If the time is less than this the tube is probably enlarged by erosion, if more it may be blocked or damaged, and the funnel should be replaced. If water is used, the time should be 26 +/- 0.5 seconds. In American practice (and most of the oil industry) the volume collected is a quart.
A 10-mesh screen is fixed near the top across half the cone. It consists of a cone 6 inches (152 mm) across and 12 inches in height (305 mm) to the apex of which is fixed a tube 2 inches (50.8 mm) long and 3/16 inch (4.76 mm) internal diameter. A Marsh funnel is a Marsh cone with a particular orifice and a working volume of 1.5 litres.
The Marsh Funnel īased on a method published in 1931 by H.N.Marsh, a Marsh cone is a flow cone with an aspect ratio of 2:1 and a working volume of at least a litre. Marsh Funnel top view showing the mesh through which drilling fluid is poured to retain particles which would not pass through the orifice.
