Sucker rods take many forms based on their specific functions. Weight and strength are key factors in sucker rod string design. The rod at the top of the string must transmit the weight of all of the sucker rods beneath it as well as the weight of the pump. Add to this the weight of the oil being lifted plus any viscous drag created with the sides of the well bore and loads can reach tens of thousands of pounds. Rod material strength versus weight is an important consideration for well string design.
Steel sucker rods are the traditional sucker rod design. They come in diameters of 0.625 to 1.125 inches. Lengths established by the American Petroleum Institute (API) are 25 and 30 feet. Steel rods are available in varying grades that range in tensile strength from 90,000 to 140,000 psi.
Fiberglass (FRP) rods offer benefits compared to steel sucker rods. Fiberglass sucker rods are stronger, lighter, and more elastic than steel sucker rods. Resulting weight and drag reduction reduces stresses on the rod string. Fiberglass sucker rods also resist corrosion. Fiberglass rods are weak when loaded in compression, however. As a result, steel sucker rods must be used on the bottom of the string to absorb the buckling forces should the pump stick on the downstroke. Several disadvantages of FRP sucker rods are premium cost, greater difficulty in installation, and somewhat greater care requirements in field operations.
Pony rods are shorter than 25 feet and vary in length. API has established that pony rods come in six lengths: 20, 44, 68, 92, 116, and 140 inches. Pony rods are used to bring the entire rod string to the desired working length. They are commonly placed adjacent to the polished rod at the top of the rod string, on top of the rod pump, and on top of the polished rod to prevent the string from falling downhole if the polished-rod clamp slips
Polished rods are the top-most rod in a rod string, and form a tight seal with the stuffing box on the wellhead. These rods come in various lengths and sizes; API polished-rod lengths are 8, 11, 16, and 22 feet. Polished rods are made of various materials, including carbon steel, stainless steel, and Monel. Though API guidelines call out a finish of between 10 and 20 micro inches, a finish of 16 micro inches will provide a balance between wear and clamping efficiency. Polished rods must be properly aligned to minimize wear.
Vigor's production of oil pumping rods strictly adheres to the standards set by API 11B and Norris, ensuring the use of high-quality materials and meticulous manufacturing processes. These rods are designed to perform exceptionally well in a variety of challenging downhole environments.
Before formal production begins, Vigor's quality team establishes production processes, sets manufacturing standards, plans production timelines, outlines final inspection criteria and assigns qualified inspectors. All these details are compiled into official documents and shared with our clients for their review and confirmation. This meticulous approach is aimed at ensuring that our clients receive exceptional products and the highest quality of service.
If you are interested in Vigor's products and services, please feel free to contact our professional technical team for the most comprehensive technical support available.
