Large, continuously operating hot-oil systems can be cleaned without shutdown using Paratherm LC system cleaner liquid. To use it, replace 10 percent of the existing heat transfer fluid with the cleaner fluid and install a 100 micron element in the sidestream filter. The cleaner dissolves accumulated sludge deposits and releases them into the flow, where they are caught and removed by the filter. Filter elements should be progressively reduced over time to 50 micron and 25 micron filters. When circulation continues for a day without requiring changeout of the 25 micron element, the system is ready to be drained and recharged.