The HX-C25EL/C45EL semi-retractable sootblower is a derivative product of the HX-C25 and HX-C45 long retractable sootblowers. Except for the part of the lance that remains inside the furnace and the addition of a lance support plate, it is identical to the long retractable sootblower. The long retractable sootblower has nozzles only at the end (the nozzle head), and when not in operation, the entire lance is outside the furnace. In contrast, the semi-retractable sootblower has a portion of its lance always inside the furnace, with multiple sets of nozzles (one or two per set) installed at both the end and the middle section of the lance. During the extension and retraction process, nozzles at different positions clean different areas, often covering a cleaning range that is twice or even more than the travel distance.