Dynasonics TFXP Series Transit Time Ultrasonic Flow Meter - Manual (Page 33)

Rev. 5/09
- 2.15 - TFXP
5. For DTTN transducers, place a single bead of couplant,
approximately 1/2 inch (12 mm) thick, on the flat face of the
transducer. See Figure 2.4 on page 2.9. Generally, a silicone-
based grease is used as an acoustic couplant, but any grease-
like substance that is rated to not “flow” at the temperature that
the pipe may operate at will be acceptable.
6. Place the upstream transducer in position and secure with a
stainless steel strap or other. Straps should be placed in the
arched groove on the end of the transducer. A screw is provided to
help hold the transducer onto the strap. Verify that the
transducer is true to the pipe — adjust as necessary. Tighten
the transducer strap securely. Larger pipes may require more
than one strap to reach the circumference of the pipe.
7. Place the downstream transducer on the pipe at the calculated
transducer spacing. See Figure 2.11 on page 2.16. Using firm
hand pressure, slowly move the transducer both towards and
away from the upstream transducer while observing signal
strength. Clamp the transducer at the position where the highest
signal strength is observed. Signal strength of between 5 and
195 percent is acceptable. The factory default signal strength
setting is 5 percent, however there are many application specific
conditions that may prevent the signal strength from attaining
this level. If after trying alternate transducer locations and/or
mounting modes the signal strength remains below 5 percent,
then reducing the Low Signal Cutoff setting may be necessary.
A minimum signal strength of 2 percent is acceptable as long as
the 2 percent signal is maintained under all flow conditions.
On certain pipes, a slight twist to the transducer may cause
signal strength to rise to acceptable levels.
8. Certain pipe and liquid characteristics may cause signal strength
to rise to greater than 195 percent. The problem with operating a
TFX with very high signal strength is that the signals may
saturate the input amplifiers and cause erratic readings. To
decrease the signal strength, one transducer can be offset
radially, as illustrated in Figure 2.6 on page 2.11, or a V-Mount
transducer mounting method may be chosen.
9. Secure the transducer with a stainless steel strap or other
fastener.
PART 2 - TRANSDUCER & RTD INSTALLATION