Why an Extrusion Gap is Important

“How much pressure can this seal handle?”

The answer to this question depends on a number of parameters and conditions. But the principle limiting factor in the pressure handling of any seal system is the extrusion gap.

Commonly referred to as the “E-Gap,” the extrusion gap is one of the most critical design aspects in any high-pressure application. Seal design, type, and material are all influenced by the extrusion gap and the desired pressure handling capability.

What exactly is an extrusion gap, and why is it so important in the successful design of a sealing system? Let’s find out.

The Basics: What is an Extrusion Gap?

In terms of sealing systems, the extrusion gap is defined as the clearance between the hardware components.

In a piston configuration, this would be the clearance between the piston and bore. In a rod configuration, this is the clearance between the rod and housing it’s passing through.

The extrusion gap can be expressed in terms of radial or diametral clearance, which can lead to some confusion. Our partners at Eclipse define the E-Gap by stating it as the radial clearance. The radial clearance is equal to the diametral clearance divided by two.


It’s important to note that while hardware components might be machined to have a specified clearance, this gap might not be perfectly realized or maintained. Continue reading Why an Extrusion Gap is Important

Customers Find Unbeatable Bearings When Using Vesconite

Moves away from bronze and rubber bearings have boosted the expansion and usage of Vesconite Hilube across the world. Vesconite lasts longer, wears less, requires less maintenance, and doesn’t require lubrication. This makes it suitable for different applications, in different industries, and on different continents.

Take the U.S. market for example.

“A state like California has banned lead so you cannot sell a bronze product. People have to find an alternative,” says Vesconite Bearings’ technical representative, Charlie Simpson. “Vesconite is getting more and more business as people move away from bronze and rubber bearings.”

Earthmoving - Vesconite BearingsVesconite doesn’t need lubrication which helps bearings last longer

Simpson says Vesconite has seen steady growth in sales from the US over the last two years. Some of this is due to the need for an alternative product; much is due to the benefits of the product, such as increased efficiency.

Simpson says the companies in the US are willing to test and try new things. “If they can get five percent more efficiency they will go for it.”

Because Vesconite doesn’t need lubrication, bearings last longer. That means less downtime, less maintenance and fewer stoppages. The end result is increased efficiency. Continue reading Customers Find Unbeatable Bearings When Using Vesconite

Kalrez® O-rings for Hydrogen Sulfide Removal

Kalrez Perfluoroelastomer Seals: Authorized DistributorAmine treatment is a process typically used for Hydrogen Sulfide removal from natural gas (sour gas). This operation is commonly referred to as gas “sweetening,” acid gas removal, or amine scrubbing

Amine units are used all over the world in oil refineries and gas plants to remove hydrogen sulfide (H2S) from a product stream. New environmental standards are more strict and require ever-decreasing contents of H2S in clean natural gas. Most of the new sources of oil and gas discovered today have high contents of H2S which demand more efficient removal technologies (the Shah Gas field in the United Arab Emirates for example has up to 30%  H2S).

The Challenge of Amine Units in Harsh Chemical Environments

Amine units operate under harsh chemical environments. H2S for example, needs to be handled with care and can cause embrittlement of metal equipment. These processes also operate at high temperature where perfluoroelastomer sealing components are required. Amines, however, are known to be aggressive to many FFKMs. When elastomers are in contact with amines, they tend to swell to a high degree, which results in a loss of mechanical properties and extrusion. This can lead to leakage, rupture of the fluid film in mechanical seals due to face seal deformation, and an increase in torque needed to operate.

Solution: Kalrez 6380 for Lower Swell Properties

kalrez spectrum o-rings

DuPont™ Kalrez® Spectrum™ 6380 perfluoroelastomer parts offer outstanding resistance to amines because it exhibits four times lower swell over general purpose perfluoroelastomer (FFKM) offerings.

