Tag Archives: Parker

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

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

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


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

Rapid gas decompressionRapid Gas Decompression

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

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

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

AbrasionAbrasion

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

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

Installation of Linear Fluid Power 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 Nathan Wells, application engineer, Engineered Polymer Systems Division.


So, you’ve unboxed the shiny new Parker seals you ordered – now what?  Installing seals for the first time can be challenging without the right know-how and tools. In this article we’ll discuss best practices for seal installation in linear fluid power systems, and how to design your system to make seal installation fast and damage-free.

SEAL GROOVE STYLES

picture of closed rod seal groove

First, let’s look at three common groove styles:

•    Closed
•    Stepped, and
•    Open (or two-piece)

Closed groove

The closed seal groove fully encapsulates the seal and is the most common style used (see Figure 1).

Closed grooves are simple to machine and offer the best support for seals. Since seals in this configuration are surrounded by solid metal, without a well-developed process, installation can be challenging. Rod seals need to be folded to fit into internal (throat) grooves and piston seals must be stretched over the outside of the piston.

picture of cylinder head and piston seals

Notice how both designs shown in Fig. 2 and Fig. 3 utilize static seals (turquoise colored seal) on the opposing side of the dynamic, primary seals. Therefore, installation in either instance requires techniques and tools for both rod and piston seals.

Stepped groove

Typically utilized to ease seal installation, stepped grooves feature a reduced diameter on the low-pressure side of the seal as shown in Fig. 4 and Fig. 5.

picture of rod stepped groove

As shown, the “step” is just wide enough to hold the seal in place as the rod or piston strokes back and forth. This way, seals don’t have to be folded or stretched nearly as much when installing. This design works well for single seals only holding pressure from one direction, like Parker FlexiSeals™.

When using multiple seals stacked in series or in systems with bi-directional pressure, a closed or two-piece groove is needed for support on both sides.

Open and two-piece grooves

Open or two-piece grooves are used when the seal is either too small to be stretched or folded into a closed groove, or if it’s made of a material that doesn’t spring back after flexing.

Figures 6 and 7 show two examples of open grooves. Figure 6 uses a washer and a snap ring to hold the seal in place. Figure 7 uses a bolt-on cap. These groove designs can be used for bi-directional seals, too. As you can see, open grooves cost more to produce but seal installation is a snap.

picture of open rod groove

Open grooves also make removing the seal much easier – useful in systems which require periodic seal replacement. Continue reading Installation of Linear Fluid Power Seals

Reduce Downtime and Costly Seal Replacements: Seal Failure Diagnosis Part 1

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

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


There are many situations where an O-Ring may not last as long as one thinks that it should. When the expectation is realistic and yet the seal fails earlier than expected, Applications Engineering teams are often asked to help discover the seal failure mode(s).

Seal failure is often due to a combination of failure modes, making root cause difficult to uncover. When beginning a failure analysis, items usually asked for include: hardware information, how the seal is installed, application conditions (temp, fluids, and pressure exposure), and how long into the service that the seal failed. These details help bring the overall application into focus and enable a quick diagnosis to help resolve seal failures. In part one of the seal failure blog series, we will discuss compression set, extrusion, and spiral failure.

Compression set

  • picture of compression setCompression set is likely the most common failure mode for elastomer seals. Compression can be defined, or rather quantified, by the seals ability to return to its original shape after compression is removed. Zero percent compression set indicates that no relaxation (permanent deformation) has occurred, while 100% compression set indicates that total relaxation (seal no longer applies a force on the mating surface). When investigating material options, note that the lower the % compression set for a given compound, the more resilient the material is. However, it is extremely important to ensure you are making equal comparison in terms of time and temperature for the test conditions.
  • There are many potential causes for compression set.
    • Poor material properties
    • Improper gland
    • Fluid incompatibility
    • Temperature exposures above the recommended range for the material.

