Spiral Seam Research Articles

Experimental and Numerical Fracture Toughness Evaluation of Spiral Seam Weld of API X65 Steel

In this research fracture toughness of spiral seam weld of API X65 is measured through the ASTM E1820 standard recommendations. According to thin-wall pipe of API X65 in this research, specimen sizes could not satisfy the plain strain condition of ASTM E399 therefore, indirect method is accomplished by evaluating the crack tip opening displacement. According to the nature of welding procedure and inhomogeneous probable defects in the different regions of seam weld, δ-R curve with multi-specimen technique of single-edge notched bend (SENB) specimens is applied for test procedure in this research. The measured CTOD and K1C are 0.23 mm and 265 MPam3/2 respectively. Furthermore, Three-dimensional finite element method numerical evaluation of crack propagation with GTN model has been performed. Good agreement with the other researches was observed for CTOD and fracture toughness of tested material. The difference was about 10 percent.

Semiclosed-loop motion control with robust weld bead tracking for a spiral seam weld beads grinding robot

• A novel two-DOF platform for the seam weld beads grinding is designed. • A semiclosed-loop motion control method is proposed for accurate grinding. • Robust weld bead tracking improved the detection and grinding accuracy of welds. Grinding robots have been widely used in industrial manufacturing, but not in the production of large steel pipes. In this paper, a grinding robot is developed for the removal of the external and internal seam weld beads at the end of a spiral welded pipe. A two-degree-of-freedom linear motion platform is added to the end of a six-degree-of-freedom industrial robot to achieve high-precision grinding and to decouple the motions. A semiclosed-loop motion control method is proposed to control the position of the grinding mechanism under the spark spatter during grinding. Based on the identification method of weld bead feature points and the closed-loop control of position, the tracking method of seam weld beads is proposed to realize robust detection and grind planning. Two sets of experiments including tracking and grinding were carried out on both external and internal seam weld beads. The results show that the developed structure and proposed methods are effective and perform well. The grinding robot with the two-degree-of-freedom linear motion component makes the robot trajectory planning and decoupling control greatly convenient.

Improving the efficiency of testing welded joints from thermally hardened steels of spiral seam pipes

When analyzing the places of the destruction of welded samples of thermally hardened steels and the relative transverse narrowing, it was found that in the range of relative thicknesses of the “soft” layer τ <0.6–0.8, when the strength of the welded samples is at the level of thermally hardened base metal. Destruction occurs both on the base metal at a distance from the weld, and along the weakened area in the heat-affected zone. At large values of τ, the destruction of the welded samples occurs, as a rule, along the weakened area near the weld. A characteristic feature of fracture of welded samples in a weakened section is a decrease in the relative transverse narrowing ψ compared to the case when the fracture occurs on the thermally hardened base metal at a distance from the weld. However, as is known, the value of ψ for thermally hardened metal is lower than for normalized. Based on the results of theoretical and experimental studies, as well as taking into account the basic principles of fracture mechanics, recommendations were developed on the choice of hydra model parameters impact testing of the pipeline on a section of 266-505 km in the Tyumen region. The obtained values of the crack depth l cr = 3.9–4.3 mm correspond to the acts of technical failures of the pipeline in section 335–337 km.

Conformational plasticity of the ClpAP AAA+ protease couples protein unfolding and proteolysis.

The ClpAP complex is a conserved bacterial protease that unfolds and degrades proteins targeted for destruction. The ClpA double-ring hexamer powers substrate unfolding and translocation into the ClpP proteolytic chamber. Here, we determined high-resolution structures of wild-type Escherichia coli ClpAP undergoing active substrate unfolding and proteolysis. A spiral of pore loop-substrate contacts spans both ClpA AAA+ domains. Protomers at the spiral seam undergo nucleotide-specific rearrangements, supporting substrate translocation. IGL loops extend flexibly to bind the planar, heptameric ClpP surface with the empty, symmetry-mismatched IGL pocket maintained at the seam. Three different structures identify a binding-pocket switch by the IGL loop of the lowest positioned protomer, involving release and re-engagement with the clockwise pocket. This switch is coupled to a ClpA rotation and a network of conformational changes across the seam, suggesting that ClpA can rotate around the ClpP apical surface during processive steps of translocation and proteolysis.

