Seamless tubes and pipes are extruded from billet or ingot, and as such are produced from long products as opposed to the plate or coil flat products used to produce welded pipe. The majority of seamless tube and pipe producers are fully integrated in that they produce their own billet. Seamless tube and pipe is made to the specifications for grades that serve consuming markets including manufacturing, automotive/ aerospace, construction, structural, decorative, oil and gas drilling, oil, gas and water transmission, geological research, power generation and refineries.
The specifications for some uses can be extremely detailed and this type of pipe is rarely held in stock. It must be ordered months in advance with mill time set aside to produce the pipe. Depending on market fundamentals, lead times can span between 2-12 months. There is, however, an active distributor and service centre network to help keep the market flowing.
Seamless Tube and Pipe Classifications
1. Seamless OCTG
Oil country tubular goods account for about 30% of seamless production and similar to welded OCTG, the pipes are made in accordance to the American Petroleum Institute API standards, or even exceed those standards. OCTG casing is used to protect the tubing, which runs inside the drilled hole, down to the oil or gas well. Tubing or lifting pipe runs down the middle of a well bringing liquid/ gas to the surface or injecting water into the well. Drill pipe (technically not considered OCTG) is tube that is used to hold the drill bit or explosives.
The most common grades of OCTG are J/K55, N80 type 1 and type Q, L80 and P110. Any pipe above API 5CT N80 type Q must be heat treated. This is a limiting factor at many mills who lack heat treatment facilities or who do not have enough heat-treating capacity.
2. Seamless Linepipe
Linepipe is classified as any tube or pipe that carries liquids or gas across land, including oil, natural gas, or water. The pipe is laid in a horizontal direction, a key difference between linepipe and OCTG material. Seamless pipes are generally more expensive and cannot be produced in large diameters. Therefore, the majority of linepipe on the market is welded. Plastics and other composite materials have taken a portion of the linepipe market share, as the material is cost competitive.
The Oil and Gas industry is main consuming market of seamless linepipe. Grades for linepipe are similar to welded linepipe grades, ie API 5L. Pipe is also often called triple certified, covering API 5L b, ASTM A53 and ASTM A106. Seamless linepipe is used in pressure piping systems by refineries, petrochemical plants, and chemical plants, power generation plants, and on-shore and off-shore applications for oil and gas in the form of separator lines, gathering lines, and metering runs. A minor application is as oil and gas distribution lines for commercial applications. In extreme environments and conditions, higher grades of linepipe are used, such as X80 and above.