The Marsh funnel is a simple device for measuring

viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

by observing the time it takes a known volume of liquid to flow from a cone through a short tube. It is standardized for use by

mud engineer A mud engineer (correctly called a drilling fluids engineer, but most often referred to as the "mud man") works on an oil well or gas well drilling rig, and is responsible for ensuring the properties of the drilling fluid, also known as drilling mu ...

s to check the quality of

drilling mud In geotechnical engineering, drilling fluid, also called drilling mud, is used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also us ...

. Other cones with different geometries and orifice arrangements are called ''flow cones'', but have the same operating principle. In use, the funnel is held vertically with the end of the tube closed by a finger. The liquid to be measured is poured through the mesh to remove any particles which might block the tube. When the fluid level reaches the mesh, the amount inside is equal to the rated volume. To take the measurement, the finger is released as a stopclock is started, and the liquid is allowed to run into a measuring container. The time in seconds is recorded as a measure of the viscosity. Marsh funnel top view

The Marsh Funnel

Based on a method published in 1931 by H.N.Marsh,H. N. Marsh (1931)''Trans AIME'' vol 92 pp 234-251 "Properties and Treatment of Rotary Mud" a Marsh cone is a flow cone with an aspect ratio of 2:1 and a working volume of at least a litre. A Marsh funnel is a Marsh cone with a particular orifice and a working volume of 1.5 litres. 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 10-mesh screen is fixed near the top across half the cone. In American practice (and most of the

oil industry The petroleum industry, also known as the oil industry or the oil patch, includes the global processes of exploration, extraction, refining, transportation (often by oil tankers and pipelines), and marketing of petroleum products. The larges ...

) the volume collected is a quart. If water is used, the time should be 26 +/- 0.5 seconds. 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. In some companies, and Europe in particular, the volume collected is a litre, for which the water funnel time should be 28 seconds. Marsh himself collected 0.50 litre, for which the time was 18.5 seconds. The Marsh funnel time is often referred to as the Marsh funnel viscosity, and represented by the abbreviation FV. The unit (seconds) is often omitted. Formally, the volume should also be stated. The (quart) Marsh funnel time for typical drilling muds is 34 to 50 seconds, though mud mixtures to cope with some geological conditions may have a time of 100 or more seconds. While the most common use is for

s, which are

non-Newtonian fluid A non-Newtonian fluid is a fluid that does not follow Newton's law of viscosity, i.e., constant viscosity independent of stress. In non-Newtonian fluids, viscosity can change when under force to either more liquid or more solid. Ketchup, for exa ...

s, the Marsh funnel is not a

rheometer A rheometer is a laboratory device used to measure the way in which a dense fluid (a liquid, suspension or slurry) flows in response to applied forces. It is used for those fluids which cannot be defined by a single value of viscosity and t ...

, because it only provides one measurement under one flow condition. However the effective viscosity can be determined from following simple formula.M. J. Pitt (2000) ''SPE Drilling and Completion'' vol 15 no1 pages 3-6 “The Marsh Funnel and Drilling Fluid Viscosity: A New Equation for Field Use” μ = ρ (t - 25) where μ = effective viscosity in

centipoise The poise (symbol P; ) is the unit of dynamic viscosity (absolute viscosity) in the centimetre–gram–second system of units (CGS). It is named after Jean Léonard Marie Poiseuille (see Hagen–Poiseuille equation). The centipoise (1 cP = 0 ...

ρ = density in g/cm³
t = quart funnel time in seconds For example, a mud of funnel time 40 seconds and density 1.1 g/cm³ has an effective viscosity of about 16.5 cP. For the range of times of typical muds above, the

shear rate In physics, shear rate is the rate at which a progressive shearing deformation is applied to some material. Simple shear The shear rate for a fluid flowing between two parallel plates, one moving at a constant speed and the other one stationary ...

in the Marsh funnel is about 2000 ^−s.

Other Flow Cones

The term Marsh cone is also used in the

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...

and oil industries. European standard EN445 and American standard C939{{Citation , title=ASTM C939-10 Standard Test Method for Flow of Grout , publisher=ASTM International , year=2010 , url=http://www.astm.org/Standards/C939.htm for measuring the flow properties of

cement A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mix ...

grout Grout is a dense fluid which hardens to fill gaps or used as reinforcement in existing structures. Grout is generally a mixture of water, cement and sand, and is employed in pressure grouting, embedding rebar in masonry walls, connecting secti ...

mixtures specify a funnel similar to the Marsh cone. Some manufacturers supply devices which they call Marsh cones, with removable tubes with size ranges from 5 to 15 mm. These can be used for quality control by selecting a tube which gives a convenient time, say 30 to 60 seconds.

The Marsh Funnel

Other Flow Cones

References

Further reading