Honeywell SmartLine SLG 700 User Manual page 62

Probe
Model Selection
SLG720 SCA
SLG726 SCB
*For an angle mounted probe reduce these limits by 50% to allow for bending from gravity.
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 Figure 3-7: Example bending torque values. For
example, if the 8mm rod probe is a total length of 4m (two 2m segments) then by checking
Table 3-9 you find probes with 2m 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 46
Probe description
Coax 22mm, 2m (6') segments
Coax 42mm, 2m (6') segments
Table 3-9 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)
SLG 700 SmartLine Level Transmitter User's Manual
Table 3-10.
Maximum Bending
Torque [Nm]*
50
100
Revision 8