SIST EN 207:2010
(Main)Personal eye-protection equipment - Filters and eye-protectors against laser radiation (laser eye-protectors)
Personal eye-protection equipment - Filters and eye-protectors against laser radiation (laser eye-protectors)
This European Standard applies to eye-protectors used for protection against accidental exposure to laser radiation as defined in EN 60825-1:2007 in the spectral range 180 nm (0,18 μm) to 1 000 μm. It defines the requirements, test methods and marking. A guide is given in Annex B for the selection and use of laser eye-protectors.
Persönlicher Augenschutz - Filter und Augenschutzgeräte gegen Laserstrahlung (Laserschutzbrillen)
Diese Europäische Norm gilt für Filter und Augenschutzgeräte, entsprechend der IEC 60825-1:2007 (d. h. Strahlung von LEDs (Licht Emittierenden Dioden) ist eingeschlossen), die beim Umgang mit Laserstrahlung im Spektralbereich zwischen 180 nm (0,18 µm) und 1000 µm Verwendung finden. Sie legt die Anforderungen, Prüfmethoden und Kennzeichnung fest. Einen Leitfaden für die Auswahl und die Anwendung gibt Anhang B.
Für Laser-Justierbrillen gilt EN 208.
ANMERKUNG Bevor Filter nach dieser Norm ausgewählt werden, sollte eine Risikoanalyse durchgeführt werden (siehe Anhang B).
Protection individuelle de l'oeil - Filtres et protecteurs de l'oeil contre les rayonnements laser (lunettes de protection laser)
La présente norme s'applique aux protecteurs de l'oeil utilisés contre les rayonnements laser tels que définis dans la CEI 60825-1:2007 (par exemple, le rayonnement de diodes électroluminescentes (LED)) dans le domaine spectral compris entre 180 nm (0,18 µm) to 1 000 µm. Elle définit les spécifications, les méthodes d'essai et le marquage. Un guide de choix et d'utilisation figure dans l'annexe B.
Les lunettes de réglage pour laser sont couvertes par l'EN 208.
NOTE Avant de choisir une protection de l'oeil conforme à la présente norme européenne, il convient de réaliser au préalable une évaluation du risque (voir annexe B).
Oprema za osebno varovanje oči - Filtri in varovala za zaščito oči pred laserskimi žarki (očala za zaščito pred laserskimi žarki)
Ta evropski standard velja za varovala za zaščito oči, ki se uporabljajo za zaščito pred nezgodno izpostavljenostjo laserskim žarkom, kot je določeno v IEC 60825-1:2007, v območju spektra od 180 nm (0,18 μm) do 1000 μm. Določa zahteve, preskusne metode in označevanje. Vodilo za izbiro in uporabo laserskih varoval za zaščito oči je podano v Dodatku B.
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Persönlicher Augenschutz - Filter und Augenschutzgeräte gegen Laserstrahlung (Laserschutzbrillen)Protection individuelle de l'oeil - Filtres et protecteurs de l'oeil contre les rayonnements laser (lunettes de protection laser)Personal eye-protection equipment - Filters and eye-protectors against laser radiation (laser eye-protectors)13.340.20Varovalna oprema za glavoHead protective equipmentICS:Ta slovenski standard je istoveten z:EN 207:2009SIST EN 207:2010en,de01-marec-2010SIST EN 207:2010SLOVENSKI
STANDARDSIST EN 207:1999/A1:2003SIST EN 207:19991DGRPHãþD
SIST EN 207:2010
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 207
December 2009 ICS 13.340.20 Supersedes EN 207:1998English Version
Personal eye-protection equipment - Filters and eye-protectors against laser radiation (laser eye-protectors)
Protection individuelle de l'oeil - Filtres et protecteurs de l'oeil contre les rayonnements laser (lunettes de protection laser)
Persönlicher Augenschutz - Filter und Augenschutzgeräte gegen Laserstrahlung (Laserschutzbrillen) This European Standard was approved by CEN on 14 November 2009.
