Viscometer: The "Guard Leg" Can Make a Difference

Viscometer: The “Guard Leg” Can Make a Difference

To evaluate food materials in the mixing process we use viscosity testing. The objective is to understand how the viscosity varies as the mixing process advances. This can have an impact on the type of mixing blades used and the power consumption. Viscometer easily performs the relevant test. A spindle is immersed in the liquid to be tested and then attached to the viscometer. The spindle rotates at various speeds, measuring and recording the associated viscosity values.

Band off metal in the shape off a “U” protects the spindle and sensing shaft, which attaches to the backside of the viscometer “pivot cop.” Its shape is designed to accommodate the spindle that come with the viscometer. Its design protects the spindle, and in turn the sensing system, from accidental bumps that can occur in the busy lab environment.

Image 1: The RV spindle set is most used for medium viscosity food items (sauces, creams, dips, yoghurts).

Image 2: For low viscosity liquids (soups, brought, beverages), the LV spindle set is appropriate.

The different shapes of RV spindles are historical, and it was introduced originally, the LV spindles came sometime later. HA and HB torque were developed later, and they are powerful enough to eliminate the need for Guard Leg protection. The width off the RV Guard Leg is greater than the LV Guard Leg because of the large diameter of the largest RV spindle, #1 RV.

The usage of the Guard Leg is essential for correct viscometer calibration, especially for bigger spindles. The Guard Leg acts as an otter boundary constraint for the sharing action imparted to the fluid by the rotating spindle. When the Guard Leg is not used for the #1RV and the #1LV spindles, the measured viscosity value can be lower by more than 15%. When consumers report viscosity values that are lower than expected, it is often because the Guard Leg is missing..

Following a well-documented test process is essential for accurate viscosity readings. The comprehensive specification of the equipment system is one of the small elements that is sometimes ignored. In this case, it is obvious that a rotational viscometer is needed. Also included should be a statement about whether the Guard Leg is required, along with choice of spindle, rotational speed, and time of spindle rotation.

By doing things correctly the first time and every time, you can save time and money. Best results come from a consistent and throughout approach to test methodology.