119 replies to this topic

[Aussierob]

Tower 4 is a two section tower with solid flanges connecting the two pieces. The lower section somehow filled with water which froze and forced the flange off the top of the bottom section of the tower. The haul rope deroped off towers 3 and 5. (3 and 2 are a cluster at the bottom of the lift). Very fortunately there were no serious injuries. I'm led to believe the the tower can be repaired.

[2milehi]

Thank goodness that there were no fatalities in this accident.

I'll speculate on how the gondola stopped. I would say that a service stop was initiated by a deropement. With the comm line in tact, there may have been no E-Stops. A service stop is typically the slowest of all the stops.

[pete_b]

Why are there not small drain holes at the bottom of the towers? That would seem to be a simple solution to prevent failure from freezing.

[TRosenbaum]

According to the WhistlerBlackcomb website, it was ice-jacking that caused the failure.

Quoting from

http://www.whistlerblackcomb.com/media/new...8-09/081217.htm

"Several factors converged to cause the tower failure. The structure of the tower is such that two
parts are spliced together. Water had seeped into the tower which had turned to ice with the
recent extreme cold temperatures. The ice build-up caused the tower splice to rupture, an
extremely unusual situation referred to as "ice-jacking"."

This post has been edited by TRosenbaum: 17 December 2008 - 07:54 AM

[Jonni]

There probably weren't any holes because this doesn't normally happen to lift towers. When I say normally happen I mean that usually the lift towers don't have any way that water could get into the tube. There also hasn't been any issues like this on other Doppelmayr lifts, so there probably wasn't any reason before this accident to believe that it would be a problem. I do remember that there was a similar episode on another lift out West somewhere (I believe that it was a double chair) where the entire tower was split laterally down the length of the tower due to filling with water and icing. If forget where it happened and the manufacturer, but I don't believe that it was Doppelmayr. After that incident (which happened at night when there was no one around) a service bulletin was issued to operators of all lifts by that manufacturer to conduct a series of tests to towers made by that manufacturer. I believe the test was called the Bong test, which involved hitting the tower with a hammer near the bottom. If the tower made a hollow BONG noise after being hit, then it was concluded that the tower was fine. If the tower made a CLUNK noise when hit it showed that there was icing occurring inside the tower.

I'll see if I can find the news report about the previous incident.

[TRosenbaum]

pete_b, on Dec 17 2008, 10:40 AM, said:

Why are there not small drain holes at the bottom of the towers? That would seem to be a simple solution to prevent failure from freezing.

Until the small drain holes themselves freeze up?

[Peter]

The previous incident was on a Hall double at Silver Mountain, ID that had previously been in Pennsylvania. I have a picture at home, it was also on a two section tower.

[pete_b]

If there are drain holes water would exit while the temperature is above freezing. Once the temperature went below freezing there would not be any significant amount of water in the tower. Snow would not be a problem.

[WBSKI]

Even SAM can't get it right:

Quote

Dear SAM Headline News Subscriber,
Today in the news...
SAM Magazine--December 16, 2008--Whistler Village Gondola Collapses

[bwilky]

How do you prevent "Ice-Jacking"?

[TRosenbaum]

bwilky, on Dec 17 2008, 12:45 PM, said:

How do you prevent "Ice-Jacking"?

Prevent water from entering the tube in the first place.

[aug]

bwilky, on Dec 17 2008, 09:45 AM, said:

How do you prevent "Ice-Jacking"?

Do not let water accumulate inside a hollow stuctural member in freezing climates.

[bwilky]

So basically, is it part of your daily chores to go around and check all the towers for any possible signs of water leaking?

[aug]

Normally part of an annual check of the tower structure. Doing a visual inspection of the footing, welds , clearing the drain hole (if one exists), sounding the tower to see if water is inside(bong test) and physically checking the tightness (torque) of the tower base bolts and the flange bolts.

This post has been edited by aug: 17 December 2008 - 11:02 AM

[bwilky]

So It can't just happen overnight?

[2milehi]

aug, on Dec 17 2008, 10:55 AM, said:

Do not let water accumulate inside a hollow stuctural member in freezing climates.

How do we know that the tower was hollow? Concrete filled?

This post has been edited by 2milehi: 17 December 2008 - 11:15 AM

[aug]

In my career I have seen terminal towers (Masts) filled with concrete but I have never seen any line towers constructed this way.

This post has been edited by aug: 17 December 2008 - 11:24 AM

[bwilky]

I'm no expert, but that tower doesn't look hollow.
 wb_buildup.JPG (47.48K)
Number of downloads: 188

This post has been edited by bwilky: 17 December 2008 - 11:30 AM

[lastchair_44]

That's because it filled with water, then froze, and that's why we're all here chatting about what happened.

[lastchair_44]

Also, I'm no expert, but tower tubes aren't exactly air tight correct? This means that air, which has water vapor, can get in and when the temperature drops it condenses creating water droplets. I demo'd a Yan lift a few years ago and when making cuts at the base of the tower in preparation for fly day, there was a tower about 3/4 of the way up the line that had water in it (about six feet). I guess my point is, it doesn't matter that the previous incident involved a Hall double that had been re-located. This can very well happen to any lift regardless of the manufacturer.