Laboratories for Cotton fibers classification
The physical and merchandise characteristics of the Cotton fibers are easily influenced by their moisture content (MC%) and by the conditioning applied to the reference samples which must be kept constant within the tolerance limits, therefore the equilibrium is defined constant climate or standard atmosphere to be applied for a period of time not less than 24 hours approved before, during and after the tests.
For the air conditioning and for test analyses on cotton the reference Standard is the ASTM D-1776-15, 2015, "Practice for conditioning and testing textiles. ASTM International, West Conshohocken, PA, www.astm.org" that sets thermo-hygrometric reference values at:
- Temperature: 21 ± 1°C (70 ± 2°F);
- Relative humidity: 65 ± 2%
The allowable limits for humidity control are fixed at ± 2%, thus the most important point.
This statement means that the important not only to achieve the value of the 65%, but specifically keeping it within the prescribed limits.
It is admittable to add compensations for slight variations on the absolute value of humidity, if the reading value of R.H. remains constant, for example, at 62% or at 63%, but it is definetely wrong to apply any compensations on continuous fluctuations of Relative humidity.
The laboratory for cotton classification must be always conditioned to the reference conditions 24/24 h and 7/7 days during cotton preparation and testing.
It's important that the climatic conditions in the laboratory just are kept inside tolerances, alternatively all test running with HVI equipments or CCS must cease immediately until the environmental conditions are reached again.
It is necessary to monitor and collect data of temperature and humidity continuously with probes or dataloggers independent from those of air handling unit.
The sensors of the probes need to be subjected to a periodical calibration by accreditation institute with a certified instrument as for example a ventilated psychrometer.
For the test on cotton fiber it is possible to calculate an average value for the records stored for a maximum period of 5 to 10 minutes. The aim is to avoid variations responsible for most of the errors of measurement on cotton fiber as well as drifts over periods of long duration.
In order to keep the laboratory conditions within the tolerance range the improvement of laboratory insulation is necessary to avoid the influence of disturbing elements as heat, radiation, solar radiations and fumes coming from the external environments and minimizing their impact through suitable thermal insulation of walls and ceiling.
Branca Idealair provides air handling units for the precision conditioning of laboratories.
The installation and insulation of the sandwich wall panels, of the insulated ceiling and of the false ceiling for the right air flow distribution are combined to the correct sizing of the Air climatic unit by Branca Idealair to ensure the best regulation of thermo-hygrometric parameters.
The climatic unit is used by several laboratories for cotton fiber classification and is designed on the basis of the foreseen power and thermal loads generated inside the laboratory.
For samples relatively wet or dry, S.T.A. Branca Idealair include in the draft a pre-conditioning chamber realized for the samples set on the dry side without the use of driers and heaters. The relative humidity inside the pre-chamber will be maintained at constant values closed to those required inside the laboratory, but with wider tolerances as requested by ASTM D5867.