Paper and board -- Determination of roughness/smoothness (air leak methods)

ISO 8791-3:2017 specifies a method for the determination of the roughness of paper and board using the Sheffield apparatus. ISO 8791-3:2017 is applicable to papers and boards which have Sheffield roughness values between 10 ml/min and about 3 000 ml/min. It is not suitable for soft papers which allow the lands of the test head to indent the surface, or for high air-permeance papers which allow a significant flow of air through the sheet, or for papers which will not lie flat during the test.

Papier et carton -- Détermination de la rugosité/du lissé (méthodes du débit d'air)

General Information

Status
Published
Publication Date
13-Aug-2017
Current Stage
6060 - International Standard published
Start Date
16-Jul-2017
Completion Date
14-Aug-2017
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INTERNATIONAL ISO
STANDARD 8791-3
Third edition
2017-08
Paper and board — Determination
of roughness/smoothness (air leak
methods) —
Part 3:
Sheffield method
Papier et carton — Détermination de la rugosité/du lissé (méthodes
du débit d’air) —
Partie 3: Méthode Sheffield
Reference number
ISO 8791-3:2017(E)
ISO 2017
---------------------- Page: 1 ----------------------
ISO 8791-3:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

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ii © ISO 2017 – All rights reserved
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ISO 8791-3:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Apparatus ..................................................................................................................................................................................................................... 2

6 Sampling ........................................................................................................................................................................................................................ 4

7 Conditioning .............................................................................................................................................................................................................. 4

8 Preparation of test pieces ........................................................................................................................................................................... 4

9 Calibration .................................................................................................................................................................................................................. 4

9.1 Variable-area flow-measuring device .................................................................................................................................. 4

9.2 Electronic flow-measuring device .......................................................................................................................................... 4

10 Procedure..................................................................................................................................................................................................................... 4

10.1 Test atmosphere .................................................................................................................................................................................... 4

10.2 Determination of roughness........................................................................................................................................................ 4

11 Calculation and expression of results ............................................................................................................................................. 5

12 Test report ................................................................................................................................................................................................................... 5

Annex A (normative) Care and maintenance of test instrument with variable-area flowmeters ........6

Annex B (normative) Calibration of flowmeters ...................................................................................................................................... 7

Annex C (informative) Conversion table ........................................................................................................................................................11

Annex D (informative) Precision ...........................................................................................................................................................................12

Bibliography .............................................................................................................................................................................................................................14

© ISO 2017 – All rights reserved iii
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ISO 8791-3:2017(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International 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, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the 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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO’s adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: w w w . i s o .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 6, Paper, board and pulps, Subcommittee

SC 2, Test methods and quality specifications for paper and board.

This third edition cancels and replaces the second edition (ISO 8791-3:2005), which has been technically

revised.
The main changes compared to the previous edition are as follows:
— editorial changes have been made;
— precision data has been added as Annex D.
A list of all parts in the ISO 8791 series can be found on the ISO website.
iv © ISO 2017 – All rights reserved
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INTERNATIONAL STANDARD ISO 8791-3:2017(E)
Paper and board — Determination of roughness/
smoothness (air leak methods) —
Part 3:
Sheffield method
1 Scope

This document specifies a method for the determination of the roughness of paper and board using the

Sheffield apparatus.

This document is applicable to papers and boards which have Sheffield roughness values between

10 ml/min and about 3 000 ml/min. It is not suitable for soft papers which allow the lands of the test

head to indent the surface, or for high air-permeance papers which allow a significant flow of air

through the sheet, or for papers which will not lie flat during the test.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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 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
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:

— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
Sheffield roughness

measure of the rate at which air flows between flat circular lands and the surface of a sheet of paper or

board under specified conditions
Note 1 to entry: The roughness is expressed in millilitres per minute.

Note 2 to entry: The Sheffield unit is not defined, since it has been found that the scale units (Sheffield units)

on different instruments can correspond to different air flows, and there is no precise physical definition. This

document requires that the flowmeters be calibrated to give a flow rate in millilitres per minute.

4 Principle

A test piece is clamped between a flat plate and two flat concentric annular lands. Air is supplied at a

specified pressure to the space between the two lands, and the rate of air flow between the lands and

the test piece is measured. The air flow rate is a measure of the roughness of the test piece.

