“After recognizing the need for advanced piston sealing solutions, we began a comprehensive benchmark of current products which focused on frictional behavior, assembly, shifting time, efficiency, service life and cost,” said Joel Johnson, global VP of technology, Simrit. “Based on the data gained from this effort, we were able to develop three new seal designs that exceeded current industry offerings.”

With the Low Friction Piston Seal TR 200, Simrit presents a sealing geometry for the smooth operation of pneumatic cylinders with significantly increased efficiency. Reducing friction by up to 50% compared to conventional systems, the Low Friction Piston Seal TR 200 shows minimal wear after 15 million cycles. The dynamic sealing function of the Low Friction Piston Seal TR 200 is achieved by a sealing area with a large radius. The required radial force is created by the design interface and eliminates the radial compression of the seal cross section, which minimizes friction and wear while also eliminating stick-slip effects.

Simrit combined the unique advantages of elastomer and PTFE materials to develop two low-energy seals that reduce initial friction, non-linear behavior and hysteresis in piston sealing systems. The TCS is a friction-optimized bonded piston that was specially developed for translatory motion as a transmission shift piston. This seal combines the superior frictional characteristics of PTFE with the rigidity, centering and lip shape (similar to that of a channel gasket) of the bonded transmission piston seal with the metal carrier that was previously used. The TCS is resistant to high temperatures, allows for the mounting of a single part, has an integral piston and offers excellent centering.

The D-ring was developed as a groove seal with PTFE foil enhancement as a friction-optimized piston seal and also employs the dual-layer enhancement procedure. Developed for use in a reciprocating application, the D-ring with PTFE enhancement is a general-purpose piston seal solution that offers very low coefficient of friction and high heat resistance. Offering a range of designs with different diameters, the seal does not twist, is resistant to gap extrusion and offers simple installation.

Simrit

Pneumatic Tips

Suitable for a wide range of seal profiles, scrapers and wear rings, Turcon MF6 is part of the Trelleborg Sealing Solutions Turcon MF range of polytetrafluoroethylene (PTFE) based sealing materials formulated for food contact, pharmaceutical and medical applications. The new Zurcon Z431 PEEK is ideal for valve and bearing applications.

“As far as we know, we are the only seal and bearing supplier who has passed a third-party verification inspection for the 3-A Sanitary Standard number 20-27 for thermoplastic materials,” says Steven Farnsworth, food, beverage and pharmaceutical segment manager for Trelleborg Sealing Solutions Americas.

The Turcon MF6 and Zurcon Z431 PEEK™ materials passed 3-A cleanability response and product immersion tests according to 3-A Sanitary Standard number 20-27. This is in addition to passing migration tests for aqueous, acidic and fatty foods in repeated contact according to directive 2002/72/EC as well as sensory tests passed at 90 cm2 per liter/52.8 in.2 per gallon surface/volume ratio at 95° C/203 ° F for 30 minutes and FDA extraction tests according to 21CFR177.2415. Turcon MF6 compound is listed by NSF International as conforming to the requirements of NSF/ANSI Standard 51-Food Equipment Materials.

Trelleborg Sealing Solutions

Pneumatic Tips

“Developed for high-volume applications in industrial, chemical, pharmaceutical and process industries, Isolast J9440 gives unbeatable value to our customers,” said Muzaffer Sheikh, Isolast product manager. “Over the past 18 months we have seen this material adopted by a number of leading manufacturers, winning significant approvals. With this improved formulation, we expect to see more.”

Isolast J94440 has a continuous operating temperature range (from -7° C / 19° F to  240° C / 464° F) and is compatible with virtually all media. The compound is available in all O-Ring sizes, as gaskets, molded parts or rubber-to-metal bonded components. It is suitable for the lacquer, paint and coating industry, chemical processing systems, cleaning agent dispensers, pumps, valves, power generation equipment, refineries and semiconductor applications. Its USP Class 6 accreditation means the material can be used in pharmaceutical and medical applications.

The improved material is part of the Isolast range of proprietary perfluoroelastomers.

Trelleborg Sealing Solutions

Pneumatic Tips

T201 is used for spring-energized seals, V-packings, 0-rings, back-up rings, valve seats & seals and machined components used in the chemical industry for processing equipment, for high temperature and for low friction sealing applications. Particular care should be taken to avoid nicking or scratching Teflon seals, as imperfections will cause leakage.