The use of DuPont™ Kalrez  Spectrum™ 6380 parts in these applications may extend the MTBR (Mean Time Between Repairs) of valves and pump mechanical seals and reduce leakage which can help contribute to reduce maintenance costs and lower emissions. The latest Kalrez 0090 parts represent another option for this application when high pressure resistance is needed. The following graph compares the chemical resistance of Kalrez Spectrum™ 6380 to other sealing materials when exposed to a typical amine/water mixture used in gas sweetening units.

picture of volume swell FFKM

Gallagher Fluid Seals is an authorized distributor and partner of Dupont Kalrez®. For more information or if you have a project / application where you need assistance, contact us today.

The original article was written by staff at Dupont and can be found here.

Using Metal Seals for High Temperature or High Pressure Situations

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

Original content can be found on Parker’s Website and was written by Vivek Sarasam, heavy duty mobile Sr. application engineer, and Jeffrey Labonte, market manager.

Parker Hannifin Engineered Materials Group has developed a wide variety of metal seals which can be formed or machined. A metal seal is a highly engineered sealing solution which provides elastic recovery or spring back to maintain good sealing, despite separation of mating surfaces due to effects of thermal cycling, flange rotation, applied mechanical or hydrostatic loads or creep.

Why use a metal seal?

A metal seal is used when the application conditions are outside the specification limits of a polymer. For example, when:

Temperature is too hot or too cold & pressure is too high or there is a vacuum.

Metal Seals are primarily used in static applications for temperatures as high as 1000°C/1832°F and pressures as high as 6825 bar/99000 psi for select applications. At low cryogenic temperatures and low pressures, such as vacuum seal applications, metal seals are far better than polymers since they do not become brittle and lose elasticity. Metal seals also have a low leakage rate down to 1 x 10-12 cc/sec per mm circumference which in comparison to high load O-rings is almost 100x better.

Medium is corrosive and seal longevity is needed.

Unlike elastomer seals, metal seals are very highly resilient to corrosive chemicals and even intense levels of radiation. With this resilience coupled with the right material selection/coating for an application, a metal seal can be a very durable seal performing dependably year after year.

Parker has a variety of in-house developed coatings which are used based on the application conditions and base material. The chart on page D-59 of the Metal Seal Design Guide (shown below) shows examples of some of the coatings based on the base material.

What X-sections can be made?

Metal seal x-sections can vary from a solid O to a Hollow O and from a C Ring to an E Ring depending on the application load and allowable leakage rate as shown in the figure below. Each x-section has benefits based on the application use and cost as indicated in the chart below.

Page A-10 of the Metal Seal Design Guide (shown below) shows some common applications in the industry and the type of metal seal used in those applications. These are examples of applications where the application conditions exceed beyond what an elastomer is capable of handling.

Importance of surface finish for metal seal applications

Continue reading Using Metal Seals for High Temperature or High Pressure Situations

Garlock Style 215 Helps Steel Products Manufacturer

Garlock Style 215 Helps Steel Products Manufacturer With Harsh Acids

picture of garlock style 215 expansion jointGarlock Style 215 Expansion Joints are PTFE concentric spool-type flexible couplings that are designed to reduce noise and compensate for expansion, contraction, and minor piping misalignment in chemical processing, air conditioning, and heating systems.

The complete assembly includes a fluorocarbon resin PTFE body, electroless nickle-plated ductile iron flanges, polyethylene-covered restriction zinc plated bolts, and stainless steel corrosion-resistant reinforcing rings.

Case Study


Primary Metals


South American manufacturer of flat and long steel products


Construction of two new facilities including a hot rolling mill.


The plant was in need of expansion joints that could handle chemicals on their pickling lines. Pickling is a metal surface treatment used to remove impurities, such as stains, inorganic contaminants, rust or scale from ferrous metals. A solution called pickle liquor, which contains strong acids, is used to remove the surface impurities. It is commonly used to clean steel in various steel making processes. The line required an expansion joint with a PTFE tube to handle the pickle liquor which included hydrochloric and sulfuric acid, but a very short overall length for installation.

Continue reading Garlock Style 215 Helps Steel Products Manufacturer

GORE Universal Pipe Gaskets Have Great Success in Aggressive Media Applications

Fiber Reinforced Plastic (FRP) pipes and flanges are increasingly used in the oil and gas industry where metal is simply too heavy and expensive. In addition to cost pressure, the need for lightweight chemically resistant materials are also driving the use of fiberglass pipes  and flanges. Innovations in FRP flange design coupled with improvements in manufacturing technology have allowed FRP piping to be used in even more demanding applications. However, these demanding applications have added challenges for sealing the bolted flange connections.

