1. Intended Use

The Falling Ball Viscometer measures accurately the viscosity of transparent Newtonian liquids and gases (with special glass ball). It is preferably used in research, in processing control and in quality control. It meets the requirements of DIN 53015 as well as ISO 12058 standard and it is accepted as an official reference instrument. its measuring accuracy when backed up by the precise temperature control.

2. Important

• When you receive the equipment, you should verify and confirm the "delivery note". If you find any damage or any discrepancy (anything abnormal), you should compile a damage report and advise immediately your supplier.
• The manufacturer's guarantee will not be valid in case that, any part of device of the equipment could be damaged because of an incorrect packing.
• Please read the instructions carefully.
• All modification, elimination or lacking maintenance in any device of the equipment, transgress the directive of use 891655/CEE and the manufacturer can assume no responsibility for any damages that could be involved.
• While this instrument is in use, it may need service. In this case, you only have to phone the office, whose address is at the bottom of the page, or to your usual supplier.
• It is advisable to have a regular maintenance for your equipment. We recommended that you check the viscometers once a year. 

3. Safety Precautions

These notes are intended to draw your attention to risk, which only you can recognize and avoid or overcome. They are intended to enhance your own safety consciousness. We have set the highest quality standards for this unit and ourselves during development and production. Every unit meets relevant safety regulations. The correct unit usage and proper handling is however solely your responsibility. The following notes must be observed:

• This instruction manual must be carefully studied. It contains important information of the connection to the local main supply, correct unit usage and safe handling.
• Check the transportation damage during unpacking. Get in contact with supplier and/or carrier for the settlement of damage claims. Do not try to start up a damaged unit before the damaged has been repaired or you have ascertained the effect of the damage.
• Ensure that this manual is always at hand for every unit operator. Only use this unit solely for the intended application. 
• Specialist personnel must only carry out repairs, alterations or modifications. Improper repairs can cause considerable damage. The Batavialab service department is at your disposal for repair work.
• Do not operate the unit with wet or oily hands.
• Do not expose the unit to spray water.
• Do not clean the unit with solvents (fire risk!) - a wet cloth soaked in household detergent is normally sufficient.
• Only use the heat transfers liquids recommended by Batavialab.

You alone are responsible for the handling of these substances. Our advise:

• If in doubt, consult a safety specialist.
• Read the product manufacturer's or supplier's "EC - Safety Data Sheet".
• Read relevant regulations concerning dangerous materials.
• Observe relevant guidelines for laboratories in your country.

4. Contents of Delivery

The following standard accessories are delivered together with the Falling Ball Viscometer.

5. Falling Ball Viscometer

5.1. Introduction

The heart of the instrument is the measuring tube made of glass and the ball. This tube carries two ring marks A and B, which are spaced 100mm apart and which limit the measuring distance (ring mark C is equidistant between A and B). The measuring tube is jacketed by means of an outer glass tube, which encloses a room to be filled with a temperature-controlled liquid. The measuring tube is fastened to the stand in such a way that its axis is inclined with respect to vertical by 10 degree during the measurement.

The measuring tube together with the jacket may be pivoted in order to turn the tube upside down again to let the ball return to the initial position before a measurement. The measuring tube is closed on both sides by two stoppers, one of which contains a capillary and a small reservoir. The stopper prevents undesirable changes of pressure in the liquid sample and has a passage for air bubbles when the temperature is being changed. The viscometer incloses all sample completely to prevent volatization and film forming. The stand may be levelled by means of its water level and levelling screws. The easily interchangeable thermometer allows a precise temperature control.

5.2. Setting Up The Equipment: Assembly

Insert the measuring tube into the stand fasten it with the knurled nut.

5.3. Principle of The Measurement

The Falling Ball Viscometer measures the viscosity of transparent Newtonian liquids. This viscosity is correlated to the time a Ball requires to fall a defined distance. The rolling and sliding movement of the ball through the sample filled into a slightly inclined cylindrical measuring tube is described by means of the fall time. The test result are given as the dynamic viscosity using the internationally standardized absolute unit of "milli Pascal-second" or (mPa.s).

Note: 1 mPa.s = 1 cP (centiPoise)

The Falling Ball Viscometer correspond to the requirements of many international standards, i.e ISO 12058 and the German standard DIN 53015.

5.4. Technical Data

6. Setting Up and Operation

6.1. Temperature Control

The Falling Ball Viscometer may be temperature controlled in a temperature range from -20 degree Celsius up to +120 degree Celsius using liquid circulator.

The sample should rest at least some 15 minutes in measuring tube at the test temperature before the measurement is started.

The temperature in the jacket around the measuring tube must be maintained within a temperature tolerance of -/+0.03 degree Celsius for rest temperature between 10 up to 80 degree Celsius.

For the test temperature beyond these limits the tolerances may be increased to +0,05 degree Celsius.

The tempering room must be free of air bubbles.

6.2. Loading The Sample

All parts of the viscometer being in direct contact with the sample must be kept clean and dry.

A sample volume of approximately 45 cm is poured into the measuring tube up to 20mm below the rim of the tube. Then the ball is placed into the tube and the hollow stopper is introduced. The liquid should reach a level just beyond the capillary. The sample in the tube must be free of air bubbles.

