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4.2 Preparing the Pipe
To prepare the pipe for transducer installation, complete the following steps:
1. Remove any rust and paint from an area 2 in. (5 cm) wide by 4 in. (10 cm) long on one side of the pipe.
2. Polish the cleaned area, taking care to preserve the original curvature of the pipe.
3. With an ultrasonic thickness gage, measure the pipe thickness at a minimum of six spots on the cleared area. Take
at least three measurements at each spot to ensure accuracy. The thickness readings should not vary by more than
5% at each spot. If you encounter more than a 5% variation at each spot, try a different section of the pipe. Verify
that the wall thickness at both transducer locations has less than the 5% variation.
4. Measure the outside diameter (OD) of the pipe using a tape measure or the supplied pipe wrap.
4.3 Obtaining the Transducer Spacing
Before installing the clamping fixture, you must obtain the calculated transducer spacing from the flowmeter. You will
need to know the transducer spacing to complete this procedure.
To obtain the transducer spacing, you must enter the measured pipe OD and the pipe wall thickness into the Pipe
Parameters menu of the flowmeter User Program The flowmeter will then calculate the correct transducer spacing for
the installation. Refer to your flowmeter User's Manual for more details.
4.4 Determining the Number of Traverses
The next step in the installation is to determine the number of traverses that you will use. The transducers can be
mounted using one of two methods (see Figure 3 on the next page):
Note: The "number of traverses" refers to the number of times the ultrasonic signal transmitted from one transducer
passes through the fluid from one side of the pipe to the other before it reaches the second transducer.
•
Double-traverse method ("V" method) - transducers are mounted on the same side of the pipe. The ultrasonic
signal is sent from one transducer to the other by bouncing it off the opposite pipe wall.
•
Single-traverse method ("Z" method) - transducers are mounted diagonally across from each other. The ultrasonic
signal is transmitted directly from one transducer to the other by traveling across the pipe.
If the pipe diameter is 4 to 20 in. (10 to 50 cm), you should always try the double-traverse method first, because it
easier to install and provides greater accuracy. The single-traverse method is preferred in the following situations:
•
pipe diameters greater than 20 in. (50 cm)
•
pipes with poor inside surface conditions
•
applications with a highly attenuating fluid
Note: For all installations, it may be useful to try both methods to determine which one yields more accurate results.
Proceed to the appropriate section to properly install your clamping fixture and transducers.
4
C-RS Ultrasonic Flow Transducer Installation Guide
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