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

Levelflex FMP53 PROFIBUS PA
Endress+Hauser
6.1.3

Notes on the mechanical load of the probe

Lateral loading capacity (flexural strength) of rod probes
FMP53
Rod 8mm (0.31") 316L
10 Nm
Rod 8mm (0.31") 316L separable
10 Nm
Lateral load (bending moment) from flow conditions
The formula for calculating the bending moment M acting on the probe:
2
M = c × ρ/2 × v × d × L × (L
w
With:
c : coefficient of friction
w
ρ [kg/m 3 ]: density of the medium
v [m/s]: flow velocity of the medium, perpendicular to the probe rod
d [m]: diameter of the probe rod
L [m]: level
LN [m]: probe length
Sample calculation
Coefficient of friction c 0.9 (assuming turbulent flow - high Reynolds number)
w
Density ρ [kg/m 3 ] 1000 (e.g. water)
Probe diameter d [m] 0.008
L = L (unfavorable conditions)
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
- 0.5 × L)
N
1.6 2 2.4 2.8 3.2
Probe length [ ] in meters
L
N
v
d
v=0.5m/s
3.6 4 v=0.7m/s
v=1.0m/s
Mounting
L
N
L
A0014175
A0014182-EN
21