Transducer Location; Cable Lengths; Transducer Cables; Installing A Flowcell - GE DigitalFlow XMT868i Startup Manual

1.3.3 Transducer Location

For a given fluid and pipe, the Model XMT868i's accuracy depends primarily on the location and alignment of the
transducers. In addition to accessibility, when planning for transducer location, adhere to the following guidelines:
•
Locate the transducers so that there are at least 10 pipe diameters of straight, undisturbed flow upstream and
5 pipe diameters of straight, undisturbed flow downstream from the measurement point. Undisturbed flow
means avoiding sources of turbulence in the fluid such as valves, flanges, expansions, and elbows; avoiding
swirl; and avoiding cavitation.
•
Locate the transducers on a common axial plane along the pipe. Locate the transducers on the side of the pipe,
rather than the top or bottom, since the top of the pipe tends to accumulate gas and the bottom tends to
accumulate sediment. Either condition will cause increased attenuation of the ultrasonic signal. There is no
similar restriction with vertical pipes. However, vertical pipes should be avoided in order to insure a full pipe at
the measurement point.

1.3.4 Cable Lengths

Locate the electronics enclosure as close as possible to the flowcell/transducers, preferably directly on the flowcell.
However, GE can supply transducer cables up to 1,000 ft (300 m) in length for remote location of the electronics
enclosure. If longer cables are required, consult the factory for assistance.

1.3.5 Transducer Cables

When installing the transducer cables, always observe established standard practices for the installation of electrical
cables. Do not route transducer cables alongside high amperage AC power lines or any other cables that could cause
electrical interference. Also, protect the transducer cables and connections from the weather and corrosive
atmospheres.
Note: If you are using your own cables to connect the transducers to the electronics console, they must have
electrical characteristics identical to the cables supplied by GE. For transducer frequencies up to 2 MHz, the
cables in each pair must be the same length within ±4 in. (10 cm). For transducer frequencies above 2 MHz,
the cables in each pair must be the same length within ±0.5 in. (1.25 cm).

1.4 Installing a Flowcell

A flowcell is the section of pipe where the transducers are mounted. It can be created either by mounting the
transducers on the existing pipeline or by mounting them on a spoolpiece. A spoolpiece is a separately manufactured
pipe section, matched to the existing pipe, which contains ports for mounting the transducers. This approach allows the
transducers to be aligned and calibrated before inserting the spoolpiece into the pipeline.
Figure 1 on page 2 shows a typical Model XMT868i spoolpiece, with a mounting bracket to hold the electronics
enclosure. For detailed instructions on installing the transducers and/or spoolpiece, refer to the supplied drawings and
the appropriate Transducer Installation Guide.
DigitalFlow™ XMT868i Startup Guide
Chapter 1. Installation
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