BS EN 927-13 pdf free download
BS EN 927-13-2019 pdf free download.Paints and varnishes — Coating materials and coating systems for exterior wood Part 13: Assessment of resistance to impact of a coating on a wooden substrate.
4 Principle A cylindrical steel weight is dropped from specified heights through a vertically-mounted guide onto a steel ball of specified diameter and hardness positioned on the test panel. The degree of damage to the test area is assessed by reference to a descriptive numerical rating code.
5 Apparatus and materials
5.1 Horizontal base which provides rigid support for the test panel. 5.2 Vertically-mounted guide tube with an inside diameter of (40 ± 5) mm (1 in Figure 1). A (10,0 ± 0,5) mm thick disc with a centre hole of diameter (14,25 ± 0,25) mm for the ball (5.4) shall be attached to the bottom end of the guide tube.
5.3 Cylindrical steel weight (2 in Figure 1) with a mass of (500 ± 5) g and a diameter that is approximately 1 mm less than the inside diameter of the guide tube. This weight shall be made of softer alloy than the ball, so that it will not make indentations on the ball. Provision shall be made for the weight to be raised and lowered.
5.4 Steel ball (3 in Figure 1) with a diameter of 14 mm and Rockwell hardness of 60 HRC to 66 HRC (see EN ISO 6508-1), a rolling bearing ball for example (see ISO 3290-1).
5.5 Microscope (magnifier) with a magnification of at least × 10 for the assessment of surface defects.
6 Procedure
6.1 Wood panels
Boards of Norway spruce (Picea abies [L]. Karst) are selected with normal growth rate (i.e. 3 annual rings to 8 annual rings per 10 mm), a density between 0,4 g/cm 3 and 0,5 g/cm 3 (measured after conditioning) and straight grain. The wood shall be free from blue stain and evidence of surface or bulk fungal infection. Abnormal porosity (caused by bacterial attack) shall be avoided (see EN 927-3:2019, A.10). From these boards, panels with the minimum dimensions 170 mm × min. 70 mm × (20 ± 2) mm free from knots, cracks and resinous streaks are produced so that the inclination of the growth rings to the test surface is 60° to 90°. The panels shall be planed to a smooth and uniform finish. In order to avoid aged wood surface, the panels shall be hand sanded (mesh 150) immediately before coating. The wood shall be conditioned at (20 ± 2) °C and a relative humidity of (65 ± 5) % in accordance with ISO 554 to an equilibrium moisture content of (13 ± 2) %. After conditioning wood density is determined according to ISO 13061-2. 6.2 Coating application For each system, select three panels on a random basis from the available supply. Apply the coating system to the front side of one panel using the method specified by the manufacturer to give a wet film thickness corresponding to the mean value ± 20 % of the manufacturer’s recommended spreading rate. Record the quantity of coating applied. The values should be stated preferably in grams per square metre, but may also be expressed as wet film thickness (in micrometres). After coating application, age the panels for 21 days in the controlled environment at (20 ± 2) °C and a relative humidity of (65 ± 5) % in accordance with ISO 554.
6.3 Assessment of resistance to impact 6.3.1 General No impact point shall be less than 15 mm from any edge of the test panel. The centres of impact points shall not be less than 15 mm apart. lf the grid pattern method detailed in 6.3.2 is to be used, then eight lines spaced at least 15 mm apart shall be marked out on the surface that is to be tested. The lines shall be perpendicular to the direction of grain. Three impact points spaced at least 15 mm apart shall be marked off along each line (see Figure 2).BS EN 927-13 pdf download.
