Brookfield BF35 - Manual (Page 15)

Brookfield Engineering Labs., Inc. Page 15 Manual No. M13-10000
Section 5 - Calibration
Calibration
The BF35 Viscometer can lose calibration while in service if the bob shaft
bearings become contaminated or if the bob shaft itself is bent. If the dial does
not read zero when it should or if there is excessive dial deflection when the main
shaft is turning, this may indicate that the bob shaft bearings are sticking. If the
spring appears to be non-linear, the bob shaft may be bent. Your viscometer will
require servicing if it exhibits any of these symptoms.
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.
Procedure
1.
Choose the certified calibration fluid using the temperature-viscosity chart
supplied with the calibration fluid to cover the viscosity range of interest.
Make sure the lot number on the chart matches the lot number on the fluid
container. Each lot of standard fluid is individually certified. The viscosity
will normally vary slightly from lot to lot.
2. Clean and dry the viscometer bob, sleeve, and cup. Place the viscometer
and the calibration fluid side-by-side on the counter top in a room with a
reasonably constant temperature (variation of less the 5˚F ± 2.5˚F). Allow
the viscometer and the fluid to stand at least two hours to equilibrate.
3. Operate the viscometer in air for two to four minutes to loosen up the
bearings and gears. Observe the rotor sleeve for excessive wobbling and
replace if necessary.
4.
Fill the cup to the scribed line with calibration fluid and place it on the
viscometer stage. Move the stage upward until the fluid level is to the fill
line on the sleeve.
Fill Line
Viscometer Sleeve
5.
Place a thermometer capable of ± 0.2˚F (0.1˚C) into the fluid and hold or
tape it in place to prevent breakage. Operate the viscometer at a low speed