Panametrics CTF878, Startup Manual

Page: 18 / 108

Chapter 2.
10 Model CTF878 Startup Guide
2.1.6 Installing Transducer Support
Since the CTF878 is specifically designed for gas measurement with clamp-on transducers, it requires the use of
specially designed fixtures and damping material to maintain the highest possible measurement accuracy.
2.1.6.1 Clamping Fixture
Panametrics Sensing supplies the CFT series of fixtures:
•
The V8 clamping fixture for pipes from 6 to 8 in. (100 to 200 mm).
• The V12 clamping fixture for pipes from 8 to 12 in. (200 to
300 mm).
• The PI clamping fixture for pipes from 12 to 24 in. (300 to
600 mm).
2.1.6.2 Damping Material
Panametrics Sensing strongly recommends applying DMP damping material in ALL permanent clamp-on
applications to help eliminate signal noise. The material comes in two versions:
• The DMP-1 self-adhesive sheet for applications up to 200°F (93°C). The material comes as three wide sheets
cut in sufficient length to wrap around a pipe OD. The material can be cut with a utility knife, and comes with a
paper backing that is removed before installation.
• The DMP-3 is a clay-like compound for all temperature applications. If the temperature is over 150°F, the PDJ
pipe damping jacket (available from the factory with preapplied DMP-3) must be used with the material.
2.1.7 Installing a CFT-V Clamping Fixture
For a given gas and pipe, the CTF878’s accuracy depends primarily on the location and alignment of the transducers.
To install the
CFT-V transducer-supporting clamping fixture (for pipes 6” to 12” O.D.), use the following guidelines:
Note: With a CFT-V clamping fixture, the damping material is installed prior to the fixture itself. To install a clamping
fixture on pipes over 12”, proceed to Installing the CFT-PI Clamping Fixture on page 16.
2.1.7.1 Locating the CFT-V Clamping Fixture
1. Choose a section of pipe with unlimited access; for example, a long stretch of pipe that is above ground.
Note: If the clamping fixture is to be mounted on an underground pipe, dig a pit around the pipe to facilitate
installation.
2. Locate the clamping fixture and transducers so that there are at least 20 pipe diameters of straight, undisturbed
flow upstream and 10 pipe diameters of straight, undisturbed flow downstream from the measurement point. To
ensure undisturbed flow, avoid the following:
• sources of turbulence in the gas such as valves, flanges, expansions and elbows
• swirl
• dips or low spots in which condensed gas may collect
3. For maximum transducer reliability, mount the clamping fixture in a location that is sheltered from ambient
precipitation such as rain.
Note: In order to shield the transducer installation from adverse accoustic effects related to rain, it may be
necessary to erect a rain shroud over and around the pipe where the transducers are mounted.
4. Because condensate or sediment at the bottom of the pipe may cause attenuation of the ultrasonic signal, set
up the clamping fixture so that the transducers are on the side of a horizontal pipe, ideally at 0° horizontal (3 and
9 o’clock). Also make sure that the transducers will not be located on or near any pipe welds or seams.
Note: Do not orient the transducers greater than ±60° from the horizontal axis. The transmit / receive pairs must be
oriented 180° from each other. The Upstream / Downstream pairs must be transmitting in the same direction
(parallel to each other).