More aggressive media and higher internal pressures have pushed the limits of the commonly used rubber gasketing materials, such as Nitrile Butadiene Rubber (NBR), Ethylene Propylene Diene Monomer (EPDM), or neoprene. Obtaining a reliable seal in FRP flanges using conventional gasketing materials has become more difficult.

Fiberglass pipes are generally known to have strength limits and a lower pressure resistance, making sealing fiberglass flanges difficult. Gore solved this problem with its patented expanded polytetrafluoroethylene (ePTFE) gasket, specifically designed to seal flanges at low stresses. This solution was successfully demonstrated in a multistage testing procedure conducted in cooperation with a globally leading manufacturer of anti-corrosive fiberglass pipe systems. Continue reading GORE Universal Pipe Gaskets Have Great Success in Aggressive Media Applications

Improving Heat Transfer in Shell-and-Tube Heat Exchangers

Shell-and-tube heat exchangers with removable tube bundles require that manufacturing clearances are present to facilitate the insertion and removal of the tube bundles for maintenance, repair or cleaning purposes.

For heat exchangers designed for multipass flows within the shell — for example, Tubular Exchanger Manufacturers Association  standard shell types F, G and H — it is common to incorporate a longitudinal baffle plate within the tube bundle design. These plates direct the shell fluid flow in desired directions to increase the
dwell time of the fluid while in contact with the tubes, thereby  increasing the heat transfer effectiveness of the exchanger.

Due to the manufactured component clearances, repair operations, and possible wear and tear, there is often a substantial gap between the edge of the baffle plate and the inside diameter of the shell. This gap creates a natural path for the shell fluid flow to deviate from the intended flow direction, effectively shortening the dwell time in the exchanger and thereby decreasing heat transfer efficiency.

KLINGER manufactures and supplies a range of metallic baffle seals with leaf-like lamellae to effectively seal any gaps between the longitudinal baffle plate and the shell’s inside diameter. Virtually no bypassing occurs, and the shell fluid flow is forced to follow its intended directional path. The result is an increase in the heat transfer effectiveness of the exchanger.

Heat transfer efficiencies could increase by up to 10 percent using a baffle seal arrangement.

picture of bundles

Increases in thermal transfer efficiency result in reduced energy costs and ultimately provide operational cost savings. Depending on the gap dimensions and condition of the components, heat transfer efficiencies could increase by up to 10 percent using a baffle seal arrangement.

A different sealing design concept is applied to the gaps between any single segmental transverse baffle plates that may be present on tube bundles and the shell’s inside diameter. In this instance, a compressible wire mesh packing is used within a holder, which itself is wrapped around the outer circumference of the baffle plate to reduce and minimize any cross-baffle flow.

The seals are manufactured from German DIN 1.4571 material (stainless steel 316Ti) as a standard, but can also be provided in other material options based on specific process media conditions. The seals are fitted easily and under most circumstances require no additional tooling, drilling or bolting of the seal to the baffle plate.

Thermoseal Inc. is an expert in and leading manufacturer of fluid sealing materials and fluid control products. The company carries a range of baffle seals at its Houston location to fit the most commonly encountered baffle plate thicknesses, from one-quarter of an inch to three-quarters of an inch. Other sizes are also available on a make-to-order basis. The seals are supplied in pairs and cut to the exact length required for any specific heat exchanger application.

For more information, contact Gallagher Fluid Seals. We are an authorized distributor for Thermoseal and can provide engineering application expertise.

Designing the Perfect Rotary Shaft Seal

When it comes to maintaining a high-functioning rotary shaft, you need to select the appropriate lip seal.

The shaft seal protects the rotary shaft from contaminants such as dust and dirt, and it keeps water out and lubricant in.

A rotary seal, also known as a radial shaft seal, typically sits between a rotary shaft and a fixed housing — such as a cylinder wall — to stop fluid leaking along the shaft. The rotary seal’s outside surface is fixed to the housing, while the seal’s inner lip presses against the rotating shaft.