Experimental Study of the Residual Stresses in Girth Weld of Natural Gas Transmission Pipeline

In order to achieve integrated condition in the girth welding of high pressure natural gas transmission pipelines, the weld zones and its surrounding area should have good mechanical properties. Residual stresses are an important defect especially in the girth welding of the pipeline. In this study, two API X70 steel pipes (with spiral seam weld) of 56 inches outside diameter and 0.780 inch wall thickness were girth welded first. The hole drilling tests were conducted for residual stress measurement on the surfaces of the pipes. The hoop tensile residual stress on the external surface of the pipe with the maximum value equal to 318-MPa was measured on the weld centerline. Hoop residual stress distributions in the internal and external surfaces of the pipe were approximately similar. The maximum axial residual stress was observed in the heat affected zone (a distance of approximately 30 mm from the weld centerline). The maximum axial residual stress on the external surface of the pipe was tensile, equal to 137 MPa, and on the internal surface of the pipe was compressive, equal to 135-MPa. Axial residual stress magnitudes in the weld centerline on the internal and external surfaces of the pipe were close together. Away from the weld centerline, axial residual stresses on the internal and external surfaces showed the opposite behavior. Therefore, in the girth welding of natural gas transmission pipelines, the peripheral direction on the internal surface of the pipe is the critical zone and have the highest tensile residual stresses.

Spiraling in Control: Structures and Mechanisms of the Hsp104 Disaggregase.

Hsp104 is a hexameric AAA+ ATPase and protein disaggregase found in yeast, which couples ATP hydrolysis to the dissolution of diverse polypeptides trapped in toxic preamyloid oligomers, phase-transitioned gels, disordered aggregates, amyloids, and prions. Hsp104 shows plasticity in disaggregating diverse substrates, but how its hexameric architecture operates as a molecular machine has remained unclear. Here, we highlight structural advances made via cryoelectron microscopy (cryo-EM) that enhance our mechanistic understanding of Hsp104 and other related AAA+ translocases. Hsp104 hexamers are dynamic and adopt open "lock-washer" spiral states and closed ring structures that envelope polypeptide substrate inside the axial channel. ATP hydrolysis-driven conformational changes at the spiral seam ratchet substrate deeper into the channel. Remarkably, this mode of polypeptide translocation is reminiscent of models for how hexameric helicases unwind DNA and RNA duplexes. Thus, Hsp104 likely adapts elements of a deeply rooted, ring-translocase mechanism to the specialized task of protein disaggregation.

Weld metal fracture characterization of API X65 steel using drop weight tear test

Measurement of fracture energy using drop weight tear test (DWTT) specimen with large dimensions (as an alternative to small Charpy test sample) gives more realistic results. Although large amounts of test data are available from DWTT experiments on different pipeline steels (base metal), apparently no information has been reported for fracture energy of welded seam of these pipe steels. In the current study, the fracture energy of spirally welded steel pipe was measured using DWTT specimens with two different notches (i.e. pressed and with chevron notch) and compared with base metal (BM) fracture energy. The test samples were machined from an actual gas pipe with a spiral seam having 1219 mm outside diameter and 14.3 mm wall thickness. The DWT tests were conducted on an impact machine with 30 kJ capacity equipped with Wheatstone load-cell. The measured total fracture energy in pressed-notch (PN) specimen (6211 J) was around 5% higher than that of chevron-notch (CN) specimen (5890 J). Based on the measurements, in both specimens a correction factor of 1.8 was suggested for welded seam (the fracture initiation energy was around 43% of the total fracture energy). Since the test samples were taken from a real pipe with original thickness, this result was more realistic than those previously reported for conventional Charpy fracture test specimens for similar steel material. The fracture energies for weld metal (WM) specifications were less than that of the base metal (7085 J). Therefore, immediate attention must be paid to DWTTs of WM in pipelines, which had not been investigated before, and the results indicate the importance of urgent improvement of the toughness of welded zone in manufacturing processes, which requires further research. Since, there is no standard for WM in the DWTT, the results of this research can lead to the development of new standards based on WM DWTT.

