The Marsh funnel viscometer is a simple device for measuring viscosity from the time it takes a known volume of liquid to flow from the base of a cone through a short tube. It is particularly used by mud engineers to check the quality of drilling of drilling mud
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 mesh is fixed near the top across half the cone. In use, it is held vertically and end of the tube closed with a finger. The liquid to be measured is poured through the mesh. (This removes any particles which might block the tube.) This ends when the mesh is reached, which gives a volume inside of about 1.5 litres. To take the measurement, the finger is released as a stopclock is started, and the liquid is allowed to 1
run into a measuring container. The time in seconds is recorded as a measure of the viscosity. In American practice (and most of the oil industry) 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 MF. 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 drilling muds, which are non-Newtonian fluids, the Marsh funnel is not a rheometer, because it only provides one measurement under one flow condition. However the effective viscosity can be determined from following simple formula. μ = ρ (t - 25)
where μ = effective viscosity in centipoise 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 the Marsh funnel is about 2000
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The term Marsh cone is sometimes used, particularly within the concrete industry, but also in the oil industry. Sometimes it means the Marsh funnel, sometimes a similar device with the same cone aspect ratio, but a different tube. European standard EN445for measuring the flow properties of cement grout mixtures specifies a funnel similar to that described above but fitted with a tube of 10 mm internal diameter and of length 60 mm, which is often referred to as a 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. Other cones of different geometries and with different orifice arrangements are in use in specialist areas, but with the same general operating principle. They are generally called flow cones. Thus 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
To model the flow of liquid through the Marsh funnel it was assumed that an inverted cone of liquid provided a hydrostatic head that caused a drop in pressure through the working orifice. This drop in pressure is partially converted to kinetic energy (fluid discharging from the orifice) and partially dissipated in fluid friction going through the orifice. Using the formula of Skelland, for a power law fluid in laminar flow through a tube (neglecting entrance effects) the energy balance gives ...equation... where h is the height of the liquid above the orifice, ρ is the density, and g is
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the acceleration due to gravity; L and r are the length and radius of the tube, respectively, and k and n are the power law constants for the fluid.
Periodically check the calibration of the Marsh Funnel by measuring the viscosity of fresh water. Using the procedure described above, one quart (946 mL) of fresh water at a temperature of 70 ± 5 F (21 ± 3 C) should outflow from the orifice in 26 ± 0.5 seconds. If the Marsh Funnel checks out of calibration, it should be cleaned again, making sure that nothing is obstructing the outlet. A T—Handle Reamer is available for removing obstructions from the outlet. If the Marsh Funnel continues to check out of calibration, the outlet tube has probably been bent out of shape and the funnel should be replaced. °
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1. Clean and dry the funnel and any other accessories thoroughly after each use. 2. Do not bend or flatten the brass orifice in the bottom of the funnel, as it can make readings inaccurate.
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1. Make a mud by the mixer (putting the bentonite or barite or putting both of them in a cylinder containing water ). 2 . Hold the clean, dry funnel in an upright position with the index finger over the outlet. 3. Pour a freshly obtained sample of the fluid to be tested through the screen until the fluid level reaches the bottom of the screen. 4. Remove the finger from the outlet and start the stopwatch, Using the measuring cup, measure the time it takes the fluid to fill to the one-quart (946 mL) mark of the cup. 5. Report the time to the nearest second as Marsh Funnel viscosity .
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is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms (and for fluids only), viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity. Put simply, the less viscous the fluid is, the greater its ease of movement (fluidity). 1. This test method allows for the assessment of an apparent viscosity of clay slurries in the laboratory and in the field. Viscosity is a fundamental characteristic for slurries in construction applications. The Marsh Funnel Viscosity test can be used for field quality control of slurries. Relative changes in slurry viscosity can be identified using Marsh Funnel measurements and modifications can be made to mixing and handling procedures. 2 .In this test, it is assumed that the apparent viscosity of a slurry is directly related to the flow duration through a specially shaped funnel (the Marsh Funnel). 3. The viscosity of a slurry must be maintained at a level high enough to assist in stabilizing the trench walls. Slurry viscosity is also directly related to filter cake permeability. 4. The Marsh Funnel Viscosity has been widely used in drilling soil and rock for water wells, oil, gas, soil stabilization, and the application of hydraulic barriers. 5. The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used
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6. The result determined using the method is referred to as the Marsh Funnel Viscosity. 7. This test can be performed in the laboratory, or used in the field to assess the apparent viscosity of a clay slurry for quality control purposes. The most commonly used slurry is a bentonite clay slurry. 8. The values stated in either SI units or inch-pound units [given in brackets] are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 9. In our Experiment the measurement of the viscosity time was 59 sec for the first experiment and 37.7 sec for the second experiment on this device and this number was slightly different from the other groups and this different may due to many reasons , may the increase or decrease of water led to this difference or the volatility of bentonite and barite during mixing or calcification of bentonite ( bentonite + barite in the 2 nd exp.) . 10. The development of the Marsh Funnel is credited to Hallan N. Marsh of Los Angeles who published the design and use of his funnel viscometer in 1931.
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