Induction Pipe Bend is a controlled means of bending pipes through the application of local heating using high frequency induced electrical power.
Originally used for the purpose of surface hardening steels, induction technology when used in Pipe Bend consists basically of an induction coil placed around the pipe to be bent. The induction coil heats a narrow, circumferential section of the pipe to a temperature of between 850 and 1100 degrees Celsius (dependant on the material to be formed). As the correct bending temperature range is reached, the pipe is moved slowly through the induction coil whilst the bending force is applied by a fixed radius arm arrangement.
Induction Pipe Bends/Spools and air/steam rings Tube Bending are manufactured by the process of induction heating in meeting diverse high quality requirements in accordance with ASTM, API, DIN, BS, ANSI, ASME PFI and other international technical specifications.
Manufacture of Induction Pipe Bends
Induction Pipe Bends are formed in a factory by passing a length of straight pipe through an induction bending machine. This machine uses an induction coil to heat a narrow band of the pipe material. The leading end of the pipe is clamped to a pivot arm.
As the pipe is pushed through the machine, a Pipe Bend with the desired radius of curvature is produced. The heated material just beyond the induction coil is quenched with a water spray on the outside surface of the pipe. Thermal expansion of the narrow heated section of pipe is restrained due to the unheated pipe on either side, which causes diameter shrinkage upon cooling.
The induction Pipe Bending process also causes wall thickening on the intrados and thinning on the extrados. The severity of thickening/thinning is dependant on the bending temperature, the speed at which the pipe is pushed through the induction coil, the placement of the induction coil relative to the pipe (closer to the intrados or extrados), and other factors.
Most induction bends are manufactured with tangent ends (straight sections) that are not affected by the induction Pipe Bending process. Field welds are made or pipe pup sections are attached to the unaffected tangent ends, allowing for fitup similar to that found when welding straight sections of pipe together.
Induction Pipe Bends come in standard Pipe Bend angles (e.g. 45°, 90°, etc.) or can be custom made to specific bend angles. Compound bends (out-of-plane) bends in a single joint of pipe can also be produced. The bend radius is specified as a function of the diameter. For example, common bend radii for induction bends are 3D, 5D and 7D, where D is the nominal pipe diameter.
Oil & Gas Sector – Onshore and Offshore Sub-Sea applications
Shipping and other Infrastructure Projects
|Size of Pipes||3″ – 14″||4″ – 36″||4″ – 48″|
|Pipe Bending Radius (mm)||1780||4575||7320|
|Thickness (mm)||5 – 50 UpTo 14” Dia Pipe||6 – 36 for 26” – 36” Dia Pipe||8 – 32 mm for 38” – 48” Dia Pipe|
ASME B16.49 Standard covers design, material, manufacturing, testing, marking, and inspection requirements for factory-made pipeline bends of carbon steel materials having controlled chemistry and mechanical properties, produced by the induction bending process, with or without tangents.
This standard covers induction bends for transportation and distribution piping applications (e.g., ASME B31.4, B31.8, and B31.11). Process and power piping have differing requirements and materials that may not be appropriate for the restrictions and examinations described herein, and therefore are not included in this Standard.
|Thickness||Upto 14” dia pipe – 5 – 50mm|
|26” – 36” dia pipe – 6 – 36mm|
|38” – 48” dia pipes – 8- 32mm|
The pre-inspected pipe having positive thickness is kept on the pipe carriage and clamped hydraulically on the rear carriage. The induction coil and cooling coils are mounted around the pipe.
The concentricity of induction coil is adjusted with 3-plane movement to assure the uniform heating by induction. The radius of bend is fixed by adjusting the radius arm and front clamp. The pointer is also set to the correct degree. The pipe is pushed forward slowly so as to clamp rigidly with front clamp. The pipe is marked for arc length and initial thickness / hardness measurements.
Before starting the bending operations the hydraulic pressure / water level / flow switches etc. are checked. The pipe is now heated by induction to the temp of 815 – 995 C. By pushing the pipe by push clamp the bending of the pipe is started slowly and carried out at speed of 10 – 40 mm/min.
The bending operation is stopped at the specified angle of bend and predetermined arc length. The bend is removed from the machine and kept on an inspection platform for measurement of tolerances.
Potential Material for Induction Pipe Bend
Carbon Steel (Seamless/Weld Seam) – (API 5L X42-52-60-65-70, P265GH, P295GH…)
Alloy Steel – ASTM A 335 Gr P11, P22, P5, P9, P9.1, P9.2, X20, 15CD205, 15Mo3, 15NiCuMo
Stainless Steel – TP 316, 316L, 304, 304L, etc
High Chrome Steel
High Nickle High Chrome Steel
Titanium (Grade 1, Grade 2, Grade 3, Grade 4, Grade 5)
Line Pipe – API 5L X52 / X65 / X70 / X80 – X100, A106 Grade.B / Grade.C / P1/ P9, A312TP304, TP316
Source: Zhejiang Yaang Pipe Industry Co., Limited (www.yaang.com)