Falling (slinging) Ice Shields 1

[JAE]

We've seen a lot of newly constructed wind turbine generators go up all over the country.

In the northland, with snow and ice, there is the fact that ice can build up on the blades and eventually fall, or get slung, off the blades.

For equipment (transformer) located near the base of the tower, there is the fear of ice damage from this ice.

Question:
Are there any design guides, codes, provisions, etc. that deal with falling ice from towers, or more specifically, from wind turbines?

 

[steve1]

Perhaps this will help

http://web1.msue.msu.edu/cdnr/icethrowseifertb.pdf

 

[JAE]

steve1 - thanks for that - I'll read.

Primarily looking for design guidance on shielding structrues over equipment - I know it is impact loading and perhaps difficult to establish, but would like to be sure that we "know" what is out there in terms of design knowledge so we can stand on the phrase: "did what a reasonable engineer would do".

 

[racookpe1978]

You will find almost no ice shields on commercial wind farm buildings. The industry doesn't consider them worth enough to bother shielding the buildings from a "low-risk" damage that they'ed rather not talk about at all. Once built (and the set up and building subsidies are spent), the financial incentives to keep them running are small compared to the costs of the extra shielding.

 

[dik]

Great paper... I'd be a little concerned about a machine that can chuck a 2 lb chunk of ice 150 m... sure wouldn't like to be on the receiving end...

Dik

 

[msquared48]

Never even thought of it, but then I never thought a glass canopy would fall two stories onto a parking garage cauing the garage to fail either.

Poses the old question of what scenarious we design for, as long as we can forsee them.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Ron]

JAE...don't have access to it at the moment, but you might check the tower design standards (TIA). Another possibility is to check the railway standards. I remember having to design a canopy under a trestle for the impact of falling brake shoes from passing trains. Gave some good info on impact loading.

Another is the missile impact tests (TAS documents) in the Florida Building Code for windborne debris.

Ron

 

[steve1]

JAE, you're welcome. I would also look into design standards for tornado born missile barriers. A lot was done in the nuclear power industy in that regard. Good luck.

 

[SteelPE]

I used to work with an engineer who was hired once to solve this problem for a local television station. They were having problems with ice falling off of the towers and destroying their transmitting equipment. The equipment was stored in a building below a tower (yes the ice would go through the roof and destroy the equipment). I guess this was becoming a very expensive problem.

The solution was to create a structure above the roof in order to support grating that would break up the ice into smaller pieces that the roof could handle. This was done many years ago, and during a site visit a few years ago, was still in use. The problem that he had during the design was coming up with the amount of falling ice and defining the force delivered to the system.