【正文】 possible. The difference between the longest and shortest spacing shall not exceed 1/5 of the latter. Scale numbering Scale numbering will be at the manufacturer39。s discretion. Examples of scale numbering are shown in annex A for accuracy classes from 0,6 to 4. Pointer dimensions The tip of the pointer that sweeps the scale mark shall be no wider than the minor scale mark. The pointer shall cover between 1/10 to 9/10 of the length of the shortest lines of the minor scale marks. The minimum lengths of pointer from the axis to the tip are shown in table 15. Table 15. Minimum length of pointer Gauge nominal size mm Minimum length of pointer mm 40 50 63 80 100 150 160 250 14 18 23 28 36 57 62 95 Mirror scales Pressure gauges of accuracy class 0,1 shall be equipped with a mirror scale. Pressure gauges of accuracy classes 0,25 and 0,6 shall incorporate provisions to minimize parallax errors, such as a knife edge pointer. A mirror scale may be fitted in addition. Information on dial a) The unit of pressure shall be marked. b) The accuracy class shall be marked, preferably at the end of the scale. c) The symbol for the type of pressure element may be marked, see table 16. d) Gauges suitable for maximum steady working pressure equal to the maximum scale value shall have an identifying mark at the maximum scale value (see figure 8). e) The symbol for the dial plane shall be marked when the manufacturer is required to calibrate the gauges other than in the vertical position (see figure 9). f) If the customer requires the gauge to be calibrated at other than the reference temperature this shall be marked. This applies to 0,1, 0,25 and 0,6 class gauges. g) If the gauge meets the accuracy requirements on only gas or liquid, then this shall be marked. This applies to 0,1, 0,25 and 0,6 accuracy class gauges. h) The EN number of this standard may be marked. i) The name or logo of the manufacturer and/or supplier shall be marked. j) Serial numbers shall be marked for accuracy classes 0,1 and 0,25, and may be marked for accuracy classes from 0,6 to 4. Serial numbers shall also be marked on all gauges which are subject to state metrological control. k) Where the gauge has wetted parts different from brass, bronze, tin or hard solder, then the material of the wetted parts may be marked. l) Safety pattern gauges shall be marked as specified in . m) Pressure gauges for use with oxygen or acetylene shall be marked as specified in . Pointer stop Gauges with maximum steady working pressure equal to the maximum scale value shall have a free zero. Gauges with maximum steady working pressure 75 % of the maximum scale value may have a free zero. Safety Safety gauges shall protect an operator from failure of the pressureresponsive element and the release of high pressure gases into the case by deflecting the blast and debris away from the front of the gauge. Blowout device gauges When a blowout device is fitted to a pressure gauge, (designated by S1, see clause 12), it shall be resistant to blocking by debris and dirt and shall operate at a pressure of not more than half of the windowburst pressure. Where the gauge is sealed for the purpose of liquidfilling a blowout device shall be fitted. These gauges shall have no special marking. Figure 8 BSI 1998 Page 12 EN 8371 : 1996 Figure 9 Safety pattern gauges This standard defines two types of safety pattern gauges: a) 40 to 80 size safety pattern gauges without a baffle wall (designated by S2, see clause 12)。 b) 40 to 250 size safety pattern gauges with a baffle wall (designated by S3, see clause 12). All types of safety pattern gauges shall meet the requirements defined in , , and . Safety pattern gauges with baffle wall shall additionally meet the requirements defined in . Energy release test Pressure gauges shall pass the energy release test defined in , which simulates the failure of a pressureresponsive element and the release of high energy gas into the case. Window The window shall be of nonsplintering material, such as laminated glass or nonsplintering plastic. Blowout back A blowout back shall be fitted. The blowout back shall be resistant to blocking by debris and dirt and shall operate at a pressure of not more than half of the window burst pressure and not more than 1,5 bar. Test as given in . The area of blowout back shall be as large as is practicable. NOTE. For safety pattern gauges without a baffle wall, a blowout device according to is sufficient. Baffle wall The baffle wall shall form a permanently fixed structural part of the case interposed between the Bourdon tube and the dial. The number and size of holes in the baffle wall shall be kept to a minimum consistent with fixing screws, pointer shaft and dial pillars and shall not exceed 5 % of the area of the baffle wall. Marking 40 to 80 size safety pattern gauges without baffle wall (designated by S2) shall have dials marked S and with the EN number of this standard. 40 to 250 size safety pattern gauges with baffle wall (designated by S3) shall have dials marked S and with the EN number of this standard. Gauges for use with oxygen or acetylene The gauges shall be of safety pattern type. All materials liable to e into contact with oxygen or acetylene shall ply with EN 29539. Gauges for use with oxygen Bourdon tubes and other parts in contact with the gas shall be free of oil and grease. Only lubricants suitable for use in oxygen at maximum working pressure shall be used. The dial shal