Badger Meter Dynasonics DXN, User Manual

Page: 18 / 112

Select a Mounting Location
At this point, consider the transducer mounting location . A guiding principle is to mount the transducers on a section of pipe
that has at least 10 pipe diameters upstream of the transducers and 5 pipe diameters downstream . See Table 1 on page 19
for additional pipe length considerations .
For example, if a 3 inch pipe is being measured, the minimum upstream pipe in front of the transducers should be 30 inches
and the minimum downstream pipe behind the transducers should be at least 15 inches .
Pipe runs shorter than the minimums may sometimes be used with reduced accuracy . There is no way to determine how
much accuracy is sacrificed without doing in-field testing . For installations where the 10/5 pipe diameters rule cannot
be followed, divide the total length of available straight pipe into thirds and mount the transducers with 2/3 of the pipe
upstream and 1/3 of the pipe downstream .
A full pipe is absolutely essential for making accurate flow measurements in either
Transit Time and Doppler mode . The flow
meter cannot determine if the pipe is full or not . If the pipe is partially full, the meter will over report the amount of flow by
the percentage of the pipe that is not filled with liquid .
An optimum transducer mounting location is defined as:
• A piping system that is completely full of liquid when measurements are being taken . The pipe may become empty during
a process cycle, which results in a “Low Signal Strength” error while the pipe is empty . This error code clears automatically
when the pipe refills with liquid . Do not mount the transducers in an area where the pipe may become partially filled .
Partially filled pipes cause erroneous and unpredictable operation of the meter .
• A piping system that contains lengths of straight pipe such as those described in Table 1 on page 19 . The optimum
straight pipe diameter recommendations apply to pipes in both horizontal and vertical orientation . The straight runs in
Table 1 apply to liquid velocities that are nominally 7 fps (2 .2 mps) . As liquid velocity increases above this nominal rate, the
requirement for straight pipe increases proportionally .
• Mount the transducers in an area where they will not be inadvertently bumped or disturbed .
• Avoid installations on downward flowing pipes unless adequate downstream head pressure is present to overcome partial
filling of or cavitation in the pipe .
Transducer Installation
Page 18 November 2016 HYB-UM-00090-EN-04