© ISO 2017 – All rights reserved 1
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ISO 8791-3:2017(E)
5 Apparatus

The apparatus, an example of which is shown in Figure 1, shall consist of an air supply (5.1), an air

pressure control (5.2) and air flow-measuring device (5.4), a test assembly (5.5) which houses a

measuring head (5.5.1) fitted with test lands, a flat plate (5.5.2), and a mechanical device for bringing

the lands into contact with the flat plate under a defined load.
Key
1 air supply 5 test assembly
2 pressure regulator 6 test piece
3 flow-measuring device 7 flat plate
4 flow impedance
Figure 1 — Example of Sheffield apparatus

5.1 Air supply, free of water, oil and other contaminants, at a pressure of 420 kPa to 950 kPa. A small

compressor using laboratory air is preferred to external compressed air.

5.2 Pressure-regulating device, consisting of a primary regulator to reduce the pressure to between

205 kPa and 210 kPa, and another regulator to adjust the pressure at the measuring head to 10,3 kPa

(variable-area flowmeters) or 9,85 kPa (electronic flowmeters).

5.3 Pressure manometer, with a range from 0 kPa to 20 kPa to enable the air pressure at the

measuring head to be set to the specified pressure within 2 % of the nominal value.

5.4 Flow-measuring device, of either a variable-area or an electronic type. The air flow shall be

measurable to an accuracy of ±5 % of the measured value.

5.4.1 Variable-area flow-measuring device, consisting of three variable-area flowmeters, each

having a tapered glass column containing a metering float suspended by the air flow in the column (see

Reference [7]). The three columns shall be chosen such that they enable measurement to be made on

a continuous scale of flow rate from 10 ml/min to 3 000 ml/min, with some overlap of scales between

columns. Each column shall be provided with a means of adjusting the flow rate (float-position knob)

2 © ISO 2017 – All rights reserved
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ISO 8791-3:2017(E)

and a means of span calibration (calibrating knob). This type of instrument shall operate at a supply

pressure of 10,3 kPa.

At air flow rates greater than 1 200 ml/min, the pressure drop in the Sheffield system is substantial and,

to ensure the reproducibility of results, it is necessary that the tubing used to connect the flowmeter to

the measuring head be carefully controlled with a length of 1,50 m ± 0,01 m and an internal diameter of

6,25 mm ± 0,25 mm. For the same reason, openings in valves and other fittings on the instrument shall

not be changed from those provided by the instrument manufacturer.

5.4.2 Electronic flow-measuring device, for measuring the air flow to the test assembly (measuring

head). The inlet pressure to the measurement device shall be controlled at 9,85 kPa.

NOTE The 9,85 kPa pressure is the typical pressure measured downstream of variable-area flow tubes that

have been calibrated using the zero and span adjustment air bleeds to atmosphere.

5.5 Test assembly.

5.5.1 The measuring head, together with a dead weight, shall have a mass of 1 640 g ± 2 g, shall have

two concentric annular lands made of, or coated with, a corrosion-resistant material and be designed

2 2

to contact the test piece. The annular lands shall have a total area of 97 mm ± 3 mm ; each land shall

have a width of 0,380 mm ± 0,010 mm. The outer diameters of the outer and inner lands shall be

47,70 mm ± 0,03 mm and 34,37 mm ± 0,03 mm, respectively.

The test assembly, an example of which is shown in Figure 2, shall include a detachable measuring head

mounted so that it can be brought into contact with a test piece placed on an optically flat plate.

Dimensions in millimetres
0,38 ±0,01 0,38 ±0,01
Figure 2 — Example of test assembly

The measuring head shall be connected to the air supply with an airtight seal and the air shall be fed

into the gap between the two measuring lands through a narrow hole bored through the material of

the measuring head. This can act as impedance in the measurement air line (see Figure 1, Key 4). The

central space inside the inner land shall be vented to the atmosphere.

The test assembly shall have a suitable coupling through which the chosen flowmeter is connected to

the tube leading to the measuring head. The tube, connecting the measuring head to the instrument,

and the tube connectors have internal diameters that provide resistance to the air flow. Alteration of

these components from those provided by the manufacturer may change the calibration and operation

of the instrument.

5.5.2 The flat plate is usually glass and shall be free from surface flaws. The measuring lands shall

be machined and the supporting plate shall be sufficiently flat so that, when the measuring lands are in

contact with the plate in the absence of any test piece, the air flow rate does not exceed 10 ml/min.

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ISO 8791-3:2017(E)

5.6 Calibration plate device, if the instrument employs an electronic flow-measuring device, the plate

device will enable the test assembly to be connected to an external calibration system (see Clause 9 and

Annex B).

NOTE 1 Although this calibration plate is necessary only with electronic devices, it can also be used in

instruments incorporating a variable-area flow-measuring device.

NOTE 2 Sheffield reference surface masters are available to check orifices for contamination and measuring

heads for wear or damage, but these are not specified
...

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