How to check a Brookfield viscometer?

Calibration Procedures

The accuracy of your Brookfield viscometer is verified using standard oils available from Labomat Essor.

Viscosity standards are Newtonian: they have the same viscosity, whatever the speed of the moving body (shear rate). The viscosity standards, calibrated at 25 ° C, are shown in Tables E-1 (silicone oils) and E-2 (mineral oils).

Container size:

For stallions

For standards ≥ 30,000 cP, use the container provided. Internal diameter: 3.25 ”(8.25 cm) Height: 4.75” (12.1 cm)

Note: the container can be larger, but never smaller.

Temperature: Identical to that indicated on the bottle +/- 0.1 ° C

Conditions: The viscometer should be adjusted according to the instructions in this manual. The water bath must be stabilized at the calibration temperature. For model “LV” or “RV” viscometers, the protective bracket must be fitted (for more information on the bracket, see Appendix F).

General information on Brookfield Viscosity Standard Oils

It is advisable to replace the Brookfield standard oils once a year (one year after the date of opening the bottle). These oils are pure silicone and do not vary over time. However, exposure to external contaminants during their use justifies annual replacement. Contamination can occur through the introduction of solvents, standard oils of different viscosity, or other foreign materials. Standard oils can be stored in the laboratory under normal conditions. For their disposal, respect the regulations in force in your country or region (as specified on the Safety Data Sheet). Brookfield does not recertify standard viscosity oils. We can provide a duplicate of an oil's Calibration Certificate within two years of the date of purchase. Brookfield Standard Oils are reusable, provided they have not been contaminated. The classic practice with a 600 mL beaker is to put the used oil back into the flask. For Low Sample Adapter, ULA Adapter, or Thermosel type accessories, the oil is usually removed.

Calibration procedure for Brookfield LV # 1-3 (# 61-63) and RV, HA, HB # 1-6 mobiles

You will notice that LV # 4 (64) and RV, HA, HB # 7 (07) mobiles are not mentioned in this procedure. Brookfield advises against using them to check the calibration of your instrument due to the small surface of the mobile in contact with viscosity oil. As a result, it is difficult to precisely locate the immersion mark and to precisely control the temperature at 25 ° C around the mobile. To check the calibration of your instrument, use one of the recommended mobiles and follow the procedure below:

1) Place the standard liquid (in an appropriately sized container) in the water bath.

2) Lower the viscometer to the measuring position (with the bracket for LV or RV models).

3) Fix the mobile on the viscometer. If you are using a disc-shaped mobile, be careful not to trap air bubbles under the disc; tilt it to submerge it, before attaching it to the viscometer.

4) Before taking measurements, leave the standard viscosity oil and the mobile in the bath for at least one hour, periodically stirring the liquid.

5) After one hour, check the temperature of the standard oil with a precision thermometer.

6) If the oil is at the calibration temperature (typically 25 ° C ± 0.1 ° C of the temperature specified on the bottle), measure the viscosity and note the displayed value. Note: The rover must turn at least 5 times before taking a measurement.

7) The viscosity read should be equal to the cP value stated on the standard oil, within the combined precision limits of the viscometer and the standard oil (as indicated later in the chapter entitled "Interpretation of calibration results" , at the end of this Appendix).

Calibration Procedure for a Small Sample Adapter

Brookfield recommends a two-step audit.

First, check the calibration of the viscometer with the spindles supplied as standard (LV # 1-3, RV # 2-6, HA # 2-6 and HB # 2-6 or cone / plane spindles) according to the procedure described. in this Annex.

Then check the calibration of the viscometer with the Small Sample Adapter. Using an accessory can increase the measurement accuracy associated with the viscometer.

If you are using a Small Sample Adapter, connect the jacketed jacket to the water bath, and wait for the temperature to stabilize at the desired level:

1) Pour the correct amount of standard liquid into the measuring chamber. This amount varies depending on the mobile / chamber combination used (See the instructions in the Small Sample Adapter chapter in this manual).

2) Place the chamber containing the sample in the thermostatic envelope.

3) Place the mobile in the standard liquid, then attach the extension, the coupling device and the mobile (or the mobile directly) to the DV2T.

4) Wait 30 minutes for the standard oil, the chamber and the rover to reach the calibration temperature.

5) Measure the viscosity and note the value displayed by the viscometer. Note: The rover must turn at least 5 times before taking a measurement.

Calibration Procedure for a Thermosel System

Brookfield recommends a two-step audit.

First, check the calibration of the viscometer with the spindles supplied as standard (LV # 1-3, RV # 2-6, HA # 2-6 and HB # 2-6 or cone / plane spindles) according to the procedure described. in this Annex.

