Welded pipe (pipe manufactured with a weld) is a tubular product made out of flat plates, known as skelp that are formed, bent and prepared for welding. The most popular process for large diameter pipe uses a longitudinal seam weld.
Spiral welded pipe is an alternative process, spiral weld construction allows large diameter pipe to be produced from narrower plates or skelp. The defects that occur in spiral welded pipe are mainly those associated with the SAW weld, and are similar in nature to those for longitudinally welded SAW pipe.
Electric Resistance Welded (ERW) and High Frequency Induction (HFI) Welded Pipe, originally this type of pipe, which contains a solid phase butt weld, was produced using resistance heating to make the longitudinal weld (ERW). But most pipe mills now use high frequency induction heating (HFI) for better control and consistency. However, the product is still often referred to as ERW pipe, even though the weld may have been produced by the HFI / HFW (High Frequency Welded Pipe) process.
Welded Pipes are manufactured from Plate or continues Coil or strips. To manufacture welded pipe, first plate or coil is rolled in the circular section with the help of plate bending machine or by a roller in the case of continues process. Once the circular section is rolled from the plate, the pipe can be welded with or without filler material. Welded pipe can be manufactured in large size without any upper restriction. Welded pipe with filler material can be used in the manufacturing of long radius bends and elbow. Welded pipes are cheaper with compared to the seamless pipe and also weak due to the weld joint. Welded pipe can be manufactured in large size without any upper restriction.
Properties of Welded Steel Pipe
Steel has salient properties that can be utilized to advantage in buried pipelines. The following are desirable requirements of buried, pressurized pipe. These requirements can be achieved by welded steel pipe.
- Strength – Steel pipe has high strength and stiffness (modulus of elasticity).
- Ease of installation – Transportation and installation of steel pipe are expedited because of light weight and toughness — tolerance for forces, deformations and impacts that fracture brittle materials.
- High-flow capacity – Frictional resistance to flow is comparatively low in steel pipe.
- Leak resistance – All buried pipe must be designed — both the pipe and the soil embedment. Welded joints are leak-proof. Gasketed joints are designed to be leak-proof and bottle-tight within recommended limits of pressure and offset angle of the adjoining pipe sections.
- Long service life – Buried pipes are the “guts” of our civil engineered infrastructure — the delivery system for many of our increasing demands for supply service. Steel pipes will figure significantly in the world’s growing infrastructures. The service life of steel pipe depends upon rates of external corrosion and internal abrasion.
- Reliability and versatility – Steel pipe is reliable because of toughness (ductility). Steel pipe is versatile because of its ductility, and because of common procedures for cutting and welding. Special sections can be fabricated to meet virtually any requirement. Steel pipe can be provided in virtually any size and strength.
- Economy – Steel pipe is cost effective over the design life of the pipe. The final cost of buried pipe includes: pipe, embedment, transportation, installation, operation, maintenance, repair, modification and risk. Transporting steel pipe is cost effective, especially in large diameters, because of thin wall and light weight. (Requirements for blocks and stulls are minimal.) Installing steel pipe is expedited by light weight. Long pipe sections reduce the number of welds (or the number of bell and spigot joints that must be gasketed and stabbed). In the event of damage, steel pipe can often be repaired on site. In the event of a massive soil wash-out, welded steel pipe sections tend to hold together and minimize the disaster caused by a break in a pipeline.
Post time: Apr-07-2022