More exploding boules

We’ve blogged before about exploding leisure boules, but until now no-one has been killed or seriously injured by such an explosion. Today, however, a Thai newspaper reports that a player in Thailand has been killed by an exploding petanque boule. The story is rather bizarre.

Apparently some Thai players believe that soaking boules in water and then heating them can somehow improve a player’s ability to put spin on the boules. In preparation for an after-work game with his buddies, a firefighter named Decho Phetchnin had been heating his set of 3 boules on an “Ang Lo” burner for about two hours when one of the boules exploded, blowing the burner apart and scattering debris in a 10-metre radius. The explosion occurred while Decho was bending over the burner stirring the boules. A metal fragment from the exploded boule struck Decho in the forehead, piercing his skull and killing him instantly.

The photo that accompanies the story looks like the boule might have been a leisure boule (rather than a competition boule), although it’s hard to be sure. The dust visible in the picture suggests that the boule (like many cheap leisure boules) was filled with sand.
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Exploding leisure boules

On Saturday, September 4, 2016, in the German town of Nettetal, near Düsseldorf, during a neighborhood party, in the middle of a tent erected for the event, a petanque boule spontanously exploded. The explosion ripped a hole in the ceiling of the tent and left a small crater in the ground, but nobody was injured. A Düsseldorf bomb squad removed the remaining seven boules in the set and safely detonated them.

The investigation of this incident is still ongoing, but it recalls a similar incident that occurred in Switzerland in 2009.  In that incident, the Swiss Federal Laboratory for Materials Science and Technology (EMPA) analyzed the remaining boules in the set in an effort to determine the cause of the explosion. The boules in question were cheap leisure boules with thin metal walls, filled with a sand-like mixture (French news reports referred to it as “mortar”) to bring them up to proper weight. The sand was damp and contaminated with iron filings.

The moisture in the sand corroded the iron filings. Inside the sealed boules, in the absence of oxygen, that chemical reaction produced hydrogen gas, which caused high pressure inside the boules. The cheap boules had poorly welded seams. Under the pressure of the hydrogen gas, the seam of one of the boules failed and the boule exploded. It literally blew its top.

In the 2009 incident the set of boules was sitting on a shelf in its original packaging. In that incident, the Swiss department store chain Coop, which sold the sets, immediately stopped selling them and launched an aggressive recall campaign.

On the Wednesday following the explosion in Nettetal, the German federal government issued a press release warning the public of the danger of cheap boules. The German Petanque Federation (DPA) recommended buying certified boules and shopping for boules in specialty stores rather than in supermarkets.

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The boules that exploded in Switzerland in 2009. The boules were stored in the black bag shown on the right. Note the top of the exploded boule on the left side of the shelf, the sand scattered about the shelf, and the dent in the shelf wall at the right. It looks like the black bag must have been standing upright against the wall when the boule exploded.

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Closeup of the bottom half of the exploded leisure boule in its original packaging.

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Cross-section of another boule in the set. In addition to the sand filling, note the thinness of the metal shell.


For an interesting short video showing EMPA testing cheap boules, see THIS.

For EMPA diagrams comparing cheap leisure boules to competition boules, see THIS.

The EMPA engineering failure analysis, “Investigation into the mechanisms leading to explosion of pétanque balls”, is available HERE.