Rating Thread Compounds for Galling Resistance

Abstract

Results are presented from an experimental study which demonstrates the feasibility of using an existing galling tester and test method as a screening device for evaluating thread compound additives for galling protection. The galling tester employs tubular pin and box specimen pairs fabricated from steel tubing used in the oil field. For the test thread compounds, four different additive packages were used, all with the same grease base of lithium stearate. For reference purposes, the lithium stearate grease base without any additives was tested as one of the thread compounds. The data obtained on contact stress at galling failure show that of the five thread compounds tested, the best galling protection is afforded by the API Modified thread compound, the industry standard for casing and tubing used by the oil industry. The other four compounds show lower galling failure contact stresses of varying degrees. Friction coefficient data obtained during the tests are also presented and discussed.