The company took its steam cracker at Geismar down on November 4 for a planned 6-10 day maintenance.
But the plant is now expected to be down longer than initially planned, resulting in the force majeure declaration, sources said.
Williams is now targeting a second half of November restart of the 1.2 billion lbs/year unit.
The outage will likely further constrain an already tight US ethylene market. In addition to the Williams outage, supply has been choked by a force majeure declaration by Ineos last week.
Ineos was forced to make the declaration after its Chocolate Bayou, Texas plant was shutdown due to a possible lightning strike.
Further supply constraints came via outages at Dow, Sasol, and Eastman.
Meanwhile, spot activity saw increased liquidity with November trading four times Tuesday, twice at 51.50 cents/lb MtB Wms and twice at 53 cents/lb MtB Wms. Additionally a November trade at 53.50 cents/lb MtB Equ was heard done.
Mont Belviue Williams (MtB Wms) and Equistar (MtB Equ) are ethylene delivery points in the US.
Wednesday morning, November offers were seen at 56 cents/lb MtB Equ and at 54 cents/lb MtB Wms while December was offered at 55 cents/lb MtB Equ and 54 cents/lb MtB Wms. Buyers though were notably absent and no corresponding bids were seen and no confirmed trades reported at time of publication.
