o-rings
- May 14, 2019
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.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?
- December 06, 2018
The O-Ring & Engineered Seals Division of Parker Hannifin Corporation, the global leader in motion and control technologies, recently announced the launch of VA179, a new extreme high temperature fluorocarbon (FKM) compound. VA179 is an innovative, 70 durometer rubber seal material providing increased high temperature limits while maintaining chemical resistance and low temperature sealing consistent with standard FKMs.
VA179 consists of a breakthrough rubber technology increasing the FKM continuous high temperature limit an additional 20°C (68ºF) over standard FKM materials on the market today. This provides a new industry sealing solution to long-term compression set issues for customers using traditional fluorocarbons and silicones.
"In markets such as aerospace, automotive, and heavy-duty, we are frequently challenged to expand the temperature capabilities of our rubber compounds,” says Nathaniel Sowder, aerospace, military and chemical processing business development engineer, O-Ring & Engineered Seals Division, “With the launch of VA179, we now have a solution that will reach higher temperatures without sacrificing the low temperature and chemical resistance attributes that make standard FKM such a popular choice.”
- October 23, 2018
Gallagher recently recorded the Rubber Energized Seals webinar, discussing rubber energized rod or piston seals, and the advantages and disadvantages to using some of the most common seal profiles. This webinar is presented in conjunction with one of our trusted partners, Eclipse Engineering, Inc. Eclipse is a designer and manufacturer of high performance engineered polymer solutions.
This section of the webinar will discuss some of the more common profiles for rubber energized seals, including x-rings, u-cups, buffer rings, cap seals, etc.
To view the webinar in its entirety, visit our Resources page and fill out the form, or
- September 18, 2018
Gallagher recently recorded the Rubber Energized Seals webinar, discussing rubber energized rod or piston seals, and the advantages and disadvantages to using some of the most common seal profiles. This webinar is presented in conjunction with one of our trusted partners, Eclipse Engineering, Inc.
- April 05, 2018
Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.
Original content can be found on Parker’s Blog.
O-Ring Selection Made Easy with the Parker O-Ring Selector
Two things are equally important for the reliable performance of an O-Ring seal: the right size and the right material. Parker’s new O-Ring Selector is an engineering tool that enables users to make the right material and size selections easily, quickly and reliably – in a single application. The accuracy of the results ensures the desired performance of the O-Ring in the subsequent application. This is primarily based on the fact that both functionalities – the material selection and the O-Ring size calculation – are closely interlinked. This achieves a new quality in calculating the total sealing system.
Overview of the O-Ring Selector
The Parker O-Ring Selector is divided into three main sections:
- Service Conditions & Material Selector
- Size Selector
- Notes
The Service Conditions & Material Selector section is focused on mapping the material-related application conditions. Entering the operating temperature range, the desired polymer family and/or material hardness will take the user to the suitable material selection. The Advanced Material Selector enables experienced users to specify the operating conditions in even greater detail. Here the medium to be sealed can be selected from a database containing 2,500 media. In addition, a search for required approvals and conformities can be run.
- April 03, 2018
Gallagher recently published its Failure Modes of Elastomers in the Semiconductor Industry White Paper, now available for download on our site. This white paper discusses common issues that occur with elastomer seals in the semiconductor industry. The excerpt below is the fourth and final section of our new white paper, discussing Volatiles (offgassing) and Particle Generation. To download the white paper in its entirety, visit our Resources Page, or click on the image to the right.
Failure Modes of Elastomers in the Semiconductor Industry
High performance elastomers are found in many applications in the semiconductor industry (see paper titled Perfluoroelastomers in the Semiconductor Industry). Though perfluoroelastomer (FFKM) seals are formulated to meet the highest performance requirements of integrated circuit (chip) manufacturers, even these elastomers can’t solve every sealing application nor will they last forever in service. Additionally, end users need to understand subtle performance differences between perfluoroelastomers in the same product line. For example, one product may be better at minimizing particle generation while another may be better for high temperature services.
- February 27, 2018
Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.
Original content can be found on Parker’s Blog.
The O-Ring & Engineered Seals Division is now offering a rapid prototype program for solid and hollow spliced O-rings that will reduce lead times on small orders to improve sample and trial testing on enclosure projects. The program provides spliced rings available in a variety of cross sections and can be purchased in either solid or hollow profiles.
Spliced ring sizes
In the event that enclosure tolerances are large or the available compressive force is low, Parker engineers can design a custom hollow seal to help absorb large tolerances while providing very low compressive force compared to solid cord. Spliced rings with large inside diameters up to 95” are available in silicone and nitrile materials. Rings with inside diameters up to 57” are available in fluorocarbon. Cross sections of .070”, .103”, .139”, .210” .250” are regularly stocked and available to splice to the ring ID needed. The chart below outlines the current compounds, cross sections, and diameters available under the program.
- January 30, 2018
Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.
Original content can be found on Parker’s Blog.One of the decisions equipment designers need to make when installing O-ring seals in their applications is how much the O-ring will be squeezed by its mating hardware to create an effective seal.
What is O-ring squeeze
Squeeze is a ratio of the amount of deformation applied to the seal expressed as a percentage of the free-state cross-sectional thickness. Deforming the seal cross-section “energizes” the elastomer matrix much like compressing a spring; the inherent elasticity of the rubber material causes it to push back against the mating components. This contact force blocks the passage of liquids, gases and dry powders, preventing them from flowing between the rubber seal and the mating hardware.
The greater the squeeze, the more force is applied against the hardware and the tighter the seal. But that doesn’t necessarily mean that designers should always specify the most squeeze (assuming they knew what that level was or why it was “the most”). There are a number of factors to consider, which include:
- January 23, 2018
O-Rings continue to be the most widely utilized sealing product. While the ‘Donut’ shaped profile has by and large been kept intact since their inception, continued elastomeric development has pushed o-ring temperature and chemical compatibility to limits unimaginable several decades ago.
Typically, O-Rings fail due to adverse effects of a number of factors, from improper installation and lubrication to incorrect size and design. The collection of videos below will help you minimize installation errors that may lead to failure (be sure to bookmark this page for future reference).
How To Install an O-Ring - Standard Male Gland
[embed]https://youtu.be/QcJBVQvTvhw[/embed]
- January 09, 2018
Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.
Original content can be found on Parker’s Blog.
Precision O-rings are manufactured by vulcanization in a closed mold using compression or injection molding. This makes it possible to produce O-rings in relatively small manufacturing tolerances and with good surface quality according to ISO 3601-1 and ISO 3601-3. Due to defined vulcanization parameters, precision O-rings