Then check the calibration of the viscometer with the Thermosel. Using an accessory can increase the measurement accuracy associated with the viscometer. With a Thermosel system, the controller stabilizes the thermal container at the test temperature.

1) Place the correct amount of high temperature standard oil in the HT-2 measuring chamber. This amount varies depending on the mobile used (see the instructions for the Thermosel in this manual)

2) Place the chamber containing the sample in the thermal container.

3) Place the mobile in the standard liquid, then attach the extension, the coupling device and the mobile (or directly the mobile) to the viscometer.

4) Wait 30 minutes for the standard oil, the chamber and the rover to reach the calibration temperature.

5) Measure the viscosity and note the value displayed by the viscometer. Note: The rover must turn at least 5 times before taking a measurement.

Calibration procedure for UL or DIN adapters

Brookfield recommends a two-step audit.

First, check the calibration of the viscometer with the spindles supplied as standard (LV # 1-3, RV # 2-6, HA # 2-6 and HB # 2-6 or cone / plane spindles) according to the procedure described. in this Annex.

Then check the calibration of the viscometer with the UL or DIN adapter. Using an accessory can increase the measurement accuracy associated with the viscometer.

With a UL or DIN UL adapter, the water bath is stabilized at the correct temperature:

1) Place the correct amount of high temperature standard oil in the UL tube (see UL adapter instructions in this manual).

2) Install the mobile on the viscometer.

3) Secure the tube to the mounting channel.

4) Lower the tube into the water bath. If you are using a ULA-40Y thermal jacket, connect the inputs / outputs to the water bath external circulation pump.

5) Wait 30 minutes for the standard oil, the chamber and the rover to reach the calibration temperature.

6) Measure the viscosity and note the value displayed by the viscometer. Note: The rover must turn at least 5 times before taking a measurement.

Calibration procedure for a Helipath stand with T-mobiles

If you are using a Helipath stand with T-shaped mobiles:

1) Remove the T-rover and choose a standard LV (# 1-3) or RV, HA, HB (# 1-6) rover. Follow the procedure for LV (# 1-3) and RV, HA, HB (# 1-6) mobiles described previously.

2) Do not use T-mobiles to check the calibration of your viscometer.

Calibration Procedure for a Spiral Adapter

Brookfield recommends a two-step audit.

First, check the calibration of the viscometer with the spindles supplied as standard (LV # 1-3, RV # 2-6, HA # 2-6 and HB # 2-6 or cone / plane spindles) according to the procedure described. in this Annex.

Then check the calibration of the viscometer with the spiral adapter. Using an accessory can increase the measurement accuracy associated with the viscometer.

1) Place the standard liquid (in the appropriate container) in the water bath (see instructions for the Coil Adapter).

2) Install the mobile. Install the chamber (SA-1Y) and attach it to the viscometer.

3) Lower the viscometer to the measuring position and rotate it at 50 or 60 RPM until the chamber is completely filled.

4) Before taking measurements, leave the standard viscosity oil and the mobile in the bath for at least one hour, stirring the liquid periodically (at 50 or 60 RPM).

5) After one hour, check the temperature of the standard oil with a precision thermometer.

6) If the oil is at the calibration temperature (typically 25 ° C ± 0.1 ° C of the temperature specified on the bottle), measure the viscosity. Note: The rover must rotate at least 5 times per minute before taking any measurements.

7) The viscosity read should be equal to the cP value stated on the standard oil, within the combined precision limits of the viscometer and the standard oil (as indicated later in the chapter entitled "Interpretation of calibration results" , at the end of this Appendix). However, the precision is equal to ± 2% of the maximum viscosity range instead of the 1% standard.

Calibration procedure for Cone & Plan viscometers

1) Follow the procedures previously described to adjust the cone to the platen.

2) Refer to Appendix A, Table A-1 to determine the correct sample volume for the selected cone.

3) Choose a standard oil allowing to obtain a viscosity value between 10% and 100% of the full scale reading. Refer to Appendix B for the cone viscosity ranges. Check with Brookfield or your LABOMAT ESSOR agent to determine the appropriate standard oil.

It is preferable to use a standard oil close to the maximum viscosity for a given cone / speed combination.

Example LV viscometer, Cone CP-42, standard oil No. 10 with a viscosity of 9.7 cP at 25 ° C

At 60 RPM, the full scale over the measuring range is 10.0 cP. The measurement displayed by the viscometer should therefore be: torsion 97% and viscosity 9.7 cP ± 0.197 cP (0.1 cP for the viscometer plus 0.097 cP for the standard oil). Accuracy is a combination of the tolerance of the viscometer and the standard oil (see Interpretation of calibration results).

