Experience in operation and maintenance of waste heat recovery equipment is valuable in planning new installations. For a number of years several waste heat recovery installations were in use at Imperial Oil Ltd. 's Sarnia refinery. Analysis of data related to these installations points to trouble areas and suggests new criteria for designing and operating future installations. Design data for one waste heat boiler, the flue gas crude exchanger and the air preheater are shown in tables. The two waste heat boilers were designed for similar conditions except that one boiler included an economizer and six sootblowers. Recommendations for practice are given.