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Polyurethanes have been around for decades as a seal material for high pressure reciprocating mobile hydraulic applications. Original equipment manufacturers select it as their “go to” seal material for mobile equipment due to fluid compatibility, cost effectiveness, long service life, and reliable sealing. These capabilities are attributable to the molecular chemistry of polyurethane that produces desirable performance characteristics such as:
Seal manufacturers are closely dialed in to the need for equipment manufacturers to extend the overall useful life of mobile equipment. In addition, there are global expectations and owner/operator use trends pushing the envelope and driving the need for polyurethane materials capable of sealing higher temperatures and higher pressures, including:
Given the trends mentioned above, how will prolonged exposure at elevated temperatures – still within range – affect seal performance and ultimately, seal life? Seals are assigned a temperature rating by manufacturers, but how much is too much when it comes to heat exposure?
Manufacturers like Parker quantify thermal capabilities of their engineered sealing materials by assigning them “Temperature Ratings” – from X to Y (min to max), but what does that really mean for equipment designers?
Temperature ratings for sealing materials are generally based upon the typical physical characteristics of the material alone. A material's suitability for a specific application, however is dependent on actual use conditions which take into account wide ranging variables which include but are not limited to: hardware attributes and configuration, seal profile geometry, fluid compatibility, and expected duration and frequency of service exposure at pressure, temperature, and speed (i.e. ambient, continuous operating, intermittent, excursion).
Assuming one has taken into account actual use conditions, specified a profile geometry, and selected a compatible material, let's next consider whether one can reasonably expect that seal performance will be constant at all temperatures within the material's broad stated range.
Supported by exhaustive mechanical test lab data representing millions of cycles and decades of experience designing sealing systems, our application engineers know that best sealing performance with polyurethane can be expected when an application’s continuous operating temperature falls well within the maximum and minimum temperature limits for a compound. This is illustrated in Figures 1 and 2.1
As a practical example, the four scenarios in Figure 1 represent expected seal performance of Parker’s high performance Resilon® 4300 polyurethane material along its stated thermal range of -65°F to 275°F as configured in the application types and profiles shown (i.e., rod/piston, rod wiper, static O-ring/head seal, bumper/damper). Figure 2 is the key showing expected performance at each color coded interval.
The purple range represents conditions where performance is compromised due to compound stiffness. In this extremely low temperature range, the polyurethane material is hardening and approaching glass transition and brittle point.
The blue range represents values where performance is compromised due to stiffness and compound rigidity. Polyurethane lip seals may require a low temperature energizer to offset compromised resiliency.
The green range represents the recommended continuous operating temperature range for best performance.
The yellow range represents extended or continuous exposure under system pressure in temperatures roughly spanning 225 to 240°F. In this scenario, continuous dynamic cycling and increased frictional heat buildup compromises three critical performance characteristics of polyurethane: tensile – most closely associated with wear resistance; modulus – most closely associated with extrusion resistance; and compression set – most closely associated with resiliency (sometimes referred to as sealing force or the ability of sealing lips to “bounce-back” after being compressed).
In thermal conditions represented in the red area, the reference material Resilon 4300, is capable only for short duration before tensile, modulus, and compression set are irreversibly compromised.
In summary, temperature ratings of polyurethane seal materials are primarily based on laboratory and service tests and should be used as a guide only. They do not take into account all of the variables that may be encountered in actual use. Seal designers will have more certainty and a better judgment of the fit of the seal material to the application. when the application’s sealing demands are in alignment with the described expected performance scenarios shown in Figure 2, there will be more certainty and a better judgment of the fit of the seal material to the application when all variables are considered and then matched to expected performance.
1It is always advisable to test material under actual service conditions before specifying.
This article was contributed by Shannon Johnson, marketing communications manager, Engineered Polymer Systems Division.
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The consequences of failure during downstream processing are severe. Following the Affinity Chromotography stage, the value of the product increases significantly at every step. A failure at the final bulk filling stage, therefore, could lead to the waste of millions of dollars’ worth of drug product.
It’s vital, therefore, to safeguard the bulk filling process. But traditional methods of conducting bulk fill operations have several disadvantages including:
This introduces the possibility of human error to the bulk filling process. It is also labour intensive, meaning that process operators need to divert their resources into this task.
When bulk filling is carried out manually, investment must be made in operator training. This can be costly, both financially and in terms of the time dedicated to it by personnel.
By using a range of components from several different suppliers in the bulk filling process, there is more potential for variation – and more time must be spent on sourcing and ordering suitable components.
In traditional bulk fill operations, laminar air flow must be maintained and validated to protect the products from contamination. This requires time and resources.
At the shipping stage, poor handling of bottles – and the use of unsuitable containers – can lead to damage to products before they even arrive at their destination.
Traditional methods of bulk filling introduce variability into the process. If bulk filling operations aren’t standardized, they can be subject to a number of factors which can impact the final product. Factors such as different flow rates applied by different operators come into play.
