How Polymer Bearing Evolution Has Affected Scroll Compressor Performance

<p style="text-align: center;"><img src="/ueditor/php/upload/image/20220407/1649319766744794.jpg" title="1649319766744794.jpg" alt="1.jpg"/></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">Polymer bearings incorporating a PTFE-based running surface were viewed as a step forward in scroll compressor performance when they were initially introduced around three decades ago.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">These&nbsp;polymer bearings&nbsp;are comprised of a polymer surface layer, a porous bronze interlayer and a steel supporting layer. This composition has grown to be prevalent in compressor applications, with continued improvements in bearing composition and performance and consequently improved environmental impact.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">The application of the polymer to the bronze bearing interlayer has usually depended on the deposition of a composite slurry to create a surface that is low friction and wear-resistant.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">This method of deposition has served the compressor application well, but the inherent nature of the slurry-based process meant that the lifespan of the bearing was essentially restricted by the integrity of the polymer integrity and thickness of the polymer layer.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">Recent advancements have seen the development of new material technology in the scroll compressor sector. This allows <a href="https://www.bearing-asia.com/products/catalogue.html" target="_blank" style="color: rgb(0, 112, 192); text-decoration: underline;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px; color: rgb(0, 112, 192);"><strong>bearing</strong></span></a> manufacturers to offer improvements in terms of durability and seizure resistance compared to the traditional methods of slurry-based deposition.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">The resulting improvements in performance have been evidenced by means of comprehensive tribological testing in general tribological testing conditions and techniques pertinent to scroll compressor conditions.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">This article outlines an assessment of bearing materials produced by multiple process technologies as well as outlining tribological results recording performance enhancement.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">The test data shown includes findings from bearing development and manufacture, as well as quali?cation tests performed by a leading manufacturer of compressors, detailing advances in bearing durability and seizure resistance.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">The successful utilization of multilayer PTFE-lined bearing materials has occurred in a wide application base. The main reason for this is the filled-PTFE running surface providing self-lubricating properties that outstrip other methods available.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">The polymer’s innate low friction properties have facilitated increased e?ciency where applications are affected by sliding friction and has led to reductions in wear in systems where bearings are vulnerable to adhesive wear.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">The traditional three-layer con?guration for polymer bearings type consists of a porous bronze inner layer that has been sintered to a steel backing and impregnated with a ?lled-PTFE compound. This purposely allows a ?lm of the same composition to remain on top.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">Known as the overlay or upper layer, it is a vital element of bearing operation. A number of options are available in terms of composition:</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">The bearing may comprise of a PTFE and lead composition - the original multilayer polymer bearing innovation in scroll compressors.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">A lead-free version that has grown in use in various applications in order to adhere to increased environmental standards.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">The established manufacturing approach involved the co-coagulation of a PTFE-based aqueous dispersion that possesses the desired particulate ?llers. This allows for the creation of a slurry-based compound that can be introduced into the porous bronze structure.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">Further advances in the process have led to the development of a dry powder process that - along with compositional improvements - enhanced fatigue and cavitation resistance.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">Modifications in size (post-installation) in powder-based or slurry-based liner methods are restricted to burnishing for both materials. The powder-based liner has been shown to be able to go through signi?cant modi?cation through burnishing while preserving tribological performance.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">It is important to note that resizing via machining for either method led to a decreased working life for the bearing and greater friction due to the increased exposure of the bronze interlayer.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">The most recent advance in the production of PTFE-based tribological layers has been a result of the process of impregnating higher-integrity polymer ?lms.5,6&nbsp;Possessing the ability to build a thicker polymer overlay, these films provide improved resistance to crucial tribological conditions such as cavitation erosion and sliding wear.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">Traditionally, overlay thickness was usually in the range of 5 to 25 μm. The enhanced overlay form is ostensibly over 100 μm thickness.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;"><br/></span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 16px;">A thicker overlay neutralized the sizing limitations of its predecessors, allowing machining after bearing installation to reach a level of precision comparable to that of metallic materials. It also allowed for favorable tribological advancements in a range of conditions central to the operation of&nbsp;scroll compressors.</span></p>