Residual stress prediction in submerged arc welded spiral pipes

Submerged arc welding (SAW) is generally the preferred method for joining the seam edges of large diameter spiral pipes. The quality control of the welded pipes usually consists of a hydrostatic test in which water is pumped into the pipe. High pressure hydrostatic tests can moderate tensile residual stress caused by the welding process. In this paper, three-dimensional finite element (FE) simulations of double SAW and hydrostatic test processes of spirally welded pipes are carried out in two simulation steps using the ANSYS commercial software. In the first step, i.e., welding, a new method, namely, unfurl-mapping (UM) is introduced to overcome the geometrical difficulties of defining the Goldak double ellipsoidal heat source of the welding process. UM virtually opens the pipe into a flat surface, and therefore, the spiral seam is mapped to a straight line. To discretize the pipe, fine brick elements are utilized for meshing the main computational zone. The rest of the model is meshed by coarse shell elements by applying the multi-point constraint technique. This non-uniform mesh structure reduces the computational requirements significantly and provides the ability to simulate the entire pipe. Therefore, in the second step, the hydrostatic test is easily simulated by defining a ramped internal pressure. The method is validated using hole drilling measurements performed before and after hydrostatic test for this research. It is observed that obtained results from the FE simulations are in good agreement with the experimental measurements.

Cracking resistance of high-strength spiral seam large-diameter pipes strengthened by heat treatment and of control rolled sheets of 09G2Fb steel

Cracking resistance of high-strength spiral seam large-diameter pipes strengthened by heat treatment and of control rolled sheets of 09G2Fb steel

Production of line pipe in Japan

Abstract Japan is one of the world's leading suppliers of line pipe. In this paper, the authors describe advances in line-pipe manufacturing technology that have been made in Japan during the past decade. Manufacturing methods have been improved, and seamless, electric-resistance, and submerged-arc (both straight and spiral seam) welding processes are all now used. Line-pipe manufacturers have had to adjust to changing requirements for pipe size (outside diameter and wall thickness), strength, toughness, corrosion resistance, and weldability. The performance of line pipe under high pressure, in use in the Arctic and in deep water, and for transporting sour gas has been evaluated. The steelmaking, hot-rolling, and pipe-forming stages of manufacture have all been tailored to the production of high-quality line pipe.

CHAPTER 3 – Standards for Steel Pipe

This article presents Chapter 3, Standards for Steel Pipe, of the AWWA Committee Report on the Design and Installation of Steel Water Pipe. The American Water Works Association has issued a number of standards dealing with steel pipe and appurtenances. Of the two which cover the pipe itself, AWWA C202 is for mill pipe, defined as “steel pipe of any size produced to meet finished‐pipe specifications.” Fabricated pipe is defined by AWWA C201 as “steel pipe fabricated from plates or sheets; the properties of the material are determined prior to fabrication.” Both straight‐seam and spiral‐seam electric‐fusion‐welded pipe of any size are covered in the standard. It should be noted that, because of the wide range of diameter and wall thickness and the use of sheets or plates in a continuous process, spiral‐welded pipe is classed as both mill and fabricated. AWWA C201 covers fabricated pipe, electric fusion welded (straight or spiral seam), in sizes 4 in. and over.

R 100

The lecturer opened with a brief and general description of R. 100, which has an overall length of 709 ft. and a diameter of 133 ft., with a cubic capacity of 5,250,000 cu. ft. There are three power cars, each with two engines. These cars are situated at a considerable distance fore and aft from the passenger accommodation, and there was therefore a minimum of noise and vibration in the latter. The ship contained some 11 miles of special spiral seam tubing. Her displacement was 156 tons. In the Graf Zeppelin the cross sectional area of the girders equalled some 12 sq. ins., whereas in the British ship the cross sectional area amounted to 3 sq. ft.