The disclosure provides methods for removing polymeric fouling on process equipment during low density polyethylene manufacture. A purge cleaning composition with ethylene gas containing at least one C3+ hydrocarbon alkene for a period of time is used to remove polymer build-up in at least one location in the polymerization plant, such as, without limitation, the reactor or in tubing between a reactor and a pre-heater or between a cooler and a preheater.

A process of cleaning a reactor includes providing an alcohol-containing material to the reactor; and providing a metathesis catalyst to the reactor. The reactor contains a high molecular weight polymer gel and an organoaluminum material. The alcohol-containing material is not an alkyl tartrate and may be selected from triisopropanolamine, 4-tert-butylcatechol, isopropanol, and phenol formaldehyde resins.