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 CEN Management Centre 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 CEN Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2009 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 207:2009: ESIST EN 207:2010
EN 207:2009 (E) 2 Contents Page Foreword .41Scope .52Normative references .53Requirements .53.1Spectral transmittance of filters and frames .53.2Luminous transmittance of filters .53.3Resistance of filters and frames to laser radiation .53.4Refractive values of filters and eye-protectors .63.5Quality of material and surface of filters .73.5.1Material and surface defects .73.5.2Diffusion of light .73.6Stability of filters and eye-protectors to ultraviolet radiation and elevated temperature .73.6.1Stability to ultraviolet radiation .73.6.2Stability at elevated temperature .73.7Resistance of filters and frames to ignition by contact with hot surfaces .73.8Field of vision of eye-protectors .73.9Construction of filters and frames .83.10Mechanical strength of eye-protectors.83.10.1Basic requirement.83.10.2Optional requirements .84Testing .84.1General .84.2Spectral transmittance of filters and frames . 104.3Luminous transmittance of filters . 104.4Resistance of filters and frames to laser radiation . 104.5Refractive value of filters and eye-protectors . 114.6Quality of material and surface of filters . 114.6.1Material and surface defects . 114.6.2Diffusion of light . 114.7Stability to UV radiation and stability to elevated temperature . 114.7.1Stability to UV radiation . 114.7.2Stability to elevated temperature . 114.8Resistance of filters and frames to ignition by contact with hot surfaces . 114.9Field of vision of eye-protectors . 124.10Determination of the protected range. 124.11Frames . 134.12Mechanical strength . 135Information supplied by the manufacturer . 136Marking . 146.1Eye-protectors . 146.2Filters . 16Annex A (informative)
Principle . 17A.1Limit values and time base . 17A.2Beam areas . 18A.3Angle dependence . 19A.4Example test report . 19Annex B (informative)
Recommendations for the use of laser radiation eye-protectors . 22B.1General . 22SIST EN 207:2010
EN 207:2009 (E) 3 B.2Types of lasers . 22B.3Determination of the scale numbers . 23B.3.1General . 23B.3.2Continuous wave laser (D) . 23B.3.3Pulsed lasers (I, R), pulse duration ≥≥≥≥ 10-9 s . 23B.3.4Mode coupled lasers (M), pulse duration < 10-9 s . 25B.4Time base . 25B.5Filters in appliances . 26Annex C (informative)
Significant technical changes between this European Standard and the previous edition . 27Annex ZA (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 89/686/EEC . 28Bibliography . 29 SIST EN 207:2010
EN 207:2009 (E) 4 Foreword This document (EN 207:2009) has been prepared by Technical Committee CEN/TC 85 “Eye protective equipment”, the secretariat of which is held by AFNOR. 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 2010, and conflicting national standards shall be withdrawn at the latest by June 2010. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 207:1998. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s). For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this document. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. SIST EN 207:2010