Common applications for shaft seals include motors, gear boxes, pumps and axles. They’re also increasingly used for food and chemical processing, as well in pressurized gas applications.

Three of the most important considerations when the choosing the best lip seal for a rotary shaft are:

  1. The material the seal is made of,
  2. the hardness of the shaft’s surface, and
  3. the roughness of the shaft’s surface.

Here’s your quick go-to guide on how to achieve optimum performance and longevity for your seals and shafts, ultimately minimizing the risk of seal failure. Presented by our partners at Eclipse Engineering: Continue reading Designing the Perfect Rotary Shaft Seal

Vesconite Hilube Plate Proves Itself in Rotary Vacuum Filter

A large food-processing company replaced several of the polyethylene plates on its rotary vacuum filters with plates made of the low-friction, high-compressive strength polymer known as Vesconite Hilube.

Rotary vacuum filters are used for dewatering, washing and clarification, and rely on a vacuum to suck the water content out of a slurry mixture in which a vacuum drum rotates. After dewatering is completed, a dry cake remains on a cloth-covered drum, while the clarified liquid in the drum is transported out of the drum through a series of pipes.

Vesconite Hilube wear plates have been successfully used at the interface between the vacuum drum and the exiting pipes at the client’s facility.

The processor’s mechanical department maintenance coordinator informs that the 800-millimetre-diameter (31.5 inches) 25-millimetre-thick (1 inch) Vesconite Hilube wear plates need to ensure that there is an adequate seal that prevents the liquid from leaking.

They also need to have sufficient compressive strength to be secured by a trunnion plate, he says, noting that the equipment agent’s wear plates were of a much softer material and that this resulted in wear and eventual leaking.

In addition, they need to have the correct pipe exiting alignment, with 16 holes in place for some of the rotary vacuum drum designs and 14 for other of the designs.

Testing continues to verify the comparative wear life of the polyethylene wear plates and their replacement Vesconite Hilube wear plates.

The processing company’s maintenance coordinator reports that the Vesconite Hilube plates have outlasted the polyethylene plates, but the exact wear life of both the polyethylene and Vesconite Hilube wear plates is unknown. Continue reading Vesconite Hilube Plate Proves Itself in Rotary Vacuum Filter

10 Reasons to Replace Metal Case Rotary Seals with Clipper® Oil Seals

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

Original content can be found on Parker’s Website and was written by Alan Wiedmeyer, application engineer, Parker Engineered Polymer Systems Division.

Clipper® Oil Seals are one of the Parker Engineered Polymer Systems (EPS) Division’s most widely used rotary seal products. They are an effective solution – especially when used as direct replacements for traditional metal case seals. This is a testament to their precision-molded rubber/aramid fiber heel construction which eliminates the metal case (see image above). In this blog we will review the benefits of using Clipper® seal profiles as direct replacements for metal case seals:

1. Improved sealing in an imperfect housing

The composite rubber/aramid fiber heel provides a gasket-like seal for improved sealing against the bore. The surface conditions of bore housings are frequently riddled with imperfections due to damage during improper seal installation and removal, or simply due to cost sensitivity in their original manufacture. Metal can seals lack the ability to conform to such imperfections, frequently necessitating the use of supplemental gaskets or bore sealants during installation to prevent bore leakage.

2. No need for compression or bore plates

The outside diameter of the flexible, composite elastomer/aramid fiber heel is slightly oversized to create a tight interference press fit. The tight fit and compression-set-resistant heel construction eliminate the necessity of compression plates for bore retention1. It’s essential to note that bore plates (shown in green) can cost as much as $100 per inch of shaft diameter because of additional part cost and added assembly time.

3. Corrosion-resistant

Clipper seals have a composite elastomer/aramid fiber heel and rubber elastomeric lip so there is no concern for rust or corrosion. The only metal component is a 302 stainless steel garter spring. The stainless spring handles higher operating temperatures and resists rust/corrosion better than carbon steel springs used in other rotary shaft seals. Continue reading 10 Reasons to Replace Metal Case Rotary Seals with Clipper® Oil Seals