Finnish marine systems group Wartsila has revealed a growing trend for container lines to keep vessels out of yards to make the most of booming rates.

The company has seen lower levels of activity in its scrubber retrofit business in the third quarter, even though activity is beginning to pick up again.

Tamara de Gruyter, president of marine systems at Wartsila, told TradeWinds that scrubbers have been a "tricky" market due to the narrowing spreads between high-sulphur and low-sulphur fuel oil.