I. Overview

The Marsh funnel viscometer is an instrument used for daily measurement of drilling fluid viscosity. Manufactured according to the American API standard, it determines the viscosity of drilling fluid by measuring the time it takes for a fixed volume of drilling fluid to flow out of the funnel. It features a simple structure and is easy to use. It is widely used in petroleum, geological exploration, and other sectors.

The viscosity and gel strength of drilling fluid are related to its rheological properties. The standard value is defined as the time required for 946 ml of standard distilled water to flow out at a temperature of 20±5°C, which is 26±0.5 seconds. The funnel body is made of sturdy and durable engineering plastic, and the precision-machined brass orifice ensures measurement accuracy.

The measurement principle of the funnel viscometer is to express the viscosity of drilling fluid by the time required for a fixed volume of drilling fluid to flow freely under gravity from a fixed funnel. It is usually denoted by "S". It roughly reflects the comprehensive indicators of all rheological parameters and physical properties of the drilling fluid and best characterizes the properties of drilling fluid at low shear rates.

Since the data measured by the funnel viscometer are largely influenced by colloidal content and density, which cause changes in the static pressure of the liquid column in the funnel, the viscosity data obtained with the funnel viscometer cannot be directly compared with data measured using a direct-reading viscometer.

II. Models and Specifications

III. Main Technical Parameters of the Instrument

IV. Operation of the Instrument

(I) Instrument Operation

1. Block the outlet at the bottom of the funnel with a finger, and pour the drilling fluid sample through the screen into the funnel until the liquid level reaches the bottom of the screen.

2. Remove the finger and start the stopwatch simultaneously, recording the number of seconds it takes for 946ml of drilling fluid to flow out of the funnel as the Marsh funnel viscosity.

3. Record the temperature of the sample.

(II) Instrument Calibration

1. Control the ambient temperature to 20±5℃, and set the stopwatch to standby mode.

2. Hold the funnel in an upright position and block the outlet of the lower conduit with a finger.

3. Use a measuring cup to measure 1500ml of distilled water (20±5℃) and pour it into the funnel.

4. Then release the finger and start timing simultaneously. Stop timing when 946ml has flowed into the volumetric flask. The time should be 26±0.5s.

Note:All instruments must be rinsed clean with water before measurement.