There are multiple peptidoglycan hydrolases associated with Bacillus subtilis 168 and these potentially lethal enzymes have been implicated in a number of important cellular processes. Several enzymes have been studied at the molecular level and their structural genes characterized. This information has begun to identify roles for individual enzymes in motility, cell separation, differentiation, and phage lysis. It has become apparent that in many cases important autolytic functions can be performed by more than one enzyme, so the complex web of mutually compensatory components can be unraveled only by making multiple mutants. One such multiple mutant has revealed the presence of several previously unknown minor autolysins, the functions of which are currently obscure.

Tandem gas metal arc welding (GMAW) differs from conventional GMAW as two welding wires are passed through the same welding torch. A single torch with two contact tips is used to feed both wires into a single weld pool. Although the potential of the multi-wire GMAW process was first explored as early as the 1950’s, it has not become commercially viable until relatively recently due to performance limitations associated with the power source technology, that resulted in process instabilities. However, with the advent of modern microprocessor-controlled inverter power sources and an improved understanding of metal transfer characteristics, tandem GMAW is now being successfully applied in many industries. Over the last four years, Cranfield University’s Welding Engineering Research Centre and TransCanada Pipelines have developed tandem GMAW for pipeline welding. Cranfield have developed a tandem GMAW torch specifically for use with narrow gap weld preparations utilized in pipeline welding. The process has been proven capable of high deposition rates and welding speeds two to three times those of conventional mechanized pipeline welding. Based upon this earlier work, the Cranfield Automated Pipewelding System (CAPS) is now being developed. This uses two tandem torches on a single carriage (dual tandem welding). The high speed of tandem GMAW is retained and two passes are deposited simultaneously which further reduces welding times. This results in a significant reduction in the number of welding stations required to achieve a given number of weld’s per day and leads to major savings in labor and equipment costs. In comparing welding systems for a recent project estimate, CAPS resulted in a 26% saving in alignment, welding, NDT and coating costs when compared with conventional mechanized welding systems. A major benefit of CAPS is that it has evolved from existing technology. It is not a ‘one-shot’ process. The completed weld has a very similar profile to conventional mechanized pipeline welds so conventional radiography and automated ultrasonic testing can be used for weld inspection. The weld metal microstructure and metallurgical properties are also similar to conventional mechanized pipeline welds. CAPS is therefore suitable for use on all linepipe materials including X80 and X100 steels. This paper reviews the development of the process and equipment together with information on productivity and metallurgical properties.

A methodology is presented for monitoring the pulsed gas metal arc welding process objectively using indices calculated from the statistical features of the welding current and voltage transient waveforms. Five monitoring indices are presented. T he indices allow the quantitative interpretation of process performance and T b , T p background and peak times; I b , I p background andgive an indication of which process parameter(s) should peak currents be altered to ensure stable pulse welding performance. 1 Idealised pulsed gas metal arc welding (PGMAW ) current waveform

The SPACES system has been proposed as an alternative for long-span bridge construction. Tubular space frames offer a structurally more efficient solution for bridges, but they have been considered too expensive because the joints at the nodal intersections of the tubular members are difficult and expensive to weld. The benefits of the SPACES system can only be realized by using a computer-integrated construction system to drive down the fabrication costs. A key component of the computerintegrated construction is the robotic welding system. This article describes the development of a lightweight automated welding system for the joining of tubular members. It addresses the geometry of intersecting cylinders and the kinematics and design of a 5-degree-of-freedom manipulator. Summary solutions are given for both. The control software is described briefly, and mention of the welding tests and overall business process is also made. A consortium of U.K. industry and universities is conducting the work.

Girth welding trials involving pipes of minimum proof strength 690 MPa (X100) from several linepipe manufacturers have been conducted. Welding consumable selections for the trials were based on background data generated at Cranfield University coupled with potential weld metal mechanical property requirements thought necessary for the implementation of X100 pipeline steels. Mechanised pulsed gas metal arc welding (PGMAW) and semi-automatic/ manual welding procedures were used to generate mechanical property data of mainline girth welds, tie-ins and repairs using equipment and procedures as close to current field practice as possible. The trials showed no detrimental weldability issues for the X100 steels examined. Testing comprised tensile, toughness (CVN and CTOD), hardness, side bend and nick break data generation, using pipeline welding specifications where possible.