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Specifications and Reference Data
October 2016
Table A-11. Required Probe Length in Chambers
Chamber manufacturer
Major torque-tube manufacture
(249B, 249C, 249K, 249N, 259B)
Masoneilan (Torque tube operated),
proprietary flange
(2)
Other - torque tube
®
Magnetrol
(spring operated)
(2)
Others - spring operated
1.
If flushing ring is used, add the ring height to the probe length.
2.
For other manufacturers, there are small variations. This is an approximate
value, actual length should be verified.
3.
Lengths vary depending on model, SG and rating, and should be verified.
For additional information, see the Replacing Displacers with
Guided Wave Radar
Technical
Probe type in chamber considerations
When installing a Rosemount 3308 in a chamber, the single lead
probe is recommended. The probe length determines if a Single
Rigid or Single Flexible probe should be used:
Less than 19.7 ft. (6.0 m):
Rigid Single Probe is recommended. Use a centering disc for
probe > 3.3 ft. (1 m). When mounting space is limited, use a
Flexible Single Probe with a heavy weight (option W3) and
centering disc.
More than 19.7 ft. (6.0 m):
Use Flexible Single Probe with a heavy weight (option W3) and
centering disc.
Centering discs
To prevent the probe from contacting the chamber or pipe wall,
centering discs are available for rigid single, flexible single, and
flexible twin lead probes. The disc is attached to the end of the
probe. Discs are made of stainless steel or PTFE.
Figure A-13. Dimension D for Centering Discs
D
Specifications and Reference Data
(1)
Probe length
Displacer + 9 in. (229 mm)
Displacer + 8 in. (203 mm)
Displacer + 8 in. (203 mm)
Displacer + between 7.8 in.
(3)
(195 mm) to 15 in.
(383 mm)
Displacer + 19.7 in.
(500 mm)
Note.
For the segmented rigid single lead probe, up to five PTFE
centering discs can be mounted along the probe, but keep a
minimum distance of two segments between the discs.
Additionally, a disc in SST or PTFE (part number 03300-1655-xxxx)
can be attached to the end of the probe.
When mounting a centering disc, it is important that it fits
correctly in the chamber/pipe. See
Dimension D.
Table A-13 on page 121
diameter to choose for a particular pipe.
Table A-12. Centering Discs Dimensions
Disc size
Actual disc diameter (D)
2 in.
1.8 in. (45 mm)
3 in.
2.7 in. (68 mm)
4 in.
3.6 in. (92 mm)
6 in.
5.55 in. (141 mm)
8 in.
7.40 in. (188 mm)
Table A-13. Centering Disc Size Recommendation for
Different Pipe Schedules
Pipe size
5s, 5 and
40s, 40 and
10s,10
2 in.
2 in.
3 in.
3 in.
4 in.
4 in.
5 in.
4 in.
6 in.
6 in.
(1)
7 in.
N/A
8 in.
8 in.
1.
Schedule is not available for pipe size.
2.
No centering disc is available.
Reference Manual
00809-0100-4308, Rev BB
Table A-12 on page 121
shows which centering disc
Pipe schedule
120
80s, 80
(1)
2 in.
N/A
(1)
3 in.
N/A
4 in.
4 in.
4 in.
4 in.
6 in.
4 in.
(1)
6 in.
N/A
8 in.
6 in.
for
160
(2)
N/A
2 in.
3 in.
4 in.
4 in.
(1)
N/A
6 in.
121
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