4) Viscometer off, remove the sample cup and pour the standard liquid into the cup. Wait 10 minutes for the temperature to stabilize.

5) Place the sample cup on the viscometer. Wait until the temperature stabilizes (approx. 15 min maximum). The stabilization time may be reduced if the cone and cup are already at the calibration temperature.

6) Measure the viscosity and note the values displayed by the viscometer in % torsion and centipoise (cP).

Notes:

1) Note: The rover must rotate at least 5 times per minute before taking measurements.

2) For Cone / Plane models, Brookfield recommends using a standard oil between 5 cP and 5000 cP. Contact Brookfield or your LABOMAT ESSOR agent if your calibration procedure stipulates higher viscosity oils.

3) Choose a standard oil allowing to obtain a viscosity value between 10% and 100% of the full scale reading. Refer to Appendix B for the cone viscosity ranges. With a Cone / Plate model, do not use a silicone standard oil with a value greater than 5000 cP. Brookfield offers a complete line of standard oils suitable for Cone / Plate viscometers (see Table E-2). Check with Brookfield or your LABOMAT ESSOR agent to determine the appropriate standard oil.

Interpretation of calibration results

When checking the calibration of your DV2T, you must combine the instrument and standard liquid accuracies to calculate the total allowable error.

With LV # 1-3, RV # 2-6, HA # 2-6 and HB # 2-6 rovers, the DV2T is accurate to (+/-) 1% of the measuring range. This value may be higher if you use accessories such as Small Sample Adapter, UL Adapter, Thermosel, Spiral Adapter or DIN Adapter. Usually the increase is small, but it can reach 1% for a total accuracy of +/- 2% of the range used.

Brookfield standard oils have an accuracy of (+/-) 1% of the indicated value.

Example: Calculation of the measurement accuracy for an RV with an RV-3 spindle at a speed of 2 RPM; Brookfield standard oil 12,500 cP with a viscosity of 12,257 cP at 25 ° C:

1) Calculation of the viscosity range:

Full scale viscosity range [cP] FSR = TK * SMC * 10,000 / RPM

TK - 1.0 for an RV viscometer - see Table D-2 SMC = 10 for RV3 spindle - see Table D-1

Full scale FSR: 1 * 10 * 10,000 = 50,000 cP 2 therefore the RV viscometer with the RV3 mobile and the speed 2 rpm has a measurement range of 5,000 to 50,000 cP with an accuracy of + - 500 cP. (i.e. 1% FSR)

2) The standard oil has a value of 12257 cP. Its precision is (+/-) 1% of 12257, i.e. (+/-) 122.57 cP.

3) The total allowed error is (122.57 + 500) cP = (+/-) 622.57 cP.

4) Therefore, a viscosity value between 11.634.4 and 12.879.6 cP indicates that the viscometer is working properly. Any value outside of these limits indicates an operational problem. Contact LABOMAT ESSOR Technical Service with your test results to determine the nature of the problem.

Example: Calculation of the measurement accuracy for a DV2TLV with an SC4-21 rover and a Small Sample Adapter at 6 - 12 - and 30 RPM. Brookfield standard oil 100 cPs with an actual value of 101.5 cP at 25 ° C.

1) Calculate the full scale viscosity using the “Rover Range Coefficient” in Appendix B of the “More Solutions to Sticky Problems” publication, or by using the Auto Range button on your viscometer.

The Range Coefficient of Rover 21 on an LV model is 4.688.

At 6 RPM, the full scale viscosity (FSR) is 781 cP. Count an accuracy of +/- 1% for the viscometer and +/- 1% for the Small Sample Adapter.

The total authorized precision is: +/- 2% x 781 cP = +/- 15.6 cP

The same calculation at 12 RPM gives FSR = 391 cP: +/- 2% x 391 cP = +/- 7.8 cP

The same calculation at 30 RPM gives FSR = 156 cP: +/- 2% x 156 cP = +/- 3.1 cP

2) The standard oil has a value of 101.5 cP. Its precision is: +/- 1% x 101.5 cP = +/- 1.015 cP or approximately +/- 1.0 cP for future calculations.

3) The total precision is equal to the sum of the values n (1) and (2):

At 6 RPM, the precision is: 15.6 cP + 1.0 cP = +/- 16.6 cP

At 12 RPM, the precision is: 7.8 cP + 1.0 cP = +/- 9.8 cP

At 30 RPM, the precision is: 3.1 cP = 1.0 cP = +/- 4.1 cP

4) Consequently, at each speed, the margin within which the measured viscosity must lie is calculated with respect to the value of the standard oil:

At 6 RPM: 84.9 cP to 118.1 cP

At 12 RPM: 91.7 cP to 111.3 cP

At 30 RPM: 97.4 cP to 105.6 cP

If your measured value is outside of these limits, contact LABOMAT ESSOR to discuss your results and determine if your instrument requires recalibration.

