Falling Rod Viscometer

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Falling Rod Viscometer (Laray Viscometer) is an instrument applicable to determinethe rheological properties ( apparent viscosity pseudoyield value shortness, etc ) of Non-Newtonian liquids (viscosityincreases with shear rate). Larya Viscometer designed and produced by ourcompany is in accordance with the specification of ASTM D 4040-10 and ISO12644:1996(E) Graphic technology Determination of rheological properties of pasteinks and vehicles by the Falling Rod Viscometer . Its principle: measuring falltimes by loading the rod with different load weights pass the gap which isfilled with the test fluid. By applying linear regression methods & bymeans of suitable flow model ( Casson model, Bingham model or Power Law model )to obtain apparent viscosity  yield value shortnessratio of sample.

Specification

• Input voltage: 220V 50Hz
• Range of apparent viscosity: 2-200Pa.s
• Dimensions of the falling rod: 12x300mm
• Weight of the falling rod: 132g
• ets of load weights (total 4075g ):25-50-100-200-200-500-1000-1000-1000g
• Overall dimensions: 140mm x 140mm x 300mm (length by width by height )
• Weight( including instrumen tweight box controller ): 18kg

Test procedure

• Prior to use,the test sample (about 5g) shall be kneaded by a spatula and equilibrated totest temperature. The sample shall be homogeneous and not contain any coarseparticles. An amount of the test sample sufficient to coat the rod and apertureis applied to the lower part of the rod.
• The bottom of the rod is inserted into the aperture of guide bush andslightly fall on the turntable, the sample is distributed uniformly around thegap, the gap is filled with the test fluid which is sheared when the rod fallsby using fingertip; lift the bottom of the rod 20mm, then fall on theturntable. 
• Load weights to be loaded on top of the rod, remove a turntable to letfalling rod fall, the rod and the aperture are wetted by the liquid; Make surethat photoswitch & temperature sensor are working normally (temperatureindicator display starting temperature when starting falling, time indicatorstarts to display seconds; temperature indicator display finishing temperaturewhen finishing falling, time indicator display actual fall time; temperatureresume to display actual temperature of guide bush after pulling up the rod,time automatically clear. 
• Avoid anyscoring operation for the rod, the metal spatula should not be allowedoperation for the rod; Don't do falling operation under the condition of notest sample. After finishing falling, the rod is lightly pulled up and restedon the support. After each run, the rod is scraped with the spatula and theliquid which was scraped off is reapplied on the lower part of the rod &the aperture of guide bush.
• The proper sets of load weights is selected according to the expectedresults. The fall time with the heaviest load weight should normally be in therange from 4s to 10s ( ASTM D4040-05 recommend 1-2s. Series of load weights arecombined to sets. Sets of load weights with the following masses should beused: (Unit: g)

• A: 5000 4000 3000 2000 1000
• B: 3000 2000 1500 500
• C: 1500 1000 800 500
• D: 800 600 400 200
• E: 400 300 200 100
• F: 200 100 50 0

The sample is tested with the heaviest load weight at the beginning of thetests, load weighs in descending order. Fall time during the test with theheaviest load weight varies less than 0.5s, the sample is tested with theselected series of load weights in descending order. The fall time shall notexceed 60s. After each run, the rod is scraped with the spatula and the liquidwhich was scraped off is reapplied on the lower part of the rod. During thetest, additional liquid shall not be added. The sample is tested with each loadweight for three times. By loading the rod with different load weights recordthe fall time every time ( correct to 0.01s), and temperature of guide bushduring measurement ( correct to 0.1).

Operationshall be done quickly and can't be interrupted, the whole operation shall befinished within 5-10 minutes. Many printing ink and vehicles have strongvolatile solvent, only if strictly control actual exposition time, otherwisevolatile loss cause large deviation of test result during operation. If foundseveral continuous falling with the same load weight, fall time could belonger, it indicates that obvious volatile loss exists. 

Viscosity is strongly temperature dependent, therefore the temperature shallbe controlled and monitored. Principally, if the test temperature varies fromreference temperature (25) by more than 0.2 before the runs, the thermostatic equipment shall be reset. if thetemperature during the test varies more than 1 the test shall be repeated.

After the test, the instrument shall be cleaned immediately with a lint-freewiper and a suitable solvent, especially the rod & guide bush.

ISO12644

Graphic technology -- Determination of rheological properties of paste inks and vehicles by the falling rod viscometer. This International Standard specifies the procedure for determining theviscosity and yield value of paste inks and vehicles which are unreactive under normal room conditions. It is applicable to inks in the apparent viscosityrange of 2 Pa s to 200 Pa s.

ASTM D 4040-10

Standard Test Method for Rheological Properties of Paste Printing and Vehicles by the Falling-Rod Viscometer. Apparent viscosity at the relatively high shear rate of 2500  does not completely define the rheological properties of printing inks but is useful in the practical control of ink viscosity during production and the specification acceptance between supplier and purchaser.

The slope of the power law plot is the preferred measure of non-New tonianism. The yield value, which is obtained by extrapolation of high-shear measurements to a shear rate approaching zero, does not conform to the definition of the true yield stress. The yield value and other low shear parameters are also subject to a high degree of variabilit