1 Introduction
Manual TRZ 03· EN08 ·2018 September, 10th
19
Notice
For reverification the meter has to be removed and tested at a test rig.
1.8 Measuring ranges
The measuring ranges are between 10 and 25,000 m3/h (flowing conditions). A
measuring range is specified for each meter size. It is limited by the minimum flow
rate Q
min
and the maximum flow rate Q
max
(
chapter 6.1 Measuring ranges / Dimen-
sions / Pressure classes TRZ03 (PTB)
and
6.2 Measuring ranges / Dimensions /
Pressure classes TRZ03-K
).
For types TRZ 03 this is the flow range where the gas meter must indicate correct
values within the error limits specified by the German Metering and Calibration
Rules.
Turbine meters of type TRZ 03 have measuring ranges up to 1:30 even under
atmospheric pressure. If a high-pressure test is conducted in compliance with
Technical Guideline G 71) (PTB), the measuring range can be extended to 1:50.
Then the minimum flow rate Q
min
HP is the lowest test point during high-pressure
testing. Types TRZ 03 may then be used for billing purposes within the specified
HP flow and density ranges.
The measuring range of type TRZ 03-K is 1:16
1.8.1 Extension of the measuring range
In the range of 0.2 Q
max
to Q
max
, the measuring behaviour of turbine meters is de-
termined by the aerodynamic conditions in the flow channel and the measuring
cross section. By means of many series of tests conducted both under atmos-
pheric pressure and under higher pressures and with an appropriate rating for
such ranges, it is possible to achieve a deviation of the calibration curve under at-
mospheric conditions and under high-pressure conditions of < 0.5% in the flow
range of 0.2 Q
max
to Q
max
.
In the lower flow range, the measuring behaviour is determined by the relationship
between the gas flow driving the measuring wheel and the slowing-down torques
due to drags (bearings and totalizer). The driving torques increase linearly with the
density and quadratically with the velocity of the gas to be measured. Due to the
physical conditions, the measuring range is therefore enlarged in relation to the