Mobile codes and models

Each mobile has a two-digit code which must be entered using the viscometer keypad. The entry code allows the viscometer to calculate viscosity, rate and shear stress. Each mobile has two constants used in these calculations. The Rover Multiplication Constant (SMC) is used for viscosity and shear stress calculations, and the Shear Rate Constant (SRC) for shear rate and stress calculations.

Note that when SRC = 0, there is no calculation of rate and shear stress; for these functions, the displayed value is zero (0).

The following table gives the spring torsion (TK) values for each viscometer model.

The 100 % of spring torsion (maximum viscosity value) corresponding to each mobile / speed combination can be obtained from the following equation:

Viscosity at 100 % of torsion (centipoise) FSR = TK * SMC * 10000 / Speed (RPM)

The measurable viscosity range for each mobile / speed combination should correspond to spring torsion values between 10 % and 100 %.

To calculate the shear rate, apply the following formula: Shear rate (1 / Sec) = SRC x RPM

Brookfield caliper

Originally, the caliper was intended to protect the mobile during use. The first versions of Brookfield viscometers made it possible to measure directly on site in 200 liter tanks. Under these conditions, it is obvious that the risk of damaging the mobile was high. The original manufacture included a sheath that protected the mobile from side impacts. More recently the RV calipers were attached to the analog box and the LV calipers at the bottom of the pivot cup with the fastening system.

The caliper consists of a "U" shaped metal strip with a fixing system on the pivot cup of Brookfield viscometers / rheometers. Because it must be attached to the pivot cup, the caliper cannot be used with Cone / Plane fixtures. A caliper is supplied with all RV and LV viscometers, but not with the HA or HB models. Its shape (illustrated in Figure 1) is suitable for mobile games. In addition, the caliper of the RV is larger than that of the LV due to the large diameter of the RV-1 rover. They are not interchangeable

The calibration of the viscometers / rheometers is determined using a 600 ml Griffin Beaker. The calibration of model LV and RV viscometers includes the caliper. The walls of the Becher (for HA / HB instruments) or the caliper (for LV / RV instruments) define what are called the “outer limits” for the measurement. The moving factors are used to convert the torque (expressed in dial reading or % torsion) in centipoise. Theoretically, if the measurements are made under different boundary conditions, for example, without the caliper or with another measuring container than a 600 ml beaker, then the factors found on the “FACTOR FINDER” ruler supplied with the models at dial can no longer be used to accurately calculate absolute viscosity. Changing the boundary conditions does not change the viscosity of the fluids, but it does change the way the torque of the device is converted to centipoise. Without modifying the mobile factors to match the new boundary conditions, the viscosity calculation from the torque of the instrument will be incorrect.

Practically, the caliper has the greatest effect on measurements when used with mobiles # 1 and # 2 from LV and RV games (Note: Rover RV / HA / HB # 1 is not included in the standard mobile set). Any other LV (# 3 & # 4) or RV (# 3 - # 7) mobile can be used in a 600 ml beaker with or without a caliper and will give correct results. The HA and HB series are not supplied with a caliper to reduce potential problems when measuring highly viscous products. Mobiles # 3 through # 7 are identical to those in the RV model set. The # 1 and # 2 mobiles have slightly different dimensions than the RV mobiles. The difference in dimension makes it possible to use the same conversion coefficient (% torsion → viscosity) for RV and HA / HB # 1 and # 2 mobiles while the boundary conditions are different

The recommended procedure specifying the use of a 600 ml beaker and caliper is often restrictive for some customers. The caliper is an additional accessory to be cleaned. For some applications, the sample volume of 500 ml required to immerse the mobiles in a 600 ml beaker is not available. In practice, a smaller container can be used if the caliper is removed. Brookfield viscometers give an accurate and repeatable torsion reading under all measurement circumstances. However, converting this torque to centipoise will only be correct if the factor used has been developed for those specific conditions. Brookfield has written a method for the recalibration of viscometers / rheometers valid in all circumstances in the manual "More Solutions to Sticky problems". It is important to note that for many viscometer users the actual viscosity is of less importance than the repeatability of day-to-day values. This repeatable value can be obtained without any effort under all measurement circumstances. However, it should be borne in mind that reading in % torque cannot be converted to the correct centipoise viscosity using Brookfield conversion factors if the boundary conditions are not those specified by Brookfield.

The caliper is part of the calibration check procedure for the Brookfield LV and RV viscometers. Our customers should be made aware of its existence, its usefulness and the effect it may have on the data. With this knowledge, the user can modify the recommended method to suit their own needs.