is so unique. Because of this, custom gaskets, seals, and other products are needed to supplement those systems.

Luckily there are many companies dedicated to providing the highest quality NSF 61 products. These trusted brands have proven materials to count-on when replacing or repairing water infrastructure:

Garlock’s NSF 61 Family of products

Parker’s NSF compliant products

Freudenberg’s new generation of NSF products

For more information on how Gallagher Fluid Seals’s engineers can help you with a custom solution, call us at 800.822.4063

A User’s Guide to Expansion Joint Control Units

Expansion Joint Control Units

Elongation settings are a vital factor to assembly effectiveness.

Diagram of Control Unit and Control Rod Components

It is no secret that one of the greatest demands for an expansion joint is the expectation to serve a long, leak-free life with little-to-no maintenance. Once installed, these flexible rubber connectors should require little attention. The preservation of this investment (and one’s sanity) can be maximized with an in-depth overview of how control units can prevent a new expansion joint from being overstressed.

The purpose of a control unit is to act as a safety device against excessive movement resulting from pressure thrust. A typical control unit assembly is comprised of threaded rods, steel gusset plates, nuts and washers (see Images 1 and 2).Diagram of Effects of Pressure Thrust

The usage of control units with an expansion joint is always beneficial; pressure spikes during a system upset can cause uncontrolled surges through the expansion joint. This is a prime example of how valuable it is to have control units installed to protect these rubber assets from damage.

Methods to the Madness

A common misconception about control units  is that they are designed to support the weight of pipe members or act as a substitute for adequate mounting. They are not. The sole purpose of a control unit is to allow the expansion joint to move freely within a specific range of movement while preventing the joint from being overstretched from pressure thrust forces.

The control units in no way impede the joint from performing its other duties beyond movement  (vibration absorption, cycling or compensation for misalignment). The few extra steps needed to install the control units with the expansion joint could pay notable dividends in the long run.

Pressure thrust plays a huge role in how an expansion joint functions. While under pressure, the forces acting on the inside walls of the expansion joint actually cause the joint to swell and elongate. In the real world, an expansion joint is held comfortably between two pipe flanges, which in most cases are restrained by a pump lagged to the floor or mounted to a structural beam. Although it may not be apparent to the naked eye, once the expansion joint sees pressure, it produces a thrust force that acts axially on both pipe flanges.

Theoretically, what would be the result if the expansion joint was unrestrained on each end while pressurized?

Without fixed ends, the pressure thrust would force the joint to elongate without bounds.

Most useful in high pressure applications, the control rods will  engage with the gusset plates once a pre-specified amount of growth for the expansion joint has been reached, restricting the joint from stretching any further. At this point, the control rods are absorbing any additional thrust  acting on the pipe flange, thus limiting the amount of stress that is exerted onto adjoining equipment.

The design theory for sizing control unit hardware is based on the pressure thrust. Nominal inside diameter (ID) and arch geometry of the expansion joint are key drivers for calculating the thrust force that will be applied to the pipe at maximum line pressure. Per

Arch Diameter Diagram

industry standards set by the Fluid Sealing Association (FSA), both control rods and gusset plates are designed to withstand no more than 65 percent of the yield strength of the material.

Magnitude of the pressure thrust can be calculated by knowing the internal pressure and the effective area of the expansion joint. Effective area is found using the arch diameter of the expansion joint, which takes into account the size of the arch.

For example, we can calculate the resulting pressure thrust for a 10-inch ID expansion joint using an arch height of 1.5 inches that is rated for a maximum pressure of 250 pounds per square inch (psi).

The equation for pressure thrust “T” is:

Equation for pressure thrust

These design limitations based around yield stress are the reasons why some control units made from lower yield strength stainless steel contain thicker components or more rods per set than the standard carbon steel control units.

Installation & Inspection

For a control unit assembly to be effective, rod positioning and elongation settings are critical during installation. Each control rod should be evenly spaced around the flange to best distribute the load. Elongation settings (see Image 5) are often overlooked, yet are a vital factor to ensure the control units fulfill their intended use.

Every expansion joint comes with movement ratings based on arch size, configuration and number. These movement design ratings of the expansion joint are critical pieces of information that are absolutely required during the installation of control units. The general rule of thumb is the gap between the gusset plate and the nut should be adjusted to match the joint’s elongation rating.

Having this information at hand during installation is great, but what about the existing control units currently in operation? Visual inspections of these components are a basic task that goes a long way toward extending the life of the joint.