Automating and enclosing bulk fill operations can address the challenges detailed above and increase safety for operators. Parker Bioscience Filtration has developed the SciLog® SciPure FD system as an automated and integrated single-use system for final bulk filtration, filter integrity testing and dispensing into final bulk product containers.
Here are some of the benefits:
This reduces the risk of human error from manual handling and allows operators’ resources to be spent on other tasks.
Standardizing operations means that training can be simplified and variations in the process can be eliminated.
Enclosing the process allows operators to process highly potent molecules and protects both the operators and the process. And, as the flow path is completely enclosed, both filtration and dispensing can be performed in areas of lower classification, eliminating the requirement for vertical laminar flow cabinets.
The SciLog® SciPure FD system benefits from innovative component selection based around material science studies, improved filling accuracy (+/-1%), and greater flexibility in the scale of filling (from 50ml samples to 20L).
The system features include a barcode reader for manifold tracking, reverse flow and purge options to maximize product recovery and fully programmable alarms and interlocks to product and process.
To reduce the risk of damage to the product when shipping, Parker Bioscience Filtration has designed a fully validated shipping solution to complement and extend the capabilities of the SciLog® SciPure FD System. Parker Bioscience Filtration has created a unique bottle design that offers manufacturers the confidence that bulk drug products will arrive at their final destinations without contamination.
Parker Bioscience Filtration drew on its extensive material science knowledge during the development of the bottle and material selection was based on an FMEA study. The bottle integrity has been validated down to -89˚C.
Parker Bioscience has also developed an anti-foaming device that eliminates foam and enables a higher filling speed.
The development of the SciLog® SciPure FD System is an example of the change in the vendor/end user relationship: by using a vendor such as Parker Bioscience Filtration, which can provide a complete solution, end users can increase their productivity and gain greater control and protection over their processes.
This post was contributed by Graeme Proctor, product manager (single-use technologies), Parker Bioscience Filtration, United Kingdom
Parker Bioscience Filtration specializes in automating and controlling single-use bioprocesses. By integrating sensory and automation technology into a process, a manufacturer can control the fluid more effectively, ensuring the quality of the final product. Visit www.parker.com/bioscience to find out more.
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In every manufacturing industry, machine safety is always a top priority. When operating in Europe, utilizing machinery and components with CE certification is the best way to ensure the reliability of the equipment that benefits both production and the operators who use the equipment.
What is the Machinery Directive?
First published in 1989, the Machinery Directive was designed to provide freedom of movement across Europe for machinery and safety of workers in an effort to reduce injuries.
In 2009, the Machinery Directive 2006/42/EC became law in Europe, and its primary role is to ensure common safety levels of machinery placed on the market and put into service.
Today this directive lays down the foundation and regulatory basis for the harmonization of Essential Health and Safety requirements (EHSR) in the field of machinery. It is unified with CE requirements and covers almost 21 distinct EN Standards to guide machine builders on safety requirements and has worked to harmonize with other safety organizations. Ultimately becoming the foremost authority on where to go to design a safe piece of equipment globally.
A unique quality of the Machinery Directive is its broad coverage for machinery design. The standards start at concept of design or designing out risk. The directive mandates a technical file be kept on the machine to show its inception and what risk avoidance was implemented to create a safer machine.
Guidance is provided to the machinery builder in the form of EN standards which mandate a risk assessment be conducted on machinery. Finally, the directive includes information on disposal at end of life of machinery. While broad, the directives do a great job of ensuring safety is addressed at every level and even account for “unintended use of machinery” at the design stage.
Another interesting note is given that one of the primary purposes of the Machinery Directive is to ensure common safety, the directive does not mandate the use of safety rated products. It does clearly differentiate standard components used in a safety application versus those products built and intended as safety rated products.
Safety rated products are classified separately and are subjected to more rigorous requirements, testing and expectations for performance.
The directive does state that common sense strategies be employed on machinery such as the use of e-stop buttons, the removal of air in a machine to protect from unexpected movement (where safe to do so) and the addition of technical measures where risk cannot be designed out. Additionally, to meet enhanced safety levels on machinery, redundancy and monitoring must be included in the controls of the machine EN ISO 13849-1 as well as validation of the system EN ISO 13849-2.
Some manufacturers offer safety rated components, such as Parker’s P33 series of safety exhaust valves, which meet the needs of the directive to remove air from machinery during either an e-stop or a faulted condition on the machine.
Knowing that products now exist which incorporate the needs of the directive and provide an enhanced level of certified safety can bring peace of mind to machinery designers and the engineers responsible for enhanced and integrated safety on machine.
If you would like to find out more about Parker’s P33 series of safety exhaust valves and the benefits they can bring to your machine-building projects, please download our white paper What You Need to Know About Safety Exhaust Valves.
Article contributed by Linda Caron, global product manager for Factory Automation, Pneumatic Division.
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