Each year, public transport ropeways in the U.S. and Canada are required by either local code or national standard to be inspected by a “qualified” inspector. But, how qualified these inspectors are can range from not at all to design engineers with significant maintenance and operation experience.
In one instance, an inspector, after trying without success to snowshoe up a T-bar lift in fresh deep snow, tried using the T-bar with snowshoes. He gave up and simply inspected the lower terminal, then retreated to the lodge where he “inspected” the remaining parts of the lift with binoculars. Although these incidents are hopefully behind us, the potential for improperly trained, poorly equipped inspectors is still with us today.
The operation of ropeways is not an exact science, and the variations between equipment, operating conditions and usage illustrate the need for an inspector to be well versed in the field. There is no inspection checklist, guideline or useful form to fall back on. There are no conditions or requirements for qualifying inspectors. And ultimately, the owner is responsible for the safe operation of ropeways. All others involved—designer, contractor, inspector and the authority having jurisdiction—can either assist or detract from the operation by their actions.
So how does an area owner insure that his ropeways are operating as safely as possible? By recognizing that an experienced and qualified inspector will help the owner operate the equipment reliably and safely, while an inexperienced inspector might divert attention away from more serious issues.
How Inspections Go Wrong
Let’s look at how the inspector’s contribution can detract from the safe operation of ropeways. If, by his actions, he causes the operator to focus on the wrong aspects of the operation to the point of neglecting those items that are more important, he is a liability.
One reason this can happen is inexperience. One example: In 1946, a bicable fixed grip chairlift was installed at Berthoud Pass, Colorado. This was a rare construction; I know of only one other ever built, at Snow King in Jackson Hole, Wyoming. Over the years the Berthoud lift was operated with a reasonable degree of success.
Ownership of Berthoud changed in the 1980s. At the time, the characteristics of this one-of-a-kind machine were known primarily by the designer, Heron, and the operator. After the sale, this knowledge base shrank. Then Heron Engineering Co. was sold and re-sold through the late 1970s and early 1980s.
The Colorado Passenger Tramway Board then subjected the lift to a series of frequent inspections:
- March 7, 1987 by PE #1
- July 29, 1987 by PE #2
- September 8, 1987 by PEs #1 and #3
- October 15, 1987 by PE #4
- December 9, 1987 by PE #5 and #6
- December 12, 1987 by PE #4
- December 14, 1987 by PE #5
That is seven inspections by six different physical engineers in a ten-month period. On December 22, 1987, there was an anomaly noted in the haul rope. On December 26, there was an accident in which the rope and carrier #5 deroped. And on January 10, 1988, carrier #3 slipped back into carrier #4 resulting in passenger injury. The most inspected lift in the country was finally closed.
The resulting question is: Did those seven inspections help or hinder the safe operation of the lift?
Here are some things to consider. The lift was unique. Few, if any, of the inspectors had any significant experience on a fixed grip bi-cable lift. The six different inspectors focused on very different aspects. The job of responding to the written items, which the inspectors noted was onerous, and “fixing” the noted “defects” just may have drawn attention away from the most critical elements of the lift.
Critical Elements
A ropeway has some unique and critical elements, mainly the rope, grip and sheaves and how they work together. First, the rope must move smoothly over, under and around the sheaves—areas often overlooked by inspectors or taken for granted. Proper sheave alignment is the first line of defense against deropement. Further, grips which have the rope lay cast into them must be installed so that they mate with the ridges and valleys in the rope—again, often overlooked by inspectors in favor of less important items, simply because some inspectors have little or no knowledge of lifts.
Another example of mixing priorities involved a missing UL label on an electrical box. However, the lift was 40 years old at the time, and the missing tag had little to do with the safe operation of the lift. One inexperienced engineer attempted to calculate the weight of the counterweight and question its proper application on a lift that had a record of 25-plus years of safe operation. Time, effort and money was spent educating the inspecting engineer that the counterweight, as designed and built, was well within the range of engineering calculations and applicable standards of the time. Better use of the limited resources could have been made.
It can be difficult for some inspectors to become familiar with the operation and maintenance of lifts without significant study. There is neither a guideline, list or standard form which covers all the items to be inspected for all ropeways, nor a description of the conditions for acceptance or rejection of continued operation. Efforts to use just the ANSI B77.1 or Z-98 standards for items important to the operational safety of the ropeway could be severely compromised—these standards were never intended as the only guide for inspectors. Subsection 3 of each section of the ANSI standard involves operation and maintenance and should be reviewed by the inspector; however, most of these items can’t be verified without also looking at the lift.