EN 207:2009 (E) 5 1 Scope This European Standard applies to eye-protectors used for protection against accidental exposure to laser radiation as defined in EN 60825-1:2007 in the spectral range 180 nm (0,18 µm) to 1 000 µm. It defines the requirements, test methods and marking. A guide is given in Annex B for the selection and use of laser eye-protectors. This European Standard does not apply to protectors for intentional exposure to laser radiation. EN 208 applies for laser adjustment eye-protectors. NOTE Before selecting eye protection according to this European Standard, a risk assessment should first be undertaken (see Annex B). 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. EN 166:2001, Personal eye-protection — Specifications EN 167:2001, Personal eye-protection — Optical test methods EN 168:2001, Personal eye-protection — Non-optical test methods EN 60825-1:2007, Safety of laser products —
Part 1: Equipment classification and requirements (IEC 60825- 1:2007) ISO 11664-1:2007, Colorimetry — Part 1: CIE standard colorimetric observers ISO 11664-2:2007, Colorimetry — Part 2: CIE standard illuminants 3 Requirements 3.1 Spectral transmittance of filters and frames When tested according to 4.2, the maximum spectral transmittance at the wavelength(s) or in the wavelength range(s) of protection shall not exceed the values specified in Table 1 for the applicable scale number. 3.2 Luminous transmittance of filters When assessed in accordance with 4.3, the luminous transmittance of the filter relative to the D65 standard illuminant (see ISO 11664-2:2007) shall be at least 20 %. However, luminous transmittance lower than 20 % may be accepted provided that the manufacturer supplies information related to the increase of the intensity of illumination at the relevant workplace in accordance with Clause 5. 3.3 Resistance of filters and frames to laser radiation When tested according to 4.4, the filters and frames shall meet the requirements of 3.1 and shall not lose their protective effect under the influence of laser radiation of the power (E) or energy density (H) as specified in Table 1 and shall not show any induced transmission (reversible bleaching). No splinters shall come away from the side of the filter facing the eye under the influence of the laser radiation. Any melting or other damage SIST EN 207:2010
EN 207:2009 (E) 6 of the surface during the course of irradiation is not considered negative if the protective effect is still maintained. Table 1 — Scale numbers (maximum spectral transmittance and resistance to laser radiation) of the filters and/or eye-protectors against laser radiations
Maximum spectral transmittance at the laser wavelength Power (E) and energy (H) density for testing the protective effect and resistance to laser radiation in the wavelength range 180 nm to 315 nm > 315 nm to 1 400 nm > 1 400 nm to 1 000 µm For test condition/pulse duration in seconds (s) Scale number D
≥ 3 × 104 I, R 10-9 to 3 × 104 M < 10-9 D > 5 × 10-4 I, R
10-9 to 5 × 10-4 M < 10-9 D > 0,1 I, R 10-9 to 0,1 M < 10-9
τ (λ) ED
W/m2 HI, R J /m2 EM
W/m2 ED
W/m2 HI, R J/m2 HM J/m2 ED
W/m2 HI, R J/m2 EM
W/m2 LB1 10-1 0,01 3 × 102 3 × 1011 102 0,05 1,5 × 10-3104 103 1012 LB2 10-2 0,1 3 × 103 3 × 1012 103 0,5 1,5 × 10-2105 104 1013 LB3 10-3 1 3 × 104 3 × 1013 104 5 0,15 106 105 1014 LB4 10-4 10 3 × 105 3 × 1014 105 50 1,5 107 106 1015 LB5 10-5 102 3 × 106 3 × 1015 106 5 × 102 15 108 107 1016 LB6 10-6 103 3 × 107 3 × 1016 107 5 × 103 1,5 × 102 109 108 1017 LB7 10-7 104 3 × 108 3 × 1017 108 5 × 104 1,5 × 103 1010 109 1018 LB8 10-8 105 3 × 109 3 × 1018 109 5 × 105 1,5 × 104 1011 1010 1019 LB9 10-9 106 3 × 1010 3 × 1019 1010 5 × 106 1,5 × 105 1012 1011 1020 LB10 10-10 107 3 × 1011 3 × 1020 1011 5 × 107 1,5 × 106 1013 1012 1021 The symbols D, I, R and M relative to the test conditions are explained in Table 4.
