Casing is a series of steel pipes that are run into a drilled oil well to stabilize the well, keep contaminants and water out of the oil stream, and prevent oil from leaching into the groundwater. Casing is installed in layers, in sections of decreasing diameter that are joined together to form casing strings.

Double submerged arc welded pipe (DSAW) derives its name from the welding process wherein the welding arc is submerged in flux while the welding takes place. Both inside and outside welds are required and are usually accomplished in separate processes. These separate welds consume a portion of the other resulting in a single high quality weld nugget.

Thick-walled steel pipe is a kind of economical section steel, which is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile transmission shafts, bicycle frames and steel scaffolding used in construction.

Galvanized steel pipe is steel pipe that has been galvanized. This coating protects the steel from corrosion, and it is most commonly used in outdoor buildings, such as fences and handrails, or for some indoor plumbing.

The application of spiral welded steel pipes can be traced back to the beginning of the last century，It has a history of nearly 100 years. First, the Germans invented the two-roll oblique piercing machine in 1885, and then invented the periodic tying machine in 1981; Tiffel invented the automatic pipe tying machine (also known as the head tying machine), and began to form the modern spiral steel pipe industry.

Solid bending, that is, compaction of the bend. During the bending process, the inner and outer rolls and the inner and outer walls of the galvanised square tube billet are compacted in both directions.

Steel pipe is a common choice for building projects for a variety of reasons, but one of the most frequently mentioned ones is steel's adaptability.

Galvanized steel can be made into a strong pipe or plumbing material, which is a material capable of resisting corrosion from water or the outside environment.

Galvanized steel pipes are steel pipes that have been galvanized. This coating protects steel from corrosion, and it is often used in outdoor construction, such as fences and handrails, or some indoor plumbing......

A106 and A153 are steel pipes that are widely used in industry. The appearance of the two pipes is similar. However, there are some differences in specs and quality.

API Coupling refers to the steel couplings that used in connecting casing pipe and tubing. Also known by OCTG coupling, it is usually manufactured in seamless type, material grade same with the pipe body (API 5CT K55/J55, N80, L80, P110 etc), same PSL or providing higher grades than requested. Same heat treatment also applicable, except there is an special requirements.

API 5CT is standard technical specifications for steel casing and tubing pipes used for oil wells in petroleum and natural gas industries. Besides casing and tubing, it also includes pup joints, coupling stock, coupling material, and accessory materials, and establishes requirements for three product specification levels (PSL-1, PSL-2, and PSL-3). The requirements for PSL-1 are the basis of this standard.