Before the final test data are taken, the ball should run through the tube up and down at least once to improve the homogeneity of the samples and its temperature uniformity.

IMPORTANT

When filling the falling tube, keep in mind that an increment of temperature will mean a dilatation into the sample. If there is no enough gap into the falling tube, when heating the viscometer, the sample dilatation can break the internal tube.

6.3. Selection of The Balls

The standard ball set contains 6 balls, which pass through the measuring tube of an inner diameter of approximately 16.34 -/+ 0.01 mm.

The measuring range for viscosity indicated are related to DIN 53015 and ISO 12058. Sometimes it may be necessary to use two different balls in order to cover a wider measuring range, i.e. when the function of viscosity versus temperature is measure over a wide temperature interval; in this case you insert two different balls at the same time into the measuring tube with smaller ball inserted first. The reduced starting distance will not influence the test result significantly, but increases the uncertainty.

7. Measurement of The Falling Times

The jacket tube snap into a defined 10° position at the bottom of the instrument.

By turning over the jacket tube, the ball is set to the measuring position. The falling time of the ball moving from the ring mark A to ring mark B is determined by using stopwatch. The time period start when the lower periphery of the ball touches the ring mark A, which must appear as a straight line. The falling time ends when the lower periphery of the ball touches the ring mark B, which again must appear as astraight line. If one uses the distance AC or CB reduce very long falling times for high viscous liquids the double of measuring time period must be taken into account.

The falling times for the ball returning may vary from the normal value (up to 1%). If the returning of the ball should also be used for exact measurements a new constant K must be determined.

Constant for the returning of the ball

K_return = (Normal falling time x Normal constant K) / Falling time when returning

When testing dark liquids it is usually very difficult to see the lower part of the ball. In this case we advise to take the ball aquator when it passes through the ring marks.

8. Evaluation of The Test Result
The dynamic viscosity ŋ (in mPa.s) is calculated using the following equation:

ŋ = K(P1-P2).t

Where:

K = Ball constant mPa.s.cm³/g.s

P1 = Density of the ball in g.cm³

P2 = Density of the liquid to be measured at the measuring temperature in g.cm³

t = Falling time of the ball in second

The dynamic viscosity n is given in units of mPa.s (cP) and must be completed by stating the sample temperature. The dynamic viscosity n may be converted to the kinematic viscosity v by using the following equation:

V = n/p

v = kinematic viscosity [mm/s -> [1 mm²/s = 1 cSt]]

n = Dynamic viscosity [mPa.s]

p = Density of the liquid  sample [g/cm³]

To evaluated the reliability of the result the following criteria may be used:

REPRODUCIBILITY (One Person, One Instrument)

If one person determines two test result under identical test condition, these results are supposted to be acceptable if they do not vary more than figures stated in the table below from average value.

COMPARABILITY (Several Persons, Several Different Instruments).

If two sets of the test result are reach in two different places under comparable conditions, these results are supposed to be acceptable if they do not vary more than the figures stated in the table below from the average value.

Non-Newtonian liquids may be fully characterized rheological by means of absolute rotational viscometer.

Example.

Sugar solution of 40%.

Density of Ball No. 2 = 2,2 g/cm³

Density of the solution = 1,18 g/cm³Ball constant K = 0,09 mPa.s.cm³/g.s

Falling time = 61 s

Measuring temperature = 20,0 °C

The absolute viscosity is…

ŋ 20°C = 0,09 x (2,2-1,18) x 61 = 5.6 mPa.s

In most cases the densities of the test liquids are known. The evaluation may be simplified by introducting a factor which includes the densities. In out example of sugar solution the exact factor is…

(p1 – p2).K = (2,2-1,18).0,09 = 0,0918 mPa.s/s

9. Viscosity Determination of Gases

The viscosity determination of gases has to be done with ball G that is made out of glass.

The measuring tube must be closed with rubber stoppers fitted with glass stopcocks.

Measuring tube, glass ball and gas must be clean and dry.

The tube is flushed several times with the gas to be tested to push out any remains of air. Then the tube filled with the gas sample is closed with stopcocks and raised to the test temperature.

The calculation of the gas viscosity is based on the comparison with the viscosity of air at +20°C

(n=1815 x 10^-5 mPa.s):

ŋ gas = (FG/FA) x 1815 x 10^-5 mPa.s

Where:

ŋ gas = Viscosity of the gas at the temperature T

FG = Falling time of the ball in the gas at temperature T

FA = Falling time of the ball in air at a temperature of +20°C

Viscosity of the air at a temperature of +20°C = 1815 x 10^-5 mPa.s

10. Cleaning the Measuring Tube

Usually the tube is cleaned by rinsing it with a suitable solvent.

High viscous liquids (glue and heavy oil, etc.) have to be removed with cleaning piston, which is optional with the instrument. Push this piston slowly through the tube. After this, there will be only a thin film of the liquid left on the walls of the tube that can be removed with a solvent.

Especially when measuring with balls 1 and G it is very important, that the tube and the ball are clean and dry.