1、BRITISH STANDARD BS ISO 8791-4:2007 Paper and board Determination of roughness/smoothness (air leak methods) Part 4: Print-surf method ICS 85.060 BS ISO 8791-4:2007 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2008 BSI 2008 ISBN
2、 978 0 580 54104 9 National foreword This British Standard is the UK implementation of ISO 8791-4:2007. The UK participation in its preparation was entrusted to Technical Committee PAI/11, Methods of test for paper, board and pulps. A list of organizations represented on this committee can be obtain
3、ed on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. Amendments/corrigenda issued since publication
4、 Date Comments Reference number ISO 8791-4:2007(E)INTERNATIONAL STANDARD ISO 8791-4 Second edition 2007-11-15 Paper and board Determination of roughness/smoothness (air leak methods) Part 4: Print-surf method Papier et carton Dtermination de la rugosit/du liss (mthodes du dbit dair) Partie 4: Mthode
5、 Print-surf BS ISO 8791-4:2007ii iii Contents Page Foreword iv 1 Scope 1 2 Normative references 1 3 Terms and definitions .1 4 Principle2 5 Apparatus .2 6 Sampling.6 7 Conditioning.6 8 Preparation of test pieces.6 9 Procedure .7 10 Calculation8 11 Precision.8 12 Test report 9 Annex A (normative) Cal
6、culation of roughness in micrometres10 Annex B (normative) Maintenance of Print-surf roughness testers 12 Annex C (normative) Calibration of variable-area flowmeters .14 Annex D (normative) Calibration of Print-surf instruments against ISO reference standards .16 Annex E (normative) Calibration of a
7、n impedance instrument for the purpose of assigning values to ISO reference standards.18 Bibliography 22 BS ISO 8791-4:2007iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing Internatio
8、nal Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO
9、, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical com
10、mittees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the
11、possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 8791-4 was prepared by Technical Committee ISO/TC 6, Paper, board and pulps, Subcommittee SC 2, Test methods and quality sp
12、ecifications for paper and board. This second edition cancels and replaces the first edition (ISO 8791-4:1992), which has been technically revised. This version of ISO 8791-4 differs from the previous (1992) version as follows: a definition of Print-surf compressibility has been added; a description
13、 of a modified backing holder for testing high-stiffness papers and board has been added; Annex D describing the calibration of Print-surf instruments has been revised and expanded; some minor editorial changes have been made. ISO 8791 consists of the following parts, under the general title Paper a
14、nd board Determination of roughness/smoothness (air leak methods): Part 1: General method Part 2: Bendtsen method Part 3: Sheffield method Part 4: Print-surf method BS ISO 8791-4:20071 Paper and board Determination of roughness/smoothness (air leak methods) Part 4: Print-surf method 1 Scope This par
15、t of ISO 8791 specifies a method for determining the roughness of paper and board using an apparatus which complies with the Print-surf method, as defined in this part of ISO 8791. It is applicable to all printing papers and boards with which it is possible to form a substantially airtight seal agai
16、nst the guard lands of the measuring head. 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 amen
17、dments) applies. 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 4094, Paper, board and pulps International calibration of testi
18、ng apparatus Nomination and acceptance of standardizing and authorized laboratories 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 Print-surf roughness mean gap between a sheet of paper or board and a flat circular land pressed against it un
19、der specified conditions NOTE The mean gap is expressed as the cube root mean cube gap calculated as specified in Annex A. The Print- surf roughness is expressed directly as the average value of roughness, in micrometres. 3.2 Print-surf compressibility K percentage decrease in surface roughness when
20、 measurements are made consecutively at the two standard clamping pressures specified in this part of ISO 8791 BS ISO 8791-4:20072 4 Principle The test piece is placed between a circular flat metal sensing surface and a resilient backing, and inner and outer circular lands form a seal with the test