AHPSEALS

Pneumatic Tips

Pneumatic actuators are key elements of material-handling and automation systems used for moving, clamping and positioning goods, boxes, flaps, gates, etc. A typical pneumatic cylinder (Figure 1) contains several static and dynamic seals. The dynamic seals are:

Double-acting piston seal (often two U-cup seals) Rod seal and dirt wiper (often combined in one element) Two cushioning seals for the adjustable pneumatic end cushioning.  The dynamic seals have to work well with: Oil-free compressed air using only the minimal grease lubrication that was applied during cylinder assembly Operating pressures to 100 psi with excursions to 360 psi during cushioning Creep velocity of 3+ ft./sec. A temperature range of -4°F to +176°F With a typical cumulative lifetime travel of at least 4,000 miles, the area of dynamic contact must maintain grease lubrication. A flexible sealing lip geometry provides low radial forces, and a rounded contact area allows the lip to float on a grease film.

If hydraulic seals were used in pneumatic cylinders, the high radial force and sharp sealing edges would scrape the grease away from the contact area. The grease would collect at the ends and the ensuing poor lubrication would result in high friction, heavy wear and shortened useful life.

Seal design refinedThe seal design follows the principles described above. Additional features ensure proper function under any operating condition.

Piston seal: U-cup-type piston seals have been used in pneumatic cylinders for many years. The design in Figure 2 has several special features. It has a thin connection between sealing lip and body to achieve low radial force. Toward the contact area, the lip is larger to give stability under pressure.

Notches at both lips and on the outer diameter of the back side avoid malfunctions. The notches on the side of the outer sealing lip ensure proper activation when the pressure increases. Notches at the outer diameter of the back and on the inner lip act as pressure-release channels in case pressure is trapped between the two U-cups in a double-acting piston. Without these notches, a pressure trap, together with friction, can tilt the seal in the groove, which results in an inoperable cylinder. The rounded contact area of the sealing lip was optimized by finite element analysis to ensure good function over the whole pressure range.

A polyurethane material was developed for the specific demands of pneumatic applications. The 83 Shore A hardness is relatively low to minimize the radial force. With its good compression set, low friction and extraordinary wear resistance, it provides the preconditions for good functional properties and long service life.

Rod seal: The rod seal is designed to suit grooves for pneumatic cylinders to ISO 15552. The seal has a sealing lip and a dirt wiper lip, and is fixed by a retainer «nose» at the outer diameter. The seal can be mounted into an unsplit gland by pushing it into the bore until the retainer nose snaps into the mating groove of the housing bore. The outer, static sealing lip is chamfered for ease of installation.

As the seal is fixed only by its retainer nose, the seal material must be stiff enough to withstand the axial forces of pressure and friction. Therefore, a harder material (94 Shore A) is used to maintain the proper seal orientation.

Cushioning seals provide smooth piston movement at the dead-end positions. The cushioning seal (Figure 5) works better than O-rings. The specific design features are:

Dynamic sealing lip gives good tightness and low friction Axial sealing edge with check valve functionality Combined notches at the lip side and on the outer diameter to allow air flow

The cushioning seal is active only at the end of the stroke. A pressure chamber, which is formed between cushioning seal and piston seal, works like an air pillow to absorb the kinetic energy smoothly. To ensure that the cushioning seal doesn’t affect movement when the cylinder reverses direction, the seal has an integrated check-valve function that forces the pressure to act on the full cylinder area. If O-rings are used as cushioning seals, the movement is delayed because the air pressure can’t act on the full cylinder area until the cushioning rod has moved out of the O-ring. Tests validated performanceA test program performed with commercially available pneumatic cylinders confirmed the material and design-development efforts. The cylinders were equipped with a rod seal-scraper, two piston seals and two cushioning seals. The test program included:

High-pressure test Bursting pressure test Low-temperature test Temperature cycling test Minimum speed test Endurance test The test procedures reflected harsh, but realistic, operating conditions using oil-free compressed air with an oil content < 0.01 mg/m3 (class 1 to ISO 8573-1). Testing monitored two indicators of seal functionality: the leak rate at two pressure values (29 psi and 145 psi) and the break-off pressure in both directions. The break-off pressure is the minimum pressure needed to move the cylinder. It’s different for outstroke and return stroke because the pressurized area of the cylinder is smaller on the rod side.

High-pressure test: This test reflects the situation at peak pressure during the cushioning cycle. To avoid having to produce and dissipate excessive energy, the test equipment included a pressure intensifier to generate an operating pressure of 360 psi. The cylinders have a short stroke of 0.59 in. to simulate only the cushioning cycles. Special high-pressure lines and high-pressure valves are used.

