BS ISO 8791-5-2020 pdf free download.Paper and board — Determination of roughness/smoothness (air leak methods) Part 5: Oken method
This document specifies the Oken method for determining the smoothness of paper and board using an apparatus which complies with the Oken method, as defined in this part of ISO 8791. It is applicable to all printing papers and boards.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 48, Rubber, vulcanized or thermoplastic — Determination of hardness (hardness between 10 IRDH and 100 IRDH)
ISO 186, Paper and board — Sampling to determine average quality
ISO 187, Paper, board and pulps — Standard atmosphere for conditioning and testing and procedure for monitoring the atmosphere and conditioning of samples
ISO 4662, Rubber, vulcanized or thermoplastic — Determination of rebound resilience
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1 oken smoothness
time required for a specific volume of air to leak from the gap between the flat measuring lands of the Oken tester and the surface of a test piece under specified conditions
Note 1 to entry: Oken smoothness is expressed in seconds per 100 ml (s/100 ml).
4 Principle
A test piece is placed between a rubber plate and measuring lands.
The air pressure on the inlet side of a narrow capillary of controlled dimensions is maintained at a constant value above atmospheric pressure. The air passes through the capillary and then leaks between the surface of the test piece and the measuring lands. The air pressure between the outlet side of the capillary and a test piece depends on the rate of flow of air between the measuring lands and the surface of the test piece. It is measured and converted to Oken smoothness. For further details regarding the measurement principle, see Annex A.
For details regarding the test method precision, see Annex B.
5 Apparatus
5.1 Oken Smoothness apparatus (two types)
Use either the water column type described in 5.2 or the electronic sensor type described in 5.3.
5.2 Water column type
5.2.1 The water column type, see Figure 1, consists of an air compressor, filter, pressure regulator, water column regulator, capillary, water column manometer, measuring head, and scale plate.
5.2.1.1 The measuring head, see Figure 2, consists of a loading weight, rubber plate, and sensing head.
5.2.1.1.1 The loading weight and rubber plate, the loading weight has a circular even surface of not less than 48 mm in diameter and a mass that clamps the test piece at a pressure of (98,1 ± 1,0) kPa.
The rubber plate has a diameter of not less than 48 mm, a thickness of (4 ± 0,2) mm, a hardness of (50 ± 5) IRHD in accordance with ISO 48, and a rebound resilience of not less than 62 % in accordance with ISO 4662.
5.2.1.1.2 The sensing head, has 10 concentric measuring lands and nine grooves. The outermost measuring land has a width of (0,5 ± 0,03) mm, and an outside diameter of (46 ± 0,03) mm. The width of the other nine measuring lands is (1 ± 0,03) mm. The inside diameter of innermost measuring land is (9 ± 0,03) mm. All grooves have a width of (1 ± 0,03) mm, and a depth of 0,5 mm to 1,2 mm. Five grooves have air outlet holes and four grooves have air inlet holes arranged alternately. A tube connects the sensing head to the pressure measuring chamber.
5.2.1.2 The air compressor and regulator, supply compressed and filtered air. The air is controlled to approximately 10 kPa by the air regulator.
5.2.1.3 The water column regulator and capillary, provide a constant pressure. The water column regulator consists of a water tank with an internal diameter of approximately 100 mm and a height of approximately 700 mm, and a constant pressure chamber with a side tube. The open end of the side tube is (500 ± 0,5) mm below the water surface.
The air at approximately 10 kPa introduced into the constant pressure chamber is controlled to (4,90 ± 0,01) kPa (500 ± 1 mmH 2 O) and transferred to the pressure measuring chamber through the capillary.
The capillary consists of a narrow tube made of stainless material with an inner diameter of approximately 0,3 mm and a length of approximately 50 mm. The capillary length shall be strictly adjusted so that constant K in Formula (1), see 5.2.1.4, is 100.BS ISO 8791-5 pdf download.