Patent No. 6,766,028 - OFI Testing Equipment, Inc.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: 832-320-7300 / Fax: 713-880-9886 / www.ote.com 14
Calibration
Standalone
The calibration procedure is easily performed by pressing the CAL button
and following the instructions as you are prompted on the unit’s display
screen. Calibrations should be routinely performed prior to rheological testing
and are necessary after changing out bearings or the torsion spring.
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 uids
should be checked monthly.
For the most accurate calibration results, calibrate the thermocouple before
performing the following procedure. Refer to page 47 for instructions.
If you use a computer with the Model 900, you must unplug the connection
before beginning the procedure.
1. Press the “CAL” button.
The viscometer will display the “Zero Offset”. This shows how much
the bob has drifted since the last calibration. If this value is greater than
±1, make sure the bob is properly installed on the unit and that it spins
freely. Then rotate the bob by hand and let it go. If the Zero Offset is still
greater than ±1, continue with the calibration. This will reset the Zero
Offset. If, after calibration, the Zero Offset is still greater than ±1, contact
OFITE Technical Support for additional help.
After verifying the offset, conrm that the P value is within the specied
range. If it is not, follow the instructions on page 49 to adjust it.
3. Add approximately 170 mL calibration uid into the clean and dry
stainless steel sample cup. Place the sample cup with calibration uid
onto the platform. Loosen the lock nut on the platform with the stainless
steel arm until the uid level reaches the scribed line on the rotor. Tighten
the lock nut on the platform.
Maximum Viscosities for
Calibration at 300 RPM
for various Torsion Springs (R1, B1):
Torsion Spring, F0.2 = 60 cP
Torsion Spring, F0.5 = 150 cP
Torsion Spring, F1.0 = 300 cP
Torsion Spring, F2.0 = 600 cP
Torsion Spring, F3.0 = 900 cP
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