Notes On The Mechanical Load Of The Probe - Endress+Hauser Levelflex FMP53 FOUNDATION Fieldbus Operating Instructions Manual

Levelflex FMP53 FOUNDATION Fieldbus
Endress+Hauser
6.1.3

Notes on the mechanical load of the probe

Bending strength of rod probes
Sensor Feature 060
FMP53 DA, DB, EA, EB
FA, FB, GA, GB, HA, HB, IA, IB
Bending load (torque) through fluid flow
The formula for calculating the bending torque M impacting on the probe:
M = c ⋅ ρ/2 ⋅ v 2 ⋅ d ⋅ L ⋅ (L
w
with:
c : Friction factor
w
ρ [kg/m 3 ]: Density of the medium
v [m/s]: Velocity of the medium perpendicular to the probe rod
d [m]: Diameter of the probe rod
L [m]: Level
LN [m]: Probe length
Calculation example
Friction factor c 0,9 (on the assumption of a turbulent current - high
w
Reynolds number)
3
Density ρ [kg/m ] 1000 (e.g. water)
Probe diameter d [m] 0,008
L = L (worst case)
N
Bending torque [M] on rod probes, diameter 8mm (1/3")
20.0
18.0
16.0
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
0.4 0.8 1.2
Probe
Rod 8mm (0.31") 316L
Rod 8mm (0.31") 316L divisible
- 0.5 ⋅ L)
N
1.6 2 2.4 2.8 3.2
Probe length [ ] in meters
L
N
Bending strength [Nm]
10
10
v
d
v=0.5m/s
v=0.7m/s
3.6 4
v=1.0m/s
Mounting
L
N
L
A0014175
A0014182-EN
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