BS-EN-1724-1999.pdf
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS EN 1724:1999 The European Standard EN 1724:1998 has the status of a British Standard ICS 53.040.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Light conveyor belts Ð Test method for the determination of the coefficient of friction Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:03:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI This British Standard, having been prepared under the direction of the Sector Committee for Materials and Chemicals, was published under the authority of the Standards Committee and comes into effect on 15 May 1999 BSI 05-1999 ISBN 0 580 32160 6 BS EN 1724:1999 Amendments issued since publication Amd. No.DateText affected National foreword This British Standard is the English language version of EN 1724:1998. The UK participation in its preparation was entrusted to Technical Committee PRI/67, Conveyor belts, which has the responsibility to: Ð aid enquirers to understand the text; Ð present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; Ð monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled ªInternational Standards Correspondence Indexº, or by using the ªFindº facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 7 and a back cover. Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:03:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI CEN European Committee for Standardization Comite  Europe Âen de Normalisation Europa Èisches Komitee fu Èr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1998 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 1724:1998 E EUROPEAN STANDARDEN 1724 NORME EUROPE ÂENNE EUROPA ÈISCHE NORM December 1998 ICS 53.040.20 Descriptors: belts, conveyor belts, mechanical tests, friction tests, determination, friction factor English version Light conveyor beltsÐ Test method for the determination of the coefficient of friction Courroies transporteuses le Âge Áres Ð Me Âthodes d'essais pour la de Âtermination du coefficient de frottement Leichte Fo Èrdergurte Ð Pru Èfverfahren fu Èr die Bestimmung des Reibwertes This European Standard was approved by CEN on 28 November 1998. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:03:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 2 EN 1724:1998 BSI 05-1999 Foreword This European Standard has been prepared by Technical Committee CEN/TC 188, Conveyor belts, the Secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 1999, and conflicting national standards shall be withdrawn at the latest by June 1999. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Contents Page Foreword2 Introduction3 1Scope3 2Normative references3 3Definitions3 4Principle3 5Apparatus4 6Test piece4 7Procedure4 8Calculation and expression of results5 9Test report5 Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:03:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 3 EN 1724:1998 BSI 05-1999 Introduction The coefficient of friction of light conveyor belts must be seen from two different aspects being relevant for the choice of the reference material. One aspect is the friction of the underside of the belt. In practice this is not critical because it is low. Regardless whether a table of steel or of wood is used, the coefficient of friction is within the range from 0,2 to 0,3 in most cases. Contrary to this the top face covers show values over an extended range depending on their actual function. To achieve this function the material itself can be modified as well as the surface pattern, but the test procedure shall be the same in every case. So it becomes clear that the chosen steel panel represents a compromise. Its main properties are reproducibility of the surface finish and uncritical friction behaviour against any kind of belt cover. This standard allows comparison of all kinds of conveyor belts to obtain reliable results as a reference. This may be helpful to buyers who need guidance in choosing the right belt for their particular application. The tests in accordance with this standard are limited to dynamic coefficients of friction (mD) up to 1,0 and static coefficients of friction (mS) up to 1,5. Higher values can show a mixture of friction, adhesion, deformation and other effects occurring especially where the surface texture is coarse and is therefore unsuitable for this test. The method using the standardized metallic test panel is intended especially to compare the coefficients of friction of different light conveyor belts. The values received under practice conditions always depend on the frictional partners. To determine these effects it is possible to choose a different frictional partner instead of the panel if required. This is mentioned in the test report. 1 Scope This European Standard describes methods of test to determine the dynamic and static coefficient of friction of light conveyor belts as described in EN 873. 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions for any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN 873, Light conveyor belts Ð Principal characteristics and applications. EN 10002-2, Metallic materials Ð Tensile testing Ð Part 2: Verification of the force measuring system of the tensile testing machine. ISO 471:1995, Rubber Ð Temperatures, humidities and times for conditioning and testing. ISO 554, Standard atmospheres of conditioning and/or testing Ð Specifications. ISO 4287, Geometrical Product Specification (GPS) Ð Surface texture: Profile method Ð Terms, definitions and surface texture parameters. ISO 6133, Rubber and plastics Ð Analysis of multi-peak traces obtained in determinations of tear strength and adhesion strength. ISO 7500-1, Metallic materials Ð Verification of static uniaxial testing machines Ð Part 1: Tensile testing machines. 3 Definitions For the purposes of this standard the following definitions apply. 3.1 dynamic coefficient of friction, mD=FD FN where FD= dynamic frictional force, sliding friction; FN= normal force. 3.2 static coefficient of friction, mS= FS FN where FS= static frictional force, stiction (break-away force); FN= normal force. 