The grease injection control head is part of the wireline pressure control package and is constructed to perform a wireline sealing operation for testing. The grease head creates a reliable seal between the interior of grease tubes and the outer diameter of the wireline.

Grease injection heads are comprised of two major sub-assemblies: the stuffing box (or pack-off) and the flow tube assembly. Flow tubes are placed around the wireline to exacting tolerances and along with flow tube sleeves, form the main length of the grease injection control head. This length generates sufficient column height to form an effective grease seal.