Strand Jacks, Pulling for You

One thing that makes the job of freelance writer interesting is the sheer diversity. In the last year I've written about drones, strategic bombers, astronauts vs. automated spacecraft, and crisis teams. Right now I'm working on war alerts, the validity of computer models, and a children's book.

Which brings me to yet another unconnected topic, the strand jack. Back when I worked in construction with my brothers, one tool that we greatly admired was the railroad jack, a heavy duty (and also very heavy) manually-operated jack sturdy enough to lift a bridge beam.

Railroad jacks push; strand jacks pull (more on that below). Here's a big strand jack, from mammoet.com:

(For those who might wonder what heavy riggers do, Mammoet does stuff like this, delivering coking units:)

Now about strand jacks, which will be critical to the success of salvage work coming up at Costa Concordia. First, the big picture, from Corriere Etrusco:

As animated in the Parbuckling Project, salvors will be pulling the cruise ship upright (that is, rotating the ship so that the superstructure moves to the left, in this photo), refloating the ship, and towing it to a drydock for scrapping.

While that may not sound too difficult, it is, for many reasons. And it's why the insurers' cost estimates are now edging $400 million.

Here's one reason for the high cost: Concordia is huge and its hull came to rest sideways on two subsea promontories, one fore and one aft. So that means the midships is sagging. While a gang of strand jacks can move any artificial object that mankind cares to build, however large, they can also tear it apart. If salvors were to just start using them to drag the ship upright, the tension on that unsupported midsection would break the hull in half.

So they've been laying down 20,000 tons of cement grout in big bags, filling in the valley (temporarily) to give the hull a sturdier foundation before the hydraulics do their stuff.

Recently Salvors have started the next phase, attaching big steel boxes called caissons to the port side. These caissons will be filled with water, and then it's time for the strand jacks. Here are a couple of the big blue machines, hanging from a formidable crane hook (Photo, Parbuckling Project):

Setting aside the caissons, here's a Parbuckling Project illustration showing how the strand jacks will be lined up along the port side, working in unison to drag the ship upright. 

The term strand jack comes from the fact that it exerts force on strands, commonly steel cables. Think of how you'd lift a bucket on a rope, hand over hand: one of your hands pulls on the rope, as the other shifts to get a new grip.

It's the same with strand jacks, which use hydraulic grips to pull cables a few inches at a time. Commonly the jacks work in groups under computer control.

Strand jacks are slow but very powerful. In 2004, strand jacks raised a 2,000-ton section of roof at the Wembley Soccer Stadium (Photo, Engineering News-Record):

 

Fertilizer-Plant Explosion in West, Texas

A little about the explosion at West, Texas. A Chemical Safety Board go-team is at the site, along with investigators from the Texas State Chemist . This news report says experts have identified the epicenter of the explosion, but aren't releasing that info yet. Later, we'll get the official word about exactly what exploded and why.

But the center is pretty clear from this photo in the Fort-Worth Star-Telegram, given streaks and the location of debris (Tony Gutierrez, Associated Press):

Note, for example, where the company's big ammonia tank sat (the round yellow foundation at upper right) and where the walls of that tank ended up. A line connecting those two locations leads to the center point of the explosion. While I haven't seen an official diagram of the plant, the epicenter looks like the north end of the dry barn mentioned in some news reports.

Here's a labeled photogram of the blast site, along with an aerial posted on Bing.com from last year. (Kudos to Bing and Pictometry for having recent aerial photographs on line):

We're told that West stored a large quantity of dry ammonium nitrate fertilizer in the dry barn, perhaps 270 tons at times. From a good piece in Chemistry World about ammonium nitrate, here's a snip:

"It is an intriguing feature of ammonium nitrate is that it should not, according to thermodynamics, even exist. It is a compound that contains nitrogen in two forms - surrounded by oxygen in one and by hydrogen in the other. In chemical parlance the nitrogen is, side-by-side, in oxidised and reduced forms. Normally one would expect them to react together, combining to form the more stable dinitrogen, dioxygen and water in a complicated partner swapping process called comproportionation. But in ammonium nitrate, this process does not happen at room temperature, making it a metastable compound, like a lake of water trapped behind a dam. Even if you are careful, ammonium nitrate is an accident waiting to happen."

When heated in a fire, ammonium nitrate doesn't always blow up but it might. If the smoke changes color to some shade of orange, that may mean the material is in a runaway reaction generating oxides of nitrogen. I interviewed a worker at a dynamite plant who once saw fumes from an overheating vat of metriol trinitrate change color in such a fashion, and he ran fast enough and far enough to survive the blast.

And one witness in West mentioned that the smoke from the fire at West Fertilizer changed color shortly before the blast.

Nightmare Range, South Korea

I'm a fan of H.P. Lovecraft. In our POW (plain old world) one doesn't often come across geographical names that measure up to Lovecraftian standards, along the lines of his Mountains of Madness. 

But here's a real one that comes close: Nightmare Range, a target-practice area in far north South Korea. It's just a hop-skip-and-a-ricochet from the DMZ, certainly reachable by shell from the DPRK's dug-in heavy artillery just north of the border.

Here's a map, from a recent naval survey of training sites, with the label for Nightmare Range highlighted at upper left, with its location to the side:

 

 

The border with North Korea is the gray line on the map just above Nightmare Range. On an island in the Yellow Sea south-southwest of Nightmare is Chik Do Range -- see the other label. Chik Do is where US bombers did practice runs last month. So we haven't been as provocative as some commentators are saying; practice bombing runs at Nightmare Range would have pushed tensions up a lot more.

Here's an aerial photo of Nightmare, from the Wikimapia site:  

This obscure location came up briefly during an August 18, 1976, meeting of the Washington Special Action Group (WASAG), a small but very influential foreign-policy advisory group in the Ford Administration and, previously, the Nixon White House.

The subject that day was what to do about a murderous attack in which a squad of North Korean soldiers jumped a small American-ROK team that was attempting to trim a poplar tree for better sightlines between observation posts in the DMZ.

Among the many response concepts bounced around by WASAG (not all of which have been declassified) was having American aircraft do practice bombing runs all the way up to Nightmare Range. That was scrubbed as too provocative, and more modest measures were taken when finishing the tree-trimming two days later ... but with a great deal of firepower waiting just over the nearest hill. Call it armed arboreal diplomacy.

For those interested in knowing more about what North Korea itself called an "ultra-tense" situation, I'm researching it as part of an article on military alerts to be published in Air&Space.