Extrusion and Nibbling

  • picture of extrusionThe driving force (pun intended) for this failure mode is the pressure load that the seal is exposed to. Extrusion most often occurs when a seal material deforms into the space between the bore and the outside of the tube (commonly referred to as the extrusion gap or “E-gap”). An approximation for the pressure rating for a seal can be determine by evaluating figure 3-2 of the Parker O-Ring handbook. The X-axis shows the size of the clearance gap (total gap, or diametral gap), and the Y-axis is the pressure load. The curves on the chart correspond to the hardness of the rubber. Extrusion can also occur due to gland overfill, when the deformation from compression of the seal fills the entire groove and lips over into the extrusion gap.
  • Face seals do not usually have an extrusion gap, so this orientation can achieve much higher pressure loads than a radial seal. Without a gap for the seal to extrude into, the risk of significant extrusion is highly diminished.
  • Extrusion in radial seals can by combated by reducing the clearance gap or by adding a back up ring.

Spiral Failure

  • picture of spiral failureSpiral failure can be more simply described as the O-Ring rolling in the groove. This failure more is most common in dynamic reciprocating O-Ring applications. However, spiral failure can also occur during installation. An image of spiral failure is unique, and relatively easy to diagnose, but the root cause of spiral failure can sometimes be difficult to pinpoint. Uneven surface finish, poor lubrication, side loading, eccentricity, or perhaps stroke speed can all contribute to spiral failure.

Check out Parker’s neat video about Seal Failure Modes:

Parker and Gallagher Fluid Seals can help diagnose seal failures and the best sealing solutions for your application.

Stay tuned for Part 2 in this series.


For more information about how Gallagher Fluid Seals can help you, contact our engineering department today.

How to Solve Large-Size Sealing Challenges at Temperatures up to 800°C (1472°F)

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

Original content can be found on Parker’s Website and was written by Thorsten Kleinert, Business Unit Manager, Composite Sealing Systems Engineered Materials Group, Europe.


When classic sealing materials reach their limits, such as temperature ranges above 300°C and below -50°C – alternative materials are sometimes required, such as metal seals with appropriate coating/plating.

picture of metal sealParker offers metal seals made of stainless steel or nickel alloys in C-rings, E-rings, and other o-ring designs characterized by high pre-loading force and significant resilience. Drawing on many years of experience in the gas turbine market, Parker has continually expanded its expertise in large diameters and developed special problem solutions that substantially increase the efficiency of the machines.

Metal Seal Types and Sizes

The most important manufacturing technologies used to produce metal seals from stainless steel or nickel alloys are rolling, forming, CNC machining, welding, heat treatment, and coating/plating. In its more than 60-year history of producing metal seals, Parker has continually tackled the challenge of manufacturing increasingly large metal seals. Currently, spring-energized C-rings with a diameter of up to 7.6 m can be produced for which special forming machines and patented welding techniques were developed. They are supported by optimized special heat treatment and electroplating processes that make it possible to manufacture high-quality products even in such large dimensions. Additionally, Parker offers non-rotationally symmetric metal seals. These E-, O- and C-seals can be produced in lengths of up to 2.3 m on machines specifically developed for this purpose.

Products

  • C-seals: ≤ 3,000 mm (118 inches)
  • Spring-energized C-seals: ≤ 7,600 mm (299 inches)
  • O-rings: ≤ 1,200 mm (47 inches)
  • E-seals:
    • Heat-treated ≤ 2,700 mm (106 inches)
    • Segmented ≤ 7,600 mm (299 inches)

Materials and Coatings

picture of gas turbineThe base materials used are special nickel alloys that withstand temperatures of more than 800 °C. These cobalt-nickel-chromium-tungsten alloys or heat-treatable nickel super-alloys make high demands on the welding technology used and are reliably processed at Parker due to optimized manufacturing processes and comprehensive suitability tests.

The choice of plating is primarily focused on wear protection, corrosion resistance and improvement of the sealing properties. For this purpose, the surface properties of the metal seal are modified and a formable external surface layer with adjusted hardness is created.


For more information about  sealing large-size applications with high temperatures, contact Gallagher’s engineering department.

Gallagher is an authorized distributor for Parker products.

Sealing Solutions for Drinking Water and Service Water Systems

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

Original content can be found on Parker’s Website and was written by Dr. Stefan Reichle, Market Unit Manager, Engineered Materials Group Europe.


picture of drinking waterWherever drinking water is obtained from any of its sources, pumped and processed, materials with low extraction levels and without any harmful ingredients are required. Sealing compounds for use in drinking water and heating applications are subject to diverse approval regulations. These regulations serve to assure the safety of water from the time of intake, via treatment, processing and transportation through to the consumer. Practically every country in the world has its own drinking water regulations specifying particular tests and including lists of approved ingredients. These regulations are complemented by physical and microbiological examinations.