3.4 Refractive values of filters and eye-protectors When assessed in accordance with 4.5, the maximum refractive values of filters and eye-protectors with no corrective effect shall be as given in Table 2. The maximum refractive values apply to the range specified in 7.1.2.1 of EN 166:2001. Table 2 — Maximum refractive values of filters and eye-protectors with no corrective effect Spherical power
m-1 Astigmatic power
m-1 Prismatic power difference horizontal vertical base out cm/m base in cm/m
cm/m ± 0,09 0,09 0,75 0,25 0,25
SIST EN 207:2010
EN 207:2009 (E) 7 3.5 Quality of material and surface of filters 3.5.1 Material and surface defects The material and surface defects of filters shall be assessed in accordance with 4.6.1. Except for a marginal area of 5 mm wide, filters shall be free from any material or surface defects likely to impair the intended use, such as bubbles, scratches, inclusions, dull spots, mould marks, scoring or other defects originating from the manufacturing process. No holes are allowed anywhere in the filters. 3.5.2 Diffusion of light The reduced luminous coefficient l* of a filter, determined in accordance with 4.6.2, shall not be greater than lxm/cd50,0*2=l (1) 3.6 Stability of filters and eye-protectors to ultraviolet radiation and elevated temperature 3.6.1 Stability to ultraviolet radiation When exposed to ultraviolet radiation in accordance with 4.7.1, the properties of filters and eye-protectors shall not change to such an extent that they can no longer satisfy the requirements of 3.1, 3.2, 3.4 and 3.5. The relative change in the luminous transmittance shall be ≤ 10 %: %10≤∆vvττ (2) The spectral transmittance for the laser wavelengths shall, however, in no case exceed the maximum spectral transmittance corresponding to the indicated scale number. 3.6.2 Stability at elevated temperature After exposure to elevated temperature in accordance with 4.7.2, filters and eye-protectors shall satisfy the requirements of 3.1, 3.2, 3.4 and 3.5. The relative change in the luminous transmittance shall not exceed 5 %: %5≤∆vvττ (3) The spectral transmittance for the laser wavelength shall, however, in no case exceed the maximum spectral transmittance corresponding to the indicated scale number. 3.7 Resistance of filters and frames to ignition by contact with hot surfaces When tested in accordance with 4.8, the filters and frames shall not ignite or continue to glow. 3.8 Field of vision of eye-protectors Eye-protectors shall have a clear field of vision of at least 40° in the vertical and horizontal directions for each eye when measured in accordance with 4.9 (see Figure 1). SIST EN 207:2010
EN 207:2009 (E) 8 3.9 Construction of filters and frames Filters shall be constructed so that when tested in accordance with 4.4 followed by a visual inspection no splinters are detached from the side of the filter facing the eye. If the filters consist of several individual filters, they shall be assembled in such a way that they cannot be interchanged. Filters shall not be interchangeable in the frame. An exception is possible if the protection to laser radiation is determined only by the filter(s) and no part of the frame lies inside the protected range as defined below. In this case the marking of the eye-protector shall be on the filter(s) and there is no requirement for the frame to satisfy 3.3 on resistance to laser radiation.
The frame shall be designed so that no laser radiation can penetrate from the side. This requirement is met if for the horizontal angle range α from - 50° (nasal side) to + 90° (temporal side) the vertical angle range β is protected within the following limit angles in degrees (°). The upward limit βu of the protected range shall be: ()()46212103,1123001,055−×−−−=−ααβu (4) The downward limit βl of the protected range shall be: ()()462522103,2221070−×+−+−=−−ααβl (5) Testing shall be done in accordance with 4.10.
