TECHNICAL STANDARDS UPDATE
Standards Committees Have Been Busy
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t has been a while since I’ve updated the activities of the ARPM standards committees. In this column I’ll look at the Belt Committee, active in ISO TC41 and with an extensive ARPM standard portfolio. The ARPM/ISO rubber belt Greg Vassmer community works in two broad areas ARPM of application: power transmission Technical Coordinator belts and conveyor belts. Its ARPM work is published in a series of specification standards numbered IP-20 to IP-27 and set of technical bulletins IP-1-1, IP-1-2, and IP-3 to IP-3-18. It also maintains IP-1, the Conveyor and Elevator Belt Handbook. Since the last update, four IP standards, the Conveyor Handbook and several ISO standards have been reviewed, some revised and one has been edited to include a major addition. Since the ISO standard activity is primarily confirmation of existing standards, focus on the IP standards and bulletins. IP-20 and IP-22, covering classic and narrow V-belts, have both been updated with new standard belt lengths added since the last revision in 2015. In addition, in IP20 the metric tolerances were updated and belt designations were added for imperial unit-sized belts. IP-27, covering toothed synchronous belts, has eased requirements on the belt tension used to measure belt length and now allow it to be treated as a reference rather than an absolute value. This tension is used by the belt manufacturer when measuring the belt length to ensure the belt meets required standard length and tolerance. Converting this to a reference value allows manufacturers to adjust the belt measuring tension to accommodate differences in belt construction and tooling. IP-3-18 for Curvilinear Synchronous Belt Drive Systems now adds misalignments due to shaft runout in the estimate of tension excursions caused by belt component tolerance. A tension excursion occurs when there is variation from nominal dimension, location or load in parts of a belt drive system. This causes variation in belt tension that needs to be minimized because it causes vibration, chatter and load spikes or, in particularly bad cases, excessive bearing wear.
24 Inside Rubber // 2022 Issue 2
How much of an excursion is okay? Less is better. The bulletin gives rough guidelines for the maximum excursion load allowed for the belt. But keep in mind, other parts of the belt drive system might be adversely affected at loads lower than the maximum belt load, and care in this area belongs to the system designer. The last update I’ll mention is the major addition to the popular IP-1, the Conveyor and Elevator Belt Handbook. A new chapter will be added outlining a method for manufacturers to measure – and for users to compare – the energy efficiency of different conveyor belts. Lower energy use means less operating cost and less environmental impact, especially in long, heavily loaded belts such as those used in mining operations. In long conveyor belt runs it has been found that the energy consumption is driven by the indentation rolling resistance (IRR). To understand IRR, picture the conveyor belt running over the top of each conveyor roller like an inverted tire (the roller), on pavement (the belt). Each roller is connected frictionally to the belt (otherwise the belt would slide over the rollers – a bad idea), each roller drains some energy from the forward motion. The rubber formulation of the rollertouching part of the belt is unique to each manufacturer and can reduce the energy loss from IRR up to 30%. To evaluate belts for a rating system the new IP-1 chapter recommends either of two types of tests. A type A test allows a direct comparison between suppliers since it requires a standard belt construction. A type B test doesn’t control the test conditions but is best for determining the impact on energy use of changing other variables in the conveyor – like increasing the roller diameter or changing the belt speed. Once a test type is selected and run per the new standard, a rating chart modelled after the energy efficiency charts used, for example, in appliances, is created displaying the test parameters and ranking achieved by the belt. This is an exciting addition to the handbook and helps the industry understand the energy impact of the equipment it uses. 2022 will be a busy year for the belters. Sixteen technical bulletins and five standards need to be reviewed. To get through the workload, and for the first time in a couple years, they plan to meet face-to-face to work through as many of these as possible.u