21、piece. Under the influence of a pressure difference, air flows across the measuring land between the measuring land and the test piece. The rate of air flow is measured on a variable-area flowmeter, or the pressure difference across the measuring land is compared to the pressure difference across a
22、known impedance. In both cases, the result is expressed as the air gap, in micrometres. 5 Apparatus 5.1 Print-surf tester (two types) 5.1.1 Print-surf tester, which operates according to one of the following principles. 5.1.1.1 Variable-area flowmeter type, in which a standard pressure difference is
23、 created across the measuring land and the air-flow rate is measured on a variable-area flowmeter. The air-flow rate varies with roughness and the flow rate is converted to roughness, in micrometres. The flow diagram for this type of instrument is shown in Figure 1. Key 1 incoming air 300 kPa to 600
24、 kPa 2 filter 3 pressure-regulator valve 4 6,2 kPa or 19,6 kPa 5 on/off valve 6 flow indicator tubes 7 to atmosphere 8 sensing head and clamping device Figure 1 Flow diagram for variable-area flowmeter type 5.1.1.2 Impedance type, in which the air from the controlled pressure source passes first thr
25、ough a fluidic impedance and then through the sensing head, after which it discharges to atmosphere. The pressure differences across the fluidic impedance and across the land are each measured by a transducer. These pressure differences vary with roughness and the signals are converted to roughness,
26、 in micrometres. The flow diagram for this type of instrument is shown in Figure 2. BS ISO 8791-4:20073Key 1 incoming air 300 kPa to 600 kPa 2 filter 3 pressure-regulator valve 4 19,6 kPa 5 fluidic impedance 6 pressure transducer 7 analog signal 8 to atmosphere 9 sensing head and clamping device Fig
27、ure 2 Flow diagram for impedance instrument type 5.1.2 Procedures for maintaining these testers in good working order are given in Annex B. 5.2 Principal components of the system 5.2.1 Air supply, supplying clean air, free of oil and water droplets, at a steady pressure within the range 300 kPa to 6
28、00 kPa. 5.2.2 Sensing-head pressure regulator, allowing setting of the sensing-head differential pressure to 19,6 kPa 0,1 kPa or, on variable-area flowmeter instruments only, to either 6,2 kPa 0,1 kPa or 19,6 kPa 0,1 kPa. 5.2.3 Sensing head, (see Figures 3 and 4), consisting of three concentric, ann
29、ular lands composed of suitable material which have coplanar, polished surfaces. The centre or measuring land shall be 51,0 m 1,5 m wide and have an effective length of 98,0 mm 0,5 mm. The two guard lands shall each be at least 1 000 m wide at any point, and the radial distance between them at any p
30、oint shall be 152 m 10 m. The measuring land shall be centred between them to within 10 m. The lands shall be mounted in an airtight mounting, constructed so that air can be passed into the gap between one guard land and the measuring land, and exhausted from the gap between the measuring land and t
31、he other guard land. The back of the mounting shall be flat and form a ground mating surface with the flat surface of a manifold fitted with air inlet and outlet ports. A spring-loaded protective collar may be fitted outside the guard lands. If such a protective collar is fitted, the force exerted b
32、y the loading spring shall be taken into account when setting the clamping pressure. NOTE In many instruments fitted with the protective collar, the force exerted by the loading spring is 9,8 N. BS ISO 8791-4:20074 Key 1 measuring land 2 guard lands 3 passage connected to air supply 4 passage leadin
33、g to flowmeters or atmosphere 5 recess vented to atmosphere Figure 3 Plan of the measuring and guard lands of the sensing head Key 1 paper 2 resilient backing 3 measuring land 4 regulated low-pressure air 5 to flowmeters or atmosphere Figure 4 The sensing head sectioned on two radii BS ISO 8791-4:20
34、075 5.2.4 Backing holders, consisting of rigid metal discs of known mass, each recessed to accommodate a resilient backing at least 10 mm greater in diameter than the outside diameter of the outer guard land. The mass of both the resilient backing and the holder shall be allowed for in the initial a
35、djustment of the clamping pressure. It has been observed that high-stiffness papers and boards can interact negatively with the flat metal backing holder and cause erroneously high roughness results. This problem can be solved by using a modified backing holder which relieves those areas of the back
