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The potentiometer mechanism and the voltage measuring circuit, which indicate consistency,
should be calibrated by using the Weight-Loaded Potentiometer Calibrating Device. This
device is used to apply torque to the potentiometer spring, using the radius of the
potentiometer frame as a lever arm.
The step-by-step calibration procedure is as follows:
1. Set the calibrator at a table's edge for free cord movement.
2. Install a potentiometer on the holder and insert the wedge into the open slot nearest the
mounting frame "Stop" contact.
3. Locate the steel cable around the potentiometer frame and over the pulley. Place the hanger
weight hook in the cord eye.
4. Install wire-end clips to the potentiometer.
5. Insert the plug on the end of the calibrator wires into the Calibrator Socket.
6. Turn on Master Switch.
7. Place 350 grams of weights on the 50 gram hanger for a total of 400 grams mass.
The Bearden Unit Gauge should read 100 Bc. (100 Bearden Units is 10 volts) The contact
points of the spring should be oiled, the weights lifted and released, and the calibrator lightly
tapped to offset friction during the calibration. If the unit does not read 100 Bc, manually
adjust the Pot Mech calibration screw located on the front panel.
The radius of the potentiometer mechanism is 5.2 centimeters and is multiplied by the total
weight on the hanger to obtain gram centimeter torque. Slurry consistency is expressed in
Bearden units where 100 Bc is equivalent to the spring deflection observed with 2080 gcm of
torque (400 grams weight) using the Weight-Loaded Calibration Device.
For further calibration details, refer to API Spec 10 booklet. This unit is supplied with weights
to accommodate the full range of tests per API specs.
Magnetic Drive
The Magnetic Drive should be flushed with clean solvent or oil whenever cement spills into
the cylinder or particles contaminate the drive.
required when high-temperature, high-pressure tests are run.
The inner magnetic shaft must be pulled and inspected. Replace the complete assembly if the
magnet sleeve is worn through or bulging at the center. Remove the magnetic housing drain
plug and flush all cement sediment from the cylinder using solvent. Dry any remaining water
on the cylinder floor using towels. Inspect and replace the following components as required.
• Carbon bearing: Remove and clean all cement from the OD and ID of the bearing. Clean
all cement from the external grooving. Replace the carbon bearings when excessive
chipping is visible. Replace the carbon bearing if the OD or ID has lost .010" of material.
The bearing must fit snugly on the shaft with no visible wobble.
SECTION 3 – MAINTENANCE
More frequent flushing of the Drive is
3-3
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