BS 746-2014 pdf free download

BS 746-2014 pdf free download.Specification for gas meter unions and adaptors.
for a period of not less than 4 h. Remove the assembly from the environmental chamber and leave the assembly at room temperature of (20 ±3) °C for a period of 2 h.
Assembly 4
Leave at room temperature of (20 ±3) C for a period of 1 h then place the assembly in an environmental chamber at a temperature of (—20 ±3) °C and leave for a period of not less than 4 h. Increase the temperature within the chamber to (60 ±3) C, and once a temperature of (60 ±3) °C is reached maintain the temperature for a period of not less than 4 h. Remove the assembly from the environmental chamber; leave the assembly at room temperature of (20 ±3) C for a period of 2 h.
NOTE If any of the groups are split into subgroups, due for example to the environmental chamber being unable to accommodate 15 samples, it is necessary to be able to show that the test conditions were the same for each subgroup.
4.2.2.2.4 After each assembly has undergone the environmental conditioning specified in 4.2.2.2.3, set the pressure in the assembly to 75 mbar. Isolate the pressure supply, then observe a 1 mm temperature stabilization. Take the pressure (P1) within the assembly and observe a test period of 2 mm. Following this, take a second pressure reading (P2). Calculate the rate of leakage during the test period using the total volume of the assembly under test and the two pressures P1 and P2. The gauge used shall be a digital pressure gauge with a resolution of 2 dcp.
NOTE 1 When undertaking the gas tightness test, care has to be taken not to affect the gas tightness of the assembly, e.g. avoid tightening against it or otherwise clamping the joint.
NOTE 2 It is not necessary to test all groups simultaneously, only that 60 samples be tested in four groups.
4.2.3 One-off test for complete assembly with new washers
4.2.3.1 Each size of washer (see Table 8 and Table 9) shall be subjected separately, as part of a complete assembly, to the gas tightness test in 4.2.3.2. When tested in accordance with 4.2.3.2, no air bubbles shall be released from the assembly.
4.2.3.2 Select five new washers of each size and assemble the washers, nuts, liners and bosses. lighten each nut to the applicable torque given in Table 1. Pressurize the assembly to 350 mbar and seal off the ends. Immerse the assembly in a water bath which is at ambient temperature and with a depth not exceeding 300 mm. Observe for a period of 30 s after any external trapped air has been dispersed.BS 746-2014 pdf free download.