The Parker Engineered Materials Group has developed a number of compounds, each of which meets a wide range of the required approvals, thus permitting the global utilization of sealing systems.

New universal compound combines excellent compression set and improved resistance against autoxidation

The peroxide-crosslinked plasticizer-free EPDM compound EJ820 was specifically developed for use in drinking water applications. The material conforms to all standard national and international drinking water approvals such as KTW, W270, W534, EN681-1 including the supplementary requirement, W534, NSF61, KIWA, WRAS, ACS. The material’s low compression set guarantees long life and thus permanent and reliable sealing of all fittings, valves and pipe systems. In addition, EJ820 exhibits enhanced resistance against autoxidation.

Parker materials cover a broad range of drinking and service water applications

  • Seals for solar thermal energy systems
  • Bathroom taps and shower heads
  • Press fittings
  • Heater valves and valve blocks
  • Drinking water applications
  • Heater pumps

Below are Parker material compounds and associated specifications:

picture of parker compounds

picture of regulations for drinking water


For more information about Parker products that are applicable for drinking water and service water systems, contact Gallagher’s engineering department.

Form-In-Place Gaskets: What They Are and What They Are Not

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

Original content can be found on Parker’s Website and was written by Ben Nudelman, Market Development Engineer, Chomerics Division.


Form-in-place EMI gaskets, also known as FIP EMI gaskets, is a robotically dispensed electromagnetic interference (EMI) shielding solution that is ideal for modern densely populated electronics packaging.

picture of CHOFORMThe most important distinction of form-in-place EMI gaskets is that they were developed for applications where inter-compartmental isolation is required to separate signal processing and/or signal generating functions.

Simply put, form-in-place gaskets are meant to reduce “noise” between cavities on a printed circuit board (PCB) or in an electronics enclosure.

In addition, form-in-place gaskets provide excellent electrical contact to mating conductive surfaces, including printed circuit board traces for cavity-to-cavity isolation. Parker Chomerics form-in-place gasket materials are known as CHOFORM.

7 reasons why form-in-place EMI gaskets can be an ideal choice

  1. Small form factor – form-in-place gaskets can be dispensed in smaller bead sizes than most traditional EMI shielding gasket solutions, 0.018” tall by 0.022” wide.
  2. Excellent adhesion – 4-12 N/cm adhesion on prepared surfaces such as machined metals, cast housings, and electrically conductive plastics.
  3. High shielding effectiveness – Parker Chomerics CHOFORM materials can provide more than 100 dB shielding effectiveness in the 200 MHz to 12 GHz frequency range.
  4. Quick programming – Because form-in-place EMI gaskets are robotically dispensed, a standard CAD file can be used to program the dispensing system and quickly map out the dispensing pattern.
  5. Complex geometries – The positional tolerance of the gasket can be held to within 0.001” and is able to follow very complex geometries including sharp turns, corners, and serpentine patterns. Other gaskets such as die cut sheets or o-rings manufacture and/or fabricate into such shapes and patterns.
  6. “T” joints – Traditional extruded gaskets are difficult to mate at intersections or “T” joints. The robot dispensing systems produce reliable junctions between bead paths to provide continuous EMI/EMC shielding and environmental sealing.
  7. Integrated solutions – CHOFORM technology combined with a Parker Chomerics supplied metal or conductive plastic housing provides an integrated solution ready for the customers’ highest level of assembly. This approach requires no additional assembly or process steps for the installation of gaskets and/or board-level auxiliary components.

Picture of Form-In-Place EMI Shielding Gaskets

Form-in-place EMI gasket limitations

  1. Large form factor enclosure sealing that can accommodate a groove. For larger areas such as machined covers that can accommodate a gasket groove, other EMI shielding solutions are better suited. In most applications, conductive elastomers such as the CHO-SEAL product line by Parker Chomerics will provide better shielding and sealing. Form in place gaskets can be dispensed in bead sizes only as large as about 0.062” tall x 0.075” wide.
  2. Enclosures requiring submersion or durable weather sealing. Because of the small form factor, FIP gaskets will not meet stringent environmental sealing requirements such as IP 67 or higher. While silicone-based, the material is better at preventing dust and environmental moisture from entering an enclosure. FIP gaskets can be paired with additional sealing gaskets for enhanced weatherproofing.

