GE DigitalFlow XGM868i, Руководство для стартапов, Страница: 11 / 92

DigitalFlow™ XGM868i Startup Guide 3
Chapter 1. Installation
1.3.2 Flowcell Location
The pipeline flowcell consists of the flow rate transducers and any pressure and/or temperature transducers employed
as part of the flow measurement system. Ideally, choose a section of pipe with unlimited access to the flowcell; for
example, a long stretch of pipe that is above ground. However, if the flowcell is to be mounted on an underground pipe,
dig a pit around the pipe to facilitate installation of the transducers.
1.3.3 Transducer Location
For a given fluid and pipe, the Model XGM868i’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:
1. Locate the 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 sources of turbulence in the fluid such as valves, flanges, expansions and elbows; and dips or low spots in
which condensed liquid may collect.
2. Because condensate or sediment at the bottom of the pipe may cause attenuation of the ultrasonic signal, locate the
transducers on the side of a horizontal pipe, when possible. If limited pipe access necessitates top-mounted
transducers and the sound beam path includes a reflection, shift the transducers to at least 10° off top dead center.
This will minimize the influence of any sediment on the reflected ultrasonic signals.
1.3.4 Cable Lengths
Locate the electronics enclosure as close as possible to the flowcell/transducers, preferably directly on the flowcell.
However, the factory 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 Temperature and Pressure Transmitters
When installing temperature and/or pressure transmitters in the flowcell, locate them downstream of the transducers.
These transmitters should be positioned no closer to the Model XGM868i transducers than 2 pipe diameters and no
further away from the transducers than 20 pipe diameters.
1.3.6 Transducer Cables
When installing the transducer cables, always observe established standard practices for the installation of electrical
cables. Specifically, 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:
When using non-GE cables to connect the flow rate transducers to the Model XGM868i electronics enclosure,
the cables must have electrical characteristics identical to the GE cables. Type RG62 a/u coaxial cable should
be used, and each cable must be the same length (within ±4 in.).