Ii. getting started ii. choice of balls, Ii.2 filling the sample tube – Brookfield Falling Ball KF20 User Manual
Page 10
Brookfield Engineering Labs., Inc.
Page 0
Manual No. M09-352-B04
II. GETTING STARTED
II. Choice of Balls
The balls are chosen in such a way that the minimum falling time is not less than what is shown
in the table and the maximum falling time is not greater than 300 s. The DIN 53015 indicates
that a falling time greater than 300 s is allowed, but for practical reasons, a shorter test time
makes more sense.
Ball
No.
Diameter
[mm]
Minimum falling
time [s]
Lower measur-
ing range limit
[
mPa•s
]
Upper
measuring range
limit [
mPa•s
]
1
15.81
60
0.5
10
2
15.60
30
2.5
130
3
15.60
30
20
700
4
15.20
30
200
7800
5
14.00
30
1000
45000
6
11.00
30
5500
70000
The specifications for the ball constant and the ball density are taken from the test certificate
which came with the equipment.
The exchange of balls or equipment components between different viscometers is not permit-
ted. Otherwise, the ball constants lose their validity.
When the falling time for the ball is less than the minimum time, turbulence may occur.
II.2 Filling the Sample Tube
To fill the sample tube:
• The sample tube is locked on the lower plate with the lower locking plug, seal, and cap.
• The liquid is filled up to approximately 25 mm beneath the top of the sample tube without
air bubbles. Use a glass filter to remove any impurities when introducing a liquid into the
tube.
• The ball is polished with the leather cloth and fibres are removed with the small cleaning
brush, before being inserted into the tube with the ball tweezers. The ball must not be touched
after polishing. The ball will travel to the bottom of the tube. Possible air bubbles in the
sample, or trapped below the ball, are removed with a suitable rod, by rotating the ball.
• Insert the upper locking plug with seal into the sample tube. In so doing, the sample must
enter the inside of the upper locking plug through the opening. The upper locking plug must
not be filled more than half way with the sample in order to minimize pressure build-up due