Dynasonics TFX Ultra Transit Time Flow Meters - Manual (Page 17)

TRANSDUCER INSTALLATION
General
The transducers that are utilized by this flow meter contain piezoelectric crystals for transmitting and receiving ultrasonic
signals through walls of liquid piping systems. DTTH, DTTL and DTTH transducers are relatively simple and straightforward to
install, but spacing and alignment of the transducers is critical to the system’s accuracy and performance. Extra care should
be taken to ensure that these instructions are carefully executed. DTTS and DTTC, small pipe transducers, have integrated
transmitter and receiver elements that eliminate the requirement for spacing measurement and alignment.
Mounting of the DTTN, DTTL, and DTTH clamp-on ultrasonic transit time transducers is comprised of three steps:
1. Selection of the optimum location on a piping system.
2. Entering the pipe and liquid parameters into either the software utility or keying the parameters into transmitter using the
keypad. The software utility or the transmitters firmware will calculate proper transducer spacing based on these entries.
3. Pipe preparation and transducer mounting.
Energy transmitters require two RTDs to measure heat usage. The flow meter utilizes 1000 Ohm, three-wire, platinum RTDs
in two mounting styles. Surface mount RTDs are available for use on well insulated pipes. If the area where the RTD will be
located is not insulated, inconsistent temperature readings will result and insertion (wetted) RTDs should be utilized.
Step 1 – Mounting location
The first step in the installation process is the selection of an optimum location for the flow measurement to be made. For this
to be done effectively, a basic knowledge of the piping system and its plumbing are required.
An optimum location is defined as:
• A piping system that is completely full of liquid when measurements are being taken. The pipe may become
completely empty during a process cycle – which will result in the error code 0010 (Low Signal Strength) being
displayed on the flow meter while the pipe is empty. This error code will clear automatically once the pipe refills
with liquid. It is not recommended to mount the transducers in an area where the pipe may become partially filled.
Partially filled pipes will cause erroneous and unpredictable operation of the meter.
• A piping system that contains lengths of straight pipe such as those described in Table 1 . 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 during
normal operation.
• 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 17 March 2014