BS EN 17526:2021 pdf free download – Gas meter一Thermal-mass flow- meter based gas meter.
d) a length of straight pipe 30 D to 45 D in length to ensure that all dust is airborne before entering the meter;
e) copper pipework with soldered or compression fittings is preferred. Steel pipe fittings are not recommended as the dust will adhere to the screw threads.
The appropriate value for D in a), and d), is given in Table 11.
Check the effectiveness of a test rig design on a regular basis, by connecting the test rig to a test box; ensure that the test box has a similar volume and shape to the meter to be tested and fitted with a filter on the outlet to minimize the dust passing through the outlet. Add 20 g of dust using the procedure mentioned above, and confirm that at least 18 g is deposited inside the test box.
5.8 Flow disturbances
5.8.1 Requirements
When tested in accordance with 5.8.2, the mean errors shall remain within the MPE and the mean error difference at each flow rate shall not exceed the values specified in Table 13. The meter shall recover from the flow disturbance to be within the initial MPE specified in Table 5.
5.8.2 Test
5.8.2.1 General
Carry out the tests specified in 5.8.2.2, 5.8.2.3 and 5.8.2.4, using air or a representative test gas at atmospheric pressure conditions.
5.8.2.2 Installation effects
The piping configurations illustrated in Figure 5 a) and Figure 5 b) consist of a pipe with nominal diameter D1 and length of S D1, where D1 is the diameter of the inlet and outlet connections of the meter, and two elbows with radius equal to 1,5 D1 not in the same plane.
Test the meter in accordance with 5.3.2, Table 6, Test b), using the flow rates specified in 5.8.2 in the following configurations:
a) with a straight pipe of length no less than 10 D1 connected to the meter inlet;
b) with the piping configurations illustrated in Figure 5 a) installed 2 D, upstream of the meter inlet; c) with the piping configurations illustrated in Figure 5 b) installed 2 D1 upstream of the meter inlet.
Check the error difference between a) and b), and between a) and c), and ensure it is within the value specified in Table 13.
5.8.2.3 Resistance to harmonic disturbances of the flow
5.8.2.3.1 General
Thermally stabilize the meter to the temperature of the test laboratory.
Connect the meter to the test equipment as shown in Figure 6 with outlet port opened.
Supply a steady flow of air at Qt and keep it running for the entire duration of the test. Ensure the absolute pressure inside the meter during the test is within (1 013,25 ± 50) mbar.
Determine the measurement error at Qt of the meter in this configuration, following the procedure specified in 5.3.2, Table 6, Test c).
Generate a pure acoustic tone of given frequency and a peak-to-peak amplitude of (90,0 ± 0,3) dB (determined according to the method indicated in 5.8.2.4) and introduce it into the flow.
Detect the measurement error at Qt, according to 5.3.2.
Repeat the tests at all frequencies below:
— 200 Hzto 500 Hz, at 50 Hz intervals (i.e. 200 Hz, 250 Hz, 300 Hz, etc.);
— 600 Hz to 2 000 Hz, at 100 Hz intervals (i.e. 600 Hz, 700 Hz, 800 Hz, etc.).