【文章內(nèi)容簡介】 Pressure connection The positions of the connections can be selected from table 9 (types of mounting and connection position). For thread forms and sizes, see table 3. 7 Dimensions General tolerances General tolerances: EN 227681. Cases and flanges The user will have to determine the dimensions for panel cutout according to the manufacturer39。s data. d1 Outside diameter of case d2 Outside diameter of flange d3 Diameter of fixing hole circle d4 Diameter of fixing holes Figure 1 Page 5 EN 8371 : 1996 BSI 1998 Table 5. Dimensions for high pressure shank Dimensions in millimetres Thread size d1 d2 0,1 d3 d4 d5 0 20,3 l1 0 20,3 l2 0 20,3 G 1/2 B (for HP) 7,14 15 17,5 19 25 22 Table 4. Dimensions of parallel threaded shanks Dimensions in millimetres Thread size d1 d2 d3 d4 min. l1 +0,5 0 l2 l3 +0,5 0 f w min. G 1/8 B 4 8 8 10 2 2 1,6 8 G 1/4 B 5 9,5 9,5 13 2 2 2 10 G 3/8 B 5,5 13 13 16 3 3 2 13 G 1/2 B 6 17,5 17,5 20 3 3 3 17 NOTE 1. For stainless steel screwed connection, f dimensions can be raised up to 50 %. NOTE 2. G 1/8 B may be made without spigot. NOTE 3. G 1/8 B may be made without groove f. In this case, the length of threading shall be equal to l1. NOTE 4. For inchangeability with previous standards, the spigot of G 1/4 B can be manufactured with diameter 4 mm. Screw threads Parallel pipe threads (symbol G) according to ISO 2281. Taper pipe threads (symbol NPT) according to ANSI/ASME . Other threads specific to certain industries are acceptable. Shanks with parallel pipe threads High pressure shank (HP) for connection with lens seal Figure 3 NOTE. Minimum height h of flats shall be patible with use of standard spanners according to ISO 10102. Figure 2 1) According to ISO 1302. Page 6 EN 8371 : 1996 BSI 1998 Table 7. Dimensions of parallel threaded tapped holes Dimensions in millimetres Thread size d1 d2 t1 20,5 t2 min. G 1/8 4,5 10 7,5 G 1/4 5,5 13 10 G 3/8 6,5 16 12 G 1/2 7 19 15 Table 6. Dimensions of taper threaded shanks Dimensions in millimetres Thread size d1 l1 min. w min. 1/827 NPT EXT 10 8 1/418 NPT EXT 13 10 1/214 NPT EXT 18 17 NOTE. Height of flats (h) shall be patible with use of standard spanners according to ISO 10102. Table 8. Dimensions of sealing washers Dimensions in millimetres Thread size d2 d3 e 0,2 G 1/8 B +0,2 8 0 1,5 G 1/4 B +0,2 9,5 0 1,5 G 3/8 B +0,3 13 0 2 G 1/2 B +0,4 17,5 0 2 Shanks with taper pipe threads Figure 4 Sealing washers For use with parallel screw threads only. NOTE. The choice of the sealing washer material depends on the pressure and the fluid to be measured. Figure 6 Parallel threaded tapped holes 4,2 0 5,2 0 5,7 0 6,2 0 20,2 20,2 20,3 20,5 Sealing lens For use with high pressure shank (HP) only, according to . Figure 5 Figure 7 1) According to ISO 1302. Page 7 EN 8371 : 1996 BSI 1998 Type of mounting and connection position The different mounting types of gauges shall be as given in table 9. When mounting, ensure that there is enough free space for the blowout device, if any. Table 9. Type of mounting and connection position Radial connection 10 11 12 Type not preferred Centre back connection 20 21 Type not preferred 22 23 Offset back connection 30 31 Type not preferred 32 33 Direct mounting Surface mounting Flush mounting Threehole fixing Clamp fixing Page 8 EN 8371 : 1996 BSI 1998 Table 11. Maximum permissible errors Accuracy classes Limits of permissible error (percentage of span) 0,1 0,1 % 0,25 0,25 % 0,6 0,6 % 1 1 % 1,6 1,6 % 2,5 2,5 % 4 4 % 8 Pressure element assembly 9 Requirements The test methods for these requirements are given in clause 10. Accuracy The total errors of indication at reference temperature 20 8C of the gauge shall not exceed the values given in table 11. Installation of the pressure gauges shall not cause any change of readings. Table 11 shows the limits of permissible error as a percentage of span at reference temperature 20 8C corresponding to accuracy classes. Page 9 EN 8371 : 1996 BSI 1998 Hysteresis Hysteresis error in pressure gauges shall not exceed the absolute value of the limits of permissible error at reference temperature 20 8C. EXAMPLE Pressure gauge with a maximum scale value of 10 bar, accuracy class 1. The maximum permissible hysteresis error is 1 %. The difference between the readings taken at decreasing and increasing pressure shall not exceed 0,1 bar (= 1 % of 10 bar). Temperature effect The variation of indication caused by effects of temperature shall not exceed the percentage values given by the formula: 0,04 3 (t2 2 t1) % of the span where: t1 is the reference temperature in degrees Celsius。 t2 is the ambient temperature in degrees Celsius. Endurance Gauges shall withstand the steady pressure, overpressures and cyclic pressures as described below without exceeding the specified change of accuracy (see ). For gauges with bined pressure and vacuum ranges the endurance test required ma