The standard "ISO 2431 Paints and varnishes - Determination of flow time using flow cups" published by the International Organization for Standardization (ISO) describes a method for determining the flow time of paints, varnishes and related products used to check consistency. This standard specifies four flow cups of similar dimensions but with orifice diameters of 3 mm, 4 mm, 5 mm and 6 mm. This standard includes two methods for checking flow cups for wear and tear.
Flow cups with interchangeable jets are not within the scope of this standard because the close tolerances in feeding the material under test into the jet are not met. Immersion flow cups, which are commonly used, are also outside the scope of this standard.
Because the manufacturing tolerances of such flow cups are greater than those of the flow cups specified in this standard, flow time determinations made with immersion flow cups provide lower accuracy than that obtained with the flow cups specified in this standard.
The method described in this standard is limited to testing materials where the breakpoint of the flow coming from the orifice of the flow vessel can be determined precisely. In materials with flow times close to the upper limit of the measuring range (100 s), this point is difficult to determine and reproduce due to deceleration effects.
For the purposes of this standard, the following definitions apply in addition to the terms and definitions given in ISO 4618:
Temperature and humidity are important parameters that affect test results. Deviations from the specified requirements may lead to non-comparable results. However, alternative parameters may be agreed upon by the parties involved and these parameters should be reported.
The effect of temperature on flow time is very important in terms of application characteristics and varies by product type.
For reference purposes, this standard specifies a test temperature of 23,0 degrees plus/minus 0,5 degrees. However, due to prevailing temperature conditions, it may be more appropriate to perform the comparative test at another agreed temperature, for example, 25 degrees.
For control by flow time, the test specimen and flow cup should be conditioned to an agreed or specified temperature and it should be ensured that the temperature change during the test does not exceed 0,5 K. The flow cup should be in a location away from air currents.
If the test is carried out in a hood and the air intake is left open, this must be stated in the test report.
The dimensions of the flow cups used in these tests and the tolerances allowed in production are shown in the figure given in the standard. The most critical tolerance is the inside diameter of the flow cup jet, since the flow duration is inversely proportional to the fourth power of this dimension.
The flow cup jet should be made of stainless steel or sintered carbide and the flow cup body should be made of a material that is corrosion resistant and unaffected by the products to be tested.
Unspecified dimensions such as wall thickness should be such that the flow vessel will not be distorted in any way during use. The external shape should preferably be as shown in the figure, but may be changed for ease of use or manufacture, provided that the projecting jet of the flow vessel is protected from accidental damage by an external protective casing as far as possible. Such a protective casing should not be immediately adjacent to the jet to prevent any capillary action when the material under test flows out. Flow vessels with an additional casing for temperature control are preferred.
The internal surfaces of flow cups, including the bore, should be smooth and free from swirl marks, cracks, protrusions and burrs that could cause random flow or entrapment of the sample or cleaning material. The required finish standard is a maximum roughness of not more than 0,5 µm.
Flow cups should be used within the measuring range given in the table provided in the standard. Meaningful data can only be obtained within this range. In addition, conversion of flow time to kinematic viscosity and vice versa should be done using the formulas given in the table.
Each flow container must be permanently and legibly marked with information such as the flow container's identification number, the manufacturer's identification number, and the manufacturer's name or trademark.
Our organization has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. Among the numerous test, measurement, analysis and evaluation studies provided for businesses in various sectors, there are also test services in accordance with the standard “ISO 2431 Paints and varnishes - Determination of flow time using flow cups”.
To get an appointment, to get more detailed information or to request an evaluation, you can ask us to fill in our form and reach you.
