KNOT Offshore Partners reported what chief executive Gary Chapman described as a “strong performance” in the second quarter, even as impairment charges on two tankers pushed its bottom line into the red.

The New York-listed shuttle tanker owner reported a second-quarter net loss of $40.4m, pulled down by a $49.6m impairment of the 59,300-dwt Dan Cisne (built 2011) and Dan Sabia (built 2012).