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Chapter 9. Diagnostics and Troubleshooting
Transport® Model PT878 Portable Liquid Flowmeter User’s Manual 211
9.4.1 Wetted Transducer Problems (cont.)
4. PHYSICAL DAMAGE
Transducers may be physically damaged by dropping them onto a hard
surface or striking them against another object. Usually the connector on the
transducer is the part that is damaged, as it is the most fragile. Minor
damage may be repaired by carefully bending the connector back into
shape. If the connector cannot be repaired, replace the transducers. Note
that transducers must be replaced in pairs. Before replacement, make sure
that the transducer number in the programmed parameters is the one
engraved on the new transducers (see Chapter 3, Programming Site Data).
9.4.2 Clamp-on Transducer Problems
1. POOR COUPLING TO PIPE
Clamp-on transducers must be in intimate contact with the pipe. The pipe
wall must be smooth and generally free of paint. The couplant material must
fill voids between the transducer and the pipe, and must be firmly coupled
or bonded to both the pipe and the transducer. The pipe and transducer must
be clean and dry for permanent couplant, such as grease or epoxy, to adhere
properly. Enough pressure must be applied to the transducer by its clamp to
hold it firmly against the pipe.
2. MISALIGNMENT
The transducer transmits relatively narrow beams of ultrasound, and
therefore transducer alignment is critical to assure that the beam can travel
from one transducer to the other without undue attenuation. Be sure to
exactly follow the instructions that came with your transducers and
clamping fixtures. Also, be sure that the transducer spacing agrees with the
calculated spacing (S).
3. INTERNAL DAMAGE
Ultrasonic transducers consist of a ceramic “crystal” bonded to the
transducer case. The bond between the crystal and the case may be damaged
by extreme shock and by temperature extremes. The crystal itself can also
be damaged by the same conditions. The internal wiring can be corroded or
shorted if contaminants enter the transducer housing.