Continuing Education: Wire Rope Understanding Traction Hoist Ropes in Today’s Elevator Installations Continuing Discussion on Perceptions of What Might Be Wrong with the Ropes by Rick Perry, Martin Rhiner and Kevin Heling system designs and the move to- Learning Objectives wards installing fewer elevators in After reading this article, you some commercial buildings. While a should have learned about: boon to building planners and archi- N Factors that can adversely affect tects, this move to do more with less hoist-rope life requires the use of smaller compo- N Why lubricating and tensioning nents, correspondingly aggressive hoist ropes are necessary sheave groove profiles, greatly in- processes creased elevator start cycles, tighter N As elevator machines age, hoist- bend radii for ropes and the use of rope life expectancy goes down sheaves requiring multiple angles of and why deflection. This places far greater stresses and demands upon the Over recent years, industry profes- ropes and ancillary equipment. Lastly, sionals have begun to acknowledge elevators themselves have evolved that increased reports of elevator from being used sporadically in facili- breakdowns connected to rope wear ties to functioning nearly continuously or rope failure are more than a simple due to increased demand and the sign of inherent rope manufacturing result of changing societal factors. or design deficiencies. Many are now This increased usage has meant that coming to see hoist rope “failure” as professionals have had to cease the result of a combination of factors measuring rope longevity as simply that more properly have their source how long (time frame only) they’ve in the initial installation phase of been in use on an elevator to instead a project or are points that are over- gauging how many starts the rope in Value: 1 contact hour looked during routine maintenance. the installation has delivered. In Indeed, many professionals are also short and most significantly, all these This article is part of ELEVATOR WORLD’s even coming to the opinion that a factors can and have combined to Continuing Education program. Elevator-industry key contributing cause behind “early” create installation environments that personnel required to obtain continuing-education hoist rope failure is potentially re- have moved from being somewhat credits can receive one hour of credit by reading lated to some industry calculations unfriendly, to ones that are decidedly the article and completing the assessment exami- that do not consider how newer, hostile to hoist ropes themselves. nation questions found on page 141. faster accelerating and decelerating This is the current reality. For this article and more continuing-education elevators are placing far greater This reality does not mean one opportunities, visit www.elevatorbooks.com strains on older, long-established rope should simply see hoist rope per- NATIONAL ASSOCIATION OF ELEVATOR CONTRACTORS selections (such as standard 8 X 19 formance as being trapped in a con- ® Approved by NAEC for CET CERTIFIED ELEVATOR TECHNICIAN sisal varieties) – strains that those stantly decreasing spiral and make EDUCATION PROGRAM ropes were not originally created no effort to address the situation. to handle. Instead, evidence shows that by Approved by NAEC for CAT Newer building designs, which paying attention to various factors, place a premium in using every bit of implementing and assuring some Approved by NAESAI for QEI floor space profitably, have helped certain preventative measures, and spur the rise of machine-room-less through the use of forethought and Continued April 2008 | ELEVATOR WORLD | 105 Continuing Education: Wire Rope Continued good planning, professionals can instead see hoist rope over the sheave (or sheaves) and then straightened again. performance levels that at least equal, if not surpass, It’s hardly surprising that a rope shows wear, or even that what they have become accustomed to seeing. a strand will break (even steel has its own inherent limits). Let us be clear. Hoist ropes are designed to higher stan- Instead, one should be amazed they perform as well as dards, are tested far more rigorously, use materials of a they do in an inherently destructive environment. higher quality and are manufactured to a degree of so- To the trained eye, a hoist rope can serve as a valuable phistication that would have been unimaginable in the messenger to alert you to upcoming problems and help past. Unfortunately, this still does not mean that they can- you better diagnose them. So, in fact, creating an inde- not fail; any moving machine part can. Forward thinking, structible hoist rope (though being quite a feat of engi- problem-solving state-of-the-art manufacturers can and neering) would actually be a disastrous development, will perform in-depth, post mortem, forensic analyses of because it would make them