Panametrics CTF878, Руководство для стартапов, Страница: 24 / 108

Chapter 2.
16 Model CTF878 Startup Guide
2.1.8 Installing a CFT-PI 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-PI clamping fixture (for pipes over 12” O.D.), use the following guidelines:
Note: A CFT-PI clamping fixture should be installed before the damping material is applied to the pipe. To install a
clamping fixture on pipes between 6” and 12” O.D., see Installing the
CFT-V Clamping Fixture on page 10.
2.1.8.1 Locating the CFT-PI 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 vapor or liquids may collect
3. For maximum transducer reliability, mount the fixture in a location that is sheltered from precipitation.
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).
2.1.8.2 Preparing for CFT-PI Clamping Fixture Installation
Before the clamps can be installed, the following procedures must be completed:
•
the pipe surface sanded
• the transducer spacing and TAG path set
Sanding the Pipe
Using a grinding tool or sand paper, smooth out the sections of the pipe where the transducers will be installed. The
best approach is to grind on both sides of the pipe an area the length of the clamping fixture and ± 60° from the
plane where the transducers are intended to be installed. Grinding such a large area ensures that the transducers
are installed on a smooth section.
Setting the Transducer Spacing and TAG path
The following procedure can be easily done before installing the
CFT-PI clamping fixture on the pipe. For a more detailed description of these steps, refer to
Programming Site Data on
page 46:
1. Power up the CTF878 flowmeter.
2. In the top-level menu, enter
Program / Transducer
to select the transducers used.
3. Proceed to
Program / Pipe
to enter the pipe characteristics:
material, outside diameter and wall thickness.
4. Enter
Program / Fluid
to select the fluid inside the pipe.