Mechanical Technology November 2015

⎪ Nota bene ⎪

Avoiding a sticky situation

Index to advertisers Afrox................................................14 Atlas Copco......................................24 Clyde Bergemann..............................31 Hytec Holdings........................OFC, OBC Immanuel Works..............................IBC Instruweld........................................34 Koike...............................................25 Martec.......................................13, 19 SAIW ..............................................27 SKF...................................................9 SMC Pneumatics...............................22 Tega Industries..................................23 Verder Pumps...................................33 Weir Minerals............................... IFC, 2 Level 1: 17-19 February, 2016 Level 2: 22-24 February, 2016 +27 11 326 2708 matthew@martec.co.za www.martec.co.za February 2016 Energy Storage 2016 Conference 3-4 February, 2016 Paris, France mahsan@acieu.co.uk Africa Energy Indaba 2016 15-17 February Sandton Convention Centre, Sandton Debbie Mankowitz debbie@siyenzaevents.co.za Orkot is a fabric-reinforced composite material that uses thermo-set resins and a fine weave fabric material with added lubricants. It is good at damping vibra- tions and operates in virtually all media. It offers long service life, low friction and is suitable for all commonly used counter surfaces. q +27 82 604 5826 www.siyenza.za.com Airborne and Structure Borne Ultrasound courses bearing materials perform well in low or zero lubrication. While when tested under a load of 40 MPa, Orkot C480 showed extremely stable low friction – signifi- cantly better than other composites. “Overall, from tests so far, Orkot C480 is meeting the latest stick-slip challenges the market is presenting,” concludes Bakker. “We’re finding that Orkot C480 offers superior smooth sliding, either under high side load or when held quasi- static for extended lengths of time. That means this latest innovation can help our customers optimise their applications, however high their demands.” Industry diary

“ F luid power applications are placing higher demands on a material’s stick-slip behavior because of the continuous quest to im- prove performance and efficiency, while reducing weight and lowering costs,” says Peter Bakker, product line direc- tor for Orkot ® , the Trelleborg Sealing Solutions’ proprietary composite bearing material. “Environmentally-friendly and explosion-safe fluids, instead of conven- tional oils, are also more challenging media for bearings to operate in.” Bakker gives a typical example of new demands from fluid power manu- facturers. In wind turbine rotors, low stick-slip is needed for very short sliding movements of just a few millimeters. By improving friction characteristics of wear rings when adjusting the pitch of the ro- tor, considerable energy efficiencies can be achieved. Wear rings are a fundamental part of hydraulic applications and contribute to optimising the performance of sealing elements by transferring side loads act- ing on the cylinder, preventing metal-to- metal contact. “To research wear-ring behaviour in

hydraulic applications, we specifically design and build test rigs,” continues Bakker. “These include machines to test linear motion, wear-ring and counter-face endurance and simulation of operating conditions in temperatures and with side loads up to the most extreme values encountered in fluid power equipment.” One of Trelleborg’s ongoing and exten- sive test programmes uses a custom-built friction and wear machine to investigate stick-slip in reciprocating movements at slow to high sliding speeds and radial loads up to 50 N/mm². This research fo- cuses on Trelleborg products such as our Turcite ® polytetrafluoroethylene (PTFE) based compounds; HiMod ® reinforced thermoplastics and Orkot composites, including Orkot C480. “Turcite is the benchmark for smooth operation of wear rings and offers the lowest level of stick-slip,” says Bakker. “However, load capability is limited to 10 N/mm² and composite bearings are the option when the side loads exceed the capabilities of PTFE.” In tests under marginally lubricated conditions, wear rings were installed outside the oil chamber. Orkot composite

Wear rings contribute to optimising the performance of sealing elements by transferring side loads acting on the cylinder.

AWS D1.1: Structural Welding Code – Steel a new course by Bob Shaw The SAIW is revamping its structural steel welding code course, AWS D1.1. The new course is being developed by Robert Shaw, a world leader in the field, who will be deliv- ering the inaugural course in Johannesburg from January 18 to 21, 2016. years with a steel fabricator, ten years with the American Institute of Steel Construction, and the past 25 years as a consultant.

He is a long-time active member of the American Welding Society’s D1 Structural Welding Committee and a member of the AISC’s Specifications Committee. He also serves on ISO TC167 Working Group 3, developing a new ISO standard on the execu- tion of steel structures. www.saiw.co.za

Bob Shaw is founder and president of the Steel Structures Technology Centre, Inc., a consulting engineering firm in Howell, Michigan, USA. He offers 42 years’ of expe- rience in steel construction, working seven

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Mechanical Technology — November 2015