Honeywell SLG 700 User Manual page 48

To calculate your probe's torque due to fluid motion use the following formula and check it
against the torque limits in
M=c ×
d
Where:
M = Moment or torque
c Friction factor
d =
ρ [kg/m
v [m/s] = Velocity of medium
perpendicular to probe
d [m] = Diameter of probe
L [m] = Level of medium
f
L [m] = Probe length
Example torque calculation for 8mm rod probe:
Friction factor (c
Density (ρ)
Probe diameter (d)
L = L
f
These values yield the torque curves in
total length of 4m (two 2m segments) then by checking
segments have a torque limit of 4.0Nm limit, which will be exceeded if fluid velocity is
0.4m/s, therefore you would need to use a coaxial or wire probe instead. If the same 8mm rod
probe is angle mounted then the limit is half of 4.0Nm, or 2.0Nm, therefore fluid velocity of
0.3m/s exceeds this limit.
Page 36
Table 3-8 and
ρ L
f
2
× v × d × L ∙ (L- )
f
2 2
3
] = Density of medium
0.9 (turbulent flow – High Reynolds number)
)
d
3
1000 kg/m (water)
0.008 m
(worst case)
Bending Torque [M] on 8mm rod probe
Probe length [L] in meters
SLG 700 SmartLine Level Transmitter User's Manual
Table 3-9.
Figure 3-4. For example, if the 8mm rod probe is a
Table 3-8 you find probes with 2m
v=0.2m/s
v=0.3m/s
v=0.4m/s
Revision 7