Dynasonics DDFXD Doppler Ultrasonic Flow Meter - Manual (Page 15)

06-DPP-UM-00147 02/12 15
PIPE PREPARATION
Before the transducer heads are mounted to the pipe surface, an area slightly larger than the flat surface
of the transducer face must be prepared. If pipe insulation is present, it must be peeled back to expose
the pipe surface. Typical preparation involves wire brush removal of loose paint, rust, scale or dirt. Paint,
if bonded well to the pipe surface, does not need to be removed. The bumps present on ductile iron
pipe do not need to be removed. Thoroughly dry the mounting surfaces so that the couplant grease will
properly bond to the surface.
NOTE: Small pits in the piping surface typically do not significantly impact ultrasonic transmission or signal reception.
COUPLANT
To assure an acoustically conductive path between the transducer face and the prepared piping surface,
a coupling compound is employed. Clamp-on ultrasonic meters will not operate without coupling com-
pound mounted between the pipe wall and the transducer face. Enclosed with the DFX system is a tube
of coupling compound that is adequate for general purpose applications. Dynasonics prefers silicone-
based valve grease or RTV (Room Temperature Vulcanizing) products or grease for Doppler installations
as they operate over a very wide temperature range. In some installations, such as automotive, silicone is
not permitted. Alternate petroleum-based products can be utilized, but verify that the grease is rated not
to flow at the maximum surface temperature anticipated on the pipe.
In general, utilize the following couplants with these transducers:
DT90, DT91, DT94, DT95 Dow 732 or Dow 111 (or equivalent)
DT92, DT93, DT96, DT97 Krytox® LVP
DP7 Not applicable
DT9 CLAMP-ON TRANSDUCER MOUNTING
Clamp-on transducers should be mounted on the pipe 180° apart and facing each other on the pipe,
with the cables on the downstream side of the transducers. If the pipe is horizontal, the preferred mount-
ing orientation is 3 and 9 o’clock, with 12 o’clock being the top of the pipe. See Figure 2.3. Orientation on
vertical pipes does not matter.