Cooperative Effort
Another way to ensure safety on ropeways is to work with the inspectors. The proper and safe operation of the lift is the responsibility of the owner, and his role in inspections is to assist the inspector in reasonably accomplishing his task. This means the inspector must know what relevant incidents and accidents have occurred, how they happened, and what their causes were. Knowledge of close calls and incidents often allows avoiding more serious events. And share the information on all lifts with all operational personnel—we can broaden their background which may otherwise be restricted to one or two lifts.
Of course, the inspector’s knowledge of the key elements of the machinery and how they interact is also critical.
Key Elements
One of the most difficult aspects of the inspection process is that tramway engineering is an inexact science. The heart of a ropeway, and the key to its design, lies at the interface of the rope and the attaching mechanism. This interface dictates the width and profile of the sheaves (with the exception of some bi-cable reversible machines). The next element is the rope and grip to sheave interface. It is imperative that the sheave assembly be in the plane of the bend of the rope. The adjustment of the sheaves where gauge changes occur can be a compromise, due in some cases to large changes in tension as loads vary. Changes in load on the rope also compromise the required location of sheaves in such gauge change locations.
Another example is the line friction values used in calculations can vary from .025 to .04 depending on the firm doing the calculations. Input data such as the weight per foot of rope is only accurate to about two decimal places. Concrete density is also a variable with an accurate weight unlikely to exceed two places. Therefore, calculations showing an accuracy beyond three decimal places are stretching reality.
Another example: In establishing the position of spread-gauge sheaves, the vertical load is a function of the weight of the bare rope, carrier weight, passenger weight and rope tension. The horizontal load is a function of rope tension. No single position of the sheave assembly will satisfy all of these varying situations. The final result will be a compromise.
With knowledge that the sheaves must be in the plane of the bend of the rope, the inspector should be able to recognize deviations from the proper position. Rope twist will result when sheaves are out of the plane of the bend of the rope. The influence on the rope will be the greatest at the sheave(s) where the length of contact is the greatest and the rope groove is smallest relative to the rope.
Rope twist at bullwheels is believed to be the predominant influence on external grips migrating along the rope. Significant rope twist occurs when the guide sheaves are improperly adjusted or become worn. This wear process is slow and insidious, and not all manufacturers provide an easy means to adjust and compensate for that wear.
Case in point: misadjustment of the guide sheaves going into and out of the bullwheel occurred on a 15-year-old platter lift at Donner Ski Ranch. The rope twist was so severe on this machine that the rope was re-spliced once or twice a year. The splicer either failed to review the cause, or, if he did, was unable to identify the problem. The lift had been inspected annually, and the inspectors had also failed to note this readily visible situation.
Another example: a lift at Pine Knob, Michigan, had an assembly with an angular misalignment. The shaft supporting the assembly showed signs of movement, indicating the unit was moved inboard. In its original position the assembly was angularly misaligned. The rope ran to the inside and cut the flanges off of both sheaves, deroping the cable to the inside where the cable catchers tore off six chairs. Failing to understand the problem, the maintenance people made the correction common to many of the untrained: If the rope is running to the inside, move the assembly in. Wrong! The rope will again cut the flange off the sheave and the accident is destined to recur. This lift had also been inspected annually, without detection of the defects.
Ropeway inspectors need to have significant knowledge of ropeways. They should be armed with the basic knowledge of how a ropeway operates. They should visually observe the lift—its towers and terminals from end to end—by either riding the lift or walking the liftline (in good weather). They should be able to identify out-of-position sheaves or adverse wear. Properly communicating these concerns to the operator will assist the operator and allow him to further evaluate the situation.
The inspector who lacks this depth of ropeway knowledge is hindered and can only report the presence or absence of items such as signs, posted operating instructions, labels, daily logs, UL stickers, etc. Although helpful, this type of inspection falls far short of what we would like to have. In some jurisdictions we have a long way to go.
OITAF-NACS Meets at Alyeska
At the 8th Symposium of OITAF-NACS, held in mid-September at Alyeska Resort, authors from several European countries, India and the United States presented papers on ropeways. Attendees included ski and tramway operators, tramway engineers, ropeway manufacturers, wire rope companies, regulators and researchers.
Bill Alsup of Diener-Alsup Wire Rope Services received the OITAF-NACS Achievement Award. Alsup has been installing lifts since the late 1950s.
Information on authors, abstracts, and papers from this and previous Symposiums is available at www.mines.edu/library/ropeway or www.ropeway.coalliance.org.
The next symposium is scheduled for September 2004. For information contact OITAF-NACS president George Boyden ([email protected]) or NSAA’s Sid Roslund ([email protected]).
