entonnoir de Marsh

CONT: L'entonnoir de Marsh [est un appareil utilisé pour mesurer la viscosité d'une boue de forage. Il] assure l'écoulement de la boue à travers un orifice calibré, mais sous une charge variable, et qui permet d'exprimer la viscosité par le temps nécessaire au remplissage d'une capacité connue [...]

OBS: It consists of a copper funnel, about 30-cm long with a 15-cm diameter at the top, which has a 10-mesh screen over half its diameter to remove debris and a 6-mm-diameter exit tube at the bottom through which the rate of flow is timed. It takes 26 seconds for a quart of clean water to flow through and correspondingly longer for muds of greater viscosity. Gel strength is measured by comparing the rate of flow of freshly agitated mud with that which has been allowed to remain quiescent for 10 minutes.