3.10 Mechanical strength of eye-protectors 3.10.1 Basic requirement Filters for protection against laser radiation shall satisfy the requirement for minimum robustness as specified in 7.1.4.1 of EN 166:2001. The frames of the eye-protectors shall satisfy the requirements of 7.1.4.2 or 7.2.2 of EN 166:2001. 3.10.2 Optional requirements If the mechanical strength of filters and eye-protectors against laser radiation is required to satisfy more stringent requirements, the requirements specified in 7.1.4.2 or the requirements specified in 7.2.2 of EN 166:2001 shall be met. 4 Testing 4.1 General The testing schedule in Table 3 shall be applied to testing of filters, frames and complete eye-protectors. The sequence of testing 1 to 9 and 13 to 16 may be changed. At least 16 filters or eight complete eye-protectors are required for testing. If testing for several wavelengths (wavelength ranges) or testing conditions according to 4.4 and/or several optional requirements has to be done, more than 16 samples may be necessary. SIST EN 207:2010
EN 207:2009 (E) 9 Table 3 —Test schedule for filters, frames and complete eye-protectors for protection against laser radiation Order of testing Requirement According to clause Number of filter/frame samples 3 3 10 Depends on specification/ requirement 1 Marking 6 + +
2 Material and surface defects 3.5.1 + +
3 Field of vision 3.8 1 frame
4 Construction of filters and frames 3.9 + +
5 Frames 3.9 + +
6 Diffusion of light 3.5.2 + +
7 Luminous transmittance 3.2 + +
8 Refractive values 3.4 + +
9 Prismatic power difference 3.4 3 frames
10 Spectral transmittance at wavelength
3.1 + + 3 filters/frames per
and test condition 3 filters/frames per
and test condition
11 Stability to UV radiation 3.6.1 +
12 Stability to elevated temperature 3.6.2 +
13 Material and surface defects 3.5.1 + +
14 Diffusion of light 3.5.2 + +
15 Luminous transmittance 3.2 + +
16 Refractive values 3.4 +
17 Spectral transmittance 3.1 + +
18 Mechanical strength 3.10
+
19 Resistance to laser radiation and spectral transmittance at wavelength
3.3
3 filters/frames per
and test condition 3 filters/frames per
and test condition
20 Ignition 3.7
3 filters/ frames
21 Optional requirements as given in EN 166:2001 according to applicable clause of EN 166:2001
depends on requirement/ test procedure Explanation of the symbols:
+
Testing to be carried out on the indicated specimen;
Empty field No testing specified. SIST EN 207:2010
EN 207:2009 (E) 10 4.2 Spectral transmittance of filters and frames The spectral transmittance shall be determined for normal incidence. Filters with angular-dependent transmittance (such as interference layers) for the wavelength range from 400 nm to 1 400 nm shall be measured at angles of incidence between 0° and 30° with polarized radiation and an orientation of the polarization direction giving the highest value of the spectral transmittance. Filters with angular-dependent transmittance for other wavelengths shall be measured at angles of incidence between 0° and 90° with polarized radiation. In this case, the scale number results from the highest of the spectral transmittance values measured. Testing shall be done in accordance with EN 167:2001, Clause 6. 4.3 Luminous transmittance of filters The luminous transmittance shall be determined for normal incidence, relative to the D65 standard illuminant (see ISO 11664-1:2007 and ISO 11664-2:2007). The test shall be performed according to EN 167:2001, Clause 6. 4.4 Resistance of filters and frames to laser radiation The test shall be carried out with laser radiation of the specified wavelengths and the power and energy densities given in Table 1. The spectral transmittance shall be measured for each laser wavelength during the exposure to laser radiation. The values of energy density (H) in Table 1 for testing the resistance against laser radiation for pulsed lasers (I, R, M) shall be multiplied with the factor N-1/4, where N is the number of pulses in 5 s. The frame shall be exposed to radiation at the point of least thickness for each of the materials used (with the exception of headbands). The diameter d63 of the laser beam during this test shall be (1 ± 0,1) mm. For pulse durations < 1 ns, the diameter d63 of the laser beam during this test shall be ≥ 0,5 mm. In the case of rectangular beams, the dimensions specified apply to the shortest side of the rectangle. The duration of the test shall be taken from Table 4. Table 4 — Duration of test for filters and eye-protectors against laser radiation Test conditions for laser type Typical laser type Pulse length s Minimum number of pulses D I R M Continuous wave laser Pulsed laser Q switch pulsed laser Mode-coupled pulse laser 5 > 10-6 to 0,25 > 10-9 to 10-6 < 10-9 1 50 50 50