Here are the top 4 anomalies to look for when performing a field inspection: Continue reading A User’s Guide to Expansion Joint Control Units

Gallagher Fluid Seals Acquires Quality Seals

Acquisition will help expand Gallagher’s industry-leading service and capabilities

Gallagher Fluid Seals, Inc., a global distributor and manufacturer of fluid sealing products located in the Greater Philadelphia area recently made an acquisition to further expand it’s industry-leading service and capabilities.

On January 2, 2019, Gallagher Fluid Seals, Inc. acquired Quality Seals based out of Bethel, Connecticut. The entire Gallagher team is excited about bringing in the Quality Seals family to start the new year.

The transition for Quality Seals’ existing customers will be smooth and precise. For those existing customers, they will continue to be serviced by members of the Bethel, Connecticut office.

This strategic acquisition will give customers – from both companies – the ability to explore new product lines while simultaneously allowing greater access to existing products & partners. It will also open a custom engineering channel to both new and existing customers of Quality Seals; they will now be able to utilize Gallagher’s Engineering Department for tailored solutions to their most difficult and challenging applications.

About Gallagher Fluid Seals, Inc.

Gallagher Fluid Seals, Inc. is a global distributor and manufacturer of Fluid Sealing products. Gallagher represents the strongest seal manufacturers in the world, in addition to operating its own gasket fabrication facility. Gallagher serves both OEM & MRO customers through the development of technical solutions that solve sealing challenges.

Gallagher Fluid Seals currently operates 3 Facilities; its headquarters in King of Prussia Pennsylvania, and it’s 40,000 square foot gasket fabrication and sales office in East Longmeadow, Massachusetts, and the newly-acquired Quality Seals office in Bethel, Connecticut.


For more information, check out our press release.

Do’s and Don’t of Installing Metal Hoses (Part 1)

Metal Hose Applications

Metal hose applications can be tricky. Hoses can fail or have a variety of other problems due to a few different factors: improper installations or outside factors from the surrounding piping system. In this video, Erik Kane, Hose Master’s Product Specialist, discusses various do’s and don’ts when installing metal hose. Follow these tips and more to help maximize the life of your hose and optimize your safety.

This video was produced by Hose Master and can be found on their Youtube channel or on their website.

85 Years of the Simmerring®

Small, nondescript and ostensibly unspectacular – it is often developments of this exact description that lead to groundbreaking innovations in the world of technology. The idea of manufacturing seal sleeves from leather scraps became the starting point in one of the most important developments in sealing technology: the Simmerring®. For 85 years, the Simmerring has been inseparable from the Freudenberg history of success, and, in Europe, its name has even become a synonym for (radial) shaft seal rings of every kind. Today the Simmerring is a high-tech product whose key functions go far beyond the sealing of the shaft against its housing.

Freudenberg SimmerringIt all started with the economic crisis of 1929, which plunged the leather industry and thus the Freudenberg tannery – which was founded in 1849 – into difficulties. To better distribute its risks in the future, Freudenberg began to diversify the company and serve a broader market. A sample of a leather sleeve from the United States was the inspiration for giving Walther Simmer and his team the job of developing a machine that could be used to produce lip seals made of leather scraps.

Continue reading 85 Years of the Simmerring®

New Sealing Material HiFluor® FB

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.
Original content can be found on Parker’s Blog.


New Sealing Material HiFluor® FB for Hygienically Sensitive Applications

HiFluor® FB - Hygienically Sensitive Sealing MaterialBe it in the production of food, pharmaceuticals and cosmetics or medical devices coming into contact with the human body, excellent purity and media resistance combined with a wide range of robust properties is always required of the materials used for the components in the manufacturing processes. Specifically for these challenging applications, Parker has developed a new sealing compound with very good mechanical properties and excellent permanent elasticity: HiFluor® FB V8991.

Fluoroelastomeric materials have proven their viability in chemical and food processing, cosmetics, pharmaceutical and life science applications involving non-polar solvents, aliphatic compounds, greases, oils and aromatic substances whenever the resistance of standard materials such as hydrogenated nitrile butadiene rubber (HNBR) and ethylene propylene rubber (EPDM) is no longer sufficient.

Innovative “Pure” Sealing Solution HiFluor® FB V8991

As a compound and seal manufacturer, Parker Prädifa, in the light of the growing demands made on sealing elements in the aforementioned markets, has developed a HiFluor® FB compound with very good mechanical properties and excellent permanent elasticity.

Continue reading New Sealing Material HiFluor® FB