24 Sealing Solutions
Eliminate grease and reduce O-ring friction High-performance thermoplastics, composites, and engineered components manufacturer, Greene Tweed, explains how one of its low friction coatings helped a customer overcome challenges with high durometer O-rings.
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large European petrochemicals company was facing difficulties installing dynamic O-rings made of Chemraz 526, a perfluoroelastomer with a durometer of 95 Shore A – the only grade suitable for their mechanical seal application. The cartridge seal would need to be disassembled, cleaned, and rebuilt using grease lubricant. Due to the force required to install the high durometer O-rings, the mechanical seal OEM realised it needed a faster and more reliable installation method without the delay a redesign would require. The challenges being faced weren’t limited to the installation of the mechanical seal into the pump; the OEM also encountered difficulty installing the seal head onto the sleeve because of the high durometer O-ring and found it hard to move the dynamic O-ring and risked hangup of the rotating face. To address these problems, Greene Tweed recommended a low friction solution to the OEM. Greene Tweed applied Enduro LF10, a low-friction, precision-applied coating to the high durometer perfluoroelastormer O-rings. Enduro LF10 coating is a proprietary vapour-deposited PTFE-based coating that can be applied to various components within manufacturing equipment, including elastomeric, thermoplastic, or metal components, to enhance their performance. The proprietary coating – used extensively in the semiconductor industry – succeeds by reducing friction and stiction to improve seal lifetime and drive down costs. The petrochemicals company wasn’t alone. In industries as diverse as pharmaceuticals, hydrocarbons, and chemical processing, many companies experience reliability challenges related to mechanical seals and friction as well as stiction of the O-ring sealing elements.
Quarter 4 2021
TESTING To investigate the performance of this high durometer O-ring coated with Enduro LF10, the OEM tested friction caused by coated and uncoated O-rings before installing the coated O-ring in a test rig. The test was conducted in a lab, where loading conditions were simulated to compare friction caused by a coated and an uncoated O-ring. The mechanical seal OEM began the test by looking at the performance of uncoated O-rings with and without grease. Next, it conducted the same test on O-rings coated with Enduro LF10. After the frictional test, the OEM tested the O-rings coated with Enduro LF10 dynamically by installing them into a mechanical seal test rig. The friction test results were clear: The O-ring coated with Enduro LF10 without grease exhibited the lowest friction. Using O-rings coated with Enduro LF10, the mechanical seal OEM could reduce the friction in ungreased mechanical seals to less than half compared to an uncoated O-ring of the same material. By reducing friction, Enduro LF10 enables the use of high durometer O-rings for dynamic seal without the need to
grease, preventing hang-up of the dynamic seal faces while improving performance. For the dynamic test, the Enduro LF10 coated O-rings endured 1800 hours of rigorous testing with exceptionally constant inlet temperature, outlet temperature, inboard (IB) face temperature, pressure, IB leakage, and outboard (OB) leakage. This consistent performance – without any dynamic seal face hang-ups – indicated extended service life of mechanical seals in pumps without the use of grease lubrication on the O-rings. CONCLUSION Enduro LF10 coating offers conclusive advantages by enabling the use of O-rings made of high durometer materials while lowering friction and eliminating the use of grease lubricants and their associated risks. That’s not all. Coated O-rings ready for installation are supplied by Greene Tweed, eliminating the variability of handapplying grease. Elastomer O-rings coated with Enduro LF10 are easier to install and can endure rigorous operating conditions with minimal leakage, consistent performance, and longer service life. chevron-circle-right www.gtweed.com www.bpma.org.uk
