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16
Calibration
The ORCADA
®
calibration program should be run before performing the first
test. Additional calibration is recommended when:
1. The bob is changed.
2. The unit has been sitting unused for several days.
3. The unit has been serviced (i.e. bearings changed).
4. If the “r^2” value displayed in the analysis model is below .99 during a
sweep.
5. The Shear Stress value on the main screen is not 0 when the rotor is
not turning.
6.
Every two weeks during normal operation.
According to API Recommended Practice 10B-2, viscometers being used
for testing well cement should be calibrated quarterly. API Recommended
Practice 13B-1 and 13B-2 specify viscometers being used for drilling fluids
should be checked monthly.
The calibration fluid should be stored at room temperature and away from
direct sunlight. The shelf life of the calibration fluid is 2 years. The calibration
fluid used during the calibration program should be checked for suspended
solids and clarity prior to being poured back into the bottle for storage. Cloudy
calibration fluid should be disposed of properly.
1. Prepare the viscometer for a test as described on page 8.
2. Open the ORCADA
®
software. From the menu bar select “Utilities” and
then “Calibrate Shear Stress”.
3. Observe the “Shear Stress Raw” value. If the Shear Stress Raw value is
not between 950 and 1000, you must adjust the transducer cap. Refer to
4. Select a calibration fluid from the “Cal Fluid Batch” drop-down list. If the
list is empty, click the “Fluid Manager” button to add new fluid batches.
Refer to page 20 for instructions.
If the “Temp Out of Range” light shines red, the current sample
temperature is out of the specified range for the calibration fluid. The
sample will have to be heated or cooled to be within the acceptable range
before calibration.
Do not attempt a calibration if the sample is not within the
appropriate temperature range.
When using the 130-81-079 spring, use 200 cP fluid with a B5 bob and
100 cP fluid with a B1 bob.