Gallagher Fluid Seals is an authorized distributor for Parker. For more information about their products, including o-rings or their various compounds, contact Gallagher Fluid Seals today.

Is an ASTM Callout the Best Way to Specify Your Elastomer Needs?

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

Original content can be found on Parker’s Website and was written by Fred Fisher, Technical Sales Manager for Parker O-Ring & Engineered Seals Division.


ASTM Elastomer Compounds

elastomer materials pictureWhen looking at drawings to define a specific application or elastomer requirement: Is there value in using an ASTM elastomer compound description versus listing an approved Parker compound number?

Specifying a compound using the ASTM callout is a good start – it clearly defines what is wanted and it sets a minimum benchmark, which makes it easy for competitive vendors to understand what the need is. The ASTM standards also set specific test parameters which makes it much more simple to do an “apples to apples” comparison between two compounds. However, over time, here is what customers have learned:

Know Your Operating Requirements

1. The ASTM standards are very general; so when a customer defines a specific FKM they need using an ASTM callout, they might receive a compliant material that just barely meets the ASTM specifications, but did not meet the actual operating requirements. Because of that, a supplier may provide a customer with the lowest cost material. Let’s say the quality of the material is on the lower-end, but it meets the ASTM criteria requested. Because of that, the customer could see a 15% increase in assemblies requiring rework, plus a rising number of warranty claims due to seal failures. The twenty cents per seal that the customer saved for their $50 application would be offset by the cost of the increased product failures. And ultimately, this would result in an unhappy customer.

Know the Fluids Your Seals Will be Exposed to

fluid exposure2.  The ASTM standard does not specifically list what actual chemicals the seal has to be compatible with as well as the operating conditions. ASTM tests compatibility based on Standardized Testing Fluids, which are: Oils, Fuels, and Service Liquids. ASTM uses standard oils, which are defined by IRM 901 and 903. Again, the ASTM standards are excellent for comparing compounds, but most people do not have their seals operating in the ASTM reference oils and many sealing applications are exposed to multiple fluids.

Know What Your ASTM is Calling Out

3.  Most engineers or folks in purchasing who review or utilize older drawings have no idea why the original engineer chose the specific compound or why they used an ASTM callout.

So what is the best way to define and specify an elastomer? Most companies go through a technical process to specify, test. and confirm that an elastomer is the correct choice for their application. All elastomers tested and approved for the application should be clearly listed on the drawing. In addition, the drawing should clearly state that  the approved materials listed were tested to confirm their suitability for the application. All substitutes or new elastomers must be tested and approved by engineering prior to use.


Gallagher Fluid Seals is an authorized distributor for Parker. For more information about their products, including o-rings or their various compounds, contact Gallagher Fluid Seals today.

Semiconductor Fabs Lower Cost of Ownership with HiFluor Materials

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

Original content can be found on Parker’s Website and was written by Nathaniel Reis, Applications Engineer for Parker O-Ring & Engineered Seals Division.


parker hifluor processIn our semiconductor entry from last month, we noted that lowering the cost of ownership is a multi-faceted goal. We discussed how one of the areas for potential improvement is mechanical design and how the Parker EZ-Lok seal is a major solution to mechanical seal failure. In this entry, we’ll investigate a notably different type of cost-reduction opportunity – material selection – and see how Parker’s innovative HiFluor compounds can reduce seal costs to as little as half.

Critical Environments

When it comes to the seal industry, the semiconductor market is well known as one where the most premium, chemical-resistant compounds are a necessity. Microelectronic manufacturing processes involve chemistries that push the limits of what elastomeric compounds can withstand in terms of both chemical aggressiveness and variety. The perfluorinated materials (FFKM) capable of withstanding these environments require intricate manufacturing processes regulated by closely-guarded trade secrets and the significant investment of resources.

