Type and technical specification of API sucker rod

Sucker rod is an important part of rod pump production equipment. The sucker rod works by connecting the pumping unit up and the pump down to transfer power. The rod string is composing of several rods connected by a collar.

The sucker rod itself is a solid rod made of round steel. With a thick forging head at both ends, and a square section connecting the thread and the wrench. The external threads of the two rod are connecting with a collar. The common coupling is using to connect the equal diameter rod, and the reducing coupling is using to connect the variable diameter rod

At present, the domestic sucker rod is dividing into two kinds from the manufacturer of materials, one is carbon steel sucker rod, and the other is alloy steel sucker rod. Carbon steel rod is generally made of 40 or 45 high-quality carbon steel.

Alloy steel rod is made of 20CrMo and 20NiMo steel. The rod is easily broken near the wellhead and thread.

The sucker rod string is composing of plain rod and underground rod. The top rod of the rod string is calling the smooth rod. The smooth rod and the wellhead sealing box cooperate to seal the wellhead.

Regular sucker rod type

The conventional sucker rod has the advantages of simple production process, low cost, small diameter and wide application range, and its utilization rate is about 90% in rod pumping Wells. Generally, the conventional steel rod is dividing into four grades: C, D, K and H.

• Class C sucker rod: for shallow Wells with light loads.
• Grade D sucker rod Steel sucker rod for medium and heavy duty Wells.
• Grade K sucker rod Steel sucker rod for corrosive light and medium duty Wells.
• Grade K, D sucker rod Steel sucker rods with the corrosion resistance of grade K sucker rods and the mechanical properties of grade D sucker rods.
• Grade H sucker rod Steel sucker rod for heavy and super-heavy duty Wells.
• Grades A and B are fiber-reinforcing plastic (fiberglass) sucker rods: the main material of the sucker rod body is fiberglass reinforcin plastic. And a steel connector is installing at each end of the sucker rod body.
• The FRP rod structure is composing of a FRP rod body and a steel joint with standard external thread of the rod at both ends. It is lightweight, corrosion-resistant, and can be using in medium pumping units to achieve deep pumping.

Sucker rod performance

The smooth rod is a special rod on the upper part of the sucker rod. Which is mainly using to connect the donkey hair braid to the downhole sucker rod, sealing by the wellhead sealing box. And transmits the surface reciprocating power to the downhole sucker rod. Smooth rod is dividing into ordinary type and one end pier thick type two.

1. Common smooth rods are identical sucker rod threads at both ends, the diameter of the rod is greater than the maximum outside diameter of the threads at both ends. Which is characterizing by the fact that the two ends are interchangeable and can be turning around if one end is badly worn.
2. One end thick smooth rod is one end of the smooth rod is thick and machined into a sucker rod thread, the other end is not thick and machined into a common thread. It is characterizing by good coarse thread connection performance, but the two ends can not be interchangeable.

Like the sucker rod, the rod is dividing into four grades, C, D, H and K, according to different strength and conditions of use.

The weight rod is a sucker rod with a large body diameter. Which is using between the sucker rod and the pump to prevent bending damage causing by the rod string compression. Which is conducive to improving the sucker rod life and pump efficiency.

A weight bar is a solid round bar with sucker rod threads on both ends. And an elevator neck and fishing neck on one end, as shown in Figure 1.

A sucker rod is a steel sucker rod with a hollow center. With the development of oil production technology, the use of hollow rod can solve the following problems:

• rod pump can effectively prevent well washing fluid from damaging oil layer and improve thermal efficiency.
• The hollow electric heating rod can be using to solve the heating problem of heavy oil and high condensate oil.
• Enables pipeless oil production.
• The use of hollow api sucker rod dosing, can solve the crude oil viscosity, point reduction and wax removal, wax prevention.
• supporting hollow pump, can solve the rod pump pumping well production test problems.
• can drive the rod screw pump, increase the transmission torque.