After 100,000 cycles, the sealing function wasn’t compromised by physical damage, seal wear or leakage. Break-off pressure was the same as when new. The sealing system proved its robustness and reliability even under extreme pressure peaks during the pneumatic end-cushioning cycle.

Bursting pressure test: This test confirms seal robustness and safety in case of abnormally high pressure. For the rod seal, this test shows the safe fixation by the retainer nose. The cylinders functioned at the target pressure of 725 psi without problem. The first leakage occurred at 942 psi, when the rod seal was partly extruded out of the housing, but no seals were damaged. After re-installing the rod seal, the cylinder was fully functional with a leak rate and break-off pressure the same as new.

Low-temperature test: This test shows the minimum temperature under which the cylinder functions properly. The cylinders were installed in a temperature chamber and connected to an external measuring station to enable measuring of leak rates and break-off pressure. An additional air dryer helped avoid water accumulation in the system. After cooling down the system, the measuring was done quickly to avoid frictional heating that would affect the result.

The low temperature limits of the piston seals depend on their location on the piston, although the two piston seals are identical. The piston seal at the bottom of the cylinder is the most critical position because it is measured with the rod extended, when the guidance clearance causes a misalignment between the piston and the cylinder tube. The piston seal at the rod side is measured with the rod retracted, when piston and cylinder tube are in good alignment. Under such good conditions, the piston seal works well at lower temperatures. So, the degree of misalignment leads to a low-temperature limit between -4°F (piston seal bottom side, rod extended) and -22°F (piston seal rod side, rod retracted). The rod seal is tight down to -40°F because the volume shrinkage from temperature reduction helps to keep the lip in sealing contact.

To summarize, testing showed that the pneumatic cylinder remains fully functional down to -4°F under worst-case conditions, and down to -13°F under normal conditions.

Temperature cycling test: This test cycles between minimum and maximum operating temperature to show the seal material’s ultimate behavior. The test equipment was the same as for low-temperature testing. Temperature cycling revealed no leakage and no change in break-off pressure, which proves that frequent changes of operating temperatures don’t affect the service life.

Minimum speed test: This test explores a cylinder’s operation at creep velocity. The cylinder, equipped with a side-load weight, is pressurized on one side while a throttle valve on the other side is closed until the cylinder begins to exhibit stick-slip mode.

The test results demonstrate how a sealing system can be optimized with material technology and design knowledge. The thorough consideration of functional aspects and use of latest development tools produce better performance. The material development, focused on the specific demands of pneumatic applications, was the second component of a high-performance polyurethane sealing system. Pneumatic equipment manufacturers and end users can be sure of the best functionality under extreme conditions, absolute reliability and outstanding service life. Thus, the costs for replacement and consequential costs from production shutdowns can be reduced.

screamnews.com

Pneumatic Tips

The pump ideally suits portable, battery-operated equipment used in a wide range of OEM applications, including gas sampling, explosives detection devices, anesthesia systems, and medical analyzers, among others.

Among features, the pump’s elastomeric diaphragm promotes high efficiency and delivers oil-free operation without any risk of contaminating the sampled gas. Pumps can be specified either with an ironless core DC motor or with a brushless DC motor offering longer service life. PEEK housings and pump heads contribute high stiffness and temperature and chemical resistance.

Depending on model, these pumps can achieve flow rates to 2.1 l/m, vacuum to 650 mbar (11 in. Hg) absolute, and continuous pressure to 0.6 bar g (9 psig). All are engineered to perform maintenance-free with low power requirements and are supplied ready for installation to operate in any position.

Chemically resistant versions are available and pumps can otherwise be customized to meet particular application demands.

KNF Neuberger, Inc.
www.knfOEM.com

Pneumatic Tips

Designed for use across a range of applications such as hydraulic and pneumatic systems, pumps and compressors and in power generation, the switches provide a stable switching point setting.

The 400 series switch converts pneumatic and hydraulic pressure into switching functions and is designed for applications that require accuracy under high loads.

The switching point is fully adjustable through an adjustment knob with the adjustment range, and includes a locking mechanism.

AMS Calibration’s switch is SPDT, and can be normally open (N.O.) or normally closed (N.C.) depending on the wiring.

The 400 Series Switch is fitted with DIN EN 175301-803 Form A connectors for fast and easy installation.

It is also available with an LED indicator on the plug for visual monitoring of the switch status, or an M12 x 1 (4-pin) electrical connection.

