The stem is a device that essentially helps to add weight to the toolstring. It provides the hammering action to the toolstring which in return allows the jars to transmit force produced by the movement of stem bars. Extra large and extra small OD stems are used based on different well conditions.
NOTE:: STEM WEIGHT GIVEN IS AT A BALANCE POINT.
The Wireline Stem, also called a weight bar, is used to add weight to the wireline tool string to counteract the wellbore pressure.
BALANCE POINT / FORCE = PRESSURE TIMES AREAFORCE IS WEIGHT REQUIRED TO BALANCE (IN POUNDS)PRESSURE IS WELL PRESSURE (IN PSI)AREA IS CROSS SECTIONAL AREA OF WIRELINE (IN INCHES SQUARED)CROSS SECTION OF CABLE =J D2 / 4WEIGHT REQUIRED (POUNDS) = PRESSURE (PSI) TIMES J D2 / 4 OF WIRE LINE