These factors drive the price of FFKM compounds to the point of being as much as 50 times the cost of any other variety. Cutting just a slice out of this cost can result in significant savings – a chance to take out a quarter or even half the pie would be advantageous to the overall bottom line. Fabricators should be continually on the lookout for more cost-effective compounds that show equal performance in their pertinent operations.

hifluor compound pictureThis is why Parker’s HiFluor compounds offer an opportunity for cost savings that shouldn’t go unnoticed. A unique hybrid of performance between FFKM and the simpler technology of fluorocarbon (FKM) elastomers, HiFluor offers the most superb chemical compatibility in the many semiconductor environments where the high temperature ratings of FFKM aren’t necessary – and at a fraction of the cost.

Not only can HiFluor be used where even FKM is lacking, but its performance in applications with aggressive plasma exposure is spectacular as well. This can be observed by its overall resistance to plasma-induced material degradation. However, Parker has also developed multiple formulations that display extremely low particle generation when most materials would be expected to suffer severe physical and chemical etch.

Solutions and Cost Savings

As an example: One major semiconductor fab had several factors (other than their seals) dictating the frequency of their preventative maintenance (PM) intervals. The fab wanted to replace their seals at these intervals as a precautionary measure to limit the chance of them becoming another PM-increasing factor. However, this caused these premium FFKM seals to be a source of inflated cost. Parker assisted with a process evaluation that resulted in over half the seals being replaced with cost-effective HiFluor O-rings, while the tool regions with more intense plasma exposure were reserved for the elite performance of Parker’s FF302.

Another major fab in the microelectronics industry switched from FKM to FFKM seals in their oxide etch process. The tool owner achieved the desired performance improvement, but soon began searching for less expensive options. The owner recognized the plasma resistance and low particulate generation of Parker’s HiFluor compound, HF355. After implementing this change, he retained the performance improvement, but at a fraction of the cost.

Semiconductor tool owners understand that their aggressive processes require the most robust, expensive FFKM seal materials. The price tag on these seals is greater than those from any other compound family. Fortunately, HiFluor is a proven sealing solution that can bridge the gap and provide the same kind of high performance at a much lower cost.


For more information about Parker O-Rings, including HiFluor, or to find a custom solutions for your application, contact Gallagher Fluid Seals today.

Semiconductor Fab Processes Benefit From Retention Ribbed EZ-Lok 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 Nathaniel Reis, applications engineer, Parker O-Ring & Engineered Seals Division.


When it comes to semiconductor fabrication processes, reducing the cost of ownership is a multi-faceted goal approached from a variety of angles. Tool engineers and equipment technicians take pride in their ability to identify factors that limit tool uptime. One constant headache they face is the mechanical failure of seals in dynamic environments. This can lead to premature downtime or reduced preventative maintenance (PM) intervals, both of which lead to a higher cost of ownership. Fortunately, tool owners have begun to implement seal designs better suited for these dynamic environments: Parker EZ-Lok is a proven solution.

Spiral Failure

picture of spiral o-ring failure

One of the more extreme forms of mechanical failure to be prevented is twisting and spiraling of an O-ring during operation. This occurs with O-rings in dovetail glands where one of the sealing surfaces is a door that opens and closes against the seal. The combination of stiction to the door and stretch in the gland causes the O-ring to roll and twist repeatedly with each cycle, resulting in permanent cyclic deformation. This means that a seal profile with a flat contact surface is vital for this type of dynamic function.

Other designs

The basic D-profile is the fundamental simple shape that serves as the basis of the EZ-Lok solution. The flat portion of the “D” holds the seal in place and prevents rolling, while the opposite, round contact surface focuses the sealing force and helps keep volume requirements at a minimum. These geometric features make for sound sealing function while preventing the drastic spiral damage seen so often in the industry.

picture of d-profile

A standard D-ring is still more limited by volume requirements than traditional seals like O-rings. In addition, a D-ring’s sharp corners can become difficult to install past the top groove radii if the seal is made much wider than the groove opening. On the other hand, a seal made any narrower would be easily removed without intention, such as that induced by stiction to the door. These reasons are why the basic D-profile alone is not the answer to these failure modes.