NOTE The pulse lengths for test conditions I and R do not follow consecutively. Neither are they a continuation of the length for test condition D. The pulse lengths indicated are characteristic values of typical lasers. It is recommended to use a laser with a pulse length in this range. Testing shall be done at least for 5 s, but in the case of pulsed operation never with less than 50 pulses. SIST EN 207:2010
EN 207:2009 (E) 11 For pulsed lasers, testing shall be done with low repetition rates (≤ 25 Hz). If it is not possible, the energy density used for testing shall be given and the product shall be marked in accordance with 6.1, d). All laser protective filters and frames shall be tested in accordance with the test condition D. If commercially available, testing at mode D shall be done with a real CW laser. If it is not feasible, testing shall be done with a pulsed laser system at a minimum pulse repetition frequency ν of ν ≥ 25 Hz. If no laser with pulse repetition rates higher than 25 Hz is available, a pulsed laser system at a minimum pulse repetition frequency of ν ≥ 5 Hz shall be used to test condition D. If additional protection against pulsed lasers is required, the filters and laser radiation eye-protectors shall be tested according to one or several of the test conditions I, R or M. Lasers which do not show spiking at the beginning of the emission shall be used. The spatial and temporal beam profile shall be documented, except for temporal profiles of M mode lasers. 4.5 Refractive value of filters and eye-protectors The test shall be carried out in accordance with Clause 3 of EN 167:2001. 4.6 Quality of material and surface of filters 4.6.1 Material and surface defects The test shall be carried out in accordance with Clause 5 of EN 167:2001. NOTE Thin film filters should be carefully examined for defects (scratches and holes) as damage of deposited layer can affect protection against laser radiation. 4.6.2 Diffusion of light The test shall be carried out in accordance with Clause 4 of EN 167:2001. If the simplified method cannot be used because the spectral transmittance is too low, the basic method shall be used. 4.7 Stability to UV radiation and stability to elevated temperature 4.7.1 Stability to UV radiation The test shall be carried out in accordance with Clause 6 of EN 168:2001, with the lamp running at a power of 450 W and an exposure time of (50 ± 0,2) h. 4.7.2 Stability to elevated temperature Filters and eye-protectors shall be stored for at least 7 h in a climatic cabinet at a temperature of (55 ± 2) °C and a relative humidity of > 60 %, and then stored for at least 2 h at room temperature. 4.8 Resistance of filters and frames to ignition by contact with hot surfaces The test shall be carried out in accordance with Clause 7 of EN 168:2001. SIST EN 207:2010
EN 207:2009 (E) 12 4.9 Field of vision of eye-protectors For measuring the field of vision, the test head specified in EN 168:2001 with the eye-protector without filters shall be mounted as shown in the example of set up illustrated in Figure 1 so that the two axes of rotation A and B and the optical axis C intersect in the middle of the front surface of one eye. Irradiation is provided by a laser beam of maximum diameter (1 ± 0,5) mm along axis C. When rotated around axis A, the difference in the angular positions at which the light beam no longer hits the eye gives the vertical field of vision. By rotating around axis B, the difference between the angular position at which the light beam no longer hits the eye and the line of vision of the test head parallel to the optical axis C gives half the horizontal field of vision. Other methods are permissible if they give identical results.
Key 1
Laser A, B, C Axis (see text) Figure 1 — Example of test set-up for the measurement of field of vision 4.10 Determination of the protected range Using the apparatus as given in 4.9 the scan shall verify that the eye-protector covers at least the range as defined by the limits βu and βl. SIST EN 207:2010
EN 207:2009 (E) 13 4.11 Frames 4.11.1 It shall be tested by means of manual and visual inspection whether the filters are interchangeable. 4.11.2 The test shall be carried out using the method given in 4.9. The zero values of the angles α
and β
are reached when the axis A, B and C of the test apparatus are perpendicular to each other. 4.12 Mechanical strength The test shall be ca
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