4 Principle 4.1 Dynamic coefficient of friction A test piece cut from the full thickness of the conveyor belt in the longitudinal or transverse direction, in accordance with the scope of the test is clamped to a table. A metallic test panel subjected to a given normal force is pulled over the test piece at a defined speed. Then the mD-value is determined by calculation, using the dynamic frictional force (FD) and the normal force. 4.2 Static coefficient of friction A metallic test panel is subjected to a normal force as in 4.1. Additionally, a pulling force is acting on the test panel, generated by a pulling mechanism moving at a defined speed. The mS-value is determined by calculation, using the static frictional force (FS) and the normal force. Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:03:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 4 EN 1724:1998 BSI 05-1999 5 Apparatus Testing apparatus as shown in Figure 3 consisting of the following main parts. 5.1 Testing table, to clamp test piece on. 5.2 Metallic test panel, see Figure 4. Dimensions: Thickness: 0,8 mm Width: (76±0,5) mm Length: 152 mm Testing area: (76±0,5) mm 3 (131,5±0,5) mm = (100±1) cm2 Materials: Steel Type: CR1/ISO 3574 Hardness: HRB 60 to HRB 70 Surface: milled Roughness: Ra= 0,9 mm to 1,3 mm (in accordance with ISO 4287) Because of the danger of the surface changing due to the abrasion of the test piece, the metallic test panel has to be replaced after max. 50 applications; however after one day of use at the latest. Because the test panel is not stainless it shall be kept in the original pack until the first use in a dry place in the laboratory. The personnel shall wear clean cotton gloves and touch the panel only at the edges. 5.3 Weight, generating a normal force of 50 N±1 N together with the metallic test panel. Dimensions: Length: (120±0,2) mm Width: (75±0,2) mm Height: (71±0,2) mm Material: Steel with a density of 7,85 g/cm3 5.4 Cable, with a low elasticity, e.g. steel cable with a diameter of approximately 1 mm. 5.5 Device for the measurement of the frictional force 5.5.1 Load cell, with a range up to 100 N. The force measuring system shall be in accordance with EN 10002-2 or ISO 7500-1, Class of machine 3 or better, (e.g. Class of machine 2). 5.5.2 Recording instrument, to record the signal of the load cell. 5.6 Pulling mechanism, for example a tensile testing machine to produce a uniform relative motion between test piece and metallic test panel. The deflection roller (see Figure 3) shall have a diameter of 40 to 50 mm and ball bearings to ensure smooth rotation. The pulling cable shall be parallel to the sliding surface. 6 Test piece 6.1 Test piece material Test piece material must be new, unused (ªvirginº), but not tested earlier than five days after manufacture. It shall be free of any kind of contamination or superficial damage. 6.2 Number and dimensions of test pieces Three test pieces shall be cut from the full thickness of the conveyor belt in the longitudinal and/or transverse direction, in accordance with the scope of the test, one from the middle of the belt, the others 100 mm from each of the belt edges. If both surfaces of the belt are to be tested more test pieces shall be taken accordingly. The test pieces must measure 600 mm long 3 100 mm wide. Each test piece shall be used only once. 6.3 Conditioning Before testing expose the test pieces to the test room climate, (23±2) 8C and (50±5) % relative humidity, in accordance with ISO 471 and ISO 554, for at least 24 h. 7 Procedure Ð Check the test room climate (23±2) 8C and (50±5) % relative humidity, in accordance with ISO 471. Ð Adjust the testing table to the horizontal position in the longitudinal and transverse directions. Ð Clamp the test piece to the table. Ð Check if the metallic test panel is free of rust; (visual control). Ð Clean the metallic test panel by using pure acetone and a soft tissue which is not dissolved by the acetone and does not leave any residue on the panel. Let the acetone evaporate and polish the panel afterwards with a new dry tissue. Then place the panel on the test piece. Ð Connect the cable to the panel and put the weight on it. Ð Measurement of mD: speed of the pulling mechanism: (1 000 ± 20) mm/min; NOTEThis speed may be slower if the maximum speed of the machine is less than 1 000 mm/min, but not below (500±20) mm/min. path of motion: 300 mm. Ð Measurement of mS: speed of the pulling mechanism: (100 ± 10) mm/min; measurement to be stopped as soon as test panel begins to move. Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:03:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 5 EN 1724:1998 BSI 05-1999 1 = start of test panel motion 2 = path of pulling mechanism 3 = force 1 = start of test panel motion 2 = path of pulling mechanism 3 = force Figure 1 Ð Typical example of recorded graph of mSwith force peak Figure 2 Ð Example of untypical graph of mSwithout peak 8 Calculation and expression of results 8.1 Dynamic friction, mD The mD-value shall be determined as a median, preferably in accordance with ISO 6133. The values registered during the last 200 mm of the path of motion shall be used. mD= FD FN where FDis the median of the dynamic frictional force; FNis the normal force. 8.2 Static friction, mS For the static coefficient of friction the first peak of the graph represents mS. mS= FS FN where FSis the static frictional force (break-away force); FNis the normal force. 8.3 Examples of the recorded graph of mS(force/path diagrams) If the recorded graph shows a peak like Figure 1, the force FScan be read off very easily and the mS-value can be calculated. If the graph looks like Figure 2, the mS-value should be determined by noting the force FSat the point P where the curve deviates from the initial straight line. Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:03:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 6 EN 1724:1998 BSI 05-1999 Key 1)load cell 2)deflection roller 3)test piece table 4)test piece 5)metallic test panel 6)weight 7)clamp Figure 3 Ð Fricti