The Solution

picture of Parker EZ-Lok seal

The solution to these dilemmas is a unique D-shaped profile with a geometry that lends itself to the spacial constrictions of dovetail glands, prevents rolling, and locks into place: the Parker EZ-Lok seal. These seals are designed with special retention ribs placed with precise frequency around the seal circumference that allows for smooth installation and keeps the seal retained in the gland. This design also removes any tendency to stretch the seal during installation, which is often seen with more conventional seals.

The combination of retention ribs with a fundamental D-ring profile makes EZ-Lok the ideal geometry for effective use of the high-performance compounds typically required for aggressive semiconductor chemistries. EZ-Lok seals allow for lower cost of ownership through PM-minimization and reduced seal overhead costs, made possible by effective mechanical design. This is an example of how Parker’s effective design engineering can reduce the cost of ownership and bring premier solutions to the table.


For more information about Parker’s full suite of solutions and sealing products, contact Gallagher Fluid Seals’ engineering department.

Why is Outgassing Critical in Optics and Electronics Applications?

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

Original content can be found on Parker’s Website and was written by Dorothy Kern, applications engineering manager, Parker O-Ring & Engineered Seals Division.


electronic boardFor some applications, a critical component of selecting a seal material is a phenomenon known as “outgassing”. However, even within the elastomer community, outgassing is not something that is commonly considered. Which begs the questions: what is outgassing and why is it important?

Outgassing is usually most relevant in vacuum applications, where the vacuum causes the elastomer to release constituent material. The constituent material could include water vapor, plasticizers, oils, byproducts of the cure reaction, or other additives used in the seal material. Outgassing becomes a problem if a thin film of those chemicals condenses and is deposited on nearby surfaces. Such a film poses major challenges in highly sensitive applications, such as optics or electronics, where cleanliness is of utmost importance. A seal material with low outgassing  is essential because it shows the seal material does not emit volatile constituents under vacuum conditions.

Weight loss of compounds in vacuum

Outgassing is most often characterized by weight loss of the seal material. The ASTM test method E595 is one way to quantify outgassing by measuring Total Mass Loss (TML %), Collected Volatile Condensable Materials (CVCM %) and a reported value for Water Vapor Regain (WVR %).  Measurements are taken following a 24 hour exposure to vacuum of 5×10-5 torr at a temperature of 257°F.

Taken together, these three parameters tell a complete story. The TML is reported as the percent of the specimen’s initial weight that is lost during the test; under standard criteria, the result must be less than 1.00% mass loss. Obviously, minimizing TML is a good thing, but it is not the only important factor. Collected volatile condensable material (CVCM) is the amount of outgassed matter from a specimen that condenses onto a collector during the maintained time and temperature. CVCM is of particular concern because any material that readily condenses in the test is likely to condense on and contaminate nearby surfaces during use. To pass the standard CVCM requirement, the amount collected relative to the initial mass of the specimen must be less than 0.10%. The final measurement, WVR, is the mass of the water vapor absorbed by the specimen after a 24-hour stabilization at 23°C in a 50% relative humidity atmosphere. There is seldom a pass/fail limit for WVR; instead this result is merely reported. In many applications, the small amount of water vapor lost by a seal may not be of concern, particularly if the application already includes a means of controlling moisture. Further, any WVR is presumed to be equal to the portion of original TML that was water vapor. The difference between TML and WVR is therefore presumed to be volatile organic material that has evaporated out of the material (only some of which condenses in the CVCM test), so minimizing the difference between TML and WVR is also of considerable importance.

To illustrate, we can look at the most recent outgassing data completed on a few popular low temperature fluorocarbon materials. Table 1 contains the results from a 3rd party laboratory to measure the outgassing properties of VM125-75 and VX065-75. Both had undetectable amounts of CVCM and very small differences between TML and WVR.  VX065-75 in particular displayed remarkably little outgassing as well as a low WVR.

There are a few additional resources detailing seal materials that are known for having low weight loss. The O-Ring Handbook ORD 5700, Table 3-19 (page 65 of the pdf), has a few legacy materials with weight loss percent after a two-week exposure to 1 x 10-6 torr vacuum level, at room temperature. Additionally, non-Parker resources such as the NASA website contain an interesting summary of a much broader range of materials.


For more information about outgassing or electronics applications, contact the Gallagher Fluid Seals engineering department.