36、ing holder not directly below the measuring land, as shown in Figure 5. Key 1 resilient backing 2 paper 3 regulated low-pressure air 4 measuring land 5 to flowmeters or atmosphere 6 new modified clamp platen showing machined cut-away Figure 5 The sensing head sectioned on two radii showing cut-away
37、platen 5.2.5 Two resilient backings, of different types, which can be held in the recessed holders by means of double-sided adhesive tape. 5.2.5.1 Soft backing, resilient, consisting of an offset printing blanket composed of a layer of synthetic rubber, at least 600 m thick, bonded to a fabric backi
38、ng giving an overall thickness of 2 000 m 200 m. The apparent hardness of the complete backing shall be 83 IRHD 6 IRHD (International Rubber Hardness Degrees). 5.2.5.2 Hard backing, resilient, usually made from a polyester film bonded at its periphery to cork, offset blanket or similar material. A s
39、mall exhaust hole shall be provided to prevent air being trapped between the film and the backing. The apparent hardness of the assembly shall be 95 IRHD 2 IRHD. 5.2.6 Clamping mechanism, allowing clamping of the resilient backing at pressures of either 980 kPa 30 kPa or 1 960 kPa 30 kPa, the pressu
40、re being calculated from the total area of the measuring and guard lands. BS ISO 8791-4:20076 NOTE 1 On some earlier instruments, these values may be displayed on the gauge as 10 kgf/cm 2and 20 kgf/cm 2 . Note that the spring loading in the protective collar (5.2.3) and the weight of the backing and
41、 its holder need to be taken into account. The rate of clamping shall be such that the pressure reaches 90 % of its final value in about 0,4 s, and 99 % of its final value in about 0,8 s. NOTE 2 A third pressure of 490 kPa (5 kgf/cm 2 ) is available on most instruments, but is not acceptable for use
42、 with this part of ISO 8791 because of a tendency for air to leak under the guard lands. Variable-area flowmeter measurement systems shall have a pressure gauge fitted to the instrument to indicate the clamping pressure, which shall be adjustable. Impedance measurement systems shall have integrated
43、pneumatic and electronic circuitry which automatically controls the clamping pressure. In each case, the actual pressure achieved shall be verified as specified in B.3. 5.3 Measuring system 5.3.1 The air-flow rate shall be measured with either a set of variable-area flowmeters or by measuring the pr
44、essure drop across an impedance. 5.3.2 Variable-area flowmeter instruments shall be fitted with flowmeters which are graduated to show the “cube root mean cube gap” between the paper and the measuring land surface, in micrometres (see Annex A). The flowmeters shall be calibrated by the procedures ou
45、tlined in either Annex C or D. 5.3.3 Impedance instruments measure air leakage by means of fluidic impedance, a pressure transducer and a function generator. They display or print the roughness, in micrometres to the nearest 0,1 m, based on automatic measurement of pressure difference, over the rang
46、e 0,6 m to 6,0 m. The value displayed shall be the value calculated after 3 s to 5 s. This device shall be calibrated by the procedure described in Annex D. 6 Sampling If the tests are being made to evaluate a lot, the sample should be selected in accordance with ISO 186. If the tests are made on an
47、other type of sample, make sure that the test pieces taken are representative of the sample received. 7 Conditioning The sample shall be conditioned in accordance with ISO 187. 8 Preparation of test pieces Prepare the test pieces in the same atmospheric conditions as those used to condition the samp
48、le. Cut at least 10 test pieces for each side to be tested. The minimum size of each test piece shall be 100 mm 100 mm, and their surfaces shall be identified in some convenient way (for example, side one or side two). The test area shall be free of all folds, wrinkles, holes or other defects, and s
49、hould not include watermarks. Do not handle that part of the test piece which will become part of the test area. BS ISO 8791-4:20077 9 Procedure 9.1 Carry out the test in the same atmospheric conditions as those used to condition the sample (see Clause 7). 9.2 Ensure that the instrument is on a rigid horizontal surface free from vibration and that it is level. Before use on any particular
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