INSTRUMENT CALIBRATION BROOKFEILD VISCOMETER

1.0 PURPOSE :
To provide a procedure for the operating Brookfield viscometer.
2.0 SCOPE :
It covers the procedure for handling Brookfield viscometer
3.0 RESPONSIBLITY :
QC officer.
4.0 PROCEDURE
4.1 Ensure the instrument is clean and free from dust.
4.2 Check the spirit level of the viscometer every time before use. The level is adjusted by using the three leveling screws on the base.. Adjust, so that the spirit level on top of the instrument is centered within the circle.
4.3 Turn the power switch located on the rear panel on the ON position.
4.4 Place the viscosity standard fluid (in a 500ml beaker) into the water bath.
4.5 The viscosity standard fluid, should be immersed in the bath for a minimum of one hour, stirring the fluid periodically, prior to taking measurements.
4.6 After one hour, check the temperature of the viscosity standard fluid with a thermometer. It must be within ±0.1°C of 25°C.
4.7 Attach the desired spindle tot he viscometer.
4.8 Measure the viscosity and record the reading including % and cPs at three different speeds using the same spindle. Calculate the mean value. The mean viscosity reading should equal the cPs value on the viscosity fluid standard to within the combined accuracy’s of the viscometer and the standard.
4.10 For a 12,500 standard fluid with a viscosity at 12,720 cPs at 25°C, the acceptance criteria is between 12,393 and 13,047 cPs by using spindle 4 at speed 30 RPM. Similarly at 20 RPM it is between 12,293 and 13,147 cPs and at 12 RPM it is between 12,093 and 13,347 cPs.
4.11 After checking the viscosity of standard then transfer the fluid back to the bottle without any contamination.
4.12 Remove the spindle clean and place it proper box after use.
4.13 Calculation for the acceptance limit of the standard fluid

Full scale viscosity range = TK x SMC x 10000 / RPM

Where,
TK à Torque constant,
SMC à Spindle multiplayer constant and
RPM à Rotation per minute.

= 20,000 cPs.

200cPs (1% of 20,000) + 127.2 cPs (1% of 12,750 cPs) = 327.2 cPs.

Table 1: SMC and TK Constants (for different spindles)

Spindle LV1
SMC 6.4
TK 0.09373

Spindle LV2
SMC 32
TK 0.09373

Spindle LV3
SMC 128
TK 0.09373


Spindle LV4
SMC 640
TK 0.09373

5.0 FREQUENCY OF CALIBRATION :
Once in a month.