useless as a guide in help- returned samples and even go to those installations ing you diagnose the root cause behind even larger where a failure occurred in order to verify results. The potential problems. Replacing sheaves and surrounding analysis of current elevator designs and the desire to cre- equipment can be an expensive proposition – hoist ropes ate ropes that better meet the vastly increased demands are far less so. in current installations have led manufacturers to offer a It’s Not Rocket Science: It’s Hoist Rope whole new generation of hoist ropes that address these If you truly want to improve the performance of your needs. So rather than blindly blaming the ropes solely for hoist ropes, there are some simple facts you should the rise in reported incidents of elevator breakdowns, we consider that are basic to professionals but still bear feel it would better profit professionals to consider other repeating. factors that have an equal (if not greater) impact on rope Think Hard about What You’re Aiming for performance in today’s brave new world of elevators. As any good craftsman will tell you, “Measure twice, First, the Facts cut once.” In other words, a little bit of planning and con- Hoist ropes are not merely a random wrapped grab sideration can save you time and money. For instance, bag of stranded wires. They are precisely engineered, have you considered what an installation’s normal yearly surprisingly complex objects made of soft steel offering a stops and starts will be? If you’re expecting more than number of moving parts. Take for instance an 8 X 19 200,000 per year (which has become more and more the Seale hoist rope: it has 152 separate moving parts (eight industry standard), then you may need to use something strands, 19 wires per strand). In addition to being crafted other than standard sisal cores made of naturally imper- to be both strong and durable, elevator ropes must be fect natural sisal. Perhaps you need a parallel steel or designed to be flexible as well. Normally, these are mutu- mixed core variety. ally exclusive goals. Rarely is any item created to provide strength required to be able to bend with the same level of proficiency as well – normally, higher strength means rigidity. Undercut U- and V-groove profiles. The kind of groove configuration is an important factor in the choice of a hoist rope. Check whether the ropes will have to deal with aggres- sive sheave groove configurations; how many and how Overhead of Brugg Sisal Core 8 X 19 rope with construction diagram close are the deflector sheaves. Consider the Brinell Ropes do not work in isolation. They are required to be Hardness of the drive sheave to be used, and factor in able to work efficiently in unison with other ropes and sur- wire tensile grades and groove pressure combinations as rounding machinery. So wire and strand elements inside a a part of your thinking process. Consider using sheave rope must be able to flex, bend and readjust as it is pulled liners when using lang-lay rope and never substitute 106 | WWW.ELEVATOR-WORLD.COM | April 2008 six-strand ropes for eight, or eight for six-strand with- goes into the core (it is the foundation of any hoist rope), out written approval from the equipment manufacturer. and you should examine its design and understand the This is an issue critical to both system design safety limits and strengths of each design offered and select and proper function that supersedes availability consid- accordingly. Lastly, you should review whether a manu- erations. facturer’s process controls lay length, helix and torsion, and how the rope components (wires and strands) are actually assembled. Remember that each manufacturer’s rope is inherently different from another in design and composition. So it is unwise to use ropes from two different rope producers on the same elevator. The number of expected bending cycles (rope life) a rope must face is a key piece of information that must be considered prior to any rope selection. Formulas already exist to make this task much easier to perform. Ask your hoist-rope manufacturer to assist you. Choose a Rope that Fits Your Needs, Rather than Hoping that Available Standard Rope Will Fit the Situation It goes without saying that you should choose a hoist rope that meets the potential needs of your particular system, and don’t make your selection based solely on The Brinell hardness of your drive sheave is an important factor that needs simple convenience. If you’d like assistance in doing cal- to be considered when deciding upon the proper hoist rope. culations, why not consult with the personnel at a state- Choose Quality Rope – This Means the Right Rope of-the-art manufacturer for their recommendation on the Maker and the Right Rope Type for Your Application proper rope to use? After all, it’s their job to keep up with all the alternatives available.