A Simple Approach to Hot Tap and Repair Sleeve Welding
Welding onto an in-service pipeline allows cost-effective installation of branch connections (hot taps) and repair sleeves by avoiding the loss of pipeline throughput and contents. When welding onto an in-service pipeline, there are two primary concerns that need to be considered. The first is for welder safety during welding, since there is a risk of the welding arc causing the pipe wall to be penetrated allowing the contents to escape. The second concern is for the integrity of the pipeline following welding, since welds made in-service cool at an accelerated rate because the flowing contents remove heat from the pipe wall. These welds, therefore, are likely to have hard heat-affected zones (HAZ) and a subsequent susceptibility to hydrogen cracking.
W. A. Bruce
What Can We Do About Our Ailing Bridges?
The December 2004 National Bridge Inventory compiled by the Federal Highway Administration (FHWA) shows 26.7% of the nation’s 593,885 bridges are structurally deficient or functionally obsolete (Ref. 1). The deficient bridges are handling today’s traffic safely, and most do not need to be replaced or rehabilitated immediately, but they will need attention at some point.
The nation will never have the funds for all the needed work, but the Safe, Accountable, Flexible Efficient Transportation Equity Act: A Legacy for Users, approved on August 10, 2005, authorized $21.6 billion (FY 2005–2009) for the federal bridge program. With the available funds at the federal, state, and local levels, officials will be able to undertake thousands of bridge replacement and rehabilitation projects each year.
T. Siewert et al
Optimizing Power Distribution for Lean Welding Processes
Probability modeling of spot welding production lines is exercised to aid in the development of the optimal power distribution system capacity. In today’s lean environment, it is not acceptable to assume weld machines fire guns randomly, which is a key assumption for classical power distribution models (Refs. 1, 4, 5, 7). Lean manufacturers stagger, interlock, or cascade machine operation to mitigate machine starve time; this affects duty cycle and the quantity of weld guns likely to fire simultaneously. Consequently, depending on network nomenclature, lean sequence control techniques can increase or decrease the power demand of the line/area. This article provides a method engineers can utilize to locate origin and magnitude of high simultaneous welding, so that the distribution network infrastructure can be optimally sized for lean manufacturing.
C. A. Wallis
Maintenance and Repair Welding in the Open Sea
With the exploration of energy resources pushing into the oceans, engineering structures for oil and gas exploration, production, processing, and transport are a common scene today on ocean waters. They exist in the shallow waters of the Gulf of Mexico, off the Brazilian continental shelf, in the Indian Ocean, off-coast West Africa, and in the deep, rough waters of the North Sea. In the lower 48 states of the United States, subsea production of oil and gas is mainly concentrated in the Gulf of Mexico. In fact, there are more than 4000 offshore platforms and many floating production systems (FPS) and floating production, storage, and off-loading (FPSO) vessels operating in the Gulf. Figure 1 shows an example of these structures.
F. Perez-Guerrero and S.
WELDING RESEARCH SUPPLEMENT
*Effects of Process Parameters on Angular Distortion of Gas Metal Arc Welded Structural Steel Plates (.pdf)
Mathematical models were developed to correlate out-of-plane distortion with process variables
V. Vel Murugan and V. Gunaraj
of Requirements for Resistance Spot Weldin g Dual-Phase (DP600) Steels
Part 1 — The Causes of Interfacial Fracture (.pdf)
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WELDING JOURNAL - November 2005, Volume 84, Number 11