A US Court has ruled that Rockwell Automation is liable for $97.6m in damages following a gas explosion in February 1999 that destroyed a 12-storey boiler at a power station operated by Kansas City Power and Light (KCPL). A Missouri appeals court has overturned an earlier ruling that had limited the damages payable by Rockwell to just over $190,000.

In 2001, KCPL filed a suit against Rockwell asserting that defects in an Allen-Bradley PLC and a troubleshooting guide had caused, or contributed to causing, the explosion at its Hawthorn 5 power plant, which is said to have cost the utility $600m. In March 2004, a jury awarded damages of $452m, allocating 70% of the blame to KCPL, and 30% to Rockwell. But a district judge subsequently decided that Rockwell`s liability was limited to the contract price - $190,867.

KCPL appealed against this judgement. The latest decision from Missouri Court of Appeals for the Western District overrules the earlier decision and raises the damages to almost $100m.

The PLC was used in a replacement burner management system (BMS) at the power plant, which controlled and monitored fuel delivery into the boiler heating system. KCPL alleges that defects in the design of the BMS and its components (including Rockwell`s PLC and troubleshooting guide) resulted in the erroneous transmission of signals that opened gas valves and igniters and led to the explosion.

Rockwell is expected to appeal against the latest ruling. Even if it loses, the cost of the damages is expected to be covered by insurance.