Emerson Rosemount 3308 Reference Manual page 113

Reference Manual
00809-XXXX-4811, Rev AA
February 2012
Probe Type in Chamber
Considerations
Centering Discs
Table A-7. Minimum Clearance
Coaxial
Recommended Enough space to fit
nozzle diameter the probe
Min. nozzle Enough space to fit
(2)
diameter the probe
Min. clearance to 0 in. (0 cm)
tank wall or
(3)
obstruction
Min. pipe / bypass 1.5 in. (3.8 cm)
diameter
(1) Probe diameter is 1.1 in. (28 mm) for standard probe.
(2) Requires special configuration and setting of Upper Null Zone.
(3) Minimum clearance from tank bottom for the coaxial and rigid single probes is 0.2 in. (5 mm).
(4) The center-most lead must be at least 0.6 in. (15 mm) away from the pipe/bypass wall.
(5) The probe must be centered in the pipe/bypass.
PRELIMINARY
When installing a Rosemount 3308 transmitter in a chamber, the single lead probe is recommended.
The recommended minimum chamber diameter is 4 in. (100 mm) for Single Flexible probe and 3 in. (75 mm)
for the Single Rigid probe. The probe should be centered to prevent it touching the sides of the well.
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). If installation requires
less head-space, use a Flexible Single Probe with a weight and centering disc.
• More than 19.7 ft. (6.0 m):
Use Flexible Single Probe with a weight and centering disc.
A short weight is available for the single flexible SST probe. It is used for measuring close to the probe end
and shall be used where the measuring range must be maximized. The height is 2 in. (50 mm) and the
diameter is 1.5 in. (37.5 mm). The option code is W2.
If a heavier weight is needed, option code W3 can be used (height is 5.5 in. (140 mm) and the diameter is 1.5
in. (37.5 mm).
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, Alloy C-276, Alloy 400, or PTFE. See Table A-9 for
Dimension D. Table A-10 shows which centering disc diameter to choose for a particular pipe.
Rigid Twin Lead
4 in. (10 cm) or more
(1)
2 in. (5 cm)
(1)
4 in. (10 cm)
(4)
2 in. (5 cm)
Flexible Twin Lead Rigid Single Lead
4 in. (10 cm) or more 6 in. (15 cm) or more
2 in. (5 cm) 2 in. (5 cm)
4 in. (10 cm) 4 in. (10 cm) if
smooth metallic wall.
12 in. (30 cm) if
disturbing objects,
rugged metallic or
concrete/plastic wall.
Consult your local 2 in. (5 cm)
Emerson Process
Management
representative.
Rosemount 3308
Flexible Single Lead
6 in. (15 cm) or more
2 in. (5 cm)
4 in. (10 cm) if
smooth metallic wall.
12 in. (30 cm) if
disturbing objects,
rugged metallic or
concrete/plastic wall.
(5)
Consult your local
Emerson Process
Management
representative.
D
A-11