FANN 240 (01) PDF Document

The FANN 240 Shearometer is a measuring device used to determine the gel strength of drilling mud. The graduated scale on the device measures gel strength in pounds per 100 square feet of area.

The FANN 240 Shearometer Kit consists of two 5-gram, 3.5 x 1.4 inch, hollow shear tubes, and a sample cup that has a graduated scale mounted in the center of the cup base.

The sample cup should be clean and dry before beginning the measurement procedure, and there should be a means available for measuring elapsed time, such as a stopwatch. Perform the steps in the following procedure to measure the initial gel strength of drilling mud:

1. Wet the hollow shearometer tube and wipe away the excess water.

2. Pour a freshly agitated mud sample into the sample cup (the mud level should be even with the bottom line of the measurement scale). The moment the surface of the mud is calm, quickly fit a hollow shearometer tube over the measurement scale protruding up from the mud sample and lower the tube to the surface of the mud.

3. Release the shearometer tube and let it sink for one minute (measured from the instant the tube is released), keeping it vertical by guiding it with the fingers only if necessary.

4. After the minute has elapsed, record the scale reading at the top of the shearometer tube. The reading should be reported in pounds per 100 square feet.

The following procedure is for measuring the gel strength of a mud sample after 10 minutes (or some other prescribed length of time):

1. Wet the shearometer tube and wipe away the excess water.

2. Pour a freshly agitated mud sample into the sample cup (the mud level should be even with the bottom line of the measurement scale). Allow the mud to stand undisturbed for 10 minutes (or some other prescribed length of time).

3. Fit a hollow shearometer tube over the measurement scale protruding up from the mud sample and lower the tube to the surface of the mud.

4. Release the shearometer tube and let it sink for one minute (measured from the instant the tube is released), keeping it vertical by guiding it with the fingers only if necessary.

5. After the minute has elapsed record the scale reading at the top of the shearometer tube. The reading should be reported in pounds per 100 square feet, for the time that has elapsed since the mud was poured into the cup.

The FANN 240 Shearometer is not recommended for testing muds that have very high or low gel strengths.

*The 20 gram Shearometer tube (206958) which is heavier than the 5 gram (206956) is available for testing heavier muds and is designed specifically for testing high gel strength muds.