Several economizer tubes in an oil-fired boiler failed near the passage of a soot-blower lance. Mechanical wear was found on the external tube surface. Possible causes including fretting by lance on tube and droplet or steam impingement. Sootblower design and the boiler operating history were analyzed in conjunction with a metallurgical analysis of one of the failed tubes. The cause of the erosion was identified as wet steam droplet impingement, the root cause being a combination of insufficient clearing of condensate from sootblower piping and excessive cycling of sootblower during operation.