Paper: Selection of Metallic Materials For Sucker Rod Pumps For Hydrogen Sulfide Environment

API Standard 11 AX, Subsurface Pumps and Fittings, sets forth specifications covering sucker rod pumps and establishes dimension requirements to assure interchangeability of component parts. No material specifications or guidelines for the proper application of the various API pumps are given. This report was prepared by NACE Task Group T-lF-12 and is intended to serve as a supplement to API 11 AX. It presents general recommendations of metallic materials for the construction of sucker rod pumps for service in a hydrogen sulfide environment. Only pumps with one piece barrels and metal plungers are considered. The recommended materials are presented in tabular form and in a preferred order of listing for nine different environments with varying degrees of abrasion and hydrogen sulfide corrosion. The materials recommended are in common use and should perform satisfactorily when used in the specified environment. In certain circumstances other materials could also be satisfactory. The materials recommended in Tables 1, 2, and 3 and the order in which they are listed are based on the experience and judgment of the Task Group members. These recommendations are not intended to preclude the development and testing of new materials for improvement of sucker rod pump performance. Tables 4-10 list some of the materials commonly used in sucker rod pumps along with pertinent chemical and physical properties. The numbering system for the steels is from the AISI classification, the brasses are identified by numbers from the Copper and Brass Research Association, and the copper-nickel alloys carry the International Nickel Company designations. The use of specific alloy numbers should be encouraged. It is recognized that there are steels utilized in subsurface pumps with hardnesses greater than Rc 22** (valves, hard cases on barrel tubes, etc.). Experience has shown, however, that these materials give satisfactory service in the proper environment. A good chemical program is considered necessary for optimum performance of sucker rod pumping equipment in a corrosive hydrogen sulfide environment. Some corrosion inhibitors control rod breaks and tubing and flowline leaks but do not significantly affect pump life. Other corrosion inhibitors significantly increase pump life by promotion of oil wetting thus reducing friction as well as reducing rod on tubing wear, rod breaks, and tubing and flowline leaks. However, in some pump designs the inhibitor cannot reach some stagnant *areas and protective films may be removed by the rubbing action. There are chemicals used downhole that extend pump life by prevention of fouling, and still others that extend pump life by prevention of scale. Control of direct attack on pump materials, however, is best accomplished by materials selection in combination with chemical treatment.