Cut Zahn

A cut Zahn is a Measuring instrument of the Viscosité. It is usually employed in industries of painting.

Description

The Zahn cut is a container in Stainless steel, pierced with a hole gauged and provided with a long handle.

The Zahn cuts are used by battery of five cuts, numbered from one to five and whose holes are increasingly large. The time of flow is grosso-modo divided by two to each time one passes from a reference to that immediately above.

Principle of measurement

The higher the Viscosity of the Liquid to be analyzed is and the more important the duration of flow of the sample is. The results are given while indicating:

the time of flow (measured in seconds using a Stop watch);
the number of the Zahn cut used;
the Temperature of the liquid or the part.

Use

To be valid, times of flow must be ranging between 20 and 40 S. Indeed, in on this side the precision strongly decreases insofar as the reaction time of the operator is proportionally more important. Beyond 40 S the stop of the flow becomes less clear what results there still in a more important error over time. Consequently it is advisable to choose the Zahn cut which will give a value in the range of time prescribed by possibly modifying the temperature so necessary. Generally this type of control is comparative compared to a preset standard or a sample-type.

In practice, the Zahn cut is plunged in the liquid to analyze for on the one hand carrying out the taking away and, on the other hand, to put it at temperature. As soon as one leaves it the liquid, the stop watch is started then stopped as soon as the last drop of liquid escapes from the opening of the cut.

Conversion of measurement

It is possible to convert the time of flow into kinematic viscosity (CST) by employing one of the following formulas, T being time in seconds.

Cut Zahn n° 1: ν = 1,1 * (T - 29)
Cut Zahn n° 2: ν = 3,5 * (T - 14)
Coupe Zahn n° 3: ν = 11,7 * (T - 7,5)
Cut Zahn n° 4: ν = 14,8 * (T - 5)
Cut Zahn n° 5: ν = 23,0 * T

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