Mitigation of air leakage through the goaf of retreat coalfaces

In HBL (Lorraine coalfield), large amounts of air are used in order to dilute methane in retreat coalfaces. A parasite flow of air exists in the goaf, leading to the risk of spontaneous combustion of remaining coal as well as to a diminution of firedamp drainage efficiency. The evaluation of various means for reducing this flow has been done through the use of models : a physical model and a numerical model based on a CFD package. The efficiency on air leakage reduction, decrease of methane concentration in the air return or increase of methane concentration of drainage has been quantified for one or more stoppings set up in the abandoned gates or for their backfilling. The influence is small but positive as regards drainage efficiency improvement but almost zero on risk mitigation of spontaneous combustion in the goaf

Influence of welding passes on grain orientation - The example of a multi-pass V-weld

International audienceThe accurate modelling of grain orientations in a weld is important, when accurate ultrasonic test predictions of a welded assembly are needed. To achieve this objective, Electricité de France (EDF) and the Laboratoire de Caractérisation Non Destructive (LCND) have developed a dedicated code, which makes use of information recorded in the welding procedure. Among the welding parameters recorded, although the order in which the welding passes are made is of primary importance in the welding process, this information is not always well known or accurately described. In the present paper we analyse in greater detail the influence of the order of welding passes, using data obtained from the Centre for Advanced Non Destructive Evaluation (CANDE), derived from a dissimilar metal weld (DMW) with buttering. Comparisons are made using grain orientation measurements on a macrograph