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Reference Manual
00809-0700-4530, Rev AA
Section 2: Installation Considerations
September 2013
Installation considerations
Probe length is between 3 ft (1 m) and 10 ft (3 m)
(1)
: Use either a rigid single or a flexible
single probe with weight and a centering disk. The rigid single is easier to clean and has smaller
transition zones, while the flexible single requires less head-space during installation and is less
likely to be damaged.
Probe length is more than 10 ft (3 m)
(1)
: Use a flexible single probe with weight and a
centering disk. Minimum chamber diameter is 3 in. (75 mm).
For very narrow chambers with a diameter less than 2 in. (50 mm), a coaxial probe can be used
to help reduce the impact of possible disturbances, such as splashing from upper inlet pipes.
However, since the coaxial probe is more sensitive to build-up, it is only recommended for very
clean liquids. For a chamber with a diameter equal to or larger than 3 in. (75 mm), the single lead
probe is therefore the preferred choice.
NOTE:
For the coaxial probe, the minimum chamber diameter is 1.5 in. (837.5 mm).
Figure 2-7. Improper and proper probe positions
To avoid bending the probe (rigid probes), or twisting (flexible probes), and coming into contact
with the chamber wall a small clearance distance between the centering disk and the chamber
bottom is recommended. A clearance distance of 1 in. (25 mm) is suggested assuming a dome
shaped chamber bottom, which may prevent the centering disk from reaching the bottom.
Transition zones, located at the very top and bottom of the probes, are regions where
measurement performance is reduced. Different factors affect the size of the transition zones -
probe type, centering disk or no centering disk, and the material and media measured (see
Table 2- 5). The weight on the flexible probes reduces the measurement range. Therefore, it is
recommended to size the cage (A, C) so it does not interfere with the effective measurement
range (B). The transition zones also limit the minimum probe length.
(1) For a Rosemount 5300 Series with DVC, only rigid probes are available in lengths up to 13 ft (4 m).
Make sure that the probe
does not come into contact
with the chamber wall, e.g.
by using a centering disk.
A clearance distance
of 1 in. (25 mm)
between the probe
end and the cage
bottom is
recommended.