The switch features a repeatability of ±2% of full scale, 360° rotatable male connections, high loadability (shock 30g, vibration 10 g) and Hirschmann (DIN EN 175301-803 Form A) with optional 36″ cable.

www.ams-ic.com.au

Pneumatic Tips

Surgeons report that medical devices such as endoscopes with the F-treated seals respond better to their touch than non-treated elastomer seals. Medical product designers claim custom F-treated seals improve nasal and liposuction canula.

Laboratory studies of a broad range of elastomer materials show the reduction of coefficient of friction of F-treated molded components. Since the modification occurs as a reaction with the polymer, the most dramatic improvement is seen with low hardness, polymer-rich elastomers such as a 55 Shore A compound.

Minnesota Rubber and Plastics
www.mnrubber.com

::Design World::

Pneumatic Tips

The BalContact™, an electrically conductive component that employs precision-engineered canted-coil™ spring technology, is being showcased at Elektrotechniek 2009 by U.S-based manufacturer Bal Seal Engineering, Inc. And according to the company, interest in the simple, versatile Bal Contact is expected to be high among engineers and manufacturers who are seeking a simple, flexible solution to high, mid and low current conducting challenges.

“When we demonstrate how the Bal Contact performs, people immediately recognize it as a solution they can apply quickly and easily,” said Josien Suntjens, a Bal Seal Territory Manager working at Elektrotechniek this week. “They’re consistently impressed with its elegance and simplicity, and they like the fact that it can help them lower manufacturing costs and simplify maintenance.”

According to Suntjens, the Bal Contact is available in a wide variety of wire sizes, coil heights and materials. Its spring is designed to maintain a nearly constant force over a
broad range of working deflections, compensating for large mating tolerances and
temperature changes without significant deviation from its initial force. Each coil in the Bal
Contact works independently, maintaining contact with the mating surface and ensuring
maximum conductivity, Suntjens said.

According to Bal Seal, typical applications for the Bal Contact include busbar connections, gas-insulated switchgear contacts, circuit breakers and industrial fuse boxes. In some environments, the Bal Contact can also be used for EMI shielding/grounding purposes.

Elektrotechniek attendees can learn more about the Bal Contact and other conducting, connecting, sealing and shielding solutions by visiting Bal Seal Engineering’s exhibit in Hall 09BV, Stand B060. A photorealistic animation of the Bal Contact at work in three different gas-insulated switchgear applications can be viewed at http://mediaroom.balseal.com/vod2

Bal Seal Engineering, Inc.

www.balseal.com

Elektrotechniek

www.elektrotechniek-online.nl

::Design World::

Pneumatic Tips

The materials engineered by Trelleborg Sealing Solutions for its new range of static seals for hygienic-design couplings have undergone extensive testing in commonly used Cleaning-In-Process (CIP) media. The tests prove that the materials are well-suited to these applications. In particular, Ethylene Propylene Diene Monomer (EPDM) E7502 and Fluorocarbon (FKM) V8T41 gave best-in-class results for their material types, with V8T41 demonstrating exceptional performance for a fluorocarbon sealing material.

“These results enable Trelleborg Sealing Solutions to give qualified advice and to recommend the optimum material for specific customer applications,” says Steven Farnsworth, Food, Beverage and Pharmaceutical Segment Manager for Trelleborg Sealing Solutions Americas. “Based on our tests we are confident that our new range of static seals for hygienic-design couplings in recommended materials will give long-term sealing integrity. This will contribute to a lower meantime between planned maintenance and overall reduced production costs for users.”

The three materials recommended for hygienic-design couplings, EPDM E7502 and FKMs V8605 and V8T41, underwent various tests, one of which was immersion in 21 commonly used CIP fluids. Along with four other characteristics, the sealing materials were measured for volume swell, a critical determinant of suitability for use in hygienic-design grooves. In all cases but one the volume change of the materials was well below ten percent, the percentage of volume swell that is deemed allowable in such applications. In fact, in most CIP media the change was less than five percent, the percentage of volume swell that is deemed perfectly acceptable in such applications.

The FKM V8T41 gave the best overall performance and one which is exceptional for a Fluorocarbon sealing material. In the demanding conditions created by a combination of a two percent solution of acidic acid, citric acid and formic acid at +140°F/+60°C volume swell of V8T41 was well below five percent. In a one percent concentration of acidic CIP media with oxygen at +104°F /+40°C, virtually no swell was recorded. In addition, the material is also suitable for hot water and steam applications up to +338°F/+170°C.

Trelleborg

www.trelleborg.com

::Design World::

Pneumatic Tips