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Sunday, December 18, 2011

Brookfield Viscometer - Operation & Calibration

BROOKFIELD VISCOMETER

SOP FOR OPERATION

1.0 PURPOSE :
To provide a procedure for the operating Brookfield viscometer.

2.0 SCOPE:
It covers the procedure for handling Brookfield viscometer( QCI – 44 ).
MODEL & MAKE : Brookfield viscometer, DV – I+.

3.0 RESPONSIBILITY :
QC chemist.

4.0 PRINCIPLE :
Viscosity is measure of fluid’s resistance to flow. It is to drive a spindle ( which is immersed in the test fluid ) through a calibrated spring. The viscous drag of the fluid against the spindle is measured by the spring deflection. Spring deflection is measured with a rotary transducer.

BrookField Viscometer

5.0 PROCEDURE :

Check the spirit level of the viscometer everytime before use. The level is adjusted by using the two leveling screw on the base. Adjust so that the spirit level on top of the instrument is centered with in the circle.
5.1 Ensure the calibration status is valid and turn the power switch located on the rear panel to the ‘ON’ position.

5.2 This will result in different screen displays and after a few seconds the screen displays REMOVE SPINDLE, PRESS ANY KEY.

5.3 After removing the spindle ( if attached to it ) and pressing any key, the instrument begins its auto zero. The screen will blink “AUTOZEROING”.
Note: Be sure that the viscometer is leveled before this operation.

5.4 After a few seconds, the blinking stops and the following is displayed REPLACE SPINDLE, PRESS ANY KEY, pressing any key at this point result is in the display of the instrument default screen.

5.5 Connect the selected spindle to the viscometer by screwing them to the lower shaft. The lower shaft should be hold in one hand and lifted up and the spindle should be screwed to the left.

5.6 Spindles are identified by the number on the side of the spindle nut.

5.7 The two digit entry code for the selected spindle should be entered by pressing the SELECT SPINDLE key, on pressing it once, the top line of the display will begin to blink.

5.8 Then press the UP or DOWN arrow keys for increasing or decreasing the number which is to the right of the ‘S’ character while ‘S’ is blinking, until the requirement spindle value is displayed.

5.9 The two digit entry code for each spindle is given below.
SPINDLE NUMBER 1 (LV1)
TWO DIGIT CODE 61
SPINDLE NUMBER 2 (LV2)
TWO DIGIT CODE 62
SPINDLE NUMBER 3 (LV3)
TWO DIGIT CODE 63
SPINDLE NUMBER 4 (LV4)
TWO DIGIT CODE 64

5.10 Then press the SELECT SPINDLE key once again after selecting the desired spindle code. This will cause the ‘S’ character to cease blinking and the new spindle code will be displayed and accepted for use.

5.11 Then select the speed for the spindle by first pressing either the UP or DOWN arrow keys, which will cause the area to the right of RPM (on the bottom line) to display the currently selected speed. If the arrow key is pressed just once and then released, the characters RPM will blink for a few seconds and then will cease blinking, resulting in no change to the speed entry.

5.12 Press the UP or DOWN arrow key until the desired speed in displayed and then release it.

5.13 Then press the AUTO RANGE key, which display the maximum calculated viscosity (full scale reading) which can be measured with the current spindle / speed setting.

5.14 If the viscosity of the test fluid is greater than the AUTO RANGE displayed, then “ cP EEEE” and ‘%EEEE’ will be displayed when operated with this test fluid.

5.15 Change either the spindle or speed to achieve a maximum accuracy with the auto range.

5.16 Pressing and holding the AUTO RANGE key during power on will enable the viscosity display tot he read cPs or m.pas. 1 cPs = 1milli pascal.

5.17 Insert and center spindle in the test material until the fluid level is at the immersion groove in the spindle shaft. Press the MOTOR ON / OFF key once to turn the motor ON.

5.18 Allow time for the indicated reading to stabilize. For maximum accuracy, readings below 10% torque must not be taken.

5.19 Press the MOTOR ON / OFF key once again to turn the motor OFF when changing a spindle / speed or changing samples.

5.20 Remove the spindle before cleaning and clean it after use.

BROOKFIELD VISCOMETER

SOP FOR CALIBRATION

1.0.PURPOSE :
To provide a procedure for the calibrating 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.




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